Carotenoid pigments are widely used as chemotaxonomic markers fordescribing the distributions and composition of primary producers in the sea. Increasingly, carotenoids are being used as trophic dynamic and geochemical probes for studying processes such as zooplankton feeding activity, detritus formation, and vertical organic fluxes. Most of these applications require the measurement of carotenoids in zooplankton guts or feces. Quantification of these measurements requires a working knowledge of whether or not carotenoid pigments are conserved during passage through the gut. At present, such information is scarce and existing data do not suggest a predictable pattern of carotenoid processing by copepods. Part of the problem seems to be that studies to date have been neither extensive nor intensive. This project provides a systematic evaluation of the fate of commonly used carotenoid marker pigments, from major phytoplankton taxa, during passage through the copepod gut. The goal of the project is to ascertain the extent to which the fate of carotenoids uring gut passage is a function of the copepod species (e.g., Do some species destroy carotenoids while others do not?), or the copepod's physiology at the time of feeding. Mass balance experiments will be used to estimate the quantities of ingested pigments that are conserved, derivatized and/or destroyed during passage through the gut. At least four species of copepods, selected as representatives of a range of habitats, ecologies and physiologies, will be used in the experiments. The study will serve, first to screen copepods from a variety of environments (e.g.,, high and low latitudes, nearshore and open coastal waters) for carotenoid-processing characteristics. Experiments will then clarify the influence of acclimation to food environment (i.e., recent feeding history), diel variability in digestive physiology and high frequency variability in food concentration (patchiness) on the processing of ingested algal carotenoids. Ultimately, this intensive approach should provide a level of predictability about the fate of carotenoids in certain food webs, and lead to an understanding of how animals and environments affect the use of pigments as trophic dynamic or geochemical probes.
