Low-dose stimulation of growth of the harmful alga, Prymnesium parvum, by glyphosate and glyphosate-based herbicides

Hormesis, the Individual and Combined Phytotoxicity of the Components of Glyphosate-Based Formulations on Algal Growth and Photosynthetic Activity

The occurrence of the market-leading glyphosate active ingredient in surface waters is a globally observed phenomenon. Although co-formulants in pesticide formulations were considered inactive components from the aspects of the required main biological effect of the pesticide, several studies have proven the high individual toxicity of formulating agents, as well as the enhanced combined toxicity of the active ingredients and other components. Since the majority of active ingredients are present in the form of chemical mixtures in our environment, the possible combined toxicity between active ingredients and co-formulants is particularly important. To assess the individual and combined phytotoxicity of the components, glyphosate was tested in the form of pure active ingredient (glyphosate isopropylammonium salt) and herbicide formulations (Roundup Classic and Medallon Premium) formulated with a mixture of polyethoxylated tallow amines (POEA) or alkyl polyglucosides (APG), respectively. The order of acute toxicity was as follows for Roundup Classic: glyphosate < herbicide formulation < POEA. However, the following order was demonstrated for Medallon Premium: herbicide formulation < glyphosate < APG. Increased photosynthetic activity was detected after the exposure to the formulation (1.5-5.8 mg glyphosate/L and 0.5-2.2 mg POEA/L) and its components individually (glyphosate: 13-27.2 mg/L, POEA: 0.6-4.8 mg/L), which indicates hormetic effects. However, decreased photosynthetic activity was detected at higher concentrations of POEA (19.2 mg/L) and Roundup Classic (11.6-50.6 mg glyphosate/L). Differences were demonstrated in the sensitivity of the selected algae species and, in addition to the individual and combined toxicity of the components presented in the glyphosate-based herbicides. Both of the observed inhibitory and stimulating effects can adversely affect the aquatic ecosystems and water quality of surface waters.

Bioaccumulation and toxicity of perfluorooctanoic acid and perfluorooctane sulfonate in marine algae Chlorella sp

The ocean is an important sink for perfluorinated alkyl acids (PFAAs), but the toxic mechanisms of PFAAs to marine organisms have not been clearly studied. In this study, the growth rate, photosynthetic activity, oxidative stress and bioaccumulation were investigated using marine algae Chlorella sp. after the exposure of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate acid (PFOS). The results showed that PFOA of <40 mg/L and PFOS of <20 mg/L stimulated algal reproduction, and high doses inhibited the algal growth. The absorbed PFOA and PFOS by algal cells damaged cell membrane and caused metabolic disorder. The photosynthesis activity was inhibited, which was revealed by the significantly reduced maximal quantum yield (Fv/Fm), relative electron transfer rate (rETR) and carbohydrate synthesis. However, the chlorophyll a content increased along with the up-regulation of its encoding genes (psbB and chlB), probably due to an overcompensation effect. The increase of ROS and antioxidant substances (SOD, CAT and GSH) indicated that PFOA and PFOS caused oxidative stress. The BCF of marine algae Chlorella sp. to PFOA and PFOS was calculated to be between 82 and 200, confirming the bioaccumulation of PFOA and PFOS in marine algae. In summary, PFOA and PFOS can accumulate in Chlorella sp. cells, disrupt photosynthesis, trigger oxidative stress and inhibit algal growth. PFOS shows higher toxicity and bioaccumulation than PFOA. The information is important to evaluate the environmental risks of PFAAs.

Photosynthesis Responses of Tibetan Freshwater Algae Chlorella vulgaris to Herbicide Glyphosate

With the development of agriculture and the widespread application of agrichemicals in Tibet, herbicide residues have become a threat to the ecological safety of Tibetan water bodies. Algae, as the producers in the food chain in water bodies, play an important role in aquatic ecosystems. Therefore, the impact of herbicides on Tibetan algae is of great significance for evaluating ecological health and the protection of Tibetan water ecosystems. In this study, we investigated the inhibitory effect of glyphosate, a herbicide, on the photosynthetic system of Chlorella vulgaris, Tibetan algae, by determining chlorophyll fluorescence and the activity of an antioxidant system. The results revealed that glyphosate at low concentration did not affect the photosynthetic activity of C. vulgaris; however, glyphosate at a high concentration significantly inhibited photosynthetic activity and reduced pigment content. Moreover, high levels of glyphosate also decreased photochemical efficiency and electron transport rate and resulted in ROS accumulation, high SOD activity, and lipid peroxidation. These results suggested that glyphosate could decrease the primary production of aquatic ecosystems and influence their performance. Therefore, reducing the herbicide levels could protect the Tibetan aquatic environment and maintain the health of ecosystems.

