Kim¹, Hae-Cheol, Eileen E. Hofmann¹, Barbara, B. Prezelin² and Walker O. Smith³

¹Center for Coastal Physical Oceanography, Old Dominion University, Norfolk, VA, Tel: 757-683-6006, Fax: 757-683-5550, E-mail: kim@ccpo.odu.edu, ²Marine Science Institute, University of Santa Barbara, Santa Barbara, CA and ³Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA

Estimation of primary production and carbon flux in Antarctic Coastal Waters: A modeling study

A bio-optical production model that is forced with simulated surface and underwater light fields is used to estimate primary production and subsequent carbon flux at a range sites along the western Antarctic Peninsula and in the Ross Sea that were chosen to represent advectically-controlled regions, diatom-dominated and phytoflagellate-dominated phytoplankton communities, and regions with high grazer impact. The primary production simulations show that diatom-dominated communities have higher production potential compared to phytoflagellate-dominated phytoplankton communities, which is not found for biomass comparisons. Sensitivity studies show a 5-to-6 fold increase in simulated primary production estimates obtained with photosynthetic parameters that have a diel periodicity versus simulations in which the parameters are constant. A similar difference is obtained using spectrally-resolved versus spectrally-neutral photosynthetic parameters. The fate of newly-produced phytoplankton carbon was investigated by estimating the magnitude of grazing, advection, and sinking from available data. This scaling analysis showed that the across-shelf and vertical components of advection are the dominant processes that remove phytoplankton carbon from the shelf waters. In particular, across-shelf advection is always high at the outer-shelf, which is typically dominated by diatoms, due to the presence of the Antarctic Circumpolar Current. The effect of grazing tends to be highest in inner-shelf waters, where Antarctic krill are abundant. This analysis allows a comparison of the physical and biological processes that control primary production and carbon flux in the western Antarctic Peninsula and Ross Sea regions and provides a first attempt at developing generalized models for estimating primary production in Antarctic coastal waters.