Evidence of Microplastic Translocation in Wild-Caught Fish and Implications for Microplastic Accumulation Dynamics in Food Webs.

The presence of microplastics within the gut of animals is well documented. Whether microplastics bioaccumulate in organisms and biomagnify in food webs remains unclear and relies on the ability of microplastics to translocate to other tissues. Here, we demonstrate the widespread presence of microplastics and other anthropogenic microparticles in the gastrointestinal tract, fillet, and livers of seven species of sportfish from Lake Simcoe, Ontario, Canada. Larger fish had a higher microplastic load compared to smaller fish, but the opposite trend was observed with translocated microplastics standardized by fish mass (i.e., smaller fish contained more translocated particles per gram wet weight than larger fish). Moreover, we observed no evidence of biomagnification as there was no significant relationship between the trophic level and total or translocated microplastics per individual. Overall, this suggests that microplastics are translocating, but that excretion of translocated particles or growth dilution may be occurring rather than bioaccumulation and biomagnification. Moreover, the assemblages of shapes and material types varied among tissues, suggesting that particle characteristics may predict biological fate. Our findings highlight the need for further work to understand the mechanisms of microplastic translocation and excretion and the implications for the dynamics of microplastics accumulation in food webs and human exposure.

Cyanotoxins within and Outside of Microcystis aeruginosa Cause Adverse Effects in Rainbow Trout (Oncorhynchus mykiss).

The global expansion of toxic Microcystis blooms, and production of cyanotoxins including microcystins, are an increasing risk to freshwater fish. Differentiating intracellular and extracellular microcystin toxicity pathways (i.e., within and outside of cyanobacterial cells) in fish is necessary to assess the severity of risks to populations that encounter harmful algal blooms in pre-to-postsenescent stages. To address this, adult and juvenile Rainbow Trout (Oncorhynchus mykiss) were, respectively, exposed for 96 h to intracellular and extracellular microcystins (0, 20, and 100 µg L-1) produced by Microcystis aeruginosa. Fish were dissected at 24 h intervals for histopathology, targeted microcystin quantification, and nontargeted proteomics. Rainbow Trout accumulated intracellular and extracellular microcystins in all tissues within 24 h, with greater accumulation in the extracellular state. Proteomics revealed intracellular and extracellular microcystins caused sublethal toxicity by significantly dysregulating proteins linked to the cytoskeletal structure, stress responses, and DNA repair in all tissues. Pyruvate metabolism in livers, anion binding in kidneys, and myopathy in muscles were also significantly impacted. Histopathology corroborated these findings with evidence of necrosis, apoptosis, and hemorrhage at similar severity in both microcystin treatments. We demonstrate that sublethal concentrations of intracellular and extracellular microcystins cause adverse effects in Rainbow Trout after short-term exposure.

Impacts of water level fluctuations on mercury concentrations in hydropower reservoirs: A microcosm experiment.

Hydropower generation, a renewable source of electricity, has been linked to elevated methylmercury (MeHg) concentrations in impoundments and aquatic biota. This study investigates the impact of water level fluctuations (WLF) on MeHg concentrations in water, sediment, and fish. Using a set of controlled microcosm experiments emulating the drawdown/refill dynamics and subsequent sediment exposure to air experienced in reservoirs, we demonstrate that less frequent WLFs, and/or increased exposure of sediment to air, can lead to elevated MeHg concentrations in sediment, and total mercury (THg) and MeHg concentrations in water. In examining the effects of WLF frequency (two-day, weekly, and monthly), the monthly treatment displayed the highest THg and MeHg water levels, while the weekly treatment was characterized by the highest MeHg levels in the sediment. Our work supports emerging evidence that longer duration between WLF creates a larger surface area of sediment exposed to air leading to conditions conducive to higher MeHg concentrations in sediments and water. In contrast, THg, MeHg, and fatty acid trends in fish were largely inconclusive characterized by similar among-treatment effects and minimal temporal variability over the course of our experiment. This result could partly be attributed to overall low mercury levels and simple "worm-forage fish" food web in our experiment. To elucidate the broader impacts of water fluctuations on aquatic chemistry and biota, other factors (e.g., longer WLF cycles, dissolved organic matter, temperature, more complex food webs) which modulate both methylation rates and food web dynamics must be considered.

Climate and landscape conditions indirectly affect fish mercury levels by altering lake water chemistry and fish size.

