Journal of Oceanography, Vol. 59 (No. 5), pp. 731-738, 2003
Shinji Hashimoto* and Yoshiaki Maita
Department of Fisheries Oceanography and Marine Science, Faculty of Fisheries, Hokkaido University, Hakodate 041-8611, Japan
(Received 24 July 2002; in revised form 6 March 2003; accepted 12 March 2003)
Abstract: Spatial and temporal variations in the vertical fluxes of amino acids and hexosamine were studied at coastal sites in the south of the Chukchi Sea, Otsuchi Bay, and the center and the entrance of Funka Bay. Amino acid fluxes were higher in the upper trap than in the lower trap material, but hexosamine fluxes were opposite to amino acid fluxes. The ratios between protein amino acids (Asp, Glu and Arg) and their decomposition products (b-Ala, g-Aba and Orn) indicate that the labile organic matter was more abundant in the upper traps than in the lower ones and increased during periods of enhanced amino acid fluxes. The ratios of Ser/Gly did not vary temporally and spatially and were nearly constant, indicating that Ser and Gly were preserved in a stable form within sinking particles. Hexosamine/amino acid ratios of these particles were higher in the lower sediment trap than in the upper trap material. This implies that the sinking particles derived from zooplankton are relatively more abundant in deep layers than in the surface layer in the water column. We suggest that the difference in amino acid flux and the composition between the upper and lower trap material is influenced by the processes of microbial decomposition and zooplankton consumption of sinking particulate organic matter.