Influence of glyphosate and its metabolite aminomethylphosphonic acid on aquatic plants in different ecological niches

Glyphosate and its metabolite aminomethylphosphonic acid (AMPA) draw great concern due to their potential threat to aquatic ecosystems. The individual and combined effects of glyphosate and AMPA on aquatic plants in different ecological niches need to be explored. This study aimed to investigate the ecotoxicity of glyphosate and AMPA on the emergent macrophyte Acorus calamus, phytoplankton Chlorella vulgaris, and submerged macrophyte Vallisneria natans after their exposure to glyphosate and AMPA alone and to their mixture. Medium and low concentrations of glyphosate (≤ 0.5 mg L^-1) significantly inhibited the growth of V. natans and promoted the growth of C. vulgaris (P < 0.05) but had no significant effect on the growth of A. calamus (P > 0.05). AMPA (≤ 5.0 mg L^-1) did not significantly influence the relative growth rate (except C. vulgaris) or malonaldehyde levels but significantly altered the expression levels of chlorophyll-related genes and superoxide dismutase [Cu-Zn] genes in the aquatic plants examined. AMPA mainly affected the oxidative phosphorylation pathway in V. natans and not those in other two plants, indicating that V. natans was more sensitive to AMPA-induced oxidative damage. Moreover, antagonistic effects on plant growth were observed when plants were exposed to low concentrations of glyphosate + AMPA (≤ 0.1 + 0.1 mg L^-1). When the concentration of glyphosate + AMPA reached 0.5 + 0.5 and 5.0 + 5.0 mg L^-1, the growth of the submerged macrophyte was additively or synergistically inhibited, but the growth of the emergent macrophyte and phytoplankton was antagonistically inhibited. Our results indicated that both the individual and combined effects of glyphosate and AMPA might alter the vertical structure of shallow lakes and accelerate the conversion of shallow lakes from grass-based to algal-based lakes.

Low Levels of Contaminants Stimulate Harmful Algal Organisms and Enrich Their Toxins

A widespread increase in intense phytoplankton blooms has been noted in lakes worldwide since the 1980s, with the summertime peak intensity amplifying in most lakes. Such blooms cause annual economic losses of multibillion USD and present a major challenge, affecting 11 out of the 17 United Nations Sustainable Development Goals. Here, we evaluate recent scientific evidence for hormetic effects of emerging contaminants and regulated pollutants on Microcystis sp., the most notorious cyanobacteria forming harmful algal blooms and releasing phycotoxins in eutrophic freshwater systems. This new evidence leads to the conclusion that pollution is linked to algal bloom intensification. Concentrations of contaminants that are considerably smaller than the threshold for toxicity enhance the formation of harmful colonies, increase the production of phycotoxins and their release into the environment, and lower the efficacy of algaecides to control algal blooms. The low-dose enhancement of microcystins is attributed to the up-regulation of a protein controlling microcystin release (McyH) and various microcystin synthetases in tandem with the global nitrogen regulator Ycf28, nonribosomal peptide synthetases, and several ATP-binding cassette transport proteins. Given that colony formation and phycotoxin production and release are enhanced by contaminant concentrations smaller than the toxicological threshold and are widely occurring in the environment, the effect of contaminants on harmful algal blooms is more prevalent than previously thought. Climate change and nutrient enrichment, known mechanisms underpinning algal blooms, are thus joined by low-level pollutants as another causal mechanism.

