Trace Metal Levels in NZ Little Neck Cockles (Austrovenus stutchburyi) from Otago Harbour, New Zealand

Abstract

Bivalves are commonly used as sentinel organisms for trace metal levels in marine environments. NZ little neck cockles (Austrovenus stutchburyi), were sampled from four sites in the Otago Harbour, New Zealand during two seasons, spring and winter. The levels of the trace metals Li , B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Ag, Cd, Ba, La, Ce, Pr, Nd, Sm, Pb and U were determined using ICP-MS techniques following microwave digestion under trace-metal-clean conditions. The data were analysed using ANOVA with GLS and discriminant analysis to investigate temporal, spatial, and tissue trends in trace metal levels in this clam species, as well as the effect that elimination of gut content (depuration) had on the trace metal levels. The levels of Ca, Mn, Ni, V, Zn, Sr and Cr were seen to change in the cockles between seasons, whilst most levels of trace metals were different in cockles collected from different sites. Depuration was observed to affect the levels of Al, Ba, K, Fe, Mn, As, Pb, Ca and V in cockles after 48 hours. A comparison of trace metal levels in the individual cockle tissues showed that they contained differing levels of V, La, Ce, Rb, Cu, Ba, Mg, Fe, Ni, Ca, As, Zn, Sr, K and Co and the maximum and minimum differed between tissues. The effect of depuration on trace metal levels in tissue groups varied across tissues groups and trace metals. Observed levels of As, Pb, Al and Cd in this study have potential toxicological effects on human health.