Seasonal variations of heavy metals in the marine bivalve Cerastoderma glaucum (Bruguière, 1789) from Temsah Lake, Ismailia, Egypt, and their relation to anti‌oxidant enzymes

Abstract

Cerastoderma glaucum is a common bivalve in Temsah Lake. It plays important direct and/or indirect roles in the nutrient cycle. This work determined the seasonal variation of heavy metals [copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), zinc (Zn), chromium (Cr), nickel (Ni), cobalt (Co), cadmium (Cd) and lead (Pb)] in the tissue of the investigated bivalve, and the effect of these metals on the antioxidant enzymes. The results revealed that the greatest values for all studied metals in the soft tissues of C. glaucum occurred during winter and autumn seasons, while the least values were recorded during spring and summer seasons. Mg and Fe concentrations were significantly higher in all seasons when compared with all other metals. The concentrations of metals, such as  Mn, Ni, Fe, and Cr were present beyond the WHO recommended standards, especially during winter and autumn seasons. Also, this study showed highly significant increase in lipid peroxidation (MDA) activity during autumn and winter seasons that was associated with a decrease in the mean activity levels of catalase (CAT) and glutathione peroxidase (GPx) than summer season and decrease in superoxide dismutase (SOD) activity than spring season. These results related to high heavy metals concentrations, such as Cu, Fe, and Zn during the autumn season, and Mg, Mn, Cr, Co, and Ni during the winter season. Moreover, the present study recorded positive significant correlations between MDA activity and Cu, Cr and Fe concentrations, and significantly negative correlations between MDA activity and SOD activity, between CAT activity and Ni and Mn, and between GPx and Mn, Cr and Fe. So, the present study suggests that MDA and antioxidant enzymes (CAT, GPx and SOD) can be used as biomarkers to reflect the level of heavy metal pollution stress, especially Fe and Cr in the soft tissues of C. glaucum.