Aquatic insects provide a critical energy subsidy to riparian food webs, yet their role as vectors of contaminants to terrestrial ecosystems is poorly understood. We investigated relationships between aquatic resource utilization and contaminant exposure for a riparian invertivore assemblage (spiders and herptiles) along a stream contaminated with polychlorinated biphenyls (PCBs). Stable carbon (delta13C) and nitrogen (delta15N) isotopes indicated that aquatic insect utilization varied among predators, with progressive enrichment of delta13C and depletion of delta15N as predators shifted from aquatic to terrestrial prey. PCB concentrations significantly increased along these isotopic gradients; delta13C and delta15N explained 65% and 15% of the variance in predator sigmaPCBs, respectively. PCBs in predators were high, exceeding 2000 ng/g wet mass (the human-health advisory prohibiting any consumption of fish tissue) in three species. Greater consideration should be given to streams as lateral exporters rather than simply as longitudinal conduits for contaminants. Persistent contaminants are underutilized for addressing landscape-level questions in subsidy research, but our results demonstrate they are an ideal in situ tracer of stream-derived energy because they label stream organic matter and invertebrates over large distances. Likewise, riparian predators such as tetragnathid spiders have great potential as biological monitors of stream condition and as an assessment tool for risk management of contaminated aquatic sediments.

Flexible, rapid, and predictive approaches that do not require the use of large numbers of vertebrate test animals are needed because the chemical universe remains largely untested for potential hazards. Development of robust new approach methodologies and nontesting approaches requires the use of existing information via curated, integrated data sets. The ecological threshold of toxicological concern (ecoTTC) represents one such new approach methodology that can predict a conservative de minimis toxicity value for chemicals with little or no information available. For the creation of an ecoTTC tool, a large, diverse environmental data set was developed from multiple sources, with harmonization, characterization, and information quality assessment steps to ensure that the information could be effectively organized and mined. The resulting EnviroTox database contains 91 217 aquatic toxicity records representing 1563 species and 4016 unique Chemical Abstracts Service numbers and is a robust, curated database containing high‐quality aquatic toxicity studies that are traceable to the original information source. Chemical‐specific information is also linked to each record and includes physico‐chemical information, chemical descriptors, and mode of action classifications. Toxicity data are associated with the physico‐chemical data, mode of action classifications, and curated taxonomic information for the organisms tested. The EnviroTox platform also includes 3 analysis tools: a predicted‐no‐effect concentration calculator, an ecoTTC distribution tool, and a chemical toxicity distribution tool. Although the EnviroTox database and tools were originally developed to support ecoTTC analysis and development, they have broader applicability to the field of ecological risk assessment. Environ Toxicol Chem 2019;9999:1–12. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

17 18Many laboratory studies have documented that mercury can be toxic to fish, but it is 19 largely unknown if mercury is toxic to fish in their natural environments. The objective of our 20 study was to investigate the toxic effects of mercury on northern pike (Esox lucius) at Isle 21 Royale, Michigan. In 124 northern pike from eight inland lakes, concentrations of total mercury 22 in skin-on fillets ranged from 0.069 to 0.622 !g/g wet wt. Concentrations of total mercury in 23 livers increased exponentially compared with concentrations in fillets, to a maximum of 3.1 !g/g 24 wet wt. Methylmercury constituted a majority of the mercury in livers with total mercury 25 concentrations <0.5 !g/g wet wt, but declined to 28-51% of the mercury in livers with total 26 mercury concentrations >0.5 !g/g wet wt. Liver color (absorbance at 400 nm) varied among 27 northern pike and was positively related to liver total mercury concentration. The pigment 28 causing variation in liver color was identified as lipofuscin, which results from lipid peroxidation 29 of membranous organelles. An analysis of covariance revealed lipofuscin accumulation was 30 primarily associated with mercury exposure, and this association obscured any normal 31 accumulation from aging. We also documented decreased lipid reserves in livers and poor 32 condition factors of northern pike with high liver total mercury concentrations. Our results 33 suggest (i) northern pike at Isle Royale are experiencing toxicity at concentrations of total 34 mercury common for northern pike and other piscivorous fish elsewhere in North America and 35(ii) liver color may be useful for indicating mercury exposure and effects in northern pike at Isle 36 Royale and possibly other aquatic ecosystems and other fish species. 37 38

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On 22 December 2008, a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Fuel Plant (TN, USA) failed, resulting in the largest coal ash spill in US history. The present study was designed to determine sediment metal concentrations at multiple site locations and to determine whether site-specific bioaccumulation of metals existed in tetragnathid spiders. Selenium and nickel were the only 2 metals to exceed the US Environmental Protection Agency sediment screening levels. Selenium concentrations in spiders were significantly higher at ash-affected sites than in those from reference sites. The ratio of methylmercury to total mercury in spiders was found to be similar to that in other organisms (65-75%), which highlights the potential use of tetragnathid spiders as an indicator species for tracing contaminant transfer between the aquatic and terrestrial ecosystems.