Mercury pollution is a global environmental problem that threatens ecosystems, and negatively impacts human health and well-being. Mercury accumulation in fish within freshwater lakes is a complex process that appears to be driven by factors such as individual fish biology and water chemistry at the lake-scale, whereas, climate, and land-use/land-cover conditions within lake catchments can be influential at relatively larger scales. Nevertheless, unravelling the intricate network of pathways that govern how lake-scale and large-scale factors interact to affect mercury levels in fish remains an important scientific challenge. Using structural equation models (SEMs) and multiple long-term databases we identified direct and indirect effects of lake-scale and larger-scale factors on mercury levels in Walleye and Northern Pike - two species that are valued in inland fisheries. At the lake-level, the most parsimonious path models contained direct effects of fish weight, DOC, and pH, as well as an indirect effect of DOC on fish mercury levels via fish weight. Interestingly, lakeshed-, climate-, and full-path models that combine the effects of both lakeshed and climate revealed indirect effects of surrounding landscape conditions and latitude via DOC, pH, and fish weight but no direct effects on fish mercury levels. These results are generally consistent across species and lakes, except for some differences between stratified and non-stratified lakes. Our findings imply that understanding climate and land-use driven alterations of water chemistry and fish biology will be critical to predicting and mitigating fish mercury bioaccumulation in the future.

Assessing the toxicity of cell-bound microcystins on freshwater pelagic and benthic invertebrates.

Cyanobacterial harmful algal blooms dominated by Microcystis frequently produce microcystins, a family of toxins capable of inflicting harm to pelagic and benthic freshwater invertebrates. Research on the effect of microcystins on invertebrates is inconclusive; from one perspective, studies suggest invertebrates can coexist in toxic blooms; however, studies have also measured negative food-associated effects from microcystins. To test the latter perspective, we examined the reproduction, growth, and survival of laboratory-cultured Ceriodaphnia dubia, Daphnia magna, and Hexagenia spp. exposed to cell-bound microcystins through a series of life-cycle bioassays. Test organisms were exposed to a concentration gradient ranging from 0.5 µg L-1 to 300 µg L-1 microcystins, which corresponds to values typically found in freshwaters during bloom season. Lethal concentrations in C. dubia (LC50 = 5.53 µg L-1) and D. magna (LC50 = 85.72 µg L-1) exposed to microcystins were among the lowest recorded to date, and reproductive effects were observed at concentrations as low as 2.5 µg L-1. Length of D. magna was significantly impacted in microcystin treatments great than 2.5 µg L-1. No lethality or growth impairments were observed in Hexagenia. This information will improve our understanding of the risks posed by microcystins to food webs in freshwaters.

A comparison of fish tissue mercury concentrations from homogenized fillet and nonlethal biopsy plugs.

The use of biopsy plugs to sample fish muscle tissue for mercury analyses is a viable alternative to lethal sampling; however, the practice has yet to be widely implemented in routine monitoring due to concerns about variability of mercury concentrations in fish muscle tissues. Here we examine distribution of mercury in fillets of four fish species (Walleye, Northern Pike, Smallmouth Bass and Lake Trout), suitability of left/right side of fillet for biopsy sampling, and appropriateness of re-using a biopsy punch. The results showed that average mercury concentrations in left and right fillets of fish are similar. Mercury concentrations in biopsy plug samples, taken from the anterior dorsal area of the fish fillet, were statistically equivalent to the mercury concentrations in homogenized fillets. There was no discernible cross contamination between samples when a biopsy punch was reused after washing in hot soapy water, and as such, biopsy punches can be recycled during sampling to reduce the sampling cost. If a tissue mass collected from a specific site on the fillet is insufficient, then we suggest sampling corresponding locations on the other fillet rather than sampling two adjacent sites on one fillet to obtain more tissue. The results presented here can improve the accuracy of fillet biopsy plug sampling, minimize fish mortality for mercury monitoring, and reduce labor and material costs in monitoring programs.

Development and Application of a Low-Volume Flow System for Solution-State in Vivo NMR.

