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Contaminants in Aquatic and Terrestrial Environments

Potentially Poisonous Plastic Particles: Microplastics as a Vector for Cyanobacterial Toxins Microcystin-LR and Microcystin-LF
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  • Carlos J. Pestana*
    Carlos J. Pestana
    School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.
    *Email: [email protected]. Tel.: +44 1224 262847.
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    Orcidhttps://orcid.org/0000-0002-5619-6968
  • Diana S. Moura
    Diana S. Moura
    School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.
    Department of Hydraulic and Environmental Engineering, Federal University of Ceará, Avenida Humberto Monte, Pici Campus Block 713 (first floor), Fortaleza, Ceará 60440-593, Brazil
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  • José Capelo-Neto
    José Capelo-Neto
    Department of Hydraulic and Environmental Engineering, Federal University of Ceará, Avenida Humberto Monte, Pici Campus Block 713 (first floor), Fortaleza, Ceará 60440-593, Brazil
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  • Christine Edwards
    Christine Edwards
    School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.
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  • Domenic Dreisbach
    Domenic Dreisbach
    Institute of Inorganic and Analytical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, Giessen D-35392, Germany
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  • Bernhard Spengler
    Bernhard Spengler
    Institute of Inorganic and Analytical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, Giessen D-35392, Germany
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    Orcidhttps://orcid.org/0000-0003-0179-5653
  • Linda A. Lawton
    Linda A. Lawton
    School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.
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Environmental Science & Technology

Cite this: Environ. Sci. Technol. 2021, 55, 23, 15940–15949
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https://doi.org/10.1021/acs.est.1c05796
Published November 10, 2021

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Abstract

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The potential of microplastics to act as a vector for micropollutants of natural or anthropogenic origin is of rising concern. Cyanobacterial toxins, including microcystins, are harmful to humans and wildlife. In this study, we demonstrate for the first time the potential of microplastics to act as vectors for two different microcystin analogues. A concentration of up to 28 times from water to plastic was observed for the combination of polystyrene and microcystin-LF achieving toxin concentrations on the plastic of 142 ± 7 μg g–1. Based on the experimental results, and assuming a worst-case scenario, potential toxin doses for daphnids are calculated based on published microplastic ingestion data. Progressing up through trophic levels, theoretically, the concentration of microcystins in organisms is discussed. The experimental results indicate that adsorption of microcystins onto microplastics is a multifactorial process, depending on the particle size, the variable amino acid composition of the microcystins, the type of plastic, and pH. Furthermore, the results of the current study stressed the limitations of exclusively investigating microcystin-LR (the most commonly studied microcystin congener) as a model compound representing a group of around 250 reported microcystin congeners.

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Synopsis

Microplastics may act as transportation vehicles for highly toxic blue-green algal metabolites in the food web.

Introduction

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Plastics are ubiquitous in the world with estimated 299 million tonnes produced in 2013. (1) According to Plastics Europe, (2) 80% of plastics produced are polyethylene, polyvinyl chloride, polystyrene, polyethylene terephthalate, polypropylene, and polyurethane. At the end of their life cycle, most plastics will enter the environment. Consumer plastic waste can enter wastewater treatment plants, where breakthrough can occur leading to plastic particles reaching the freshwater environment. (1) Larger plastic particles are reduced by physical, chemical, and biological processes; (3) plastic particles thus reduced to sizes of ≤5 mm (in all dimensions) are considered microplastics. Another source of microplastics are particles originally manufactured in microplastic dimensions, for example, beads for abrasive blasting used in coatings and paints. Microplastic occurrence in aquatic systems globally has been recognized as an environmental risk factor (4−8) as it has been found that microplastic particles can be contaminated with organic pollutants. (9) Microplastics act as mobile reservoirs of toxic compounds due to their high surface-to-volume ratio. Adsorption is a surface process and therefore a high surface-to-volume ratio favors adsorption of increased amounts of pollutants. (9−11) Microplastics, including any adsorbed contaminants, can enter the food web by ingestion by aquatic organisms such as fish, zooplankton, and crustaceans where desorption in the gut can lead to bioaccumulation of the contaminants in the food web. (7)
Cyanobacteria and their secondary metabolites are encountered in most aquatic systems globally. During blooms, seasonal or perennial mass occurrences of cyanobacteria, high concentrations of potentially toxic secondary metabolites can be detected in the surrounding water. (12) Evidence suggests that with increasing global warming, the frequency and intensity of blooms will increase. (13,14) One of the most frequently reported groups of cyanobacterial toxins is microcystins (MCs) with over 240 congeners. (15) MCs are hepatotoxic heptapeptides with two variable amino acids that inhibit protein phosphatases and can act as tumor promoters. Different congeners of MC display different chemical behaviors due to their amino acid composition and other chemical differences such as (de)methylation. MC-LR is one of the most commonly reported analogues; however, MC-LF is of increasing concern as it presents similar toxicity but is more hydrophobic and thus more readily enters the target organs (Figure 1). (16−20)

Figure 1

Figure 1. Chemical structures of the two MC congeners used in the present study (MC-LR left and MC-LF right) with variable amino acids indicating leucine (blue) and arginine (green) (MC-LR) and leucine (blue) and phenylalanine (red) (MC-LF). (21,22) The variable amino acids within the MC structure are largely responsible for the overall hydrophobicity of the congener.

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The World Health Organization (WHO) has set a recommended maximum allowable level of 1 μg L–1 of total MCs in potable water. (23,24) Currently, little is known about the partitioning of MCs on microplastics. MC-contaminated microplastics could pose a significant environmental risk acting as a concentration vehicle and unlike other natural particulates and sediment microplastics can be mistaken as food by aquatic biota representing a gateway into the food web via ingestion by aquatic organisms.
With increased frequency of toxic cyanobacterial blooms and increasing microplastic presence in freshwater systems, it stands to reason that co-occurrence of microplastic particles and MCs frequently takes place.
Thus, the current study sets out to determine, for the first time, if microplastic particles can act as a vector for MCs. Four different plastics (polystyrene [PS], polyvinyl chloride [PVC], polyethylene [PE], and polyethylene terephthalate [PET]) were exposed to two MC congeners (MC-LR and MC-LF). The effects of pH, exposure time, and particle size were evaluated. Furthermore, an estimate of the amount of toxin that could be transported into the food web by microplastics was made.

Materials and Methods

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All plastics were obtained from Goodfellows Ltd. (UK) and processed to produce microplastics of known sizes. PVC was received as 1 m rods (5 mm diameter) and cut into approximately 5 mm length with stainless steel shears. The remaining three plastics (PS, PE, and PET) were received as pellets (3–5 mm). The material received was characterized by Fourier transform infrared (FTIR) spectroscopy (Nicolet iS10, Thermo Fisher Scientific, UK) to confirm the polymers received. All plastics were reduced in size individually in an industrial stainless steel blender (Waring, USA). Size reduction was achieved by pulsing the blender for 20 s with 1–2 min cooling intervals to avoid thermally altering the plastics. Size-reduced plastics were then sieved to three standardized specific particles sizes of >1 mm (and <5 mm), 0.25–0.5 mm, and 0.09–0.125 mm (sieves from Fisher Scientific, UK; sieving apparatus from Retsch Ltd., UK). Artificial freshwater (AFW), used as the experimental medium, was prepared with ultrapure water (18.2 MΩ) and the addition of CaCl2 2H2O (58.5 mg L–1), MgSO4 7H2O (24.7 mg L–1), NaHCO3 (12.0 mg L–1), and KCl (1.2 mg L–1). (25) The pH was adjusted to the required level (pH 2, pH 5, pH 7, pH 9, and pH 11) either with HNO3 or NaOH. MC (LR or LF) solutions (5 μg mL–1) in AFW were prepared and combined with the individual microplastics (10 g L–1). All pH conditions were tested with the three sizes for each plastic and a control sample containing no plastic particles. Samples were continuously horizontally agitated on an orbital shaker at 250 rpm and 25 °C in the dark for 48 h. Samples (100 μL) were extracted with a glass syringe with a stainless steel needle at time points 0, 2, 6, 12, 24, and 48 h and spin-filtered in microcentrifuge filter tubes (0.22 μm cellulose acetate filters, Corning, USA); these polypropylene filter tubes displayed <2% adsorption of MC congeners (data not shown) and were deemed safe for use. Samples were directly analyzed by HPLC-PDA (Section S2.2). Controls containing no microplastics were prepared for all conditions. All experiments and controls were conducted in triplicate. In all experiments, contact between MCs and any types of plastics other than the tested type of microplastic was eliminated.
To confirm the presence of MC-LF on the surface of PS, samples were prepared for 3D surface matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) according to the study of Kompauer et al.; (26) in short, a sample (2 μL) of a suspension containing 10 g L–1 PS (0.09–0.125 mm particle size) that had been exposed to MC-LF for 48 h was applied to a PTFE-coated glass slide and dried for 30 min in a desiccator. A matrix solution of 30 mg mL–1 2,5-dihydroxybenzoic acid in acetone/water (0.2% TFA) 1:1 v/v was freshly prepared, and a volume of 80 μL was sprayed onto the sample surface with a flow rate of 10 μL min–1 and a rotation of 500 rpm using an ultrafine pneumatic sprayer system (SMALDIPrep, TransMIT GmbH, Germany). 3D optical microscope images of the sample surface were obtained with a Keyence VHX-5000 digital microscope (Keyence Deutschland GmbH, Germany) before and after matrix application. For data acquisition, Xcalibur software on a Q Exactive HF orbital trapping mass spectrometer (Thermo Fisher Scientific GmbH, Germany) equipped with an AP-SMALDI5 AF (TransMIT GmbH, Germany) MSI system was used. Ion images of selected m/z values were generated using Mirion imaging software (27) with a mass bin width of Δ(m/z) = 0.01. MS images were normalized to the highest intensity measured for each ion separately. No further image processing steps such as smoothing, interpolation, or TIC normalization were employed.
The zeta potential of the plastics in the experimental medium under pH 3–10 was measured using a Malvern Zetasizer instrument (Nano ZS, UK, Table S3).
A t-test was performed to determine significance testing (Supporting Information S6). Pearson correlation (R2) was used to evaluate the relationship between the variables. For all statistical tests, a significance level (p value) of 5% was set.

Results and Discussion

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Microplastics are encountered in aquatic systems globally, (2,28) and a number of studies (4−8,29,30) have demonstrated that microplastics can act as a vehicle for the concentration of organic pollutants such as pyrene, phenanthrene, bis-2-ethylhxyl phthalate, and dichlorodiphenyltrichloroethane. In the present study, we were able to demonstrate that three sizes of microplastics, small (0.09–0.125 mm), medium (0.25–0.5 mm), and large size (>1 mm), can also act as a concentration vehicle for MCs (Figure 2). Throughout the study, adsorption of MC was determined by the reduction in the MC concentration in solution compared to controls without microplastics. Typically used in biomedical science, MALDI MSI provides untargeted and label-free analysis of various molecular classes in the spatial context of tissues and cells. Here, recent technical developments in 3D surface MALDI MSI (26) were utilized to confirm the adsorption of MC congeners on plastic surfaces.

Figure 2

Figure 2. 3D surface MALDI MSI of MC-LF adsorbed to the PS microplastic. (a) Optical microscope image of PS particles before matrix application. (b) MS image showing the spatial distribution of [MC-LF + Na]+ at m/z 1008.5053. (c) Single-pixel mass spectrum for a mass range m/z of 985 to 1025 obtained from the PS microplastic. Three different adducts for MC-LF were labeled with measured mass and mass deviation. MS images were generated with 170 × 174 pixels, a pixel size of 12 μm, and an image bin width of Δ(m/z) = 0.01. The scale bar is 500 μm.

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The obtained 3D surface MALDI MSI results clearly show the adsorption of MC-LF on the surface of the PS particles. All three adducts (H+, Na+, and K+) of MC-LF were detected and assigned, based on accurate mass measurements (Figure 2c), showing identical spatial distributions (Figure 2b for [MC-LF + Na]+ and Figure S5 for [MC-LF + H]+ and [MC-LF + K]+). By comparing the optical image with the ion images, the MSI results demonstrate that MC-LF was primarily detected on PS particles, thus unambiguously confirming adsorption to the surface of the plastic particle and directly visualizing MCs adsorbed to the microplastic for the first time.
The adsorption behavior of both MC-LR and MC-LF onto four different microplastics was investigated by monitoring the diminishing toxin concentration in solution, and a control containing no microplastic particles was also analyzed at each pH to monitor the toxin stability at the corresponding pH concentration (Figure 3). The MC-LR concentration was stable under all tested pH concentrations with a maximum toxin loss of 20% at pH 2 and no more than 9% loss at pH 5–11. The MC-LF concentration was also comparatively stable at pH 5–11 with a decrease of no more than 14% over time. At pH 2, the toxin concentration decreased by 43% over the first 6 h of the experiment with a final loss of 44% after 48 h. Harada et al. (31) had previously reported on the detrimental effect of low pH concentrations on the stability of MCs.

Figure 3

Figure 3. Influence of pH on MC-LR and MC-LF adsorption onto PS, PVC, PE, and PET particles of different sizes (>1 mm [red], 0.25–0.50 mm [blue], and 0.009–0.125 mm [yellow]) (Test conditions: 10 g L–1 plastics, 5 μg mL–1 MC, 48 h agitation time, 25 °C, and control [black] contained no microplastic). %RSD ≤ 10%, n = 3.

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For MC-LR, equilibrium was achieved after approximately 2 h (pH 5–11) for all three size ranges investigated. After an initial decrease, concentrations remained stable with little to no additional adsorption occurring onto any of the microplastics of any size. At pH 2, equilibrium was only achieved for the large- and medium-sized particles of PS. For all four plastics, the greatest adsorption of MC-LR was observed at pH 2 for the smallest size with the highest adsorption occurring with PE (∼21% at pH 2, p value = 0.02) and the least with PET (∼1% at pH 9, p value = 0.15). At pH 2, the initial concentration rapidly declined over the first 6 h, and this loss is likely caused by a combination of the acidic conditions (decline is mirrored in the control samples─Figure 3) and adsorption to the microplastic particles as the decrease is dependent on the type of the microplastic. For PE and PS, a 20% concentration decrease was observed (compared to 10% in the control); for PVC, the decrease was 17% and for PET 13%, showing greater adsorption to PE and PS.
Adsorption of MC-LF was observed for all four types of plastic with equilibrium achieved by 48 h for most of the large-sized plastics (PE, PET, and PVC), for some of the medium-sized plastics (PVC and PE), and none for any of the small-sized plastic particles. The highest degree of adsorption was observed for the small particle sizes for all plastics at all pH values investigated. Most adsorption occurred onto PS (∼60% at pH 7 when adjusted with the control) and the least onto PET (∼10% at pH 5–11). As was observed for MC-LR at pH 2, there was a rapid initial decrease of the toxin concentration in the first 6 h of the experiment. Most adsorption in this initial phase occurred onto PE (83%) and PS (85%) compared to the control (43%), PVC (76%), and PET (65%), which also showed marked decreases in toxin concentration. With the exception of PET, all microplastic types showed significant differences for the MC-LF concentration at pH 2 compared with the control after 48 h contact. The adsorption of MC-LF follows a similar pattern (rapid initial decrease in toxin concentration followed by a slower decrease) across the other pH concentrations investigated.
During cyanobacterial bloom events, pH in the surrounding water frequently increases to above pH 9. (32) Thus, when focusing on what could be considered the most environmentally relevant pH concentrations of pH 5–9, markedly more MC-LF than MC-LR is adsorbed onto microplastic particles. This becomes particularly apparent when considering the total amounts of MC-LR and MC-LF adsorbed over 48 h (Figure 4).

