13C Tracer Methodology in Microbial Ecology with Special Reference to Primary Production Processes in Aquatic Environments

Abstract

Photosynthetic production by phytoplankton supplies organic material and energy to the aquatic food web consisting of bacteria, zooplankton, fish, water bird, whale, etc., and it may well be the most important step in the biological processes in aquatic environments. The estimation of primary productivity, thus, is essential to elucidating the dynamics of the microbial community and organic material. The importance of biological processes for the transfer of CO2 across the sea surface has recently been much discussed in relation to global changes (e.g., Berger et al., 1989; Longhurst, 1991). The dynamics of primary productivity, in particular, has a significant role in the global carbon cycle. Although there have been new approaches to assessing the dynamics, such as satellite imaging and time series sediment trapping, the direct measurement of the carbon uptake rate by phytoplankton photosynthesis can be regarded as the most reliable and basic estimate.