Characterization of a new selenoprotein methionine sulfoxide reductase from Haematococcus pluvialis and its antioxidant activity in response to high light intensity, hydrogen peroxide, glyphosate, and cadmium exposure

Selenium incorporates into selenocysteine (Sec) which is a key component of selenoproteins implicated in antioxidant defense and redox homeostasis. Methionine sulfoxide reductases (Msr) play crucial roles in cellular defense against environmental stress. Whereas mammals have the MsrB selenoprotein form, unicellular organisms have MsrA. The Sec residue at the conserved catalytic sites of selenoprotein MsrA confers a metabolic advantage over the non-selenoprotein type MsrA. In the present study, the novel selenoprotein HpMsrA from Haematococcus pluvialis was cloned by the rapid amplification of cDNA ends and transformed into the model green alga Chlamydomonas reinhardtii. Alignment of homologs revealed the presence of the conserved catalytic domain GUFW and showed that the HpMsrA protein comprises Sec (U) at the N-terminus but no recycled Cys at the C-terminus. We studied the response of HpMsrA expression to selenite, high light intensity, hydrogen peroxide, cadmium nitrate, and glyphosate exposure via real-time quantitative PCR and enzyme activity analysis. The results demonstrated that HpMsrA protects cellular proteins against oxidative and environmental stressors. Compared with wild type C. reinhardtii, the transformant exhibited a superior antioxidant ability. The discoveries made herein shed light on the antioxidant physiology and environmental stress resistance mechanisms of the selenoproteins in microalgae. This information may aid in conducting environmental risk assessments of aquatic ecosystems involving microalgae known to respond rapidly and quantitatively to abiotic stress factors promoting excessive reactive oxygen species generation.

Air, land, and water variables associated with the first appearance and current spatial distribution of toxic Prymnesium parvum blooms in reservoirs of the Southern Great Plains, USA

This study examined the association of air, land, and water variables with the first historical occurrence and current distribution of toxic Prymnesium parvum blooms in reservoirs of the Brazos River and Colorado River, Texas (USA). One impacted and one reference reservoir were selected per basin. Land cover and use variables were estimated for the whole watershed (WW) and a 0.5-km zone on either side of streams (near field, NF). Variables were expressed in annual values. Principal component and trend analyses were used to determine (1) differences in environmental conditions before and after the 2001 onset of toxic blooms in impacted reservoirs (study period, 1992-2017), and (2) traits that uniquely discriminate impacted from reference reservoirs (2001-2017). Of thirty-three variables examined, two positively aligned with the reoccurring appearance of blooms in impacted reservoirs (air CO₂ and herbicide Glyphosate) and another two negatively aligned (insecticides Terbufos and Malathion). Glyphosate use was observed throughout the study period but a turning point for an upward trend occurred near the year of first bloom occurrence. While the relevance of the decreased use of insecticides is uncertain, prior experimental studies reported that increasing concentrations of air CO₂ and water Glyphosate can enhance P. parvum growth. Consistent with prior findings, impacted reservoirs were of higher salinity than reference reservoirs. In addition, their watersheds had far lower wetland cover at NF and WW scales. The value of wetlands in reducing harmful algal bloom incidence by reducing nutrient inputs has been previously recognized, but wetlands can also capture pesticides. Therefore, a diminished wetland cover could magnify Glyphosate loads flowing into impacted reservoirs. These observations are consistent with a scenario where rising levels of air CO₂ and Glyphosate use contributed to the establishment of P. parvum blooms in reservoirs of relatively high salinity and minimal wetland cover over their watersheds.

Trends in science on glyphosate toxicity: a scientometric study

As part of the most used herbicides, glyphosate is the most successful ingredient of agrochemical companies. The main objective of this study was to demonstrate research trends related to the glyphosate toxicity and its main effects on human and environmental health. For this purpose, 443 articles published, from 1995 to 2020, on the platform Web of Science™ Thomson Reuters were selected. The main toxicity results related in literature are genotoxicity, cytotoxicity, and endocrine disruption. The environmental effects come mostly from the contamination of groundwater and soils. Several studies have concluded that herbicide concentrations right below the official safety limits induced toxic effects. The results presented a highlighted harmful effect of glyphosate on both human and environmental health. It has been observed that countries where publish the most about the glyphosate toxicity are great investors in large-scale agriculture. It is important to ponder that these countries are in a route of ecosystem exploitation that includes not only fauna and flora, but also human beings. Unfortunately, science does not provide concise data for these pesticide disapproval in the global consumer market. It is necessary to search sustainable global interest alternatives to increase agriculture production based on peoples' food sovereignty.

