Natural seasonal variations of the whole-body concentrations of six trace-metals in Mytilus californianus were determined by sampling fortnightly (‘biweekly’) for one year in a relatively pristine environment. Mussels of similar size were collected from a single mussel-bed, and within a discrete tidal range, in order to reduce variability unrelated to the availability of metals in the environment. The accumulation of iron, aluminium, and manganese, and to a lesser extent lead, was directly related to the input to inshore waters of terrigenous material via storm-generated runoff and bottom resuspension during the winter months.
Variations in the accumulation of copper appeared to be related to elevated concentrations of organic Cucomplexing compounds in the water-column both during the winter (e.g. humic acid, introduced via runoff) and during upwelling (e.g. extractable organic material from decomposing phytoplankton). Increased accumulation of cadmium by mussels during the spring was directly proportional to increased surface nutrient concentrations, indicating that Cd is upwelled to inshore waters.
Quantities of both Cd and Pb available to mussels during the Upwelling period appeared to be depleted by, and diluted within, the increased phytoplankton biomass present at that time. No relationship was observed between concentrations of any of the trace-metals analyzed and the reproductive condition of M. californianus.