Validation and update of a model used to predict copper toxicity to the marine bivalveMytilus sp.

Abstract

A model was recently published that relates the toxicity of copper to the most sensitive taxa in the U.S. Environmental Protection Agency's criteria database (Mytilus sp.) with dissolved organic carbon concentrations in saltwater. This model was developed for potential use in risk assessment and in the development of site-specific criteria (SSC) for copper in saltwater environments where Mytilus sp. is considered an appropriate indicator species. This manuscript presents the results of a field validation study of that model. Effective concentration 50% (EC(50)) values (n = 21) for seven sites were all predicted by the model within the previously established range of acceptability. Slopes and intercepts of the two data sets were not significantly different. Consequently, the data were pooled, and new equations were developed. Dissolved copper EC(50) values were highly correlated (r(2) = 0.76, n = 75, P < 0.0001) across a wide range of sample dissolved organic carbon (DOC) concentrations (0.3-12 mg C/L) and were explained by the equation EC(50) = 11.22 DOC(0.60). Two updated equations are proposed for consideration as a means of estimating site-specific final chronic criteria (FCC) and final acute criteria (FAC) for copper in marine and estuarine environments (copper FCC(DOC) = 3.59 DOC(0.60); copper FAC(DOC) = 5.61 DOC(0.60)).

Development of Site-Specific Water Quality Criteria for the Arpa Harbor Wastewater Treatment Plant in Tipalao Bay, Guam

“…The WER study from five stations provided a multiplier of 1.40, which adjusts the chronic criterion from 3.1-to 4.34-μg DCu/L (and the site-specific recalculated criterion from 4.1-to 5.75-μg DCu/L). The positive correlation between EC50 and DOC was expected, as DOC has been repeatedly shown to buffer against copper toxicity (Arnold, 2005;Arnold, Cotsifas, and Corneillie, 2006;Chadwick et al, 2008;Rosen et al, 2009), and is the basis of the marine BLM (HDR│ HydroQual, 2012). Note, however, that this study provided a 'preliminary' WER based on one sampling event.…”

“…The dissolved organic carbon (DOC) concentration was quantified for the Pago Bay dilution water, as DOC increasingly plays an important role in modeling of metal toxicity (Arnold 2005;Arnold et al, 2006;Deforest and Schlekat, 2013). We filtered seawater through 0.7-µm nominal pore size precombusted glass fiber filters and immediately transferred to 125-mL amber glass bottles containing 8-µL 85% H 3 -PO 4 .…”

“…The collection of DOC data alongside toxicity tests, however, may be helpful for understanding its role in potentially reducing nickel toxicity. A Biotic Ligand Model for copper in seawater is well developed, and is largely driven by DOC concentration (Arnold, 2005;Arnold et al, 2006;Chadwick et al, 2008). The role of DOC is not nearly as well understood for nickel toxicity in saltwater, with no clear relationship recently observed using sensitive test endpoints at ranges between 0.22 and 2.7 mg/L (Deforest and Schlekat, 2013).…”

“…Overwhelming evidence shows that site-specific physical and chemical characteristics (e.g., dissolved organic carbon, suspended solids, natural ligands, etc.) of seawater have the potential to bind with metals, rendering them less bioavailable to marine organisms (e.g., Knezovich, Harrison, and Tucker, 1981;Stauber et al, 2000;Eriksen, Mackey, van Dam, and Nowak, 2001;Lorenzo, Nieto, and Beiras, 2002;Rosen, Rivera-Duarte, Kear Padilla, and Chadwick, 2005;Arnold, Cotsifas, and Corneillie, 2006;Bosse et al, 2014). Therefore, individual water bodies differ in their potential to buffer against metal toxicity due to site-specific water quality characteristics (e.g., pH, temperature, alkalinity, hardness, suspended solids, and dissolved organic carbon).…”

“…In many of these studies, the magnitude of the WER was linked to the concentration of dissolved organic carbon (DOC) concentrations at the sites. In particular, DOC concentration appears to reliably predict mussel embryo EC50s exposed to dissolved copper (Arnold, 2005;Arnold, Cotsifas, and Corneillie, 2006;HydroQual, 2012).…”