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W4 PM Sediment Quality Assessment
(RIN-1112-123370) A long-term bioassay of lead (Pb) toxicity in two generations of the marine amphipod Elasmopus levis, with implications for current sediment quality criteria.
Ringenary, Mark1, 1 Polytechnic University, Brooklyn, New York, USA
ABSTRACT- Sediments usually are evaluated for toxicity by measuring mortality in a single cohort of amphipods in either acute (10-day) or chronic (28-day) amphipod bioassays. These tests were developed by the United States Environmental Protection Agency and the American Society for Testing and Materials, and do not estimate sublethal effects on population growth rate. This study differed from conventional bioassay in three ways: Sublethal effects (fecundity) were estimated; the test period was 60+ days; and not one but two generations of amphipods (Gammaridae: Elasmopus levis Smith) were tested. Four test sediments were spiked to 58 ppm, 118 ppm, 234 ppm, and 424 ppm lead; the culture sediment 30 ppm served as Control. Sex ratio overall did not depart from 1:1, although counted offspring varied with number of females in a chamber, and with the ratio of males to females. Bioaccumulated lead at 60 days varied as a linear function of lead concentration in the sediments. The number of offspring produced per test chamber as an inverse function of lead sediment concentration is best described by a curvilinear exponential equation. Although the current lead sediment quality guideline indicates that 218 ppm lead will probably have effect, amphipods in this study showed a strong response to 118 ppm lead, particularly in the second generation which had been exposed during the egg stage: Recruitment into the adult breeding population (28 days) was lower than observed in Control; longevity (total breeding life) was shorter; fecundity as estimated by Offspring-per-Chamber, Offspring-per-Adult, and/or Percent Reproductive success was lower than observed in Control; and sexual maturation was delayed. It was concluded that Elasmopus levis exposed to 118 ppm and higher could not maintain a population as large as that in Control. Even 58 ppm lead affected survivorship in second-generation amphipods; a density-dependent increase in fecundity compensated, however. This laboratory study demonstrates for the first time that exposure to toxicants during the egg stage, which occurs in nature, is so crucial that the current guideline of 218 ppm lead should be reconsidered.
Key words: sediment quality guidlines, marine amphipod, sediment toxicity bioassay, lead
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