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Impacts of elevated pCO2 on Mediterranean mussel (Mytilus galloprovincialis): Metal bioaccumulation, physiological and cellular parameters

Sezer, Narin, Kılıç, Önder, Sıkdokur, Ercan, Çayır, Akın, Belivermiş, Murat
Marine environmental research 2020 v.160 pp. 104987
Mytilus galloprovincialis, acid-base balance, adults, bioaccumulation, biochemical pathways, cadmium, carbon dioxide, carbon dioxide enrichment, cell viability, depuration, filtration, greenhouse gas emissions, hemocytes, juveniles, mussels, nucleic acids, ocean acidification, seawater, silver, tissue distribution
Ocean acidification alters physiology, acid-base balance and metabolic activity in marine animals. Near future elevated pCO₂ conditions could be expected to influence the bioaccumulation of metals, feeding rate and immune parameters in marine mussels. To better understand such impairments, a series of laboratory-controlled experiment was conducted by using a model marine mussel, Mytilus galloprovincialis. The mussels were exposed to three pH conditions according to the projected CO₂ emissions in the near future (one ambient: 8.10 and two reduced: 7.80 and 7.50). At first, the bioconcentration of Ag and Cd was studied in both juvenile (2.5 cm) and adult (5.1 cm) mussels by using a highly sensitive radiotracer method (¹¹⁰ᵐAg and ¹⁰⁹Cd). The uptake and depuration kinetics were followed 21 and 30 days, respectively. The biokinetic experiments demonstrated that the effect of ocean acidification on bioconcentration was metal-specific and size-specific. The uptake, depuration and tissue distribution of ¹¹⁰ᵐAg were not affected by elevated pCO₂ in both juvenile and adult mussels, whereas ¹⁰⁹Cd uptake significantly increased with decreasing pH in juveniles but not in adults. Regardless of pH, ¹¹⁰ᵐAg accumulated more efficiently in juvenile mussels than adult mussels. After executing the biokinetic experiment, the perturbation was sustained by using the same mussels and the same experimental set-up, which enabled us to determine filtration rate, haemocyte viability, lysosomal membrane stability, circulating cell-free nucleic acids (ccf-NAs) and protein (ccf-protein) levels. The filtration rate and haemocyte viability gradually decreased by increasing pCO₂ level, whereas the lysosomal membrane stability, ccf-NAs, and ccf-protein levels remained unchanged in the mussels exposed to elevated pCO₂ for eighty-two days. This study suggests that acidified seawater partially shift metal bioaccumulation, physiological and cellular parameters in the mussel Mytilus galloprovincialis.