Transformations of Carotenoids in the Oceanic Water Column.

In an effort to understand the more general mechanisms and rates of pre-depositional reactions that transform organic matter, the types and relevant time scales of reactions that transform carotenoid pigments in the oceanic water column were studied. Suspended particulate matter collected from surface waters of Buzzards Bay, Massachusetts and the Peru upwelling system has a carotenoid distribution reflecting the phytoplanktonic source of the material. The carotenoid distribution of sediment trap samples collected in these same areas was dominated by transformation products. Fucoxanthin, the primary carotenoid of marine diatoms, typically constituted 77-100 of the total fucopigments in suspended particulate material. In sediment trap samples this pigment constituted only 4-85 of the total. The remaining 15-96 of the pigments consisted of the fucoxanthin transformations products free alcohols 2-94, dehydrates 0-6, and opened epoxides 0-19. Preliminary results suggest that carotenoid esters are hydrolyzed to free alcohols at a rate determined by the turnover of primary productivity.