Trace metal concentrations and partitioning in zooplankton, neuston, and benthos from the south Texas outer continental shelf

Abstract

A variety of marine biota, including zooplankton, sargassum, surface plankton, squid, shrimp, and fish collected along the south Texas Outer Continental Shelf, were analyzed for Cu, Zn, Cd, Pb, Cr, Ni, Fe, and Mn. Although there is a great deal of variation in the chemical content of the various samples, both within species and between species, the variations all fall within the range of values published for similar organisms collected elsewhere. An increase in Pb concentration from north to south, and an increase in Cd concentration from nearshore to further offshore in the zooplankton mirrors the sediment patterns. Statistical analysis of the chemical and biological data for these samples indicates that relatively small percentages of the biological makeup of the sample can markedly affect the concentrations of Pb, Cd, Ni, and Zn. This is particularly true for the larvacea, ostracoda, and mollusca. Chemical analyses of the exoskeletons of shrimp and the skin of both squid and fish indicate that they generally contain higher metal levels in comparison with the flesh from the same organism. This is probably the result of either adsorption from seawater and/or an internal detoxification procedure employed by the organism. The analysis of a composite sample of squid 'pens' indicates that they contain enriched Cu, Cd, Zn, Pb, and Fe levels in comparison with the skin and flesh. These elevated levels are probably the result of an internal detoxification procedure and/or may represent a means of storing necessary metabolites, at least in the case of Cu and Zn, but can not be attributed to adsorption as the chitinous 'pen' is imbedded in tissue and is not directly exposed to seawater.