VERTICAL PROFILES OF PIGMENTS, FATTY-ACIDS AND AMINO-ACIDS - EVIDENCEFOR UNDEGRADED DIATOMACEOUS MATERIAL SEDIMENTING TO THE DEEP-OCEAN INTHE BELLINGSHAUSEN-SEA, ANTARCTICA

The organic carbon content and biochemical composition of suspended pa rticulate material was investigated at five stations in the marginal i ce zone of the Bellingshausen Sea during the austral spring of 1992, S tations, each consisting of profiles of between four and eight depths, were sampled along longitude 85 degrees W from fast ice conditions to open water. Samples were collected using large volume in situ filtrat ion systems. The horizontal and vertical distribution of organic carbo n, fatty acids, pigments and amino acids reflected strongly the physic al environment and planktonic species composition. Concentrations of t otal hydrolysable amino acids, total fatty acids and photosynthetic pi gments all exhibited marked reductions with depth. At an open water st ation, significant levels of labile fatty acids (16 :4n - 1 and 20 : 5 n - 3) and the xanthophyll fucoxanthin were present at a depth of 3900 m, indicating the sedimentation of undegraded, diatom derived materia l into the deep ocean. Amino acid, fatty acid and pigment concentratio ns suggest that degradation rates of particulate material below 500-10 00 m were very low. The results show that in some circumstances undegr aded material of photosynthetic origin reaches the deep ocean. However , the significance and contribution of this material to the nutrition of deep water pelagic and benthic communities remains to be establishe d. The results are discussed in terms of the transfer of biogenic mate rial from the euphotic zone into the deep ocean and the implications f or deep water ecosystems. (C) 1998 Elsevier Science Ltd. All rights re served.