THE ROLE OF DISSOLVED ORGANIC-MATTER RELEASE IN THE PRODUCTIVITY OF THE OLIGOTROPHIC NORTH PACIFIC-OCEAN

Based on a long-term set of observations and measurements at a station in the subtropical North Pacific Ocean, it now appears that contempor aneous rates of primary production in low-nutrient open ocean regions and perhaps in the ocean as a whole may be greater than had been consi dered in field studies conducted in previous decades. Data collected a t the Hawaii Ocean Time-Series (HOT) Station ALOHA from October 1988 t o July 1997 indicate that daytime particulate organic carbon (POC) pro duction, based on 12-h C-14 in situ incubations, averages 472 mg C m(- 2) d(-1) (SD = 125 mg C m(-2) d(-1); n = 70). This carbon production r ate is two- to three-fold greater than most of the pre-1980 estimates. We present evidence that particulate production rates may have been o verestimated by up to 30% as a result of C-14-labeled dissolved organi c carbon (C-14-DOC) adsorption onto glass fiber filters. More importan tly, when one considers the C-14-DOC that is produced but not adsorbed onto the filters, gross primary production rates (C-14-POC plus C-14- DOC) in the subtropical North Pacific Ocean may approach 1 g C m(-2) d (-1). We hypothesize that the large flux of C-14-DOC may be a manifest ation of decade-scale habitat changes resulting from variations in cli mate. The balance between POC and DOC production will ultimately influ ence the structure of the food web, especially the interactions of phy toplankton and heterotrophic bacterial populations, and the mechanisms and rates of carbon sequestration by the biological pump.