In vivo nuclear magnetic resonance (NMR) spectroscopy is a particularly powerful technique, since it allows samples to be analyzed in their natural, unaltered state, criteria paramount for living organisms. In this study, a novel continuous low-volume flow system, suitable for in vivo NMR metabolomics studies, is demonstrated. The system allows improved locking, shimming, and water suppression, as well as allowing the use of trace amounts of expensive toxic contaminants or low volumes of precious natural environmental samples as stressors. The use of a double pump design with a sump slurry pump return allows algal food suspensions to be continually supplied without the need for filters, eliminating the possibility of clogging and leaks. Using the flow system, the living organism can be kept alive without stress indefinitely. To evaluate the feasibility and applicability of the flow system, changes in the metabolite profile of 13C enriched Daphnia magna over a 24-h period are compared when feeding laboratory food vs exposing them to a natural algal bloom sample. Clear metabolic changes are observed over a range of metabolites including carbohydrates, lipids, amino acids, and a nucleotide demonstrating in vivo NMR as a powerful tool to monitor environmental stress. The particular bloom used here was low in microcystins, and the metabolic stress impacts are consistent with the bloom being a poor food source forcing the Daphnia to utilize their own energy reserves.

What's hot about mercury? Examining the influence of climate on mercury levels in Ontario top predator fishes.

Mercury (Hg) levels in Ontario top predator fishes have been increasing in recent decades. These increases may be a result of many additive factors, including global climate change. Only recently has research been conducted on how climate change may impact Hg levels in freshwater fishes at large-scales. We examined the relationship between Hg trends and (1) local weather, (2) large-scale climate drivers, and (3) anthropogenic Hg emissions, in native cool water (walleye and northern pike) and warm water (smallmouth bass and largemouth bass) predatory fishes in Ontario, Canada, for historical (1970-1992) and recent (1993-2014) time periods. For each fish species studied, > 25% of Ontario's secondary watersheds shifted from historically declining to recently increasing fish Hg trends, and ≥ 50% of watersheds experienced increasing trends between 1993 and 2014. Recent fish Hg increased at up to 0.20µg/g/decade; which were significant (p < 0.05) for walleye, northern pike and smallmouth bass. Multiple linear regressions revealed a complex interplay of local weather, large-scale climate drivers, and anthropogenic Hg emissions influencing fish Hg levels. Recent Hg levels for walleye and largemouth bass increased with changes in global climate drivers, while higher precipitation influenced smallmouth bass Hg levels the most. Walleye Hg levels increased during the positive phases of global climate drivers, reflecting the local influence of local temperatures and precipitation indirectly. Differentiating the effects of climate-related parameters and emissions is increasingly crucial to assess how changing multiple environmental stressors may impact health of wildlife and humans consuming fish.

Projecting Fish Mercury Levels in the Province of Ontario, Canada and the Implications for Fish and Human Health.

Fish mercury levels appear to be increasing in Ontario, Canada, which covers a wide geographical area and contains about 250 000 lakes including a share of the North American Great Lakes. Here we project 2050 mercury levels in Ontario fish, using the recently measured levels and rates of changes observed during the last 15 years, and present potential implications for fish and human health. Percentage of northern Ontario waterbodies where sublethal effects of mercury on fish can occur may increase by 2050 from 60% to >98% for Walleye (WE), 44% to 59-70% for Northern Pike (NP), and 70% to 76-92% for Lake Trout (LT). Ontario waterbodies with unrestricted fish consumption advisories for the general population may deteriorate from 24-76% to <1-33% for WE, 40-95% to 1-93% for NP, and 39-89% to 18-86% for LT. Similarly, Ontario waterbodies with do not eat advisories for the sensitive population may increase from 32-84% to 73-100% for WE, 9-72% to 12-100% for NP, and 19-71% to 24-89% for LT. Risk to health of Ontario fish and humans consuming these fish may increase substantially over the next few decades if the increasing mercury trend continues and updated advisories based on continued monitoring are not issued/followed.

Evaluation and interconversion of various indicator PCB schemes for ∑PCB and dioxin-like PCB toxic equivalent levels in fish.

