Mixtures of tritiated water, zinc and dissolved organic carbon: Assessing interactive bioaccumulation and genotoxic effects in marine mussels, Mytilus galloprovincialis

Publication date: July 2018
Source:Journal of Environmental Radioactivity, Volume 187
Author(s): Holly B.C. Pearson, Lorna J. Dallas, Sean D.W. Comber, Charlotte B. Braungardt, Paul J. Worsfold, Awadhesh N. Jha
Release of tritium (³H) in the marine environment is of concern with respect to its potential bioaccumulation and detrimental impact on the biota. Previous studies have investigated the uptake and toxicity of this radionuclide in marine mussels, and the interaction of ³H with dissolved organic ligands and elevated temperature. However, despite the well-established view that toxicity is partly governed by chemical speciation, and that toxic effects of mixture of contaminants are not always additive, there have been no studies linking the prevailing chemistry of exposure waters with observed biological effects and tissue specific accumulation of ³H in combination with other constituents commonly found in natural waters. This study exposed the marine mussel Mytilus galloprovincialis for 14 days to mixtures of ³H (as tritiated water, HTO) and zinc (Zn) at 5 Mbq L⁻¹, and 383, 1913 and 3825 nM Zn, respectively, to investigate (a) ³H and Zn partitioning in soft tissues of mussels, and (b) DNA damage in haemocytes, determined using the single cell gel electrophoresis or the comet assay. Additionally, the extent of association of ³H with dissolved organic carbon (DOC, added as humic acid) over the exposure period was investigated in order to aid the interpretation of biological uptake and effects. Results concluded a clear antagonistic effect of Zn on ³H-induced DNA damage at all Zn concentrations used, likely explained by the importance of Zn in DNA repair enzymes. The interaction of DOC with ³H was variable, with strong ³H-DOC associations observed in the first 3 d of the experiment. The secretion of ³H-binding ligands by the mussels is suggested as a possible mechanism for early biological control of ³H toxicity. The results suggest risk assessments for radionuclides in the environment require consideration of potential mixture effects.



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