Satellite-derived total and new phytoplankton production in the Gulf of Mexico

Abstract

Integrated total (PTint) and new production (Pnewint) (gC m⁻² d⁻¹) were calculated for the Gulf of Mexico with semi-analytical models from the literature, using chlorophyll a concentrations (Chlsat) and the vertical attenuation coefficients of light (K₄₉₀) from monthly composites of the satellite sensor SeaWIFS (1997–2004). The phytoplankton biomass vertical distribution associated with Chlsat, and the vertical distribution of the f-ratio [f(z) = Pnew(z)/PT(z)], were deduced from historic oceanographic data. Based on bathimetry, surface T ºC, Chl and nutrients, the Gulf was partitioned into three regions: Yucatan, Deep-waters, and Mississippi. The year was divided into two periods for the Deep-waters region, “cool” and “warm.” The whole year was treated as a single period for the Yucatan and Mississippi regions. Average values for PTint had a significant seasonal variation for the Deep-waters region (0.37-0.44 and 0.22-0.24 gC m⁻² d⁻¹, for the “cool” and “warm” periods, respectively), and similarly for Pnewint (0.023-0.026 and 0.013-0.014 gC m⁻² d⁻¹). Ranges for the average PTint values were 1.18 – 1.22, and 1.60 – 1.68 gC m⁻² d⁻¹, for the Yucatan and Mississippi regions, respectively. Ranges for Pnewint were 0.97 – 1.05, and 1.38 – 1.44 gC m⁻² d⁻¹. The present, limited data, do not show a significant interannual PTint and Pnewint variability in any region of the Gulf. Longer satellite time series for more complete future work may lead to the description of significant interannual primary production variability in the Gulf.