Daniels¹, Robert M., Hugh W. Ducklow¹, Tammi L. Richardson², George A. Jackson² and Michael R. Roman³

¹School of Marine Sciences, The College of William and Mary, Gloucester Point, USA, Tel: 804-684-7439, Fax: 804-684-7293, E-mail: bdaniels@vims.edu, ²Dept. of Oceanography, Texas A&M University, College Station, USA and ³Horn Point Laboratory, Cambridge, USA

Reconstruction of plankton food web structure from the North Atlantic Bloom Experiment (May, 1989) and the West Antarctic Peninsula (Jan., 1996 and Jan., 1999) using an inverse method

We are investigating relationships between food web structure and function across different oceanic biomes using an inverse method to recover estimates of material flows in food webs from sparse data. Specifically, we focus on how food web structure, as defined by the relative magnitude of C and N flows, influences particle export, nutrient regeneration, and dissolved organic carbon (DOC) cycling. Our model food web for NABE includes large and small phytoplankton, meso-and microzooplankton, bacteria, dissolved and particulate detritus, ammonium and nitrate. For the West Antarctic Peninsula (WAP), the model food web contains the same groupings as above as well as krill, salps, myctophids, and penguins.

The initial nitrogen solution for NABE was unobtainable given the measured data. A solution was obtained when the the observed new and regenerated productions were allowed to vary, but the f ratio was much higher than measured. When the inverse method was altered to allow the solution to reproduce the measurements within a range of constraints rather than exactly, a solution was reached with an f ratio agreeing with the measured value. The carbon solution was also recalculated using observations as constraints. After analyzing the C:N relationships between the two solutions and finding a few of the flows were unreasonable, further constraints (C:N of 3-20) were put on the Nitrogen model. Analysis of the NABE solution shows that DOC and DON flows were two to three times the detrital flows and an active microbial loop along with microzooplankton grazing dominated the processing of carbon and nitrogen.