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BENTHIC COMMUNITY RESPONSE TO SEDIMENT AMENDMENTS
Citation:
Arias-Thode, Y. M., G. Rosen, J. Kan, A. Obraztsova, J. Leather, Y. Wang, AND K. G. SCHECKEL. BENTHIC COMMUNITY RESPONSE TO SEDIMENT AMENDMENTS. Presented at Annual Meetings Of The Society Of Environmental Toxicology And Chemistry, Tampa, FL, November 16 - 20, 2008.
Impact/Purpose:
To evaluate the toxicity to several estuarine and marine benthic community surrogates that were exposed to sediment amendments singly, and in combination.
Description:
The amendments apatite, organoclay, acetate, chitin, and geotextile reactive mats containing apatite and apatite + organoclay are currently under examination for remediation of contaminated sediments. The objective of this research is to evaluate toxicity to several estuarine and marine benthic community surrogates exposed to the amendments singly, and in combination. Amphipods (Eohaustorius estuarius), polychaetes (Neanthes arenaceodentata), sheepshead minnows (Cyprinodon variegatus), and purple sea urchins (Strongylocentrotus purpuratus) were exposed to the various amendments (at concentrations up to 5% by weight) in uncontaminated sediment for up to 28 days in the laboratory. Bacterial counts and basic microbiology were performed in the overlying water column. The geotextile mats had no observable effects on any of the organisms except bacterial growth. Although not statistically significant, there was an increase in sea urchin fertilization success observed in all treatments that included loosely mixed apatite. Acetate treatments resulted in reduced polychaete survival in some beakers, as well as reduced minnow growth. Polychaete mortality was attributed to a temporary, but sharp, decline in dissolved oxygen concentration (to 1.3 mg/L) that was observed on day 5 of the exposure. Enhanced growth of N. arenaceodenatata relative to controls, however, was observed in acetate treatments. Chitin treatments resulted in overlying water and pore water ammonia concentrations substantially higher than any of the other treatments. Microbial activities play critical roles in remediation in natural environments. Results indicate that bacterial cell counts (~ 2 x 105 cell ml-1) in the overlying water did not change significantly over time for treatments, except those containing acetate, chitin, and apatite. By day 28, cell counts in the presence of acetate increased by three orders of magnitude, while counts in chitin treatments increased one order of magnitude. It was concluded by the authors that there was not inherent toxicity associated with the amendments. Toxicity to the macro benthic community from acetate and chitin likely resulted from the increase in bacterial growth and the subsequent impairment of water quality.