Figure 4

Figure 4. Effect of particle size and pH on the amount of MC-LR and MC-LF adsorbed onto four different microplastics (green: PET, yellow: PVC, blue: PE, and red: PS) (Test conditions: 10 g L–1 plastics, 5 μg mL–1 MCs, 48 h agitation time, and 25 °C). %RSD ≤ 10%, n = 3.

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Across all pH levels, particle sizes, and types of microplastics, more MC-LF than MC-LR was adsorbed in the environmentally relevant range of pH 5–9. On average, 130 μg g–1 MC-LF adsorbed onto the smallest particle size of PS, with 89 μg g–1 MC-LF adsorbed to PE, 99 μg g–1 MC-LF adsorbed onto PVC, and 12 μg g–1 MC-LF adsorbed onto PET, with maximum adsorption of MC-LF of 156 μg g–1 achieved with PS. The maximum adsorption of MC-LR in the environmentally important range (pH 5–9) was achieved with PS at pH 5 (56 μg g–1) and average adsorption of MC-LR was achieved with PS of 28 μg g–1, PE of 8 μg g–1, PVC of 14 μg g–1, and PET of 6 μg g–1. From these results, it is apparent that the hydrophobicity, due to variable amino acid composition of the MC congener, strongly determines the amount of adsorption. (17) In the current study, MC-LR and MC-LF differ in the fact that the arginine (R) in MC-LR is replaced with the more hydrophobic phenylalanine (F) in MC-LF. Therefore, as would be expected, MC-LF adsorbs more readily to the microplastic particles than MC-LR (Table 1 and Figures 1 and 2). Connected to the hydrophobicity of the sorbent, the pH of the surrounding matrix will affect the behavior of the MCs. As de Maagd et al. (33) and McCord et al. (34) have demonstrated, the hydrophobicity of MCs, expressed as the pH-dependent octanol–water partitioning coefficient (DOW), changes as the pH of the test matrix is altered. As the pH decreases, the log10(DOW) as a function of the hydrophobicity increases, increasing the likelihood of the MC analogue to adsorb onto the microplastic. The log10(DOW) of MC-LR increases from −1.2 (pH 7) to 1.67 (pH 2), whereas the log10(DOW) of MC-LF increases from 0.06 (pH 7) to 2.75 (pH 2). (33,34) Increasing adsorption with decreasing surrounding pH was also observed in this investigation (Figures 2 and 3) with maximum adsorption for both MC-LR (small-sized PE: 181.6 μg g–1) and MC-LF (small-sized PET: 187.5 μg g–1) occurring at pH 2. Altaner et al. (35) also found a correlation between the pH of an MC-containing solution and the amount of adsorption onto polypropylene (PP) laboratory pipette tips, observed after repeated use (eight times) of the tip. The more acidic the solution, the more likely MCs adsorbed to the PP pipette tips, similar to the observations made for the microplastics studied in the current investigation. Altaner et al.’s (35) observation is explained with the fact that at low pH, most MCs tend to be positively charged due to carboxyl and guanidine moieties being protonated; (33,34,36,37) while the surface of PE, for example, is negatively charged due to the dissociation of carboxyl groups as part of oxidation processes during polymerization. (38) Similar observations were made by Hyenstrand et al. (37) when they tested adsorption of MC-LR onto laboratory PP tips. According to Kamp et al. (39) the change of surface charge is an important factor affecting the adsorption potential of contaminants on microplastics. The plastics investigated showed a negatively charged surface under all pH values measured (Table S3). Although the surface charge of the microplastics changed under different pH conditions, no correlation between the surface charge of plastics and the adsorption behavior of MC-LR and MC-LF was apparent. In the pH range tested in their study (pH 6–10), pH did not markedly affect the adsorption behavior, which correlates to the observations made for the microplastics investigated in the current study (albeit both studies are not directly comparable). Observations made in the current study are further corroborated by a study testing different materials for MC sampling in which Kamp et al. (39) found that MC-LF more readily adsorbed onto bottles made from a range of plastics (PE, PS, PP, polyethylene terephthalate glycol, and polycarbonate) in drinking water compared to MC-LR at near neutral pH. After 48 h in the study by Hüffer and Hofmann, (40) MC-LR adsorption onto PS and PE occurred to a similar degree (<10% adsorption), while for MC-LF, less adsorption occurred (∼20% adsorption) compared with small-sized microplastics in the current study (PS ∼63% adsorption and PE ∼43% adsorption). Compared to large-sized microplastic particles, greater adsorption was observed by Hüffer and Hofmann, (40) since, in the current study, no adsorption occurred on any of the plastics of size >1–5 mm. However, our investigation and the study by Kamp et al. (39) are again not directly comparable as there were marked differences in the study design (size of the exposed surface, agitation, and temperature during storage).
Table 1. Comparison of Maximum MC-LR and MC-LF Adsorption onto Four Types of Microplasticsa
plasticmaximum MC-LR adsorption (μg g–1)maximum MC-LF adsorption (μg g–1)ASCRTg (°C)
polyethylene terephthalate (PET)0.000.00469
polyethylene (PE)0.8976.641.7–125
polyvinyl chloride (PVC)11.6481.222.781
polystyrene (PS)22.10119.541.8100
a

Experimental conditions: 10 g L–1 plastics, 5 μg mL–1 MCs, pH 7, particle size 0.009–0.125 mm, 48 h, and 25 °C. ASCR (44) is reported in the literature studies (n = 12 studies). For ASCR, a score of 1 indicates the highest sorption capacity and increasing values indicate types of plastics that exhibit lower sorption capacities as reported in the Tg of the polymers used in the current study, (42) giving an indication of the prevalence of amorphous or glassy regions of a given polymer.

While in the majority of cases the highest degree of adsorption was observed for the small particle size, this was not true in all instances (e.g., maximum adsorption of MC-LR onto PVC at pH 2 was observed for the medium-sized particles, Figure 3). As partitioning of organic compounds onto microplastics is a surface process, logic would dictate that the smaller the particle, the higher the potential adsorption that can be achieved. This was largely observed in the present study; however, Hüffer and Hofmann (40) determined that sorption of organic compounds to microplastic particles in aqueous solutions did not exclusively occur according to the particle size as their model sorbents (seven hydrophobic aromatic and nonaromatic hydrocarbons) preferably adsorbed to the largest particle size of PS in their study. Hydrophobicity of the sorbent and π–π interactions between the PS and the model sorbents were proposed as potential explanations for this observation. Hu et al., (41) however, determined increased adsorption as a function of particle size. Their (41) findings are however difficult to compare to the current study or to the study by Hüffer and Hofmann (40) as Hu et al. (41) investigated the adsorption of lubrication oil on micro- and nanoparticulate plastic particles. Hu et al. (41) did not find a significant impact of pH on the partitioning behavior of lubrication oil to either type of microplastic tested (PE and PS), illustrating that in the case of MCs, pH influences the sorbate (MCs) more than the sorbent (microplastics).
As established in the current study, the chemical properties of the adsorbent and the particle size of the receiving material critically affect the adsorption of MCs onto microplastic particles. The type of microplastics showed a strong correlation (R2 > 0.9) regarding adsorption of MC-LR and MC-LF. A further factor is the chemical composition and surface morphology of this receiving material, specifically, in the case of microplastics, whether the surface of the constituent polymer is glassy or amorphous. (42) By far, most adsorption occurs on the amorphous regions of the surface. The glass transition temperature (Tg) of a polymer is a measure of whether a polymer is considered rubber-like or glass-like. If the ambient temperature is higher than the Tg of a given polymer, it is considered rubber-like at that temperature. If the ambient temperature is lower than the Tg of a given polymer, it is considered glass-like. For example, under the experimental conditions of the current study (25 °C), only PE would be considered rubber-like (Table 1). For the other three microplastics, ambient temperature was <Tg; thus, PS, PET, and PVC would be considered glass-like. Guo et al. (43) found that by decreasing the glassiness and increasing the abundance of amorphous sites on PS, the sorption capacity for organic compounds could be increased, confirming that glassiness plays an important part in the reduced partitioning of organic compounds onto microplastics. In a survey of 12 published studies, Alimi et al. (44) have created average sorption capacity ranking (ASCR; from 1 = highest sorption potential to >1 decreasing sorption potential) for key plastics.
The results of the current investigation follow the proposed ASCR (Table 1), especially for MC-LF that showed a strong negative correlation (R2 > −0.8) between the sorption capacity ranking and the adsorption on microplastics. For PET, with an ASCR score of 4, almost no adsorption of either MC analogue could be detected, whereas PS, which has a comparatively low ASCR score of 1.8, showed the greatest adsorption potential for both MC analogues investigated. Despite having a higher ASCR score (2.7 compared to 1.7) than PE, PVC showed similar or higher adsorption of MCs across all samples evaluated. While the ASCR score is derived from a number of studies, there are exceptions for each of the plastics where they display a higher or a lower adsorption capacity than would be expected from their ASCR score and glassiness as a function of Tg. These exceptions are explained by the individual chemistry of the polymer and the specific interaction with the chemistry of sorbate as well as the surface morphology of the microplastic particle. (44) Investigating the surface of the microplastic particles applied in the current study shows that PS, PE, and PET present a comparatively smooth surface, while PVC presents a pockmarked surface (10,000× magnification, Figure 5). Increased adsorption to PVC could thus, in part, be explained by the rougher surface.

Figure 5

Figure 5. Scanning electron microscope (SEM) imaging of the plastics utilized in the current study clearly displaying the surface morphology of each type. For each type of plastic, a particle size of 1–5 mm was investigated.

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At 500× magnification, it can be observed that all the plastics except PET present a rough morphology with crevasses and ridges, which could further contribute to the increased adsorption of those types of microplastic compared to PET, which presents a comparatively smooth surface. The effect of surface morphology on adsorption was also observed by Fotopoulou and Karapanagioti (45) when comparing the surface morphologies of virgin and eroded PE, PP, and PVC. Comparing the SEM images of the surface morphology in our study and the study by Fotopoulou and Karapanagioti, (45) similarities between our microplastic and the eroded plastic in their studies are apparent.
The overriding parameter for MC adsorption onto the selected plastics, however, appears to be the hydrophobicity of the MC analogue determined by the variable amino acid rather than the type of microplastic (e.g., PVC over PET) and particle size (small over large). However, establishing a clear hierarchical order of factors determining the adsorption of MCs onto microplastics is difficult as the effects of MC hydrophobicity, particle size, and pH are all interwoven and interdependent representing a multifactorial system. While on the one hand, the surface area-to-volume ratio of the plastic will influence adsorption onto the surface of the microplastic, (9) on the other hand, the hydrophobicity, that is, the variable amino acid composition of the MC molecule will strongly influence adsorption. Additionally, surface morphology, availability of amorphous regions on the polymers, and pH concentration will also influence adsorption.
The results of the current study have demonstrated that under all conditions investigated, MC-LF is more likely to adsorb onto microplastic particles compared to MC-LR. This finding should be viewed in an environmental context: MC-LR is the most frequently studied MC congener and most countries’ legislature relating to maximal allowable levels of MCs in, for example, drinking water are often maybe based solely on MC-LR presence or MC-LR toxicity equivalence. However, in recent years, it has repeatedly been demonstrated that MC-LF presents greater toxicity than MC-LR. (16,19) In light of this, the WHO has recently amended its guidelines for maximum allowable levels of MCs in drinking water to use the total MC concentration rather than toxicity equivalence. (24) As demonstrated in the present study, MC-LF preferably adsorbed to microplastic particles compared to MC-LR, which is concerning in light of its greater toxicity. The results of the current study demonstrate the limitations of exclusively using MC-LR as a single representative of the wider group of MCs.
Generally, eutrophicated waters, that is, water bodies with a high nutrient load, are preferred habitats of aquatic cyanobacteria. Wastewater treatment plants and effluents are good examples with routine mass occurrences (blooms) of cyanobacteria. (46,47) Microplastic particles are likely to be encountered in wastewaters, and co-occurrence of microplastic particles and MCs frequently takes place. Having demonstrated the presence of MCs on microplastics (Figure 5) and the load per mass of plastic determined (Figure 3), theoretical exposure of aquatic organisms to MC on microplastic particles can be calculated as there is a concern that pollutants adsorbed to microplastics could enter the food web. (4,6) Assuming that all MCs adsorbed onto the microplastic particles will desorb in the gut of biota and all desorbed toxin will be bioavailable, the following worse-case scenario could be imagined: a recent study by Canniff and Hoang (3) has demonstrated that the water flea Daphnia magna can consume microplastic particles in a size range of 63–75 μm. The smallest particle size investigated in the current study is in the range of 90 to 125 μm. While this is larger than the particles used in the Canniff and Hoang (3) study, it was used to predict a theoretical MC uptake by Daphnia sp. by means of feeding on MC-laden particles. Canniff and Hoang (3) demonstrated that up to 15 particles were ingested by individual Daphnia magna in 21 days of exposure (with the first particles being ingested within 6 h); by calculating the amount of the two different MC congeners per plastic particle in the current study (Supporting Information S4), it was possible to predict the MC load per individual Daphnia (Table 2). Correlating this toxin load to the published lethal concentrations of MC-LR for Daphnia demonstrated that the amount of MC-LR would not constitute a lethal dose for Daphnia. However, assuming a similar, or even higher, toxicity of MC-LF compared to MC-LR (as proposed by Faassen and Lürling (16)), it could be demonstrated that ingestion of 15 MC-LF-laden particles would be lethal if desorbed from the microplastic (with the caveat that the reported lethal concentration does not directly correspond to the lethal ingested dose). While this prediction is based on a number of assumptions and data based on different species of Daphnia, it nonetheless demonstrates the potential of biologically relevant amounts of MCs entering the food web by means of toxin-laden microplastic ingestion.
Table 2. Predicted MC-LR and MC-LF Amounts per Plastic Particle after 48 h of Exposure, Hypothetical Amounts of MCs Ingested by Daphnia sp., and Lethal Doses (LD50) of MC-LR in Daphnia sp.a
plastictoxin (μg g–1) on plastic after 48 htoxin (pg) per particletheoretical toxin amount (pg) ingested by daphnidsblethal ingested dose of MC (pg) for daphnidsc
MC-LR
PET000510–915
PVC13.8512.4186
PE1.060.6496
PS26.3123.6354
MC-LF
PET000510–915d
PVC96.6986.71300
PE91.2355.1826
PS142.311271910
a

Experimental conditions: 10 g L–1 plastics, 5 μg mL–1 MCs, and horizontal agitation in the dark at pH 7.

b

Derived from the study of Canniff and Hoang (3) which observed uptake of up to 15 microplastic particles per Daphnia sp. individual in a feeding study.

c

Derived from the study of Rohrlack et al. (48) which state MC-LR toxicity as 10.2 to 18.3 ng mg–1 wet weight in Daphnia sp. and from the study of Badouin and Ravera (49) stating the dry weight of individual mature Daphnia sp. as 21.33 μg wet weight, which was assumed to be 200% of the dry weight.

d

Assuming similar toxicity to MC-LR as proposed by Faassen and Lürling. (16)

In a feeding study, Christoffersen (50) demonstrated that the arctic tadpole shrimp (Lepidurus arcticus (L. arcticus)) was capable of predating on a Daphnia species. Larger L. arcticus was shown to have consumed 5 to 15 Daphnia. Extrapolating from the data in Table 2, this would represent concentrations of 1.77 to 5.31 ng and 9.55 to 28.65 ng of MC-LR and MC-LF, respectively (adsorbed to PS particles). While there are no toxicity data of the effect of MCs on tadpole shrimp, this example demonstrates the theoretical accumulation of toxin in the food web, with increasing trophic level, with plastics as a vector.