Growth of the harmful alga, Prymnesium parvum (Prymnesiophyceae), after gradual and abrupt increases in salinity

Prymnesium parvum is a euryhaline, toxin-producing microalga. Although its abundance in inland waters and growth potential in the laboratory is reduced at high salinity (>20), the ability of inland strains to adjust their growth after long-term residence in high salinity is uncertain. An inland strain of P. parvum maintained at salinity of 5 in modified artificial seawater medium (ASM-5) was subjected to the following treatments over five sequential batch culture rounds: ASM-5 (control); modified ASM at salinity of 30, raised with NaCl; modified ASM at salinity incrementally increased to 30 with NaCl; and Instant Ocean^® at salinity of 30 (IO-30). Exponential growth rate (r) was reduced when salinity was increased from 5 to 30 in ASM but returned to control values during the second round. When salinity was incrementally increased, a reduction in r still occurred when salinity reached 25-30. Maximum density was reduced at salinity of 30 in ASM upon abrupt transfer or incremental increase, and compensation did not occur. Growth performance in IO-30 was comparable to control values. In conclusion, (i) long-term compensation for acute inhibitory effects of high salinity occurred for r but not maximum density, (ii) incremental increases in salinity did not prevent growth inhibition, suggesting the existence of a salinity threshold of 25-30 for onset of salinity stress, and (iii) the presence of a seawater-like salt mixture prevented growth inhibition by high salinity. These findings provide new insights on P. parvum's long-term ability to adjust its growth in environments of different salinity and ionic composition.

Glyphosate, aminomethylphosphonic acid, and glufosinate ammonium in agricultural groundwater and surface water in China from 2017 to 2018: Occurrence, main drivers, and environmental risk assessment

Glyphosate and glufosinate ammonium are the main herbicides used to control weeds in no-tillage agricultural fields in China. However, their leaching risk to groundwater and ecological risk to aquatic organisms remain unclear. From the agricultural basins among 10 provinces of China, glyphosate, its main metabolite aminomethylphosphonic acid (AMPA), and glufosinate ammonium were detected in 1.01%, 0.86%, 0% of 694 groundwater samples with the maximum concentrations of 2.09, 5.13, and <0.05 μg/L, and were detected in 14.3%, 15.8%, and 2.6% of 196 surface water samples with the maximum levels of 32.49, 10.31 and 13.15 μg/L. Furthermore, to evaluate the main drivers of exposure to the targets in water bodies, the fate models were used. The model simulation indicated that spray drift and overflow runoff were the key factors affecting the exposure to targets in surface water adjacent to rice field, whereas the spray drift deposition, runoff, and erosion induced the exposure to the targets in pond water close to dry land crop fields under different meteorological conditions and soil characteristics. The targets in groundwater posed a low risk to water consumption, while fish embryos might be at unacceptable risk due to glufosinate ammonium exposure in surface water with median risk quotient (RQ) equal to 55.6. The results highlight the spatial and seasonal distribution of glyphosate, AMPA, and glufosinate ammonium in groundwater and surface water in agricultural basins of China, providing the first evidence to the environmental risk of the targets to drinking water consumption and aquatic organism safety in China agriculture system.

Proteomic mechanisms for the combined stimulatory effects of glyphosate and antibiotic contaminants on Microcystis aeruginosa

A single exposure to glyphosate or antibiotic may facilitate cyanobacterial growth at currently reported concentrations due to hormesis. However, the influence of these contaminants on cyanobacteria under combined exposure conditions has not been reported. In this study, proteomic mechanisms for the combined effects of glyphosate and a quaternary antibiotic mixture of amoxicillin, sulfamethoxazole, tetracycline, and ciprofloxacin in a dominant bloom-forming cyanobacterium (Microcystis aeruginosa) were investigated and compared with those for single exposure to glyphosate. The growth rate of M. aeruginosa, photosynthetic activity indicated by Fv/Fm, and microcystin production ability showed a typical U-shaped hormetic dose-response to glyphosate exposure. Upregulated proteins related to photosynthesis and biosynthesis, as well as increased photosynthetic activity, were responsible for the stimulated growth induced by 0.1-5 μg/L glyphosate, while the upregulation of mcyB protein contributed to increased microcystin synthesis in glyphosate-treated cells. The presence of 0.04-0.2 μg/L mixed antibiotics significantly (p < 0.05) enhanced the stimulation effects of glyphosate. Combined exposure to glyphosate and mixed antibiotics promoted microcystin synthesis through the upregulation of six microcystin synthesis regulatory proteins (mcyC, mcyF, mcyG, mcyI, MAE_56520, and ntcA) and stimulated cyanobacterial growth through the upregulation of proteins involved in photosynthesis, cell division, carbon fixation, pentose phosphate, translation, and chlorophyll synthesis. Combined exposure to glyphosate and antibiotic contaminants promoted cyanobacterial growth at no-effect concentrations of single exposure (0.04 μg/L for mixed antibiotics; 0.05, 10 and 100 μg/L for glyphosate), suggesting an increased threat from combined contamination to aquatic ecosystems through promoting the formation of cyanobacterial bloom.

