PROGRESS IN MICROBIAL ECOLOGY, pp 163-172

Oceanic Carbon Cycle and Global Environmental Change: A Microbiological Perspective

David M. Karl

School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA

The oceanic carbon reservoir plays a vital role in global biogeochemical cycles. Transformations of carbon are determined by the distributions and metabolic activities of marine microorganisms. These reversible, reduction-oxidation reactions collectively define the oceanic carbon cycle. Longterm records of microbiological variables in the marine environment are rare, so it is presently impossible to differentiate natural variability from that induced by anthropogenic activities. Since 1988, we have conducted time-series measurements of bioelement (C, N, P, Si) cycle processes at a site characteristic of the N. Pacific gyre. Natural variability is large and appears to be controlled by global scale atmosphere-ocean forcing. Time-series studies will ultimately contribute the data sets that are necessary to validate existing ecological models and have already provided a source of novel hypotheses.