Implications

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The current study has, for the first time, demonstrated that at least three types of microplastics (PVC, PE, and PS) can act as vectors for MCs; an almost 40-fold concentration compared to the dissolved concentration was observed for some MC congener-microplastic combinations (e.g., MC-LF + PS). Adsorption of MCs to microplastic particles is a multifactor process. The current study demonstrated that the particle size of the microplastics, pH conditions, the type of polymer, and the MC congener affect adsorption. Even under environmentally relevant pH conditions (pH 7), MC-LF adsorbed to microplastic particles. A theoretical worst-case scenario demonstrated that the amount of MC adsorbed onto certain types of plastics, if desorbed, would constitute a lethal dose to daphnids. Furthermore, this study highlights that adopting MC-LR as a model for all MCs is a poor choice as the chemical diversity created by the two variable amino acids can lead to widely varying adsorption behaviors. This was demonstrated by the significantly greater adsorption of MC-LF compared to MC-LR under the same experimental conditions. Microplastics could act as a vector for MCs, highlighting an, as of yet, unexplored pathway for cyanobacterial toxins to enter the food web.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.1c05796.

  • Chemical structures of the four plastic monomers; list of chemicals, materials, devices, and auxiliaries; 3D surface MALDI imaging of MC-LF bound to PET microplastic particles; calculations for prediction of amount of toxin per individual plastic particle; evaluation of the electrostatic charge of each type of microplastic under five pH conditions; and statistical analysis (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
  • Authors
    • Diana S. Moura - School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.;  Department of Hydraulic and Environmental Engineering, Federal University of Ceará, Avenida Humberto Monte, Pici Campus Block 713 (first floor), Fortaleza, Ceará 60440-593, Brazil
    • José Capelo-Neto - Department of Hydraulic and Environmental Engineering, Federal University of Ceará, Avenida Humberto Monte, Pici Campus Block 713 (first floor), Fortaleza, Ceará 60440-593, Brazil
    • Christine Edwards - School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.
    • Domenic Dreisbach - Institute of Inorganic and Analytical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, Giessen D-35392, Germany
    • Bernhard Spengler - Institute of Inorganic and Analytical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, Giessen D-35392, Germany;  Orcidhttps://orcid.org/0000-0003-0179-5653
    • Linda A. Lawton - School of Pharmacy and Life Sciences, Robert Gordon University, Sir Ian Wood Building, Garthdee Road, Aberdeen AB10 7GJ, U.K.
  • Notes
    The authors declare the following competing financial interest(s): B.S. is a consultant and D.D. is a part-time employee of TransMIT GmbH (Giessen, Germany).

Acknowledgments

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The authors would like to thank the Engineering and Physical Science Research Council UK [EP/P029280/1] and the Newton Mobility Grant [NMG\R2\170134] for funding this research project. In addition, the authors would like to thank Len Montgomery for proof-reading the manuscript and Iain Tough for the SEM imaging. Furthermore, technical support provided by TransMIT GmbH and by Thermo Fisher Scientific (Bremen) GmbH and financial support by the Deutsche Forschungsgemeinschaft DFG [Sp314/23-1] are gratefully acknowledged.