Glyphosate Accelerates the Proliferation of Microcystis aeruginosa, a Dominant Species in Cyanobacterial Blooms

Glyphosate is a commonly used herbicide known for its high performance in killing certain plants and grasses; however, its use is regulated due to its harmful effects on the aquatic environment. The present study investigated and compared the toxic mechanisms of glyphosate on Microcystis aeruginosa (a toxin-producing cyanobacterium) under 2 conditions: 0‰ saline media (experiment I) and 2.5‰ saline media (experiment II). The results indicated that an appropriate concentration of glyphosate provided a phosphate source for M. aeruginosa, resulting in an increased specific growth rate in both experimental groups compared with the controls. Glyphosate-enhanced alkaline phosphatase (ALP) activity increased by up to 1.37-fold in experiment I and 1.68-fold in experiment II. Moreover, the activities of superoxide dismutase (SOD) and catalase (CAT) decreased at glyphosate concentrations below 1.2 mg L-1 but increased at concentrations greater than 1.2 mg L-1 in experiment I, whereas SOD and CAT activities decreased in experiment II and declined by 64 and 49% in the 30 mg L-1 treatments. Furthermore, the transcript abundances of the pyruvate carboxylase (pcB), microcystin synthetase B (mcyB), and paired-like homeobox (phoX) genes were up-regulated by up to 6.92-, 3.63-, and 2.27-fold in experiment I and 6.74-, 6.55-, and 4.86-fold in experiment II after 96 h of incubation. The addition of glyphosate stimulated the production of dissolved organic matter including tryptophan-like substances, fulvic acid-like substances, (marine) humic acid-like substances, and microcystin-leucine-arginine in the culture. In conclusion, glyphosate stimulates the proliferation of M. aeruginosa and enhances the release of dissolved organic matter in saltwater ecosystems. Environ Toxicol Chem 2021;40:342-351. © 2020 SETAC.

Pollutant toxicology with respect to microalgae and cyanobacteria

Microalgae and cyanobacteria are fundamental components of aquatic ecosystems. Pollution in aquatic environment is a worldwide problem. Toxicological research on microalgae and cyanobacteria can help to establish a solid foundation for aquatic ecotoxicological assessments. Algae and cyanobacteria occupy a large proportion of the biomass in aquatic environments; thus, their toxicological responses have been investigated extensively. However, the depth of toxic mechanisms and breadth of toxicological investigations need to be improved. While existing pollutants are being discharged into the environment daily, new ones are also being produced continuously. As a result, the phenomenon of water pollution has become unprecedentedly complex. In this review, we summarize the latest findings on five kinds of aquatic pollutants, namely, metals, nanomaterials, pesticides, pharmaceutical and personal care products (PPCPs), and persistent organic pollutants (POPs). Further, we present information on emerging pollutants such as graphene, microplastics, and ionic liquids. Efforts in studying the toxicological effects of pollutants on microalgae and cyanobacteria must be increased in order to better predict the potential risks posed by these materials to aquatic ecosystems as well as human health.

