MEPS 290:27-33 (2005)  -  doi:10.3354/meps290027

Contrasting transfer of polonium-210 and lead-210 across three trophic levels in marine plankton

Gillian M. Stewart1,*, Scott W. Fowler2, Jean-Louis Teyssié2, Olivier Cotret2, J. Kirk Cochran1, Nicholas S. Fisher1

1Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, USA
2Marine Environment Laboratory, International Atomic Energy Agency, 4 Quai Antoine 1er, 98000 Monaco

ABSTRACT: The naturally occurring radionuclides 210Po and 210Pb can be used as geochemical tracers in marine systems, but their interactions with biota in surface waters need to be understood before oceanographic data can be interpreted unambiguously. We compared the food chain dynamics of these radionuclides in plankton assemblages by measuring the uptake and trophic transfer of 210Po and 210Pb from phytoplankton to brine shrimp Artemia sp. to euphausiids Meganyctiphanes norvegica under controlled laboratory conditions. The ratio of 210Po:210Pb within organisms increased 5- to 12-fold with each trophic level (phytoplankton to grazer to carnivore), reflecting a preferential bioaccumulation of 210Po over 210Pb. M. norvegica assimilated 44% of the polonium ingested but only 3.5% of the 210Pb ingested. Because 210Pb was unassimilated, the ratio of 210Po:210Pb was 1 to 2 orders of magnitude smaller in zooplankton fecal pellets than in the animals producing them. These results suggest that in surface waters 210Po has the potential to build up in food chains and be biologically recycled, whereas 210Pb would not build up in marine food chains and would display shorter residence times. Since euphausiids comprise an important link between small plankton and larger predatory animals in many marine ecosystems, they may serve as an important conduit of 210Po to those predators consumed as seafood by humans.

KEY WORDS: Polonium · Lead · Trophic transfer · Plankton · Bioaccumulation · Residence time · Artemia · Krill

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