WP3 Metals in the Environment: Chemistry and Fate Issues
254 Portland Ballroom
1:20 PM - 4:40 PM, Wednesday
() Measuring Strong Bio-Ligand Suppression of Silver Toxicity to Sea Urchins in Seawater.
Kramer, J1, Ward, T2, Boeri, R2, Wyskiel, D2, 1 McMaster University, Hamilton, ON, Canada2 T.R. Wilbury Laboratories, Marblehead, MA, USA
ABSTRACT- Free silver ion concentration, [Ag+], is buffered by the high concentration of Cl- ion in seawater. In addition, sea urchins (SU), in embryo and adult chronic tests, develop significant amounts of strong ligand (SL), between 40-180 nM, enough to reduce [Ag+] significantly. The biological SL formation is indicated by the differences of [Ag+calc], calculated assuming only [AgCln1-n] species, and [Ag+elec], determined with a specific ion electrode. Whereas [Ag+calc] stays constant for a defined Ag dose, [Ag+elec] deviates from [Ag+calc]. At low total Ag exposure of 3-9 micro-gm/L, [Ag+] is reduced to 0.06 nano-gm/L (0.6 pM), which is maintained more-or-less stable over the 30-day toxicity test period. At intermediate exposures of 19 micro-gm/L total Ag, [Ag+] is reduced to 0.13 nano-gm/L (1.2 pM), but is not maintained in the later part of the exposure. At high levels of 33-75 micro-gm/L Ag, SU can not produce enough SL to lower the [Ag+], and the SU die. Biological effects follow the [Ag+], giving credence to the free-ion toxicity concept (Biotic Ligand Model). Two day embryo exposures show significant SL formation, thus lowering the [Ag+], but proportionally less as the Ag exposure concentration increases. Development of SL seems to correlate with the feeding of the SU on kelp. See Boeri et al. for the biological aspects of this study.
Key words: silver toxicitgy, biothiols, sea urchins