Salinity, dissolved organic carbon, and interpopulation variability hardly influence the accumulation and effect of copper in Mytilus edulis

Abstract

To improve the ecological relevance of environmental risk assessment, an improved understanding is needed of 1) the influence of environmental conditions on the toxicity of pollutants, and 2) the effect of these factors in combination with possible interpopulation variability. The influences of salinity and dissolved organic carbon (DOC) on the accumulation and effect of copper (Cu) to settled mussels were investigated with mussels from a North Sea and a Baltic Sea population. We found that both populations were equally Cu-sensitive, even though the Baltic Sea population lives in suboptimal conditions. Baltic Sea mussels, however, accumulated more Cu. This suggests that these populations may have different ways of coping with excess Cu. The influence of salinity on Cu toxicity to settled mussels was limited for both populations. An increase in DOC did not decrease the Cu accumulation or effect in either population. This suggests that DOC-Cu complexes are bioavailable for settled mussels. These findings are in contrast with previous research which indicated that DOC decreased the toxicity and accumulation of Cu in the D-larvae life stage. As a consequence, the mussel larval stage is not the most Cu-sensitive life stage at high DOC concentrations. Furthermore, a DOC correction factor for Cu toxicity cannot be used for settled mussels. This should be accounted for in future marine Cu environmental risk assessment. Environ Toxicol Chem 2017;36:2074-2082. © 2017 SETAC.

Modelling copper toxicokinetics in the zebra mussel, Dreissena polymorpha, under chronic exposures at various pH and sodium concentrations

“…These Cu levels are at environmentally relevant exposure concentrations and close to the reported effect concentration (Kraak et al, 1992), as applied in a number of chronic experiments on bivalves (e.g. Mersch et al, 1993;Giacomin et al, 2013;Deruytter et al, 2017). In the standard set, pH was not adjusted (8.3) while Na þ was not added.…”

Effects of copper on olfactory, behavioral, and other sublethal responses of saltwater organisms: Are estimated chronic limits using the biotic ligand model protective?

“…Based on the documented influence of DOC, pH, and salinity on Cu toxicity to saltwater organisms in several studies, the USEPA released draft BLM-based saltwater Cu criteria in 2016, with the critical water chemistry parameters being DOC, pH, salinity, and temperature (US Environmental Protection Agency 2016). However, in one recent study, discussed further as part of the present evaluation, neither DOC nor salinity had a strong influence on Cu toxicity to juvenile blue mussels (Mytilus edulis; Deruytter et al 2017).…”

“…The absence of a protective DOC effect in the 14‐d experiments with settled mussels is not consistent with the protective effect of DOC that has been consistently observed in short‐term tests with mussel larvae (Arnold ; Arnold et al , ; Nadella et al ; Deruytter et al ). As Deruytter et al () note, different life stages of the same species may not respond in the same way to changes in bioavailability conditions. However, because this is the first study we are aware of in which Cu toxicity did not decrease as DOC concentration increased, an independent verification study would help to validate or better understand that unexpected result.…”

“…Mussel. Deruytter et al (2017) conducted 3 experiments on the effects of Cu on settled blue mussels. In the third of their experiments, the effects of Cu on clearance rate by the mussels, following a 14-d exposure, were tested at a salinity of 30 ppt and a DOC concentration of either 1.8 or 6.1 mg C/L.…”

“…For the present evaluation, we estimated Cu EC20 values for each of the 2 tests. The Cu EC50 value was derived from a log-logistic model with a slope of 8.6 (table S3 from Deruytter et al 2017). From the reported EC50 and slope for the pooled model, we calculated a Cu EC20 of 10.6 mg Cu/L.…”