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The embryotoxicity of extracts of American eels (Anguilla rostrata) was measured to determine whether maternally derived contaminants contribute to the declining recruitment of eels to Lake Ontario. Sexually maturing, large yellow and silver eels were sampled in 2007 and 2008 from 5 locations in eastern Canada, including Lake Ontario; positive controls included eels from the Hudson River, United States, and Canal Dessel-Schoten, Belgium (European eel, Anguilla anguilla). Japanese medaka eggs were injected immediately after fertilization with 1 or 10 nL of eel extract and, after 12 d, scored for signs of toxicity. Eel extracts did not cause dioxin-like embryotoxicity, reflecting the low concentrations of total dioxin equivalents measured chemically in these same extracts. Embryo mortality and reduced hatching success at high doses of eel extracts may reflect the bioaccumulation of legacy or emerging chemicals of concern. The results were consistent with long-term trends of declining concentrations of persistent organic pollutants (POPs) in tissues of eels and other fish species from Lake Ontario, trends of declining embryotoxicity of eel tissue extracts, and recent increases of recruitment of juvenile eels to Lake Ontario. If dioxin-like compounds contributed in the past to the decline of recruitment and abundance of American eels in Lake Ontario, these data suggest that recruitment should recover, following the same trends as the recovery of lake trout reproduction in Lake Ontario. Environ Toxicol Chem 2018;37:1061-1070. © 2017 SETAC., (© 2017 SETAC.)

This study reports the history of contamination of American eels (Anguilla rostrata) from eastern Lake Ontario (LO) by persistent organic pollutants (POPs). Three groups of 10 large female eels captured in eastern LO in each of 1988, 1998, and 2008 were analysed for polychlorinated dibenzo-p-dioxins and furans, polychlorinated biphenyls, several organochlorine pesticides, and polybrominated diphenyl ethers. Mean concentrations were up to 3-fold lower in 2008 compared to previous years. When combined with the results of previous studies, these data show that concentrations of POPs in American eels have declined exponentially since the early 1980s by an average of 9.1±1.9% per year. Toxic equivalent (TEQ) concentrations of dioxin-like compounds (DLCs) were calculated from fish toxic equivalency factors. Assuming an efficient transfer of DLCs to their eggs, egg TEQs prior to 2000 exceeded the threshold for chronic toxicity to embryos of European eels (Anguilla anguilla) and lake trout (Salvelinus namaycush) (4-5 pg/g ww of TEQ). These results suggest that embryotoxicity of maternally-derived DLCs from LO eels, historically a major contributor to the spawning stock of American eels, could have impaired the reproductive and recruitment success of the species., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Concerns regarding the impacts of pesticides on aquatic species and drinking water sources have increased demands on water quality monitoring programs; however the costs of sample analysis can be prohibitive. In this study we investigated enzyme-linked immunosorbent assay (ELISA) as a cost-effective, high through-put method for measuring pesticide concentrations in surface waters. Seven hundred and thirty-nine samples from 158 locations throughout Ontario were analysed for atrazine and metolachlor from April to October 2007. Concentrations ranged from <0.1 to 3.91 μg L(-1) (median=0.12 μg L(-1)) for atrazine and from <0.1 to 1.83 μg L(-1) (median=0.09 μg L(-1)) for metolachlor. Peak concentrations occurred in late spring/early summer, in rural agricultural locations, and decreased over the remainder of the growing season for both herbicides. About 3% of the samples that had ELISA results occurring above the limit of quantification (0.10 μg L(-1)) were evaluated against gas chromatography-mass spectrometry (GC-MS). Linear regression analysis revealed a R(2) value of 0.88 and 0.39, for atrazine and metolachlor, respectively. ELISA tended to overestimate concentrations for atrazine and metolachlor, most likely because the ELISA kits also detect their metabolites. Atrazine data suggest that ELISA may be used complementary with GC-MS analysis to enhance the spatial and temporal resolution of a water quality monitoring study. The commercially available metolachlor ELISA kit requires further investigation. ELISA may be used to detect atrazine and metolachlor in surface water samples, but it is not recommended as a quantitative replacement for traditional analytical methods., (Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.)