Applied radiotracer techniques for studying pollutant bioaccumulation in selected marine organisms (jellyfish, crabs and sea stars)

摘要

Obtaining specific information on contaminant biokinetics in marine biota is often necessary for properly interpreting monitoring data on trace contaminant levels in bioindicator species living under varying environmental conditions. Radiotracers have been employed in laboratory experiments to assess the uptake, distribution and retention of selected heavy metals and PCB congeners in three potential marine bioindicators occupying different ecological niches in the coastal zone. Pelagic and benthic jellyfish readily accumulated Co, Ag, Zn, Cd, ~(137)Cs and ~(241)Am from both water and food and retained them with biological half-lives (T_(b1/2)) ranging from a few days to several weeks. Zinc and silver were accumulated to the greatest degree (CF ～ 4 x 10~2), with benthic jellyfish having a greater affinity for metals than the pelagic species. Results from light-dark experiments indicate that the enhanced metal uptake in the benthic jellyfish is due to the presence of endosymbiotic photosynthetic zooxanthellae situated in the arms of organisms. Shore crabs ingesting Ag, a sewage-related contaminant, readily accumulated the metal with male crabs assimilating some 71% and female crabs 51% of the Ag from their food. Moreover, the assimilated fraction of Ag remained virtually immobile in their tissues as evidenced by an extremely long T_(b1/2) for depuration of 7.3 years. Sea stars exposed to ~(14)C-labelled PCB congener #153 in sea water accumulated the congener mainly in the body wall and podia reaching lipid weight CFs that ranged between approximately 2 x 10~5 to 4 x 10~5. In contrast, following exposure in radio-labelled sediments, the corresponding PCB transfer factors in the same tissues were much lower, viz., 3 x 10~2 to 5 x 10~2. Nevertheless, regardless of the exposure mode, CFs of PCB in the other tissues (digestive system, gonads, pyloric and rectal caeca) were consistently one to two orders of magnitude lower, an observation which suggests that sea star body wall and podia could serve as target tissues in biomonitoring studies assessing these toxic compounds.