Particulate protein in coastal waters, with special reference to seasonal variation

Abstract

The quantities and the behavior of particulate proteinous carbon (PPC) were investigated at an experimental station in Funka Bay, southern Hokkaido from February 1974 to January 1975 using R. V. “Ushio Maru”. The amino acid composition of PPC, quantity of particulate organic carbon (POC), PPC:POC ratio, concentration of plant pigments and the primary productivity and heterotrophic activity in situ were measured to clarify PPC status. The net production was ca. 100 g C m-2 year-1. The inflow of Oyashio water and stagnation during early spring and summer may increase productivity. The net production during this period attained 70% of the net production for the whole year. The concentration of chlorophyll changed monthly parallel to changes in the primary production of the surface waters. The concentration of PPC and the PPC:POC ratio in the surface layer decreased gradually during the stagnation period of the Oyashio water. This implies that the PPC in the particulate organic matter was more easily consumed than the other organic constituents by the increased heterotrophic activity in summer. In contrast, low concentrations of PPC and high PPC:POC ratios were found during the stagnation period of Tsugaru warm water from autumn to winter. Concentrations of PPC and POC were not evenly distributed throughout the year; they decreased with depth during the stagnation period in summer. On the other hand, higher concentrations of PPC and POC, and an increased PPC:POC ratio were noted in samples collected near the sea bed, compared with the concentration and the ratio of the upper layer throughout the year. It seems likely that the particulate organic matter, originating from resuspension of bottom sediments containing proteins, was produced by the benthos. The turnover time of PPC in the upper layer was 7 to 11 days in summer and 45 to 100 days in winter; the turnover time for POC was 14 to 28 days in summer and 97 to 147 days in winter.