Abstract
Copper contamination of coastal waters is a long-standing problem in many regions. Copper water quality criteria in marine waters is often determined with bivalve embryo-larval toxicity tests which measure survival and normal development as endpoints. Gene expression data is increasingly incorporated into such assays as a complementary and sensitive marker of contaminant exposure or toxicity. Here we measured the impacts of copper on Mytilus californianus larval transcriptional profiles, and identified sensitive biomarkers of copper exposure. Key functional categories that were identified among these genes include biomineralization/shell formation, metal binding, and development. Finally, we compared the transcriptional response of larvae to that of adult gill tissue, and show in both datasets that patterns of declining transcript expression occur at lower copper concentrations than those required to induce increases in transcript expression, suggesting that down-regulated genes serve as the most sensitive marker of copper exposure.
Highlights
In recent decades, improvements in coastal water quality have been achieved by regulation of discharges of contaminants from point sources
Mytilus are highly sensitive to their chemical environment, so short-term bivalve embryo-larval toxicity assays are standard to determine the toxicity of metals, effluent, and numerous other chemicals (EPA, 1995; E50 Committee, 2013), and LC50 data arising from laboratory testing of these effects serve as the criteria for setting water quality regulations (Rivera-Duarte et al, 2005)
Adult M. californianus were collected from Santa Monica, California and transported to the Wrigley Marine Science Center (WMSC) on Catalina Island, where they were held in a subtidal cage hanging from the dock for 1.5 years prior to spawning
Summary
Improvements in coastal water quality have been achieved by regulation of discharges of contaminants from point sources. These regulations have been based in part on toxicity testing of marine species and on documenting the accumulation of contaminants in their tissues (EPA, 1985). Mytilus are highly sensitive to their chemical environment, so short-term bivalve embryo-larval toxicity assays are standard to determine the toxicity of metals, effluent, and numerous other chemicals (EPA, 1995; E50 Committee, 2013), and LC50 data arising from laboratory testing of these effects serve as the criteria for setting water quality regulations (Rivera-Duarte et al, 2005). From these datasets, biomarker genes can be identified that are highly correlated with toxin exposure (Nordberg, 2010), or with some negative outcome at the whole-organism or population level (Ankley et al, 2010; Connon et al, 2010)
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