Degree Name

Master of Science (MS)

Semester of Degree Completion

1979

Thesis Director

L. Stephen Whitley

Abstract

In November 1978, specimens of oysters (Crassostrea virginica), clams (Rangia cuneata), crabs (Callinectes sapidus) and water and sediment samples were collected from Calcasieu Estuary, Louisiana. The concentrations of cadmium, chromium and lead were determined in the samples with an inductively coupled argon plasma direct reading emission spectrophotometer. Crab claw muscle, gill and carapace tissues were analyzed separately. Oysters and clams were separated into shell and whole soft tissue samples which were analyzed separately. The concentration order of the metals in crab carapace and in oyster shells was similar to that of the sediments, (Pb>Cr>Cd). The sediments and exoskeletons seem to be indicative of long-term conditions and/or of an adsorptive concentrating mechanism being present. Concentration order of the metals in water samples, in crab claw muscle and gill tissues, and in clam whole soft tissues were similar (Cr>Pb>Cd). These findings suggest that soft tissues of clams and crabs are indicative of the short-term availability of these metals to the biota and/or the presence of an absorptive concentration mechanism. It was expected that oyster soft tissues would provide similar results, however, they did not. Results show that C. sapidus, R. cuneata and C. virginica don't concentrate cadmium, chromium and lead uniformly in all anatomical body regions. Concentration of these metals seemed to be evident in the estuarine food chain in which crabs, in most cases, concentrated metals to greater extents than did clams and oysters. The possibility of a synergistic mechanism concentrating metals in each species was noted. Concentrations of cadmium, chromium and lead were independent of body weights.

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