NATURAL CD AND PB VARIATIONS IN MYTILUS CALIFORNIANUS DURING THE UPWELLING SEASON

The short term variability of Cd and Pb in Mytilus californianus in re lation to upwelling events was studied. Sea water and mussel samples w ere taken daily for 4 weeks during the upwelling season (late summer) on the west coast of Vancouver Island. Upwelling indicators (PO4, T an d S) were measured and related to the variations in dissolved Cd and P b in sea water. High variability in Cd and Pb mussel concentrations we re detected, with significant differences found from one day to anothe r. After normalizing, to account for the variability due to the condit ion of the mussel, significant differences among samples were still de tected. The differences in mussel Cd were associated with the variatio ns in dissolved Cd due to upwelling. Mussel Bb, however, was not relat ed to variations in dissolved Pb. Principal component analysis was use d to unravel patterns of variation among all variables measured. Paral lel to the sampling of natural mussel beds, a transplant experiment wa s performed to compare the variability of intertidal vs. subtidal muss els. The transplanted mussels exhibited a less variable condition inde x and revealed more clearly the relation of dissolved Cd with the conc entrations in the mussels. Lead in mussels, again, did not show a rela tionship with dissolved Pb. In addition, the mantle edge (from 3 days with highest and lowest Cd concentrations) was analyzed as an alternat ive indicator which could exhibit less variability. The Cd variability in the mantle edge was compared with that of the gills and the remain der. The mantle edge, even though it showed less variability than the gills and the remainder, still exhibited significant differences betwe en days. (C) 1997 Elsevier Science B.V.