References

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    Climate change is likely to stimulate the development of harmful cyanobacterial blooms in eutrophic waters, with neg. consequences for water quality of many lakes, reservoirs and brackish ecosystems across the globe. In addn. to effects of temp. and eutrophication, recent research has shed new light on the possible implications of rising atm. CO2 concns. Depletion of dissolved CO2 by dense cyanobacterial blooms creates a concn. gradient across the air-water interface. A steeper gradient at elevated atm. CO2 concns. will lead to a greater influx of CO2, which can be intercepted by surface-dwelling blooms, thus intensifying cyanobacterial blooms in eutrophic waters. Bloom-forming cyanobacteria display an unexpected diversity in CO2 responses, because different strains combine their uptake systems for CO2 and bicarbonate in different ways. The genetic compn. of cyanobacterial blooms may therefore shift. In particular, strains with high-flux carbon uptake systems may benefit from the anticipated rise in inorg. carbon availability. Increasing temps. also stimulate cyanobacterial growth. Many bloom-forming cyanobacteria and also green algae have temp. optima above 25 °C, often exceeding the temp. optima of diatoms and dinoflagellates. Anal. of published data suggests that the temp. dependence of the growth rate of cyanobacteria exceeds that of green algae. Indirect effects of elevated temp., like an earlier onset and longer duration of thermal stratification, may also shift the competitive balance in favor of buoyant cyanobacteria while eukaryotic algae are impaired by higher sedimentation losses. Furthermore, cyanobacteria differ from eukaryotic algae in that they can fix dinitrogen, and new insights show that the nitrogen-fixation activity of heterocystous cyanobacteria can be strongly stimulated at elevated temps. Models and lake studies indicate that the response of cyanobacterial growth to rising CO2 concns. and elevated temps. can be suppressed by nutrient limitation. The greatest response of cyanobacterial blooms to climate change is therefore expected to occur in eutrophic and hypertrophic lakes.
  14. 14
    Paerl, H. W.; Paul, V. J. Climate Change: Links to Global Expansion of Harmful Cyanobacteria. Water Res. 2012, 46, 1349– 1363,  DOI: 10.1016/j.watres.2011.08.002
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    Climate change: Links to global expansion of harmful cyanobacteria
    Paerl, Hans W.; Paul, Valerie J.
    Water Research (2012), 46 (5), 1349-1363CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
    Cyanobacteria are the Earth's oldest (∼3.5 bya) oxygen evolving organisms, and they have had major impacts on shaping our modern-day biosphere. Conversely, biospheric environmental perturbations, including nutrient enrichment and climatic changes (e.g. global warming, hydrol. changes, increased frequencies and intensities of tropical cyclones, more intense and persistent droughts), strongly affect cyanobacterial growth and bloom potentials in freshwater and marine ecosystems. We examd. human and climatic controls on harmful (toxic, hypoxia-generating, food web disrupting) bloom-forming cyanobacteria (CyanoHABs) along the freshwater to marine continuum. These changes may act synergistically to promote cyanobacterial dominance and persistence. This synergy is a formidable challenge to water quality, water supply and fisheries managers, because bloom potentials and controls may be altered in response to contemporaneous changes in thermal and hydrol. regimes. In inland waters, hydrol. modifications, including enhanced vertical mixing and, if water supplies permit, increased flushing (reducing residence time) will likely be needed in systems where nutrient input redns. are neither feasible nor possible. Successful control of CyanoHABs by grazers is unlikely except in specific cases. Overall, stricter nutrient management will likely be the most feasible and practical approach to long-term CyanoHAB control in a warmer, stormier and more extreme world.
  15. 15
    Spoof, L.; Catherine, A. Appendix 3, Tables of Microcystins and Nodularins. In Handbook of Cyanobacterial Monitoring and Cyanotoxin Analysis; Meriluoto, J., Spoof, L., Codd, G. A., Eds.; John Wiley & Sons: Chichester, UK, 2017; 526– 537,  DOI: 10.1002/9781119068761.app3 .
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    Faassen, E. J.; Lürling, M. Occurrence of the Microcystins MC-LW and MC-LF in Dutch Surface Waters and Their Contribution to Total Microcystin Toxicity. Mar. Drugs 2013, 11, 2643– 2654,  DOI: 10.3390/md11072643
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    16
    Occurrence of the microcystins MC-LW and MC-LF in Dutch surface waters and their contribution to total microcystin toxicity
    Faassen, Elisabeth J.; Luerling, Miquel
    Marine Drugs (2013), 11 (7), 2643-2654, 12 pp.CODEN: MDARE6; ISSN:1660-3397. (MDPI AG)
    Microcystins (MCs) are the most frequently found cyanobacterial toxins in freshwater systems. Many MC variants have been identified and variants differ in their toxicity. Recent studies showed that the variants MC-LW and MC-LF might be more toxic than MC-LR, the variant that is most abundant and mostly used for risk assessments. As little is known about the presence of these two variants in The Netherlands, we detd. their occurrence by analyzing 88 water samples and 10 scum samples for eight MC variants ((dm-7-)MC-RR, MC-YR, (dm-7-)MC-LR, MC-LY, MC-LW and MC-LF) by liq. chromatog. with tandem mass spectrometry detection. All analyzed MC variants were detected and MC-LW and/or MC-LF were present in 32% of the MC contg. water samples. When MC-LW and MC-LF were present, they contributed to nearly 10% of the total MC concns., but due to their suspected high toxicity, their av. contribution to the total MC toxicity was estd. to be at least 45%. Given the frequent occurrence and possible high toxicity of MC-LW and MC-LF, it seems better to base health risk assessments on the toxicity contributions of different MC variants than on MC-LR concns. alone.
  17. 17
    Vesterkvist, P. S. M.; Misiorek, J. O.; Spoof, L. E. M.; Toivola, D. M.; Meriluoto, J. A. O. Comparative Cellular Toxicity of Hydrophilic and Hydrophobic Microcystins on Caco-2 Cells. Toxins 2012, 4, 1008– 1023,  DOI: 10.3390/toxins4111008
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    Comparative cellular toxicity of hydrophilic and hydrophobic microcystins on Caco-2 cells
    Vesterkvist, Pia S. M.; Misiorek, Julia O.; Spoof, Lisa E. M.; Toivola, Diana M.; Meriluoto, Jussi A. O.
    Toxins (2012), 4 (), 1008-1023CODEN: TOXIB7; ISSN:2072-6651. (MDPI AG)
    Microcystins (MC), cyanobacterial peptide hepatotoxins, comprise more than 100 different variants. They are rather polar mols. but some variants contain hydrophobic amino acid residues in the highly variable parts of the mol. In MC-LF and MC-LW, the more hydrophobic phenylalanine (F) and tryptophan (W), resp., have replaced arginine (R) in MC-LR. Depending on the structure, microcystins are expected to have different in vivo toxicity and bioavailability, but only a few studies have considered the toxic properties of the more hydrophobic variants. The present study shows that MC-LF and MC-LW have more pronounced cytotoxic effects on Caco-2 cells as compared to those of MC-LR. Treatment of Caco-2 cells with MC-LW and esp. MC-LF showed clear apoptotic features including shrinkage and blebbing, and the cell-cell adhesion was lost. An obvious redn. of cell proliferation and viability, assessed as the activity of mitochondrial dehydrogenases, was obsd. with MC-LF, followed by MC-LW and MC-LR. Cytotoxicity was quantified by measuring lactate dehydrogenase leakage. The more hydrophobic MC-LW and MC-LF induced markedly enhanced lactate dehydrogenase leakage compared to controls and MC-LR, indicating that the plasma membrane was damaged. All of the three toxins examd. inhibited protein phosphatase 1, with MC-LF and MC-LW to a weaker extent compared to MC-LR. The higher toxic potential of the more hydrophobic microcystins could not be explained by the biophys. expts. performed. Taken together, our data show that the more hydrophobic microcystin variants induce higher toxicity in Caco-2 cells.
  18. 18
    Fischer, A.; Hoeger, S. J.; Stemmer, K.; Feurstein, D. J.; Knobeloch, D.; Nussler, A.; Dietrich, D. R. The Role of Organic Anion Transporting Polypeptides (OATPs/SLCOs) in the Toxicity of Different Microcystin Congeners in Vitro: A Comparison of Primary Human Hepatocytes and OATP-Transfected HEK293 Cells. Toxicol. Appl. Pharmacol. 2010, 245, 9– 20,  DOI: 10.1016/j.taap.2010.02.006
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    18
    The role of organic anion transporting polypeptides (OATPs/SLCOs) in the toxicity of different microcystin congeners in vitro: A comparison of primary human hepatocytes and OATP-transfected HEK293 cells
    Fischer, A.; Hoeger, S. J.; Stemmer, K.; Feurstein, D. J.; Knobeloch, D.; Nussler, A.; Dietrich, D. R.
    Toxicology and Applied Pharmacology (2010), 245 (1), 9-20CODEN: TXAPA9; ISSN:0041-008X. (Elsevier B.V.)
    Cellular uptake of microcystins (MCs), a family of cyclic cyanobacterial heptapeptide toxins, occurs via specific org. anion transporting polypeptides (OATPs), where MCs inhibit serine/threonine-specific protein phosphatase (PP). Despite comparable PP-inhibitory capacity, MCs differ greatly in their acute toxicity, thus raising the question whether this discrepancy results from MC-specific toxicokinetic rather than toxicodynamic differences. OATP-mediated uptake of MC congeners MCLR, -RR, -LW, and -LF was compared in primary human hepatocytes and Hek 293 cells stably expressing recombinant human OATP1B1/SLCO1B1 and OATP1B3/SLCO1B3 in the presence/absence of OATP substrates taurocholate (TC) and bromosulfophthalein (BSP) and measuring PP inhibition and cytotoxicity. Control vector expressing Hek 293 were resistant to MC cytotoxicity while TC and BSP competition expts. reduced MC cytotoxicity in Hek 293-OATP transfectants, thus confirming the requirement of OATPs for transmembrane transport. Despite comparable PP-inhibiting capabilities, MCLW and -LF elicited cytotoxic effects at lower equimolar concns. than MCLR and MCRR, hence suggesting congener selective transport into Hek 293-OATP transfectants and primary human hepatocytes. Primary human hepatocytes appeared one order of magnitude more sensitive to MC congeners than the corresponding Hek 293 -OATP transfectants. Although the latter may be due to a much lower level of PPs in primary human hepatocytes, the presence of OATPs other than 1B1 or 1B3 may have added to an increased uptake of MCs. In view of the high sensitivity of human hepatocytes and currently MCLR only based risk calcns., the actual risk of human MC intoxication and ensuing liver damage could be underestimated in freshwater cyanobacterial blooms where MCLW and -LF predominate.
  19. 19
    Feurstein, D.; Holst, K.; Fischer, A.; Dietrich, D. R. Oatp-Associated Uptake and Toxicity of Microcystins in Primary Murine Whole Brain Cells. Toxicol. Appl. Pharmacol. 2009, 234, 247– 255,  DOI: 10.1016/j.taap.2008.10.011
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    19
    Oatp-associated uptake and toxicity of microcystins in primary murine whole brain cells
    Feurstein, D.; Holst, K.; Fischer, A.; Dietrich, D. R.
    Toxicology and Applied Pharmacology (2009), 234 (2), 247-255CODEN: TXAPA9; ISSN:0041-008X. (Elsevier B.V.)
    Microcystins (MCs) are naturally occurring cyclic heptapeptides that exhibit hepato-, nephro- and possibly neurotoxic effects in mammals. Org. anion transporting polypeptides (rodent Oatp/human OATP) appear to be specifically required for active uptake of MCs into hepatocytes and kidney epithelial cells. Based on symptoms of neurotoxicity in MC-intoxicated patients and the presence of Oatp/OATP at the blood-brain-barrier (BBB) and blood-cerebrospinal-fluid-barrier (BCFB) it is hypothesized that MCs can be transported across the BBB/BCFB in an Oatp/OATP-dependent manner and can induce toxicity in brain cells via inhibition of protein phosphatase (PP). To test these hypotheses, the presence of murine Oatp (mOatp) in primary murine whole brain cells (mWBC) was investigated at the mRNA and protein level. MC transport was tested by exposing mWBCs to three different MC-congeners (MC-LR, -LW, -LF) with/without co-incubation with the OATP/Oatp-substrates taurocholate (TC) and bromosulfophthalein (BSP). Uptake of MCs and cytotoxicity was demonstrated via MC-Western blot anal., immunocytochem., cell viability and PP inhibition assays. All MC congeners bound covalently and inhibited mWBC PP. MC-LF was the most cytotoxic congener followed by -LW and -LR. The lowest toxin concn. significantly reducing mWBC viability after 48 h exposure was 400 nM (MC-LF). Uptake of MCs into mWBCs was inhibited via co-incubation with excess TC (50 and 500 μM) and BSP (50 μM). MC-Western blot anal. demonstrated a concn.-dependent accumulation of MCs. In conclusion, the in vitro data support the assumed MC-congener-dependent uptake in a mOatp-assocd. manner and cytotoxicity of MCs in primary murine whole brain cells.
  20. 20
    Vesterkvist, P. S. M.; Meriluoto, J. A. O. Interaction between Microcystins of Different Hydrophobicities and Lipid Monolayers. Toxicon 2003, 41, 349– 355,  DOI: 10.1016/S0041-0101(02)00315-X
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    Interaction between microcystins of different hydrophobicities and lipid monolayers
    Vesterkvist, Pia S. M.; Meriluoto, Jussi A. O.
    Toxicon (2003), 41 (3), 349-355CODEN: TOXIA6; ISSN:0041-0101. (Elsevier Science Ltd.)
    Microcystins (MC) are a group of amphiphatic peptide hepatotoxins and protein phosphatase inhibitors produced by certain cyanobacteria (blue-green algae). Microcystins are believed to require an active transport mechanism to penetrate the plasma membranes of animal cells. In this study the surface barostat technique showed that two more hydrophobic microcystins MC-LF, contg. Leu and Phe, and MC-LW, contg. Leu and Trp, had a higher surface activity on an egg phosphatidylcholine-cholesterol (7:3, molar ratio) monolayer as compared to that of a more hydrophilic variant MC-LR, contg. Leu and Arg. Fluorescence anisotropy measurements of 1-[4-(trimethylamine)phenyl]-hexa-1,3,5-trien (TMA-DPH) were used to assess changes in the fluidity or lipid packing of model membranes in the presence of toxins. All three toxins caused a decrease in the steady-state anisotropy of TMA-DPH, suggesting that the toxins interacted with the membranes. The change in anisotropy was more pronounced for MC-LF and MC-LW than for MC-LR. Moreover, the fluorescence emission max. of Trp in MC-LW was shifted slightly towards a shorter wavelength and the intensity was enhanced when allowed to interact with lipid vesicles, suggesting that the single Trp in MC-LW moved into a more unpolar environment when interacting with the vesicles. The differences between hydrophilic and hydrophobic microcystins could result in changes in organotropism, toxicokinetics and bioaccumulation.
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    Royal Society of Chemistry. Microcystin-LR structure.
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    Royal Society of Chemistry. Microcystin-LF structure.
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    WHO. Guidelines for Drinking-Water Quality; WHO Press: Geneva, Switzerland, 2008.
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    WHO, Cyanobacterial Toxins : Microcystins. Background Document for Drinking-Water Quality and Guidelines for Safe Recreational Water Environments; W. H. O. Geneva, 2020.
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    Akkanen, J.; Kukkonen, J. V. K. Biotransformation and Bioconcentration of Pyrene in Daphnia Magna. Aquat. Toxicol. 2003, 64, 53– 61,  DOI: 10.1016/S0166-445X(03)00023-7
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    Biotransformation and bioconcentration of pyrene in Daphnia magna
    Akkanen, Jarkko; Kukkonen, Jussi V. K.
    Aquatic Toxicology (2003), 64 (1), 53-61CODEN: AQTODG; ISSN:0166-445X. (Elsevier Science B.V.)
    Water fleas (Daphnia magna) were exposed to [14C]pyrene in the presence and absence of piperonyl butoxide (PBO), a general cytochrome P 450 (CYP) inhibitor, in org. carbon-free artificial freshwater (AFW, DOC<0.2 mg l-1) and in natural lake water (DOC=19.9 mg l-1) for 24 h. The bioconcn. of total radioactivity after 24 h exposure was 50% lower in the natural lake water, indicating decreased bioavailability of pyrene by the dissolved org. matter. However, the proportions of parent compd. were only ca. 12 and 19% of the total body burden in daphnids exposed in AFW and natural lake water, resp. Therefore, the tissue concn. of the parent pyrene was not significantly different in the daphnids exposed in the 2 different waters. Due to extensive biotransformation the bioconcn. factor (BCF) of parent pyrene was only 16 and 23% of the BCF calcd. on the basis of total radioactivity in the daphnids in AFW and natural lake water, resp. The proportion of parent pyrene was significantly higher (over 60%) in the daphnids exposed simultaneously to PBO, which indicates the involvement of CYP monooxygenases in the biotransformation. Furthermore, increasing PBO concn. decreased the accumulation of total radioactivity in AFW but not in the natural lake water. The data demonstrate capability and importance of CYP monooxygenases in biotransformation of polycyclic arom. hydrocarbons in D. magna.
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    Kompauer, M.; Heiles, S.; Spengler, B. Autofocusing MALDI Mass Spectrometry Imaging of Tissue Sections and 3D Chemical Topography of Nonflat Surfaces. Nat. Methods 2017, 14, 1156– 1158,  DOI: 10.1038/nmeth.4433
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    Autofocusing MALDI mass spectrometry imaging of tissue sections and 3D chemical topography of nonflat surfaces
    Kompauer, Mario; Heiles, Sven; Spengler, Bernhard
    Nature Methods (2017), 14 (12), 1156-1158CODEN: NMAEA3; ISSN:1548-7091. (Nature Research)
    We describe an atm. pressure matrix-assisted laser desorption-ionization mass spectrometry imaging system that uses long-distance laser triangulation on a micrometer scale to simultaneously obtain topog. and mol. information from 3D surfaces. We studied the topog. distribution of compds. on irregular 3D surfaces of plants and parasites, and we imaged nonplanar tissue sections with high lateral resoln., thereby eliminating height-related signal artifacts.
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    Paschke, C.; Leisner, A.; Hester, A.; Maass, K.; Guenther, S.; Bouschen, W.; Spengler, B. Mirion - A Software Package for Automatic Processing of Mass Spectrometric Images. J. Am. Soc. Mass Spectrom. 2013, 24, 1296– 1306,  DOI: 10.1007/s13361-013-0667-0
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    Mirion--A Software Package for Automatic Processing of Mass Spectrometric Images
    Paschke, C.; Leisner, A.; Hester, A.; Maass, K.; Guenther, S.; Bouschen, W.; Spengler, B.
    Journal of the American Society for Mass Spectrometry (2013), 24 (8), 1296-1306CODEN: JAMSEF; ISSN:1044-0305. (Springer)
    Mass spectrometric imaging (MSI) techniques are of growing interest for the Life Sciences. In recent years, the development of new instruments employing ion sources that are tailored for spatial scanning allowed the acquisition of large data sets. A subsequent data processing, however, is still a bottleneck in the anal. process, as a manual data interpretation is impossible within a reasonable time frame. The transformation of mass spectrometric data into spatial distribution images of detected compds. turned out to be the most appropriate method to visualize the results of such scans, as humans are able to interpret images faster and easier than plain nos. Image generation, thus, is a time-consuming and complex yet very efficient task. The free software package "Mirion," presented allows the handling and anal. of data sets acquired by mass spectrometry imaging. Mirion can be used for image processing of MSI data obtained from many different sources, as it uses the HUPO-PSI-based std. data format imzML, which is implemented in the proprietary software of most of the mass spectrometer companies. Different graphical representations of the recorded data are available. Furthermore, automatic calcn. and overlay of mass spectrometric images promotes direct comparison of different analytes for data evaluation. The program also includes tools for image processing and image anal.
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    Dris, R.; Imhof, H.; Sanchez, W.; Gasperi, J.; Galgani, F.; Tassin, B.; Laforsch, C. Beyond the Ocean: Contamination of Freshwater Ecosystems with (Micro-)Plastic Particles. Environ. Chem. 2015, 12, 539,  DOI: 10.1071/en14172
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    Beyond the ocean: contamination of freshwater ecosystems with (micro-)plastic particles
    Dris, Rachid; Imhof, Hannes; Sanchez, Wilfried; Gasperi, Johnny; Galgani, Francois; Tassin, Bruno; Laforsch, Christian
    Environmental Chemistry (2015), 12 (5), 539-550CODEN: ECNHAA; ISSN:1449-8979. (CSIRO Publishing)
    Environmental context Microplastics in freshwater ecosystems are an increasingly important environmental issue, with the few available studies suggesting high contamination worldwide. Reliable data on concns., fluxes and polymer types in continental aquatic environments, including urban water systems, are needed. High environmental and ecol. risk polymers and assocd. or adsorbed chems. have to be identified, as well as their effects on both organisms and ecosystems. Abstr. Massive accumulation of plastic particles has been reported for marine ecosystems around the world, posing a risk to the biota. Freshwater ecosystems have received less attention despite most plastic litter being produced onshore and introduced into marine environments by rivers. Some studies not only report the presence of microplastics in freshwater ecosystems, but show that contamination is as severe as in the oceans. In continental waters, microplastics have been obsd. in both sediments (predominantly lake shores but also riverbanks) and water samples (predominantly surface water of lakes and rivers). This review highlights recent findings and discusses open questions, focussing on the methodol. of assessing this contaminant in freshwater ecosystems. In this context, method harmonisation is needed in order to obtain comparable data from different environmental compartments and sites. This includes sampling strategies (at spatial and temporal scales), sample treatment (taking into consideration high levels of org. matter and suspended solids) and reliable anal. methods to identify microplastics.
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    Wang, J.; Tan, Z.; Peng, J.; Qiu, Q.; Li, M. The Behaviors of Microplastics in the Marine Environment. Mar. Environ. Res. 2016, 113, 7– 17,  DOI: 10.1016/j.marenvres.2015.10.014
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    The behaviors of microplastics in the marine environment
    Wang, Jundong; Tan, Zhi; Peng, Jinping; Qiu, Qiongxuan; Li, Meimin
    Marine Environmental Research (2016), 113 (), 7-17CODEN: MERSDW; ISSN:0141-1136. (Elsevier Ltd.)
    Despite the pollution of microplastics being internationally recognized, the understanding of their behaviors in marine environment is still developing. Microplastics are ubiquitous in the marine environment, with the potential to cause harm to marine ecosystem. Here, we would classify the behaviors of microplastics as phys. behaviors (i.e. migration, sedimentation and accumulation), chem. behaviors (i.e. degrdn. and adsorption) and biobehaviors (i.e. ingestion, translocation and biodegrdn.), and a further discussion on their behavioral mechanisms were presented to better understand their impacts for the marine environment.
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    Wang, W.; Wang, J. Comparative Evaluation of Sorption Kinetics and Isotherms of Pyrene onto Microplastics. Chemosphere 2018, 193, 567– 573,  DOI: 10.1016/j.chemosphere.2017.11.078
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    Comparative evaluation of sorption kinetics and isotherms of pyrene onto microplastics
    Wang, Wenfeng; Wang, Jun
    Chemosphere (2018), 193 (), 567-573CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
    Concerns regarding microplastics pollution and their potential to conc. and transport org. contaminants in aquatic environments are growing in recent years. Sorption of org. chems. by microplastics may affect the distribution and bioavailability of the chems. Here sorption process of pyrene (Pyr), a frequently encountered polycyclic arom. hydrocarbon in aquatic environments, on three types of mass-produced plastic particles (high-d. polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)), was investigated by comparative anal. of different sorption kinetic and isotherm models. Optimum kinetic and isotherm models were predicted by the linear least-squares regression method. The pseudo-second-order kinetic model was more appropriate in describing the entire sorption process (R2 > 0.99). Sorption rates of Pyr onto microplastics were mainly controlled by intraparticle diffusion. PE exhibited the highest affinity for Pyr, followed by PS and PVC. The sorption equil. data were best fitted to the Langmuir isotherm (R2 > 0.99), indicating monolayer coverage of Pyr onto the microplastics.
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    Harada, K.; Tsuji, K.; Watanabe, M. F.; Kondo, F. Stability of Microcystins from Cyanobacteria – III. Effect of PH and Temperature. Phycologia 1996, 35, 83– 88,  DOI: 10.2216/i0031-8884-35-6S-83.1
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    Wilhelm, S. W.; Bullerjahn, G. S.; McKay, R. M. L. The Complicated and Confusing Ecology of Microcystis Blooms. MBio 2020, 11, 1– 5,  DOI: 10.1128/MBIO.00529-20
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    De Maagd, P. G. J.; Hendriks, A. J.; Seinen, W.; Sijm, D. T. H. M. PH-Dependent Hydrophobicity of the Cyanobacteria Toxin Microcystin-LR. Water Res. 1999, 33, 677– 680,  DOI: 10.1016/S0043-1354(98)00258-9
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    McCord, J.; Lang, J. R.; Hill, D.; Strynar, M.; Chernoff, N. PH Dependent Octanol–Water Partitioning Coefficients of Microcystin Congeners. J. Water Health 2018, 16, 340– 345,  DOI: 10.2166/wh.2018.257
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    pH dependent octanol-water partitioning coefficients of microcystin congeners
    McCord James; Lang Johnsie R; Hill Donna; Chernoff Neil; Strynar Mark
    Journal of water and health (2018), 16 (3), 340-345 ISSN:1477-8920.
    Hazardous algal blooms can generate toxic compounds with significant health impacts for exposed communities. The ubiquitous class of algal toxins known as microcystins exhibits significant heterogeneity in its peptide structure, which has been minimally studied, given the significant impact this has on hydrophobicity, acid/base character and related environmental fate and health effects. Octanol-water partition coefficients for the microcystin congeners MCLR, MCRR, MCLY, MCLF, and MCLA were calculated over an environmentally and physiologically relevant pH range. Microcystin-LR log(Kow) partition coefficient values were found to be consistent with previously established literature values, 1.67 to -1.41 between pH 1 and 8. Microcystin RR was found to be pH insensitive with a log(Kow) of -0.7. The remaining congeners exhibit similar pH dependence as MCLR, with systematic increases in hydrophobicity driven by the introduction of more hydrophobic residues to their variable amino acid region. The variation in pH dependent hydrophobicity suggests increased propensity for bioaccumulation and alternate environmental fates for differing microcystin forms, requiring further investigation.
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    Altaner, S.; Puddick, J.; Wood, S. A.; Dietrich, D. R. Adsorption of Ten Microcystin Congeners to Common Laboratory-Ware Is Solvent and Surface Dependent. Toxins 2017, 9, 129,  DOI: 10.3390/toxins9040129
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    Adsorption of ten microcystin congeners to common laboratory-ware is solvent and surface dependent
    Altaner, Stefan; Puddick, Jonathan; Wood, Susanna A.; Dietrich, Daniel R.
    Toxins (2017), 9 (4), 129/1-129/15CODEN: TOXIB7; ISSN:2072-6651. (MDPI AG)
    Cyanobacteria can produce heptapetides called microcystins (MC) which are harmful to humans due to their ability to inhibit cellular protein phosphatases. Quantitation of these toxins can be hampered by their adsorption to common lab.-ware during sample processing and anal. Because of their structural diversity (>100 congeners) and different physico-chem. properties, they vary in their adsorption to surfaces. In this study, the adsorption of ten different MC congeners (encompassing non-arginated to doubly-arginated congeners) to common lab.-ware was assessed using different solvent combinations. Sample handling steps were mimicked with glass and polypropylene pipettes and vials with increasing methanol concns. at two pH levels, before anal. by liq. chromatog.-tandem mass spectrometry. We demonstrated that MC adsorb to polypropylene surfaces irresp. of pH. After eight successive pipet actions using polypropylene tips ca. 20% of the MC were lost to the surface material, which increased to 25%&40% when solns. were acidified. The obsd. loss was alleviated by changing the methanol (MeOH) concn. in the final solvent. The required MeOH concn. varied depending on which congener was present. Microcystins only adsorbed to glass pipettes (loss up to 30% after eight pipet actions) when in acidified aq. solns. The latter appeared largely dependent on the presence of ionizable groups, such as arginine residues.
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    Liang, G.; Xie, P.; Chen, J.; Yu, T. Comparative Studies on the PH Dependence of DOW of Microcystin-RR and -LR Using LC-MS. Sci. World J. 2011, 11, 20– 26,  DOI: 10.1100/tsw.2011.17
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    Hyenstrand, P.; Metcalf, J. S.; Beattie, K. A.; Codd, G. A. Effects of Adsorption to Plastics and Solvent Conditions in the Analysis of the Cyanobacterial Toxin Microcystin-LR by High Performance Liquid Chromatography. Water Res. 2001, 35, 3508– 3511,  DOI: 10.1016/S0043-1354(01)00068-9
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    Effects of adsorption to plastics and solvent conditions in the analysis of the cyanobacterial toxin microcystin-LR by high performance liquid chromatography
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    Water Research (2001), 35 (14), 3508-3511CODEN: WATRAG; ISSN:0043-1354. (Elsevier Science Ltd.)
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    Cyanobacterial harmful algal blooms occur in freshwater lakes, ponds, rivers, and reservoirs, and in brackish waters throughout the world. The wide variety of cyanotoxins and their congeners can lead to frequent exposure of humans through consumption of meat, fish, seafood, blue-green algal products and water, accidental ingestion of contaminated water and cyanobacterial scum during recreational activities, and inhalation of cyanobacterial aerosols. Cyanotoxins can also occur in the drinking water supply. In order to monitor human exposure, sensitive anal. methods such as enzyme linked immunosorbent assay and liq. chromatog.-mass spectrometry are often used. Regardless of the anal. method of choice, some problems regularly occur during sample collection, treatment, storage, and prepn. which cause toxin loss and therefore underestimation of the true concn. To evaluate the potential influence of sample treatment, storage and prepn. materials on surface and drinking water samples, the effects of different types of materials on toxin recovery were compared. Collection and storage materials included glass and various types of plastics. It was found that microcystin congeners LA and LF adsorbed to polystyrene, polypropylene, high d. polyethylene and polycarbonate storage containers, leading to low recoveries (<70%), cylindrospermopsin and saxitoxin did not adsorb to the containers tested. Therefore, this study shows that glass or polyethylene terephthalate glycol containers are the materials of choice for collection and storage of samples contg. the cyanotoxins cylindrospermopsin, microcystins, and saxitoxin. This study also demonstrated that after 15 min chlorine decreased the concn. of microcystin LR to <40%, microcystin LA and saxitoxin to <15%, therefore quenching of drinking water samples immediately upon sample collection is crit. for accurate anal. In addn., the effect of various drinking water treatment chems. on toxin recovery and the behavior of those chems. in the enzyme linked immunosorbent assays were also studied and are summarized.
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    The presence of microscale polymer particles (i.e., microplastics) in the environment has become a major concern in recent years. Sorption of org. compds. by microplastics may affect the phase distribution within both sediments and aq. phases. To investigate this process, isotherms were detd. for the sorption of seven aliph. and arom. org. probe sorbates by four polymers with different physico-chem. properties. Sorption increased in the order polyamide < polyethylene < polyvinylchloride < polystyrene. This order does not reflect the particle sizes of the investigated microplastics within the aq. dispersions, indicating the influence of addnl. factors (e.g., π-π-interactions) on the sorption of arom. compds. by polystyrene. Linear isotherms by polyethylene suggested that sorbate uptake was due to absorption into the bulk polymer. In contrast, non-linear isotherms for sorption by PS, PA, and PVC suggest a predominance of adsorption onto the polymer surface, which is supported by the best fit of these isotherms using the Polanyi-Manes model. A strong relationship between the sorption coeffs. of the microplastics and the hydrophobicity of the sorbates suggests that hydrophobic interactions are of major importance.
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Cite this: Environ. Sci. Technol. 2021, 55, 23, 15940–15949
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https://doi.org/10.1021/acs.est.1c05796
Published November 10, 2021

