Stable isotope ratios and contaminant concentrations in a sewage-distorted food web

Abstract

Concentrations of selected neutral organic contaminants and stable isotope ratios of carbon, nitrogen and deuterium/hydrogen in invertebrates and fish were compared from near a large, 60 m deep municipal waste outfall near Los Angeles, California, where waste has a measurable influence on the structure of the marine food web, and from a reference area off Santa Barbara, California. On the basis of the delta super(13)C and delta super(15)N of the fishes, the estimated contribution of nitrogen and carbon from sewage was about 15 to 20% of their requirements for these elements. The delta super(13)C and delta super(15)N values increased in the fishes in the order of Microstomus pacificus, Citharichthys sordidus and Zaniolepis latipinnis . The Cs/K ratio of the latter species was also significantly higher than the former 2 species, also indicating its higher trophic position. Concentrations of chlorinated hydrocarbons on a lipid-weight basis changed this order so that it more closely resembled the trophic structure revealed by the stable isotope ratio and Cs/K ratio data. Increases of both Sigma DDT and Aroclor 1254, from deposit-feeding invertebrates through fish, were evident in foodwebs of the outfall and reference areas as positive correlations with delta super(13)C.