Carotenoid transformations in coastal marine waters

Abstract

Rapidly sinking large particles contribute a major portion of the mass flux from marine surface waters to the sea floor. The recognition that organic matter associated with these particles undergoes major alterations in its chemical composition during vertical transit has raised new questions on the role of rapid transformation processes in carbon and nitrogen cycling, benthic nutrition, and post-depositional degradation¹. Analysis of specific organic compounds has established some of the compositional changes of these transformations^2–4. However, most of the changes observed represent the sum of biological production and degradation. For example, bacterial and chemical degradation of fatty acids in the water column may be completely masked by an even greater production of these compounds by zooplankton. Hence it is often difficult to distinguish between competing degradative processes, and to assess the relative significance of each. Carotenoid pigments have characteristics which make them particularly suitable for use as organic tracers to distinguish between short-term degradation processes. Carotenoids are widely distributed in both photosynthetic and nonphotosynthetic organisms; many of them are source specific; they contain diverse functional groups; and they represent one of the more labile biogenic compound classes in the sea. We report here for the first time the isolation and identification of carotenoid transformation products from sediment trap experiments conducted in coastal marine waters, and discuss the source and significance of observed transformation products with respect to a proposed degradation pathway.