Microbial decomposition of phyto- and zooplankton in seawater I Changes in organic matter

Abstract

Fluctuations in the concentrations of various types of organic matter during decomposition of the diatom Skeletonema costatum (Grev.) Cleve and the copepod Tigriopus japonicus Morl were investigated under laboratory conditions. During decomposition of the diatom, concentration of particulate protein increased for the first few days in spite of continual decrease in particulate organic carbon (POC). During decomposition of the copepod, on the other hand, concentration of particulate protein decreased parallel to that of POC. The decrease of POC in the copepod body was rather slow, presumably because of the chitinous exoskeleton. These results suggest that detritus, especially that derived from phytoplankton, becomes nitrogen-rich during early stages of decomposition due to growth of bacteria on the detritus.