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  • Abstract

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    Figure 1

    Figure 1. Chemical structures of the two MC congeners used in the present study (MC-LR left and MC-LF right) with variable amino acids indicating leucine (blue) and arginine (green) (MC-LR) and leucine (blue) and phenylalanine (red) (MC-LF). (21,22) The variable amino acids within the MC structure are largely responsible for the overall hydrophobicity of the congener.

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    Figure 2

    Figure 2. 3D surface MALDI MSI of MC-LF adsorbed to the PS microplastic. (a) Optical microscope image of PS particles before matrix application. (b) MS image showing the spatial distribution of [MC-LF + Na]+ at m/z 1008.5053. (c) Single-pixel mass spectrum for a mass range m/z of 985 to 1025 obtained from the PS microplastic. Three different adducts for MC-LF were labeled with measured mass and mass deviation. MS images were generated with 170 × 174 pixels, a pixel size of 12 μm, and an image bin width of Δ(m/z) = 0.01. The scale bar is 500 μm.

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    Figure 3

    Figure 3. Influence of pH on MC-LR and MC-LF adsorption onto PS, PVC, PE, and PET particles of different sizes (>1 mm [red], 0.25–0.50 mm [blue], and 0.009–0.125 mm [yellow]) (Test conditions: 10 g L–1 plastics, 5 μg mL–1 MC, 48 h agitation time, 25 °C, and control [black] contained no microplastic). %RSD ≤ 10%, n = 3.

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    Figure 4

    Figure 4. Effect of particle size and pH on the amount of MC-LR and MC-LF adsorbed onto four different microplastics (green: PET, yellow: PVC, blue: PE, and red: PS) (Test conditions: 10 g L–1 plastics, 5 μg mL–1 MCs, 48 h agitation time, and 25 °C). %RSD ≤ 10%, n = 3.

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    Figure 5

    Figure 5. Scanning electron microscope (SEM) imaging of the plastics utilized in the current study clearly displaying the surface morphology of each type. For each type of plastic, a particle size of 1–5 mm was investigated.

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  • References

    This article references 50 other publications.

