TRANSPORT OF CADMIUM AND ZINC TO ROCKY REEF COMMUNITIES IN FECES OF THE BLACKSMITH (CHROMIS-PUNCTIPINNIS), A PLANKTIVOROUS FISH

The blacksmith (Chromis punctipinnis), an abundant planktivorous reef fish off southern California, releases fecal material as it forages in the water column during the day and shelters in reefs at night. This behavior results in direct transportation of cadmium and zinc to reef communities. Cadmium and zinc concentrations, measured in fish feces a fter digestion in weak hydrochloric acid to better assess metal levels potentially available to detritivores, averaged 24.2 mug cadmium and 368 mug zinc g-1 dry weight of feces. Concentrations of both metals va ried significantly among the five sampling dates. Fresh feces spiked w ith Cd-109 and Zn-65 adsorbed additional metals for 9 and 6 h, respect ively, but the increase was negligible (<0.1%). The total amount of we ak-acid-leachable cadmium and zinc egested by sheltering blacksmiths i s approximately 4.4 mug and 66.8 mug m-2 night-1, respectively, and ma y represent more cadmium and almost as much zinc as is transported by the passive settlement of particulate material from the water column. This transport mechanism between planktonic and benthic communities vi a feces of reef fishes is probably widespread in temperate and tropica l seas.