Polychlorinated biphenyls (PCBs) remain chemicals of concern more than three decades after the ban on their production. Technical mixture-based total PCB measurements are unreliable due to weathering and degradation, while detailed full congener specific measurements can be time-consuming and costly for large studies. Measurements using a subset of indicator PCBs (iPCBs) have been considered appropriate; however, inclusion of different PCB congeners in various iPCB schemes makes it challenging to readily compare data. Here, using an extensive data set, we examine the performance of existing iPCB3 (PCB 138, 153, and 180), iPCB6 (iPCB3 plus 28, 52, and 101) and iPCB7 (iPCB6 plus 118) schemes, and new iPCB schemes in estimating total of PCB congeners (∑PCB) and dioxin-like PCB toxic equivalent (dlPCB-TEQ) concentrations in sport fish fillets and the whole body of juvenile fish. The coefficients of determination (R(2)) for regressions conducted using logarithmically transformed data suggest that inclusion of an increased number of PCBs in an iPCB improves relationship with ∑PCB but not dlPCB-TEQs. Overall, novel iPCB3 (PCB 95, 118, and 153), iPCB4 (iPCB3 plus 138) and iPCB5 (iPCB4 plus 110) presented in this study and existing iPCB6 and iPCB7 are the most optimal indicators, while the current iPCB3 should be avoided. Measurement of ∑PCB based on a more detailed analysis (50+ congeners) is also overall a good approach for assessing PCB contamination and to track PCB origin in fish. Relationships among the existing and new iPCB schemes have been presented to facilitate their interconversion. The iPCB6 equiv levels for the 6.5 and 10 pg/g benchmarks of dlPCB-TEQ05 are about 50 and 120 ng/g ww, respectively, which are lower than the corresponding iPCB6 limits of 125 and 300 ng/g ww set by the European Union.

A Bayesian assessment of the mercury and PCB temporal trends in lake trout (Salvelinus namaycush) and walleye (Sander vitreus) from lake Ontario, Ontario, Canada.

Polychlorinated biphenyls (PCBs) and total mercury (THg) are two of the most prevalent contaminants, resulting in restrictive advisories on consuming fish from the Laurentian Great Lakes. The goal of this study is to examine the temporal trends of the two contaminants in walleye (Sander vitreus) and lake trout (Salvelinus namaycush) for Lake Ontario. We employed Bayesian inference techniques to parameterize three different strategies of time series analysis: dynamic linear, exponential decay, and mixed-order modeling. Our analysis sheds light on the role of different covariates (length, lipid content) that can potentially hamper the detection of the actual temporal patterns of fish contaminants. Both PCBs and mercury demonstrate decreasing temporal trends in lake trout males and females. Decreasing PCB trends are evident in walleye, but the mean annual mercury levels are characterized by a "wax and wane" pattern, suggesting that specific fish species may not act as bio-indicators for all contaminants. This finding may be attributed to the shifts in energy trophodynamics along with the food web alterations induced from the introduction of non-native species, the intricate nature of the prey-predator interactions, the periodicities of climate factors, and the year-to-year variability of the potentially significant fluxes from atmosphere or sediments. Finally, a meaningful risk assessment exercise will be to elucidate the role of within-lake fish contaminant variability and evaluate the potential bias introduced when drawing inference from pooled datasets.

Fish mercury levels appear to be increasing lately: a report from 40 years of monitoring in the province of Ontario, Canada.

Recent mercury levels and trends reported for North America suggest a mixed (positive/negative) outlook for the environmental mercury problem. Using one of the largest consistent monitoring data sets in the world, here we present long-term and recent mercury trends in Walleye, Northern Pike, and Lake Trout from the Province of Ontario, Canada, which contains about one-third of the world's fresh water and covers a wide geographical area (1.5 and 3 times larger than France and Germany, respectively). Overall, the results indicate that the fish mercury levels either declined (0.01-0.07 µg/g decade) or remained stable between the 1970s and 2012. The rates of mercury decline were substantially greater (mostly 0.05-0.31 µg/g decade) during the 1970s/80s possibly in response to reductions in mercury emissions. However, Walleye and Pike levels have generally increased (0.01-0.27 µg/g decade) in recent years (1995-2012), especially for northern Ontario (effect sizes for differences between the two periods ranged from 0.39 to 1.04). Proportions of Walleye and Pike locations showing a flat or increasing trend increased from 26-44% to 59-73% between the 1970s/80s and 1995-2012. Mercury emissions in North America have declined over the last few decades, and as such it is logical to expect recovery in fish mercury levels; however, other factors such as global emissions, climate change, invasive species, and local geochemistry are likely affecting the response time and magnitude.

Risk-benefit of consuming Lake Erie fish.