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      Anderson, Julie C.; Park, Bradley J.; Palace, Vince P.
      Environmental Pollution (Oxford, United Kingdom) (2016), 218 (), 269-280CODEN: ENPOEK; ISSN:0269-7491. (Elsevier Ltd.)
      Microplastics have been increasingly detected and quantified in marine and freshwater environments, and there are growing concerns about potential effects in biota. A literature review was conducted to summarize the current state of knowledge of microplastics in Canadian aquatic environments; specifically, the sources, environmental fate, behavior, abundance, and toxicol. effects in aquatic organisms. While we found that research and publications on these topics have increased dramatically since 2010, relatively few studies have assessed the presence, fate, and effects of microplastics in Canadian water bodies. We suggest that efforts to det. aquatic receptors at greatest risk of detrimental effects due to microplastic exposure, and their assocd. contaminants, are particularly warranted. There is also a need to address the gaps identified, with a particular focus on the species and conditions found in Canadian aquatic systems. These gaps include characterization of the presence of microplastics in Canadian freshwater ecosystems, identifying key sources of microplastics to these systems, and evaluating the presence of microplastics in Arctic waters and biota.
    9. 9
      Crawford, C. B.; Quinn, B. Microplastic Pollutants; Elsevier Ltd: Amsterdam, 2017, 131– 154.
      There is no corresponding record for this reference.
    10. 10
      Massos, A.; Turner, A. Cadmium, Lead and Bromine in Beached Microplastics. Environ. Pollut. 2017, 227, 139– 145,  DOI: 10.1016/j.envpol.2017.04.034
      10
      Cadmium, lead and bromine in beached microplastics
      Massos, Angelo; Turner, Andrew
      Environmental Pollution (Oxford, United Kingdom) (2017), 227 (), 139-145CODEN: ENPOEK; ISSN:0269-7491. (Elsevier Ltd.)
      Samples of microplastic (n = 924) from two beaches in south west England have been analyzed by field-portable-x-ray fluorescence (FP-XRF) spectrometry, configured in a low-d. mode and with a small-spot facility, for the heavy metals, Cd and Pb, and the halogen, Br. Primary plastics in the form of pre-prodn. pellets were the principal type of microplastic (>70%) on both beaches, with secondary, irregularly-shaped fragments representing the remainder of samples. Cadmium and Pb were detected in 6.9% and 7.5% of all microplastics, resp., with concns. of either metal that exceeded 103 μg g-1 usually encountered in red and yellow pellets or fragments. Resp. correlations of Cd and Pb with Se and Cr were attributed to the presence of the colored, inorg. pigments, cadmium sulfoselenide and lead chromate. Bromine, detected in 10.4% of microplastics and up to concns. of about 13,000 μg g-1, was mainly encountered in neutrally-colored pellets. Its strong correlation with Sb, whose oxides are effective fire suppressant synergists, suggests the presence of a variety of brominated flame retardants arising from the recycling of plastics originally used in casings for heat-generating elec. equipment. The max. bioaccessible concns. of Cd and Pb, evaluated using a physiol. extn. based on the chem. characteristics of the proventriculus-gizzard of the northern fulmar, were about 50 μg g-1 and 8 μg g-1, resp. These concns. exceed those estd. for the diet of local seabirds by factors of about 50 and 4, resp.
    11. 11
      Rochman, C. M.; Hoh, E.; Hentschel, B. T.; Kaye, S. Long-Term Field Measurement of Sorption of Organic Contaminants to Five Types of Plastic Pellets: Implications for Plastic Marine Debris. Environ. Sci. Technol. 2013, 47, 1646– 1654,  DOI: 10.1021/es303700s
      11
      Long-Term Field Measurement of Sorption of Organic Contaminants to Five Types of Plastic Pellets: Implications for Plastic Marine Debris
      Rochman, Chelsea M.; Hoh, Eunha; Hentschel, Brian T.; Kaye, Shawn
      Environmental Science & Technology (2013), 47 (3), 1646-1654CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Concerns regarding marine plastic pollution and its affinity for chem. pollutants led us to quantify relations between different types of mass-produced plastic and org. contaminants in an urban bay. At 5 locations in San Diego Bay, California, we measured sorption of polychlorinated biphenyls (PCBs) and polycyclic arom. hydrocarbons (PAHs) throughout a 12-mo period to the 5 most common types of mass-produced plastic: polyethylene terephthalate (PET), high-d. polyethylene (HDPE), polyvinyl chloride (PVC), low-d. polyethylene (LDPE), and polypropylene (PP). During this long-term field expt., sorption rates and concns. of PCBs and PAHs varied significantly among plastic types and among locations. Our data suggest that for PAHs and PCBs, PET and PVC reach equil. in the marine environment much faster than HDPE, LDPE, and PP. Most importantly, concns. of PAHs and PCBs sorbed to HDPE, LDPE, and PP were consistently much greater than concns. sorbed to PET and PVC. These data imply that products made from HDPE, LDPE, and PP pose a greater risk than products made from PET and PVC of concg. these hazardous chems. onto fragmented plastic debris ingested by marine animals.
    12. 12
      Bláha, L.; Babica, P.; Maršálek, B. Toxins Produced in Cyanobacterial Water Blooms - Toxicity and Risks. Interdiscip. Toxicol. 2009, 2, 36– 41,  DOI: 10.2478/v10102-009-0006-2
      12
      Toxins produced in cyanobacterial water blooms - toxicity and risks
      Blaha Ludek; Babica Pavel; Marsalek Blahoslav
      Interdisciplinary toxicology (2009), 2 (2), 36-41 ISSN:.
      Cyanobacterial blooms in freshwaters represent a major ecological and human health problem worldwide. This paper briefly summarizes information on major cyanobacterial toxins (hepatotoxins, neurotoxins etc.) with special attention to microcystins-cyclic heptapeptides with high acute and chronic toxicities. Besides discussion of human health risks, microcystin ecotoxicology and consequent ecological risks are also highlighted. Although significant research attention has been paid to microcystins, cyanobacteria produce a wide range of currently unknown toxins, which will require research attention. Further research should also address possible additive, synergistic or antagonistic effects among different classes of cyanobacterial metabolites, as well as interactions with other toxic stressors such as metals or persistent organic pollutants.
    13. 13
      Visser, P. M.; Verspagen, J. M. H.; Sandrini, G.; Stal, L. J.; Matthijs, H. C. P.; Davis, T. W.; Paerl, H. W.; Huisman, J. How Rising CO2 and Global Warming May Stimulate Harmful Cyanobacterial Blooms. Harmful Algae 2016, 54, 145– 159,  DOI: 10.1016/j.hal.2015.12.006
      13
      How rising CO2 and global warming may stimulate harmful cyanobacterial blooms
      Visser, Petra M.; Verspagen, Jolanda M. H.; Sandrini, Giovanni; Stal, Lucas J.; Matthijs, Hans C. P.; Davis, Timothy W.; Paerl, Hans W.; Huisman, Jef
      Harmful Algae (2016), 54 (), 145-159CODEN: HAALDD; ISSN:1568-9883. (Elsevier B.V.)
      Climate change is likely to stimulate the development of harmful cyanobacterial blooms in eutrophic waters, with neg. consequences for water quality of many lakes, reservoirs and brackish ecosystems across the globe. In addn. to effects of temp. and eutrophication, recent research has shed new light on the possible implications of rising atm. CO2 concns. Depletion of dissolved CO2 by dense cyanobacterial blooms creates a concn. gradient across the air-water interface. A steeper gradient at elevated atm. CO2 concns. will lead to a greater influx of CO2, which can be intercepted by surface-dwelling blooms, thus intensifying cyanobacterial blooms in eutrophic waters. Bloom-forming cyanobacteria display an unexpected diversity in CO2 responses, because different strains combine their uptake systems for CO2 and bicarbonate in different ways. The genetic compn. of cyanobacterial blooms may therefore shift. In particular, strains with high-flux carbon uptake systems may benefit from the anticipated rise in inorg. carbon availability. Increasing temps. also stimulate cyanobacterial growth. Many bloom-forming cyanobacteria and also green algae have temp. optima above 25 °C, often exceeding the temp. optima of diatoms and dinoflagellates. Anal. of published data suggests that the temp. dependence of the growth rate of cyanobacteria exceeds that of green algae. Indirect effects of elevated temp., like an earlier onset and longer duration of thermal stratification, may also shift the competitive balance in favor of buoyant cyanobacteria while eukaryotic algae are impaired by higher sedimentation losses. Furthermore, cyanobacteria differ from eukaryotic algae in that they can fix dinitrogen, and new insights show that the nitrogen-fixation activity of heterocystous cyanobacteria can be strongly stimulated at elevated temps. Models and lake studies indicate that the response of cyanobacterial growth to rising CO2 concns. and elevated temps. can be suppressed by nutrient limitation. The greatest response of cyanobacterial blooms to climate change is therefore expected to occur in eutrophic and hypertrophic lakes.
    14. 14
      Paerl, H. W.; Paul, V. J. Climate Change: Links to Global Expansion of Harmful Cyanobacteria. Water Res. 2012, 46, 1349– 1363,  DOI: 10.1016/j.watres.2011.08.002
      14
      Climate change: Links to global expansion of harmful cyanobacteria
      Paerl, Hans W.; Paul, Valerie J.
      Water Research (2012), 46 (5), 1349-1363CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
      Cyanobacteria are the Earth's oldest (∼3.5 bya) oxygen evolving organisms, and they have had major impacts on shaping our modern-day biosphere. Conversely, biospheric environmental perturbations, including nutrient enrichment and climatic changes (e.g. global warming, hydrol. changes, increased frequencies and intensities of tropical cyclones, more intense and persistent droughts), strongly affect cyanobacterial growth and bloom potentials in freshwater and marine ecosystems. We examd. human and climatic controls on harmful (toxic, hypoxia-generating, food web disrupting) bloom-forming cyanobacteria (CyanoHABs) along the freshwater to marine continuum. These changes may act synergistically to promote cyanobacterial dominance and persistence. This synergy is a formidable challenge to water quality, water supply and fisheries managers, because bloom potentials and controls may be altered in response to contemporaneous changes in thermal and hydrol. regimes. In inland waters, hydrol. modifications, including enhanced vertical mixing and, if water supplies permit, increased flushing (reducing residence time) will likely be needed in systems where nutrient input redns. are neither feasible nor possible. Successful control of CyanoHABs by grazers is unlikely except in specific cases. Overall, stricter nutrient management will likely be the most feasible and practical approach to long-term CyanoHAB control in a warmer, stormier and more extreme world.
    15. 15
      Spoof, L.; Catherine, A. Appendix 3, Tables of Microcystins and Nodularins. In Handbook of Cyanobacterial Monitoring and Cyanotoxin Analysis; Meriluoto, J., Spoof, L., Codd, G. A., Eds.; John Wiley & Sons: Chichester, UK, 2017; 526– 537,  DOI: 10.1002/9781119068761.app3 .
      There is no corresponding record for this reference.
    16. 16
      Faassen, E. J.; Lürling, M. Occurrence of the Microcystins MC-LW and MC-LF in Dutch Surface Waters and Their Contribution to Total Microcystin Toxicity. Mar. Drugs 2013, 11, 2643– 2654,  DOI: 10.3390/md11072643
      16
      Occurrence of the microcystins MC-LW and MC-LF in Dutch surface waters and their contribution to total microcystin toxicity
      Faassen, Elisabeth J.; Luerling, Miquel
      Marine Drugs (2013), 11 (7), 2643-2654, 12 pp.CODEN: MDARE6; ISSN:1660-3397. (MDPI AG)
      Microcystins (MCs) are the most frequently found cyanobacterial toxins in freshwater systems. Many MC variants have been identified and variants differ in their toxicity. Recent studies showed that the variants MC-LW and MC-LF might be more toxic than MC-LR, the variant that is most abundant and mostly used for risk assessments. As little is known about the presence of these two variants in The Netherlands, we detd. their occurrence by analyzing 88 water samples and 10 scum samples for eight MC variants ((dm-7-)MC-RR, MC-YR, (dm-7-)MC-LR, MC-LY, MC-LW and MC-LF) by liq. chromatog. with tandem mass spectrometry detection. All analyzed MC variants were detected and MC-LW and/or MC-LF were present in 32% of the MC contg. water samples. When MC-LW and MC-LF were present, they contributed to nearly 10% of the total MC concns., but due to their suspected high toxicity, their av. contribution to the total MC toxicity was estd. to be at least 45%. Given the frequent occurrence and possible high toxicity of MC-LW and MC-LF, it seems better to base health risk assessments on the toxicity contributions of different MC variants than on MC-LR concns. alone.
    17. 17
      Vesterkvist, P. S. M.; Misiorek, J. O.; Spoof, L. E. M.; Toivola, D. M.; Meriluoto, J. A. O. Comparative Cellular Toxicity of Hydrophilic and Hydrophobic Microcystins on Caco-2 Cells. Toxins 2012, 4, 1008– 1023,  DOI: 10.3390/toxins4111008
      17
      Comparative cellular toxicity of hydrophilic and hydrophobic microcystins on Caco-2 cells
      Vesterkvist, Pia S. M.; Misiorek, Julia O.; Spoof, Lisa E. M.; Toivola, Diana M.; Meriluoto, Jussi A. O.
      Toxins (2012), 4 (), 1008-1023CODEN: TOXIB7; ISSN:2072-6651. (MDPI AG)
      Microcystins (MC), cyanobacterial peptide hepatotoxins, comprise more than 100 different variants. They are rather polar mols. but some variants contain hydrophobic amino acid residues in the highly variable parts of the mol. In MC-LF and MC-LW, the more hydrophobic phenylalanine (F) and tryptophan (W), resp., have replaced arginine (R) in MC-LR. Depending on the structure, microcystins are expected to have different in vivo toxicity and bioavailability, but only a few studies have considered the toxic properties of the more hydrophobic variants. The present study shows that MC-LF and MC-LW have more pronounced cytotoxic effects on Caco-2 cells as compared to those of MC-LR. Treatment of Caco-2 cells with MC-LW and esp. MC-LF showed clear apoptotic features including shrinkage and blebbing, and the cell-cell adhesion was lost. An obvious redn. of cell proliferation and viability, assessed as the activity of mitochondrial dehydrogenases, was obsd. with MC-LF, followed by MC-LW and MC-LR. Cytotoxicity was quantified by measuring lactate dehydrogenase leakage. The more hydrophobic MC-LW and MC-LF induced markedly enhanced lactate dehydrogenase leakage compared to controls and MC-LR, indicating that the plasma membrane was damaged. All of the three toxins examd. inhibited protein phosphatase 1, with MC-LF and MC-LW to a weaker extent compared to MC-LR. The higher toxic potential of the more hydrophobic microcystins could not be explained by the biophys. expts. performed. Taken together, our data show that the more hydrophobic microcystin variants induce higher toxicity in Caco-2 cells.
    18. 18
      Fischer, A.; Hoeger, S. J.; Stemmer, K.; Feurstein, D. J.; Knobeloch, D.; Nussler, A.; Dietrich, D. R. The Role of Organic Anion Transporting Polypeptides (OATPs/SLCOs) in the Toxicity of Different Microcystin Congeners in Vitro: A Comparison of Primary Human Hepatocytes and OATP-Transfected HEK293 Cells. Toxicol. Appl. Pharmacol. 2010, 245, 9– 20,  DOI: 10.1016/j.taap.2010.02.006
      18
      The role of organic anion transporting polypeptides (OATPs/SLCOs) in the toxicity of different microcystin congeners in vitro: A comparison of primary human hepatocytes and OATP-transfected HEK293 cells
      Fischer, A.; Hoeger, S. J.; Stemmer, K.; Feurstein, D. J.; Knobeloch, D.; Nussler, A.; Dietrich, D. R.
      Toxicology and Applied Pharmacology (2010), 245 (1), 9-20CODEN: TXAPA9; ISSN:0041-008X. (Elsevier B.V.)
      Cellular uptake of microcystins (MCs), a family of cyclic cyanobacterial heptapeptide toxins, occurs via specific org. anion transporting polypeptides (OATPs), where MCs inhibit serine/threonine-specific protein phosphatase (PP). Despite comparable PP-inhibitory capacity, MCs differ greatly in their acute toxicity, thus raising the question whether this discrepancy results from MC-specific toxicokinetic rather than toxicodynamic differences. OATP-mediated uptake of MC congeners MCLR, -RR, -LW, and -LF was compared in primary human hepatocytes and Hek 293 cells stably expressing recombinant human OATP1B1/SLCO1B1 and OATP1B3/SLCO1B3 in the presence/absence of OATP substrates taurocholate (TC) and bromosulfophthalein (BSP) and measuring PP inhibition and cytotoxicity. Control vector expressing Hek 293 were resistant to MC cytotoxicity while TC and BSP competition expts. reduced MC cytotoxicity in Hek 293-OATP transfectants, thus confirming the requirement of OATPs for transmembrane transport. Despite comparable PP-inhibiting capabilities, MCLW and -LF elicited cytotoxic effects at lower equimolar concns. than MCLR and MCRR, hence suggesting congener selective transport into Hek 293-OATP transfectants and primary human hepatocytes. Primary human hepatocytes appeared one order of magnitude more sensitive to MC congeners than the corresponding Hek 293 -OATP transfectants. Although the latter may be due to a much lower level of PPs in primary human hepatocytes, the presence of OATPs other than 1B1 or 1B3 may have added to an increased uptake of MCs. In view of the high sensitivity of human hepatocytes and currently MCLR only based risk calcns., the actual risk of human MC intoxication and ensuing liver damage could be underestimated in freshwater cyanobacterial blooms where MCLW and -LF predominate.
    19. 19
      Feurstein, D.; Holst, K.; Fischer, A.; Dietrich, D. R. Oatp-Associated Uptake and Toxicity of Microcystins in Primary Murine Whole Brain Cells. Toxicol. Appl. Pharmacol. 2009, 234, 247– 255,  DOI: 10.1016/j.taap.2008.10.011
      19
      Oatp-associated uptake and toxicity of microcystins in primary murine whole brain cells
      Feurstein, D.; Holst, K.; Fischer, A.; Dietrich, D. R.
      Toxicology and Applied Pharmacology (2009), 234 (2), 247-255CODEN: TXAPA9; ISSN:0041-008X. (Elsevier B.V.)
