A comparison of the roles of direct absorption and phytoplankton ingestion in accumulation of chromium by sea urchin larvae

Abstract

Larvae of the sea urchin Pseudechinus novaezealandiae were exposed to cells of the marine planktonic alga Dunaliella primolecta which had been cultured in the presence or absence of 6 μg Cr ml −1. Larvae exposed to the algal cells which had elevated Cr concentrations (2800 μg Cr g −1 dry weight), accumulated up to 657 μg Cr g −1 dry weight. The presence of the Cr had no adverse effect on either larval survival or growth rates. Additional cultures of larvae were exposed to Cr-free algal cells and Cr added from a stock Cr(III) solution. Again the Cr had no detectable adverse effects, however, larvae accumulated Cr in significantly lower concentrations (71 μg Cr g −1 dry weight) when the metal was added in solution, compared to when it was added in association with the algal cells. The significance of these findings with regard to the entry of Cr to the marine food chains is discussed.