Primary production in the Argentine Sea during spring estimated by field and satellite models

Abstract

In satellite images of the world ocean the Argentine Sea is one of the areas of highest chlorophyll-a (Chl a) concentration. Here we analyze the spatial variability in primary production in relationship to phytoplankton biomass, and some relevant optical and physical characteristics observed during spring 2005. High Chl a concentrations were found in frontal areas, mainly at the shelf-break (19.0 mg m−3) and Grande Bay (28.6 mg m−3), with the lowest values offshore (0.4 mg m−3). Integrated production also varied widely from ∼275 to 5480 mg C m−2 d−1. Variations in the Chl a/in vivo-fluorescence, and photosynthetic parameters were related to the absorption characteristics of phytoplankton, indicating the influence of variations in the phytoplankton community composition. Surface Chl a explained only 51% of the variance in integrated primary production. Neither integrated production, nor the photosynthetic parameters were significantly related to seawater temperature. The simple satellite model used here resulted in significant underestimation of field primary production values (Absolute Percentage Difference > 50%). Our results indicate that a more adequate satellite model of production, making use of local photosynthetic parameters and vertical distribution of biomass, should be developed for this region.