Title: Low concentrations of glyphosate in water and sediment after direct over-water application to control an invasive aquatic plant

When an invasive wetland grass degrades a Ramsar wetland and Important Bird Area, decisive management action is called for. To limit the extent and spread of European Phragmites australis, the Ontario government began the first, large-scale application of glyphosate (Roundup CustomⓇ) over standing water to control an invasive species in Canadian history. Between 2016 and 2018, over 1000 ha of marsh were treated. To assess the concentration, movement and longevity of this herbicide in treated marshes, we measured the concentration of glyphosate, its primary breakdown product aminomethylphosphonic acid (AMPA), and the alcohol ethoxylate-based adjuvant AquasurfⓇ in water and sediments in areas of the highest exposure and up to 150 m into adjacent bays. The maximum observed concentration of glyphosate in water was 0.320 mg/L, occurring within 24 hr of application. The maximum glyphosate concentration in sediment was 0.250 mg/kg, occurring within about 30 days of application. AMPA was detectable in water and sediment, indicating microbial breakdown of glyphosate in the marsh, but at low concentrations (maxwater = 0.025 mg/L, maxsed = 0.012 mg/kg). The maximum distance from the point of application that glyphosate was detected in the water was 100 m, while AMPA was detectable only at the edge of where glyphosate was applied (0 m). Concentrations in water returned to pre-treatment levels (0.005 mg/kg) for over one year but less than two years. Concentrations of alcohol ethoxylates were variable in space and time, following a pattern that could not be attributed to AquasurfⓇ use. The direct, over-water application of Roundup CustomⓇ with AquasurfⓇ to control invasive P. australis did not reach concentrations deemed to pose toxicological concern to aquatic biota by the Canadian Council of Ministers of the Environment.

Glyphosate but not Roundup® harms earthworms (Eisenia fetida)

Glyphosate is the active ingredient in Roundup® formulations. While multiple studies have documented the toxicity, environmental persistence, and tendency to spread for glyphosate and Roundup®, few studies have compared the toxicity of glyphosate-based formulations to the toxicity of pure glyphosate for soil invertebrates, which contact both the herbicide and the formulations. Hundreds of formulations exist; their inert ingredients are confidential; and glyphosate persists in our food, water, and soil. In this experiment, we held glyphosate type and concentration constant, varying only formulation. Using Roundup Ready-to-Use III®, Roundup Super Concentrate®, and pure glyphosate, we delivered 26.3 mg glyphosate in the form of isopropylamine salt per kg of soil to compost worms (Eisenia fetida). We found that worms living in soil spiked with pure glyphosate lost 14.8-25.9% of their biomass and survived a stress test for 22.2-33.3% less time than worms living in uncontaminated soil. Worms living in soil spiked with Roundup Ready-to-Use III® and Roundup Super Concentrate® did not lose body mass and survived the stress test as well as worms living in uncontaminated soil. No contaminant affected soil microbial or fungal biomass over the 40-day period of this experiment. We suggest that the nitrates and phosphates in the formulations offset the toxic effects of glyphosate by spurring microbial growth and speeding glyphosate degradation. We also found a 26.5-41.3% reduction in fungal biomass across all treatments over the course of this experiment, suggesting that the worms consumed fungi and spores.

Transcriptional Analysis of Chlorella Pyrenoidosa Exposed to Bisphenol A

Bisphenol A (BPA) is the raw material of 71% of polycarbonate-based resins and 27% of epoxy-based resins which are used for coating metal-based food and beverage cans. Meanwhile, it is taken into account as a typical environmental pollutant. Hormesis may occur in algae exposed to BPA. In this study, the effects of BPA on Chlorella pyrenoidosa were assessed based on growth inhibition and transcriptome analysis. We have focused on two exposure scenarios as follows: (1) exposure to a low stimulation concentration (0.1 mg.L⁻¹, 19.35% promotion in cell density on the 3rd day); (2) exposure to a high inhibition concentration (10 mg.L⁻¹, 64.71% inhibition in cell density on the 3rd day). Transcriptome analysis showed enrichment in nucleotide transport, single-organism transport, cellular respiration. Among them, adenosine triphosphate (ATP) synthase and Nicotinamide adenine dinucleotide (NADH) dehydrogenase were upregulated under 0.1 mg.L⁻¹ BPA treatment. These changes enhanced the physiological and energy metabolic pathways of C. pyrenoidosa, thereby stimulating cell proliferation. At exposure to the high BPA, severe inhibited changes in the expression levels of several pathways were observed, which were related to tricarboxylic acid (TCA) cycle, glycolysis, fatty acid metabolism, oxidative phosphorylation, and photosynthesis. Therefore, BPA could negatively affect growth inhibition through the multiple energy metabolism processes. These results may result in a deeper insight into BPA-induced biphasic responses in algae, and provide vital information to assess the potential ecological risks of exposure to BPA in an aquatic ecosystem.