Primary production in the Gulf of Mexico coastal waters using “remotely-sensed” trophic category approach

Attempts to derive ocean-color based estimates of pigment and primary production in coastal waters have been complicated by the contributions of signals from non-pigment materials to the water leaving radiance. An ocean-color model to estimate primary production was evaluated for coastal waters of the northern Gulf of Mexico. The model utilizes Csat, (mg m−3) (a variable that accounts for the pigment sensed by the satellite sensor), photosynthetically available radiation (PAR, J m−2 day−1) and a parameter.ψ* m2 (g Chl)−1, the water column chlorophyll specific cross-section for photosynthesis. Csat and PAR were treated as variables whileψ* was a site-specific parameter in the model. The model uses the approach outlined in Morel and Berthon (1989)Limnology and Oceanography,34, 1545–1562, but with site-specific statistical relationships to estimate the integrated pigment in the water column from Csat and site-specific trophic categories (oligotrophic to eutrophic) based on pigment concentration in the water column. The statistical relationships perform extremely well within the ranges of Csat and integral chlorophyll normally encountered in the coastal waters of the northern Gulf of Mexico.ψ* varies between 0.054 and 0.063 m2 (g Chl)−1 and are comparable to values observed in other regions. The ability of the model to predict production usingψ* within each of the trophic categories was demonstrated. erall performance of the model has been encouraging for two reasons: (a) the possibility of estimating production from future ocean-color sensors, and (b) the fact that the model performs well in a dynamic coastal area.