Cadmium content of the marine sponge Microciona prolifera, other sponges, water and sediment from the eastern Florida panhandle: possible effects on Microciona cell aggregation and potential roles of low pH and low salinity

Abstract

Marine sponges from shallow bays and estuaries along the Florida panhandle contained cadmium (Cd), 1.78–27.9 μg g −1 (dry weight). Levels>7 μg g −1 were never found in a variety of other benthic invertebrates. Water levels of Cd were of the order 0.22–0.43 μg ml −1 and did not differ significantly between the two study areas (Panacea and St. Joseph Bay). Cd in organic sediment however, was significantly ( P=0.033) higher around Panacea (0.343±0.063 S.E.M.) than in St. Joseph Bay (0.18±0.223 S.E.M.). Salinity of 10 and pH 6.5 were recorded following heavy rains, and can constitute a hostile environment for these organisms. Temporal variations of Cd and Cu but not Zn were observed in Microciona prolifera over a period of 2 years in St. Joseph Bay, and a negative correlation was observed between Cd content and the Ca 2+-induced aggregation of Microciona cells suspended in Ca 2+/Mg 2+-free artificial seawater. Cells unresponsive to Ca 2+ aggregated in response to releasers of Ca 2+ from internal stores (thapsigargin, A23187 and tetredecylamine), suggesting that they were viable but dormant. In vitro studies showed that Cd 2+ is about equipotent with Ca 2+ in inducing aggregation of Microciona cells, whereas lower concentrations (1–2×10 −3 M), added 10 min before inducing aggregation with CaCl 2, inhibited aggregation, possibly by blocking Ca 2+ uptake. Microciona contained a metallothionein (MT)-like protein. Taken together these results suggest that naturally-acquired Cd may interfere with cell regulatory processes in Microciona. Possible effects of low pH and salinity on Cd uptake and detrimental effects on cell function are discussed.