T7 PM Metals and Bioaccumulation
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 327-329

(PIC-1117-750122) Accumulation of inorganic and organic mercury in phytoplankton and the subsequent trophic transfer to crustaceans.

Pickhardt, P¹, Fisher, N¹, ¹ Stony Brook University, Stony Brook, NY, USA

ABSTRACT- Phytoplankton concentrate mercury (Hg) from their aqueous surroundings and represent the primary entry point for this toxin to aquatic food webs. Mercury associated with phytoplankton transfers to macrozooplankton and other crustaceans which are consumed by planktivores and subsequently higher trophic levels. Here we used the gamma emitting ²⁰³Hg as either Hg²⁺ or CH₃Hg⁺ to test for the effects of different phytoplankton species on Hg accumulation dynamics in two natural waters containing significantly different concentrations of dissolved organic carbon (DOC). Additionally, we fed phytoplankton exposed previously to either Hg²⁺ or CH₃Hg⁺ to Daphnia pulex in both water types. After 24 h of exposure to aqueous Hg, volume concentration factors (VCFs) for Hg²⁺ in the 4 cells types used were similar across the two waters, but varied significantly across species. However, for CH₃Hg⁺, VCFs at 24 h for 3 of the 4 cell types concentrated more Hg in the water with the higher DOC concentrations, but VCFs were generally similar across phytoplankton species. Likewise, Daphnia pulex accumulated more Hg²⁺ and CH₃Hg⁺ from diatoms exposed to Hg in the high DOC water implicating high DOC with more efficient trophic transfer of Hg.

Key words: mercury, bioaccumulation, biomagnification, phytoplankton