RELATIONSHIP BETWEEN THYMIDINE METABOLISM, BACTERIOPLANKTON COMMUNITYMETABOLIC CAPABILITIES, AND SOURCES OF ORGANIC-MATTER

Numerous investigations have been directed at verifying and calibratin g methods for measuring bacterioplankton production, particularly meth ods based on the incorporation of thymidine (TdR) into DNA. Careful ex amination of these data can provide insights into other aspects of the ecology of aerobic heterotrophic microbial communities. Once method-s pecific biases are eliminated, these measurements indicate that there are broad-scale patterns in the metabolic fate of TdR, differences tha t seem to reflect broad differences in community metabolic capabilitie s. Based on work conducted primarily in San Francisco and Tomales Bays , California, I suggest that the metabolic fate of TdR in a given envi ronment may reflect the relative importance to bacterioplankton nutrit ion of detritus versus fresh phytoplankton carbon. This is probably du e to differences in community composition that result from growth on q ualitatively different carbon sources. If true, the metabolic fate of TdR may provide a broadly applicable, but simple, index that can be us ed to assess the relative importance of these general sources of organ ic matter. Such an index could be very useful in characterizing lacust rine, estuarine, and nearshore environments.