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

Abstract

Release of tritium (H) 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 H 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 ofH in combination with other constituents commonly found in natural waters. This study exposed the marine mussel Mytilus galloprovincialis for 14 days to mixtures of H (as tritiated water, HTO) and zinc (Zn) at 5 Mbq L, and 383, 1913 and 3825 nM Zn, respectively, to investigate (a) H 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 ofH 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 H-induced DNA damage at all Zn concentrations used, likely explained by the importance of Zn in DNA repair enzymes. The interaction of DOC withH was variable, with strong H-DOC associations observed in the first 3 d of the experiment. The secretion ofH-binding ligands by the mussels is suggested as a possible mechanism for early biological control of H toxicity. The results suggest risk assessments for radionuclides in the environment require consideration of potential mixture effects.

Relative comparison of tissue specific bioaccumulation and radiation dose estimation in marine and freshwater bivalve molluscs following exposure to phosphorus-32

“…This technique, which used polymerase chain reaction (PCR) primers to amplify a specific region of the Glu-5' gene (Gene Bank accession no. D63778), confirmed the species used in our laboratory to be M. galloprovincialis (Pearson et al, 2018). We further confirmed the species prior to the present set of experiments using the same methodology (data not included).…”

“…Adult MG and DP were collected from Trebarwith strand (Dallas et al, 2013) and Bude, Cornwall, UK (50.828059, -4.549053), respectively. Maintenance of the mussels has been described in detail in previous publications (Dallas et al 2013;Dallas et al 2016a;Pearson et al 2018). As Hilbish et al (2002) reported the occurrence and distribution of Mytilus edulis, M. galloproviancialis and their hybrids in the coastal regions of south-west England, we ensured species homogeneity in our experiments based on the method of Inoue et al (1995).…”

“…5 Bioaccumulative abilities in aquatic bivalves, an important group of invertebrates of ecological and economic importance, has been identified in scientific literature. This is notably to ubiquitous, long-lived radionuclides such as 134 Cs,210 Po,210 Pb and 3 H (Evans 1984;Jha et al 2005;Kalaycı et al 2013;Feroz Khan et al 2014;Dallas et al 2016a;Metian et al 2016;Pearson et al 2018). However whole body accumulation and dose are often (but not always) the focus of such studies.…”

“…Whole-body determination of radionuclide bioaccumulation levels is important for risk assessments, however for biomonitoring and biological response studies (including sensitive transcriptomics and proteomics studies), it is important that tissue specific information is generated. Radionuclide uptake disparity amongst tissues has been highlighted in studies from Jha et al (2005), Jaeschke et al (2011), Dallas et al (2016a) and Pearson et al (2018) where tritium accumulation in bivalve (Mytilus sp.) tissues were observed to be highly specific.…”

“…Exposure to ionising radiations (IR) can occur via multiple aqueous and dietary pathways, the behaviour and fate of radionuclides when accumulated in specific biological tissues or organs in the aquatic biota could be influenced by many factors and may vary significantly under different exposure scenarios (Pearson et al, 2018). Given that radionuclides accumulate differentially in the tissues, from a biomonitoring perspective, whole-body bioaccumulation monitoring is therefore not necessarily sufficient in fully protecting aquatic biota from the exposure.…”