Cobalt speciation and bioavailability in marine organisms

Abstract

Describes the uptake and retention of cobalt species in a simple marine food chain which includes phytoplankton (Dunaliella tertiolecta and Chaetoceros pseudocurvisetum), mixed copepods (mainly Centropages sp.), and fish (sea perch Serranus scriba). Phytoplankton accumulated >60 times as much Co-cobalamine as CoCl2 from the water, and retained the metal for a significantly longer period (retention half-time of 4.4 vs 0.6 d). Accumulation of CoCl2 after ingestion of radiolabelled phytoplankton by copepods was not measurable, whereas retention of Co-cobalamine reached 42% of the quantities ingested. Fish accumulated Co-cobalamine 21 times more rapidly from seawater than CoCl2 and retained ingested Co-cobalamine 20 times more efficiently (100%) than ingested CoCl2 (5%). Two thirds of the ingested Co-cobalamine was retained in the fish with a retention half-time of 7 d. The remaining third of the organic form was retained with a half-time of 54 d, a value which was not significantly different from that of CoCl2 (47 d). -from Authors