BACKGROUND: Consumption of fish is promoted as a healthy way to obtain essential fatty acids (EFA) in the diet, yet the risk of ingesting harmful contaminants remains a concern. A recent study concluded that the risk-benefit of consuming fish from the North American Laurentian Great Lakes, which sustain important commercial and recreational fisheries, is currently unclear. We report the fatty acid (FA) content in skin-off fillets of fifteen fish species from Lake Erie and assess whether recommended dietary requirements for two EFA (EPA and DHA) can be met by safely consuming Lake Erie fishes, as an example of a risk-benefit analysis. METHODS: A total of 146 samples were analyzed for FA and contaminant content. A simulated fish consumption advisory (maximum recommended number of meals per month, up to 32) was calculated for each sample, and used to calculate the maximum amount of EPA+DHA that would be consumed if the consumption advisory was followed. RESULTS: All fifteen species had nutritionally desirable PUFA:SAFA (>0.4) and n-3:n-6 (>1). Large, fatty species had the highest EPA+DHA content, but had the most restrictive consumption advisories due to high PCB concentrations. To minimize contaminant exposure while maximizing EPA+DHA intake, consumers should consider small lake whitefish and lake trout, small panfish species, and/or walleye. However, very few species had an EPA+DHA content sufficient to safely meet the highest dietary guidelines while following advisories. CONCLUSIONS: Consumption of certain Lake Erie fish, an important recreational and commercial fishery, within the limits of our simulated fish consumption advisories, can be a good supplemental source of beneficial n-3 long chain PUFA.

Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes.

BACKGROUND: Microplastics are a pervasive contaminant cycling through food webs-leading to concerns regarding exposure and risk to humans. OBJECTIVES: We aimed to quantify and characterize anthropogenic particle contamination (including microplastics) in fish caught for human consumption from the Humber Bay region of Lake Ontario. We related quantities of anthropogenic particles to other factors (e.g., fish size) that may help in understanding accumulation of microplastics in fish. METHODS: A total of 45 samples of six fish species collected from Humber Bay in Lake Ontario near Toronto, Ontario, Canada, were examined for anthropogenic particles in their gastrointestinal (GI) tracts and fillets. Using microscopy and spectroscopy, suspected anthropogenic particles were identified and characterized. RESULTS: We observed anthropogenic particles in the GI tracts and fillets of all species. Individual fish had a mean±standard deviation of 138±231 anthropogenic particles, with a single fish containing up to 1,508 particles. GI tracts had 93±226 particles/fish (9.8±32.6 particles/gram), and fillets had 56±61 particles/fish (0.5±0.8 particles/gram). Based on a consumption rate of 2 servings/week, the average yearly human exposure through the consumption of these fish fillets would be 12,800±18,300 particles. DISCUSSION: Our findings suggest that consumption of recreationally caught freshwater fish can be a pathway for human exposure to microplastics. The elevated number of particles observed in fish from Humber Bay highlights the need for large-scale geographic monitoring, especially near sources of microplastics. Currently, it is unclear what the effects of ingesting microplastics are for humans, but given that recreationally caught freshwater fish are one pathway for human exposure, these data can be incorporated into future human health risk assessment frameworks for microplastics. https://doi.org/10.1289/EHP13540.

Lake Erie fish safe to eat yet afflicted by algal hepatotoxins.

Toxic harmful algal blooms (HABs) pose serious threats to human health and instances of wildlife death have been documented across taxa. However, the extent of toxicological impacts on wildlife species is largely unresolved, raising uncertainty about the repercussions of increasingly severe HABs on the biodiversity and functioning of aquatic ecosystems. Here, we conducted a field study to assess human health risks from consuming fish caught across all stages of a HAB and to determine the pervasiveness of potentially harmful levels of the cosmopolitan toxin microcystin on fish populations. We collected 190 fish in 2015 and 2017 from Lake Erie, a large freshwater ecosystem that is highly productive for fisheries and is an epicenter of HABs and microcystin toxicity events. Fish muscles and livers were analyzed for total microcystins, which was used to conduct a human health risk assessment for comparison against fish consumption advisory benchmarks available for Lake Erie. We found microcystins pose low risks to human health from fillet consumption (mean 1.80 ng g-1 ww) but substantial risks to fish health and recruitment from liver concentrations measured well before and after seasonal bloom events (mean 460.13 ng g-1 ww). Our findings indicate HABs are a previously underappreciated but pervasive threat to fish populations.

Cyanotoxins accumulate in Lake St. Clair fish yet their fillets are safe to eat.