      Microcystins (MCs) are naturally occurring cyclic heptapeptides that exhibit hepato-, nephro- and possibly neurotoxic effects in mammals. Org. anion transporting polypeptides (rodent Oatp/human OATP) appear to be specifically required for active uptake of MCs into hepatocytes and kidney epithelial cells. Based on symptoms of neurotoxicity in MC-intoxicated patients and the presence of Oatp/OATP at the blood-brain-barrier (BBB) and blood-cerebrospinal-fluid-barrier (BCFB) it is hypothesized that MCs can be transported across the BBB/BCFB in an Oatp/OATP-dependent manner and can induce toxicity in brain cells via inhibition of protein phosphatase (PP). To test these hypotheses, the presence of murine Oatp (mOatp) in primary murine whole brain cells (mWBC) was investigated at the mRNA and protein level. MC transport was tested by exposing mWBCs to three different MC-congeners (MC-LR, -LW, -LF) with/without co-incubation with the OATP/Oatp-substrates taurocholate (TC) and bromosulfophthalein (BSP). Uptake of MCs and cytotoxicity was demonstrated via MC-Western blot anal., immunocytochem., cell viability and PP inhibition assays. All MC congeners bound covalently and inhibited mWBC PP. MC-LF was the most cytotoxic congener followed by -LW and -LR. The lowest toxin concn. significantly reducing mWBC viability after 48 h exposure was 400 nM (MC-LF). Uptake of MCs into mWBCs was inhibited via co-incubation with excess TC (50 and 500 μM) and BSP (50 μM). MC-Western blot anal. demonstrated a concn.-dependent accumulation of MCs. In conclusion, the in vitro data support the assumed MC-congener-dependent uptake in a mOatp-assocd. manner and cytotoxicity of MCs in primary murine whole brain cells.
    20. 20
      Vesterkvist, P. S. M.; Meriluoto, J. A. O. Interaction between Microcystins of Different Hydrophobicities and Lipid Monolayers. Toxicon 2003, 41, 349– 355,  DOI: 10.1016/S0041-0101(02)00315-X
      20
      Interaction between microcystins of different hydrophobicities and lipid monolayers
      Vesterkvist, Pia S. M.; Meriluoto, Jussi A. O.
      Toxicon (2003), 41 (3), 349-355CODEN: TOXIA6; ISSN:0041-0101. (Elsevier Science Ltd.)
      Microcystins (MC) are a group of amphiphatic peptide hepatotoxins and protein phosphatase inhibitors produced by certain cyanobacteria (blue-green algae). Microcystins are believed to require an active transport mechanism to penetrate the plasma membranes of animal cells. In this study the surface barostat technique showed that two more hydrophobic microcystins MC-LF, contg. Leu and Phe, and MC-LW, contg. Leu and Trp, had a higher surface activity on an egg phosphatidylcholine-cholesterol (7:3, molar ratio) monolayer as compared to that of a more hydrophilic variant MC-LR, contg. Leu and Arg. Fluorescence anisotropy measurements of 1-[4-(trimethylamine)phenyl]-hexa-1,3,5-trien (TMA-DPH) were used to assess changes in the fluidity or lipid packing of model membranes in the presence of toxins. All three toxins caused a decrease in the steady-state anisotropy of TMA-DPH, suggesting that the toxins interacted with the membranes. The change in anisotropy was more pronounced for MC-LF and MC-LW than for MC-LR. Moreover, the fluorescence emission max. of Trp in MC-LW was shifted slightly towards a shorter wavelength and the intensity was enhanced when allowed to interact with lipid vesicles, suggesting that the single Trp in MC-LW moved into a more unpolar environment when interacting with the vesicles. The differences between hydrophilic and hydrophobic microcystins could result in changes in organotropism, toxicokinetics and bioaccumulation.
    21. 21
      Royal Society of Chemistry. Microcystin-LR structure.
      There is no corresponding record for this reference.
    22. 22
      Royal Society of Chemistry. Microcystin-LF structure.
      There is no corresponding record for this reference.
    23. 23
      WHO. Guidelines for Drinking-Water Quality; WHO Press: Geneva, Switzerland, 2008.
      There is no corresponding record for this reference.
    24. 24
      WHO, Cyanobacterial Toxins : Microcystins. Background Document for Drinking-Water Quality and Guidelines for Safe Recreational Water Environments; W. H. O. Geneva, 2020.
      There is no corresponding record for this reference.
    25. 25
      Akkanen, J.; Kukkonen, J. V. K. Biotransformation and Bioconcentration of Pyrene in Daphnia Magna. Aquat. Toxicol. 2003, 64, 53– 61,  DOI: 10.1016/S0166-445X(03)00023-7
      25
      Biotransformation and bioconcentration of pyrene in Daphnia magna
      Akkanen, Jarkko; Kukkonen, Jussi V. K.
      Aquatic Toxicology (2003), 64 (1), 53-61CODEN: AQTODG; ISSN:0166-445X. (Elsevier Science B.V.)
      Water fleas (Daphnia magna) were exposed to [14C]pyrene in the presence and absence of piperonyl butoxide (PBO), a general cytochrome P 450 (CYP) inhibitor, in org. carbon-free artificial freshwater (AFW, DOC<0.2 mg l-1) and in natural lake water (DOC=19.9 mg l-1) for 24 h. The bioconcn. of total radioactivity after 24 h exposure was 50% lower in the natural lake water, indicating decreased bioavailability of pyrene by the dissolved org. matter. However, the proportions of parent compd. were only ca. 12 and 19% of the total body burden in daphnids exposed in AFW and natural lake water, resp. Therefore, the tissue concn. of the parent pyrene was not significantly different in the daphnids exposed in the 2 different waters. Due to extensive biotransformation the bioconcn. factor (BCF) of parent pyrene was only 16 and 23% of the BCF calcd. on the basis of total radioactivity in the daphnids in AFW and natural lake water, resp. The proportion of parent pyrene was significantly higher (over 60%) in the daphnids exposed simultaneously to PBO, which indicates the involvement of CYP monooxygenases in the biotransformation. Furthermore, increasing PBO concn. decreased the accumulation of total radioactivity in AFW but not in the natural lake water. The data demonstrate capability and importance of CYP monooxygenases in biotransformation of polycyclic arom. hydrocarbons in D. magna.
    26. 26
      Kompauer, M.; Heiles, S.; Spengler, B. Autofocusing MALDI Mass Spectrometry Imaging of Tissue Sections and 3D Chemical Topography of Nonflat Surfaces. Nat. Methods 2017, 14, 1156– 1158,  DOI: 10.1038/nmeth.4433
      26
      Autofocusing MALDI mass spectrometry imaging of tissue sections and 3D chemical topography of nonflat surfaces
      Kompauer, Mario; Heiles, Sven; Spengler, Bernhard
      Nature Methods (2017), 14 (12), 1156-1158CODEN: NMAEA3; ISSN:1548-7091. (Nature Research)
      We describe an atm. pressure matrix-assisted laser desorption-ionization mass spectrometry imaging system that uses long-distance laser triangulation on a micrometer scale to simultaneously obtain topog. and mol. information from 3D surfaces. We studied the topog. distribution of compds. on irregular 3D surfaces of plants and parasites, and we imaged nonplanar tissue sections with high lateral resoln., thereby eliminating height-related signal artifacts.
    27. 27
      Paschke, C.; Leisner, A.; Hester, A.; Maass, K.; Guenther, S.; Bouschen, W.; Spengler, B. Mirion - A Software Package for Automatic Processing of Mass Spectrometric Images. J. Am. Soc. Mass Spectrom. 2013, 24, 1296– 1306,  DOI: 10.1007/s13361-013-0667-0
      27
      Mirion--A Software Package for Automatic Processing of Mass Spectrometric Images
      Paschke, C.; Leisner, A.; Hester, A.; Maass, K.; Guenther, S.; Bouschen, W.; Spengler, B.
      Journal of the American Society for Mass Spectrometry (2013), 24 (8), 1296-1306CODEN: JAMSEF; ISSN:1044-0305. (Springer)
      Mass spectrometric imaging (MSI) techniques are of growing interest for the Life Sciences. In recent years, the development of new instruments employing ion sources that are tailored for spatial scanning allowed the acquisition of large data sets. A subsequent data processing, however, is still a bottleneck in the anal. process, as a manual data interpretation is impossible within a reasonable time frame. The transformation of mass spectrometric data into spatial distribution images of detected compds. turned out to be the most appropriate method to visualize the results of such scans, as humans are able to interpret images faster and easier than plain nos. Image generation, thus, is a time-consuming and complex yet very efficient task. The free software package "Mirion," presented allows the handling and anal. of data sets acquired by mass spectrometry imaging. Mirion can be used for image processing of MSI data obtained from many different sources, as it uses the HUPO-PSI-based std. data format imzML, which is implemented in the proprietary software of most of the mass spectrometer companies. Different graphical representations of the recorded data are available. Furthermore, automatic calcn. and overlay of mass spectrometric images promotes direct comparison of different analytes for data evaluation. The program also includes tools for image processing and image anal.
    28. 28
      Dris, R.; Imhof, H.; Sanchez, W.; Gasperi, J.; Galgani, F.; Tassin, B.; Laforsch, C. Beyond the Ocean: Contamination of Freshwater Ecosystems with (Micro-)Plastic Particles. Environ. Chem. 2015, 12, 539,  DOI: 10.1071/en14172
      28
      Beyond the ocean: contamination of freshwater ecosystems with (micro-)plastic particles
      Dris, Rachid; Imhof, Hannes; Sanchez, Wilfried; Gasperi, Johnny; Galgani, Francois; Tassin, Bruno; Laforsch, Christian
      Environmental Chemistry (2015), 12 (5), 539-550CODEN: ECNHAA; ISSN:1449-8979. (CSIRO Publishing)
      Environmental context Microplastics in freshwater ecosystems are an increasingly important environmental issue, with the few available studies suggesting high contamination worldwide. Reliable data on concns., fluxes and polymer types in continental aquatic environments, including urban water systems, are needed. High environmental and ecol. risk polymers and assocd. or adsorbed chems. have to be identified, as well as their effects on both organisms and ecosystems. Abstr. Massive accumulation of plastic particles has been reported for marine ecosystems around the world, posing a risk to the biota. Freshwater ecosystems have received less attention despite most plastic litter being produced onshore and introduced into marine environments by rivers. Some studies not only report the presence of microplastics in freshwater ecosystems, but show that contamination is as severe as in the oceans. In continental waters, microplastics have been obsd. in both sediments (predominantly lake shores but also riverbanks) and water samples (predominantly surface water of lakes and rivers). This review highlights recent findings and discusses open questions, focussing on the methodol. of assessing this contaminant in freshwater ecosystems. In this context, method harmonisation is needed in order to obtain comparable data from different environmental compartments and sites. This includes sampling strategies (at spatial and temporal scales), sample treatment (taking into consideration high levels of org. matter and suspended solids) and reliable anal. methods to identify microplastics.
    29. 29
      Wang, J.; Tan, Z.; Peng, J.; Qiu, Q.; Li, M. The Behaviors of Microplastics in the Marine Environment. Mar. Environ. Res. 2016, 113, 7– 17,  DOI: 10.1016/j.marenvres.2015.10.014
      29
      The behaviors of microplastics in the marine environment
      Wang, Jundong; Tan, Zhi; Peng, Jinping; Qiu, Qiongxuan; Li, Meimin
      Marine Environmental Research (2016), 113 (), 7-17CODEN: MERSDW; ISSN:0141-1136. (Elsevier Ltd.)
      Despite the pollution of microplastics being internationally recognized, the understanding of their behaviors in marine environment is still developing. Microplastics are ubiquitous in the marine environment, with the potential to cause harm to marine ecosystem. Here, we would classify the behaviors of microplastics as phys. behaviors (i.e. migration, sedimentation and accumulation), chem. behaviors (i.e. degrdn. and adsorption) and biobehaviors (i.e. ingestion, translocation and biodegrdn.), and a further discussion on their behavioral mechanisms were presented to better understand their impacts for the marine environment.
    30. 30
      Wang, W.; Wang, J. Comparative Evaluation of Sorption Kinetics and Isotherms of Pyrene onto Microplastics. Chemosphere 2018, 193, 567– 573,  DOI: 10.1016/j.chemosphere.2017.11.078
      30
      Comparative evaluation of sorption kinetics and isotherms of pyrene onto microplastics
      Wang, Wenfeng; Wang, Jun
      Chemosphere (2018), 193 (), 567-573CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
      Concerns regarding microplastics pollution and their potential to conc. and transport org. contaminants in aquatic environments are growing in recent years. Sorption of org. chems. by microplastics may affect the distribution and bioavailability of the chems. Here sorption process of pyrene (Pyr), a frequently encountered polycyclic arom. hydrocarbon in aquatic environments, on three types of mass-produced plastic particles (high-d. polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)), was investigated by comparative anal. of different sorption kinetic and isotherm models. Optimum kinetic and isotherm models were predicted by the linear least-squares regression method. The pseudo-second-order kinetic model was more appropriate in describing the entire sorption process (R2 > 0.99). Sorption rates of Pyr onto microplastics were mainly controlled by intraparticle diffusion. PE exhibited the highest affinity for Pyr, followed by PS and PVC. The sorption equil. data were best fitted to the Langmuir isotherm (R2 > 0.99), indicating monolayer coverage of Pyr onto the microplastics.
    31. 31
      Harada, K.; Tsuji, K.; Watanabe, M. F.; Kondo, F. Stability of Microcystins from Cyanobacteria – III. Effect of PH and Temperature. Phycologia 1996, 35, 83– 88,  DOI: 10.2216/i0031-8884-35-6S-83.1
      There is no corresponding record for this reference.
    32. 32
      Wilhelm, S. W.; Bullerjahn, G. S.; McKay, R. M. L. The Complicated and Confusing Ecology of Microcystis Blooms. MBio 2020, 11, 1– 5,  DOI: 10.1128/MBIO.00529-20
      There is no corresponding record for this reference.
    33. 33
      De Maagd, P. G. J.; Hendriks, A. J.; Seinen, W.; Sijm, D. T. H. M. PH-Dependent Hydrophobicity of the Cyanobacteria Toxin Microcystin-LR. Water Res. 1999, 33, 677– 680,  DOI: 10.1016/S0043-1354(98)00258-9
      There is no corresponding record for this reference.
    34. 34
      McCord, J.; Lang, J. R.; Hill, D.; Strynar, M.; Chernoff, N. PH Dependent Octanol–Water Partitioning Coefficients of Microcystin Congeners. J. Water Health 2018, 16, 340– 345,  DOI: 10.2166/wh.2018.257
      34
      pH dependent octanol-water partitioning coefficients of microcystin congeners
      McCord James; Lang Johnsie R; Hill Donna; Chernoff Neil; Strynar Mark
      Journal of water and health (2018), 16 (3), 340-345 ISSN:1477-8920.
      Hazardous algal blooms can generate toxic compounds with significant health impacts for exposed communities. The ubiquitous class of algal toxins known as microcystins exhibits significant heterogeneity in its peptide structure, which has been minimally studied, given the significant impact this has on hydrophobicity, acid/base character and related environmental fate and health effects. Octanol-water partition coefficients for the microcystin congeners MCLR, MCRR, MCLY, MCLF, and MCLA were calculated over an environmentally and physiologically relevant pH range. Microcystin-LR log(Kow) partition coefficient values were found to be consistent with previously established literature values, 1.67 to -1.41 between pH 1 and 8. Microcystin RR was found to be pH insensitive with a log(Kow) of -0.7. The remaining congeners exhibit similar pH dependence as MCLR, with systematic increases in hydrophobicity driven by the introduction of more hydrophobic residues to their variable amino acid region. The variation in pH dependent hydrophobicity suggests increased propensity for bioaccumulation and alternate environmental fates for differing microcystin forms, requiring further investigation.
    35. 35
      Altaner, S.; Puddick, J.; Wood, S. A.; Dietrich, D. R. Adsorption of Ten Microcystin Congeners to Common Laboratory-Ware Is Solvent and Surface Dependent. Toxins 2017, 9, 129,  DOI: 10.3390/toxins9040129
      35
      Adsorption of ten microcystin congeners to common laboratory-ware is solvent and surface dependent
      Altaner, Stefan; Puddick, Jonathan; Wood, Susanna A.; Dietrich, Daniel R.
      Toxins (2017), 9 (4), 129/1-129/15CODEN: TOXIB7; ISSN:2072-6651. (MDPI AG)
      Cyanobacteria can produce heptapetides called microcystins (MC) which are harmful to humans due to their ability to inhibit cellular protein phosphatases. Quantitation of these toxins can be hampered by their adsorption to common lab.-ware during sample processing and anal. Because of their structural diversity (>100 congeners) and different physico-chem. properties, they vary in their adsorption to surfaces. In this study, the adsorption of ten different MC congeners (encompassing non-arginated to doubly-arginated congeners) to common lab.-ware was assessed using different solvent combinations. Sample handling steps were mimicked with glass and polypropylene pipettes and vials with increasing methanol concns. at two pH levels, before anal. by liq. chromatog.-tandem mass spectrometry. We demonstrated that MC adsorb to polypropylene surfaces irresp. of pH. After eight successive pipet actions using polypropylene tips ca. 20% of the MC were lost to the surface material, which increased to 25%&40% when solns. were acidified. The obsd. loss was alleviated by changing the methanol (MeOH) concn. in the final solvent. The required MeOH concn. varied depending on which congener was present. Microcystins only adsorbed to glass pipettes (loss up to 30% after eight pipet actions) when in acidified aq. solns. The latter appeared largely dependent on the presence of ionizable groups, such as arginine residues.
    36. 36
      Liang, G.; Xie, P.; Chen, J.; Yu, T. Comparative Studies on the PH Dependence of DOW of Microcystin-RR and -LR Using LC-MS. Sci. World J. 2011, 11, 20– 26,  DOI: 10.1100/tsw.2011.17
      There is no corresponding record for this reference.
    37. 37
      Hyenstrand, P.; Metcalf, J. S.; Beattie, K. A.; Codd, G. A. Effects of Adsorption to Plastics and Solvent Conditions in the Analysis of the Cyanobacterial Toxin Microcystin-LR by High Performance Liquid Chromatography. Water Res. 2001, 35, 3508– 3511,  DOI: 10.1016/S0043-1354(01)00068-9
      37
      Effects of adsorption to plastics and solvent conditions in the analysis of the cyanobacterial toxin microcystin-LR by high performance liquid chromatography
      Hyenstrand, P.; Metcalf, J. S.; Beattie, K. A.; Codd, G. A.
      Water Research (2001), 35 (14), 3508-3511CODEN: WATRAG; ISSN:0043-1354. (Elsevier Science Ltd.)
      Effects of adsorption to plastics and solvent conditions in the HPLC anal. of the cyanobacterial toxin microcystin-LR were studied. Aq. microcystin-LR readily adsorbed to the disposable polypropylene pipet tips commonly used in lab. manipulations. This was not affected by the pH or salinity of the soln. Dilns. of microcystin-LR in varying concns. of methanol and acetonitrile influenced the quantification of the microcystin-LR concn. by HPLC.
