Sterols in ocean sediments: novel tracers to examine habitats of cetaceans, pinnipeds, penguins and humans

Abstract

The role of marine mammals in the biogeochemical flux of oceanic carbon is largely unknown. Capillary gas chromatography and gas chromatography/mass spectrometry after organic solvent extraction and compound class separation of feces from cetaceans (toothed and baleen whales), pinnipeds and penguins (collected in 1987 from Monterey Bay, off the coast of California or from Sea World, San Diego, California, USA) indicate that the unusual sterol profile in the Antarctic sediments, with epicoprostanol predominating over its isomer, coprostanol, originates from baleen whales (blue and fin whales). The sterol distribution in feces from ballen whales is different from that of other animals studied here and also from anthropogenic sewage (collected in 1987 from wastewater outfalls off the coast of southern California, USA). The data from the current investigation thus provide the first geochemical evidence of a recognizable native mammalian contribution to the flux of carbon in the ocean. The results also illustrate how the marine mammalian contribution can be delineated from human impact around many coastal regions of the globe including Antarctic research stations. The relative distribution of the two isomers in the sediments deposited during preanthropogenic periods could help evaluate the historical migratory routes and habitats of cetaceans, pinnipeds and penguins. The presence of coprostanone in marine mammalian feces, which has also previously been detected in human feces, implies that at least part of the conversion of cholesterol into coprostanol in the intestine of marine mammals occurs via the formation of an intermediate, Δ4-cholesten-3-one. © 1989 Springer-Verlag.