Consuming fish exposed to cyanobacterial harmful algal blooms (HABs) may be a major route of microcystin toxin exposure to humans. However, it remains unknown whether fish can accumulate and retain microcystins temporally in waterbodies with recurring seasonal HABs, particularly before and after a HAB event when fishing is active. We conducted a field study on Largemouth Bass, Northern Pike, Smallmouth Bass, Rock Bass, Walleye, White Bass, and Yellow Perch to assess the human health risks to microcystin toxicity via fish consumption. We collected 124 fish in 2016 and 2018 from Lake St. Clair, a large freshwater ecosystem in the North American Great Lakes that is actively fished pre- and post-HAB periods. Muscles were analyzed using the 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) Lemieux Oxidation method for total microcystins, which was used to perform a human health risk assessment for comparison against fish consumption advisory benchmarks available for Lake St. Clair. From this collection 35 fish livers were additionally extracted to confirm the presence of microcystins. Microcystins were detected in all livers at widely varying concentrations (1-1500 ng g-1 ww), suggesting HABs are an underappreciated and pervasive stressor to fish populations. Conversely, microcystin levels were consistently low in muscles (0-15 ng g-1 ww) and presented negligible risk, empirically supporting that fillets may be safely consumed before and after HAB events following fish consumption advisories.

Organohalogen contaminants of emerging concern in Great Lakes fish: a review.

Organohalogen chemicals of emerging concern (CECs) have attracted much attention during the past decade and are of special importance for the Great Lakes of North America, which are together the largest surface freshwater resource on the earth. In this paper we review and summarize detection and levels of legacy contaminants in Great Lakes fish, lessons learned from legacy contaminants in advancing the analytical detection of CECs, progress and challenges in measuring CECs, and levels of CECs in Great Lakes fish reported to date. The CECs considered include chlorinated paraffins, polychlorinated naphthalenes and other chlorinated aromatics, halogenated flame retardants, and perfluorinated compounds.

Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region.

A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78 % to 121 %. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145 ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2 ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045 ± 0.023 ng/g. Mean concentrations of PFOA were not significantly different (p > 0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032 ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.

Long-term changes in fish mercury levels in the historically impacted English-Wabigoon River system (Canada).

The English-Wabigoon River system in Northwestern Ontario, Canada, was one of the most heavily mercury-contaminated waterways in the world due to historical discharges in the 1960s from a chlor-alkali plant. This study examines long-term (1970-2010) monitoring data to assess temporal trends in mercury contamination in Walleye, Northern Pike and Lake Whitefish, three species important for sport and subsistence fishing in this region, using dynamic linear modeling and piecewise regression. For all lakes and species, there is a significant decline (36-94%) in mercury concentrations through time; however, there is evidence that this decline is either slowing down or levelling off. Concentrations in the English-Wabigoon fish are elevated, and may still present a potential health risk to humans consuming fish from this system. Various biotic and abiotic factors are examined as possible explanations to slowing rates of decline in mercury concentrations observed in the mid-1980s.

Organophosphate esters in Great Lakes fish: An improved analysis to assess concentrations and human exposure via consumption.

Organophosphate esters (OPEs) are flame retardant and plasticizer chemicals added to electronics, furniture, textiles, and other building materials and consumer products. In this study, fillets of fish often caught by anglers in the North American Great Lakes, Lake Trout (Salvelinus namaycush) across four Great Lakes and nearshore fish species near the large urban and industrial centers of Toronto and Hamilton, Canada, were analyzed for 22 OPEs. A rapid microextraction of homogenized tissues with methanol dramatically reduced preparation and sample handling time while achieving recoveries of 69-141%, and the optimized liquid chromatographic separation improved isomeric separations, including aryl-OPEs. Twelve of the 22 OPEs were detected, with frequencies of detection ranging from 8.3% to 98%, and five compounds were detected in >50% of the fish. The average ± standard deviation for the sum of 12 OPEs (ΣOPE12) ranged from 9.6 ± 0.9 (L. Erie 2017) to 74 ± 44 (L. Superior 2001) ng/g wet weight in Lake Trout, and 12 ± 2.7 to 35 ± 30 ng/g wet weight in nearshore fish species from the Toronto and Hamilton areas. The aryl-OPEs were dominant in Lake Trout, comprising 32-77% of total ΣOPE12 concentrations. In nearshore fish, the OPE patterns reflected the relative degree of exposure to run-off and wastewater inputs in the sampled receiving environments. The intake of OPEs via human consumption of Great Lakes Lake Trout and nearshore fish was estimated to range 6.5-31 ng/kg body weight/day, which is approximately 1-2 orders of magnitude lower than exposures via indoor air and ingestion/inhalation of dusts, and 3 orders of magnitude lower than estimated reference doses. The inclusion of additional OPE analytes enabled patterns of exposure and accumulation to be distinguished in fish of different species and location, and were related to source and food web influences.