    38. 38
      Beneš, P.; Paulenová, M. Surface Charge and Adsorption Properties of Polyethylene in Aqueous Solutions of Inorganic Electrolytes - II. Radiochemical Investigation. Colloid Polym. Sci. 1974, 252, 472– 477,  DOI: 10.1007/BF01554753
      38
      Surface charge and adsorption properties of polyethylene in aqueous solutions of inorganic electrolytes. II. Radiochemical investigation
      Benes, P.; Paulenova, M.
      Colloid and Polymer Science (1974), 252 (6), 472-7CODEN: CPMSB6; ISSN:0303-402X.
      The adsorption and desorption of trace amts. of Ba2+ [22541-12-4], Hg(OH)2 [12135-13-6] mols., and colloidal Fe(OH)3 [1309-33-7] on polyethylene (I) were detd. by the radiotracer method as functions of electrolyte concn. and compn., pH, and age of the soln. and compared with the effects of these factors on the zeta potential of I. A neg. zeta potential indicated that cation adsorption was possible in the outer part of the surface double layer, but the degree of adsorption was not simply proportional to the zeta potential. The adsorption of mols. and colloids on I was not related to the zeta potential. The effects of electrolytes on sorptions were attributed to changes of the I-soln. interface properties or to coagulation of colloids.
    39. 39
      Kamp, L.; Church, J. L.; Carpino, J.; Faltin-Mara, E.; Rubio, F. The Effects of Water Sample Treatment, Preparation, and Storage Prior to Cyanotoxin Analysis for Cylindrospermopsin, Microcystin and Saxitoxin. Chem.-Biol. Interact. 2016, 246, 45– 51,  DOI: 10.1016/j.cbi.2015.12.016
      39
      The effects of water sample treatment, preparation, and storage prior to cyanotoxin analysis for cylindrospermopsin, microcystin and saxitoxin
      Kamp, Lisa; Church, Jennifer L.; Carpino, Justin; Faltin-Mara, Erin; Rubio, Fernando
      Chemico-Biological Interactions (2016), 246 (), 45-51CODEN: CBINA8; ISSN:0009-2797. (Elsevier Ireland Ltd.)
      Cyanobacterial harmful algal blooms occur in freshwater lakes, ponds, rivers, and reservoirs, and in brackish waters throughout the world. The wide variety of cyanotoxins and their congeners can lead to frequent exposure of humans through consumption of meat, fish, seafood, blue-green algal products and water, accidental ingestion of contaminated water and cyanobacterial scum during recreational activities, and inhalation of cyanobacterial aerosols. Cyanotoxins can also occur in the drinking water supply. In order to monitor human exposure, sensitive anal. methods such as enzyme linked immunosorbent assay and liq. chromatog.-mass spectrometry are often used. Regardless of the anal. method of choice, some problems regularly occur during sample collection, treatment, storage, and prepn. which cause toxin loss and therefore underestimation of the true concn. To evaluate the potential influence of sample treatment, storage and prepn. materials on surface and drinking water samples, the effects of different types of materials on toxin recovery were compared. Collection and storage materials included glass and various types of plastics. It was found that microcystin congeners LA and LF adsorbed to polystyrene, polypropylene, high d. polyethylene and polycarbonate storage containers, leading to low recoveries (<70%), cylindrospermopsin and saxitoxin did not adsorb to the containers tested. Therefore, this study shows that glass or polyethylene terephthalate glycol containers are the materials of choice for collection and storage of samples contg. the cyanotoxins cylindrospermopsin, microcystins, and saxitoxin. This study also demonstrated that after 15 min chlorine decreased the concn. of microcystin LR to <40%, microcystin LA and saxitoxin to <15%, therefore quenching of drinking water samples immediately upon sample collection is crit. for accurate anal. In addn., the effect of various drinking water treatment chems. on toxin recovery and the behavior of those chems. in the enzyme linked immunosorbent assays were also studied and are summarized.
    40. 40
      Hüffer, T.; Hofmann, T. Sorption of Non-Polar Organic Compounds by Micro-Sized Plastic Particles in Aqueous Solution. Environ. Pollut. 2016, 214, 194– 201,  DOI: 10.1016/j.envpol.2016.04.018
      40
      Sorption of non-polar organic compounds by micro-sized plastic particles in aqueous solution
      Hueffer, Thorsten; Hofmann, Thilo
      Environmental Pollution (Oxford, United Kingdom) (2016), 214 (), 194-201CODEN: ENPOEK; ISSN:0269-7491. (Elsevier Ltd.)
      The presence of microscale polymer particles (i.e., microplastics) in the environment has become a major concern in recent years. Sorption of org. compds. by microplastics may affect the phase distribution within both sediments and aq. phases. To investigate this process, isotherms were detd. for the sorption of seven aliph. and arom. org. probe sorbates by four polymers with different physico-chem. properties. Sorption increased in the order polyamide < polyethylene < polyvinylchloride < polystyrene. This order does not reflect the particle sizes of the investigated microplastics within the aq. dispersions, indicating the influence of addnl. factors (e.g., π-π-interactions) on the sorption of arom. compds. by polystyrene. Linear isotherms by polyethylene suggested that sorbate uptake was due to absorption into the bulk polymer. In contrast, non-linear isotherms for sorption by PS, PA, and PVC suggest a predominance of adsorption onto the polymer surface, which is supported by the best fit of these isotherms using the Polanyi-Manes model. A strong relationship between the sorption coeffs. of the microplastics and the hydrophobicity of the sorbates suggests that hydrophobic interactions are of major importance.
    41. 41
      Hu, J. Q.; Yang, S. Z.; Guo, L.; Xu, X.; Yao, T.; Xie, F. Microscopic Investigation on the Adsorption of Lubrication Oil on Microplastics. J. Mol. Liq. 2017, 227, 351– 355,  DOI: 10.1016/j.molliq.2016.12.043
      41
      Microscopic investigation on the adsorption of lubrication oil on microplastics
      Hu, Jian-Qiang; Yang, Shi-Zhao; Guo, Li; Xu, Xin; Yao, Ting; Xie, Feng
      Journal of Molecular Liquids (2017), 227 (), 351-355CODEN: JMLIDT; ISSN:0167-7322. (Elsevier B.V.)
      The different size of microplastic in the environments may affect the fate and effects of traditional hydrophilic chems. The effect of reaction time, pH, salinity and concn. on the adsorption of lubrication oil on the 20-140μm sized polystyrene (micro-PS) and 50 nm polyethylene (nano-PE) were presented. The adsorption kinetics and isotherms of nano-PE and micro-PS can be satisfactorily fitted by pseudo-second-order kinetic model and Langmuir, resp. The adsorption of lubrication oil on nano-PE and micro-PS significantly increased with increasing concn. of salinity, indicating that the outer-sphere surface complexation dominated lubricating oil sorption on nano-PE and micro-PS. The max. adsorption capacity of lubricating oil on nano-PE and micro-PS was 6.8 and 5.2 g/g at pH 5.0 and 293 K, resp. These results are of crucial importance to the application of microplastics as the promising adsorbent in natural environments.
    42. 42
      Endo, S.; Koelmans, A. A. Sorption of Hydrophobic Organic Compounds to Plastics in the Marine Environment: Equilibrium. In Hazardous Chemicals Associated with Plastics in the Marine Environment; Takada, H., Karapanagioti, H., Eds.; Springer: Switzerland, 2016.
      There is no corresponding record for this reference.
    43. 43
      Guo, X.; Wang, X.; Zhou, X.; Kong, X.; Tao, S.; Xing, B. Sorption of Four Hydrophobic Organic Compounds by Three Chemically Distinct Polymers: Role of Chemical and Physical Composition. Environ. Sci. Technol. 2012, 46, 7252– 7259,  DOI: 10.1021/es301386z
      43
      Sorption of Four Hydrophobic Organic Compounds by Three Chemically Distinct Polymers: Role of Chemical and Physical Composition
      Guo, Xiaoying; Wang, Xilong; Zhou, Xinzhe; Kong, Xiangzhen; Tao, Shu; Xing, Baoshan
      Environmental Science & Technology (2012), 46 (13), 7252-7259CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      The sorption behavior of four hydrophobic org. contaminants (HOCs) (i.e., phenanthrene, naphthalene, lindane, and 1-naphthol) by 3 types of polymers, i.e. polyethylene (PE), polystyrene (PS), and polyphenyleneoxide (PPO) was examd. The org. carbon content-normalized sorption coeffs. (Koc) of phenanthrene, lindane, and naphthalene by PEs of same compn. but distinct phys. makeup of domains increased with their crystallinity redn. (from 58.7 to 25.5%), suggesting that mobility and abundance of rubbery domains in polymers regulated HOC sorption. Crosslinking in styrene-divinylbenzene copolymer (PS2) created substantial surface area and porosity, thus, Koc values of phenanthrene, lindane, naphthalene, and 1-naphthol by PS2 were as high as 274.8, 212.3, 27.4, and 1.5 times of those by the linear polystyrene (PS1). The Koc values of lindane, naphthalene, and 1-naphthol by polar PPO were approx. 1-3 orders of magnitude higher than those by PS1, and PPO had comparable sorption for phenanthrene but higher sorption for naphthalene and 1-naphthol than PS2. This can be a result that a portion of O-contg. moieties in PPO were masked in the interior part, while leaving the hydrophobic domains exposed outside, therefore demonstrating the great influence of the spatial arrangement of domains in polymers on HOC sorption.
    44. 44
      Alimi, O. S.; Farner Budarz, J.; Hernandez, L. M.; Tufenkji, N. Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport. Environ. Sci. Technol. 2018, 52, 1704– 1724,  DOI: 10.1021/acs.est.7b05559
      44
      Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport
      Alimi, Olubukola S.; Farner Budarz, Jeffrey; Hernandez, Laura M.; Tufenkji, Nathalie
      Environmental Science & Technology (2018), 52 (4), 1704-1724CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      A review is given. Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degrdn. of plastics from macro- to micro- and even to nanosized particles <100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. Here, we 1st present estd. loads of plastics in different environmental compartments. We also provide a crit. review of the current knowledge vis-a-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and critically analyzed. Factors affecting contaminant sorption onto plastic debris are discussed, and we show how polyethylene generally exhibits a greater sorption capacity than other plastic types. We highlight key knowledge gaps that need to be addressed to improve our ability to predict the risks assocd. with these ubiquitous contaminants in the environment by understanding their mobility, aggregation behavior and their potential to enhance the transport of other pollutants.
    45. 45
      Fotopoulou, K. N.; Karapanagioti, H. K. Surface Properties of Beached Plastics. Environ. Sci. Pollut. Res. 2015, 22, 11022– 11032,  DOI: 10.1007/s11356-015-4332-y
      45
      Surface properties of beached plastics
      Fotopoulou, Kalliopi N.; Karapanagioti, Hrissi K.
      Environmental Science and Pollution Research (2015), 22 (14), 11022-11032CODEN: ESPLEC; ISSN:0944-1344. (Springer)
      Studying plastic characteristics in the marine environment is important to better understand interaction between plastics and the environment. In the present study, high-d. polyethylene (HDPE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) samples were collected from the coastal environment in order to study their surface properties. Surface properties such as surface functional groups, surface topog., point of zero charge, and color change were important factors that changed during degrdn. Eroded HDPE demonstrated an altered surface topog. and color and new functional groups. Eroded PET surface was uneven, yellow, and occasionally, colonized by microbes. A decrease in Fourier transform IR (FTIR) peaks was obsd. for eroded PET suggested that degrdn. had occurred. For eroded PVC, its surface became more lamellar and a new FTIR peak was obsd. These surface properties were obtained due to degrdn. and could be used to explain the interaction between plastics, microbes, and pollutants.
    46. 46
      Pestana, C. J.; Hobson, P.; Robertson, P. K. J.; Lawton, L. A.; Newcombe, G. Removal of Microcystins from a Waste Stabilisation Lagoon: Evaluation of a Packed-Bed Continuous Flow TiO2 Reactor. Chemosphere 2020, 245, 125575  DOI: 10.1016/j.chemosphere.2019.125575
      46
      Removal of microcystins from a waste stabilisation lagoon: Evaluation of a packed-bed continuous flow TiO2 reactor
      Pestana, Carlos J.; Hobson, Peter; Robertson, Peter K. J.; Lawton, Linda A.; Newcombe, Gayle
      Chemosphere (2020), 245 (), 125575CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
      Photocatalysis has been shown to successfully remove microcystins (MC) in lab. expts. Most research to date has been performed under ideal conditions in pure or ultrapure water. In this investigation the efficiency of photocatalysis using titanium dioxide was examd. in a complex matrix (waste stabilization lagoon water). A flow-through photocatalytic reactor was used for the photocatalytic removal of four commonly occurring microcystin analogs (MC-YR, MC-RR, MC-LR, and MC-LA). Up to 51% removal for single MC analogs in waste lagoon water was obsd. Similar removal rates were obsd. when a mixt. of all four MC analogs was treated. Although treatment of MC-contg. cyanobacterial cells of Microcystis aeruginosa resulted in no decline in cell nos. or viability with the current reactor design and treatment regime, the photocatalytic treatment did improve the overall quality of waste lagoon water. This study demonstrates that despite the presence of natural org. matter the microcystins could be successfully degraded in a complex environmental matrix.
    47. 47
      Praptiwi, R. A.; Pestana, C. J.; Sawade, E. T.; Swain, N.; Schroeder, G.; Newcombe, G. Treatment Challenge of a Cyanobacterium Romeria Elegans Bloom in a South Australian Wastewater Treatment Plant – a Case Study. Environ. Technol. 2017, 38, 782– 788,  DOI: 10.1080/09593330.2016.1262454
      47
      Treatment challenge of a cyanobacterium Romeria elegans bloom in a South Australian wastewater treatment plant - a case study
      Praptiwi, Radisti A.; Pestana, Carlos J.; Sawade, Emma T.; Swain, Nick; Schroeder, Gretchen; Newcombe, Gayle
      Environmental Technology (2017), 38 (6), 782-788CODEN: ENVTEV; ISSN:0959-3330. (Taylor & Francis Ltd.)
      A bloom of the non-toxic cyanobacterium Romeria elegans in waste stabilization ponds (WSPs) within Angaston waste water treatment plant (WWTP) has posed an unprecedented treatment challenge for the local water utility. The water from the WSPs is chlorinated for safety prior to reuse on nearby farmland. Cyanobacteria concns. of approx. 1.2 × 106 cells mL-1 increased the chlorine demand dramatically. Operators continuously increased the disinfectant dose up to 50 mg L-1 to achieve operational guideline values for combined chlorine (0.5-1.0 mg L-1) prior to reuse. Despite this, attempts to achieve targeted combined chlorine residual (CCR) failed. In this study, samples from the waste stabilization pond at Angaston WWTP were chlorinated over a range of doses. Combined chlorine, disinfection byproduct formation, cyanobacteria cell concn., Escherichia coli inactivation, as well as dissolved org. carbon and free ammonia were monitored. This study shows that, in the occurrence of cyanobacterial blooms, CCR does not directly suggest pathogen removal efficiency and is therefore not an ideal parameter to evaluate the effectiveness of disinfection process in WWTP. Instead, E. coli removal is a more direct and practical parameter for the detn. of the efficiency of the disinfection process.
    48. 48
      Rohrlack, T.; Christoffersen, K.; Dittmann, E.; Nogueira, I.; Vasconcelos, V.; Börner, T. Ingestion of Microcystins by Daphnia: Intestinal Uptake and Toxic Effects. Limnol. Oceanogr. 2005, 50, 440– 448,  DOI: 10.4319/lo.2005.50.2.0440
      48
      Ingestion of microcystins by Daphnia: Intestinal uptake and toxic effects
      Rohrlack, Thomas; Christoffersen, Kirsten; Dittmann, Elke; Nogueira, Isabel; Vasconcelos, Vitor; Boerner, Thomas
      Limnology and Oceanography (2005), 50 (2), 440-448CODEN: LIOCAH; ISSN:0024-3590. (American Society of Limnology and Oceanography)
      We investigated the intestinal uptake and adverse effects of microcystins ingested with Microcystis on Daphnia galeata. The gut structure, blood microcystin concn., appearance, and movements of Daphnia fed Microcystis PCC 7806 or a microcystin-deficient PCC 7806 mutant were monitored over time. Microcystins were rapidly taken up from the digestive cavity into the blood. This process apparently required a preceding disruption of the gut epithelium by an as-yet-unknown Microcystis factor. Once microcystins entered the blood, they affected the neuromuscular communication or another life function that influences major muscle systems. Consequently, the beat rates of the thoracic legs, mandibles, and second antennae as well as the activity of the foregut decreased, whereas the midgut muscles were stimulated. Finally, the animals exhibited symptoms of exhaustion and died. The present results suggest that an ingestion of between 10.2 ng and 18.3 ng of microcystin per 1 mg of Daphnia body fresh wt. is sufficient to kill D. galeata within 2 days.
    49. 49
      Baudouin, M. F.; Ravera, O. Weight, Size, and Chemical Composition of Some Freshwater Zooplankters: Daphnia Hyalina (Leydig). Limnol. Oceanogr. 1972, 17, 645– 649,  DOI: 10.4319/lo.1972.17.4.0645
      49
      Weight, size, and chemical composition of some freshwater zooplankters. Daphnia hyalina
      Baudouin, M. F.; Ravera, O.
      Limnology and Oceanography (1972), 17 (4), 645-9CODEN: LIOCAH; ISSN:0024-3590.
      Size, dry wt., ash, and concn. of C, H, N, P, and Ca of D. hyalina from Lago Monate (northern Italy) were investigated. The concn. of the elements varied with age of the individuals. Eggs had max. concn. of C and H, the newborn of P, and the young of N. No seasonal variation was obsd. for individuals of the same size.
    50. 50
      Christoffersen, K. Predation on Daphnia Pulex by Lepidurus Arcticus. Hydrobiologia 2001, 442, 223– 229,  DOI: 10.1023/A:1017584928657
      There is no corresponding record for this reference.

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    • Chemical structures of the four plastic monomers; list of chemicals, materials, devices, and auxiliaries; 3D surface MALDI imaging of MC-LF bound to PET microplastic particles; calculations for prediction of amount of toxin per individual plastic particle; evaluation of the electrostatic charge of each type of microplastic under five pH conditions; and statistical analysis (PDF)


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