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 C sat, (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. C sat 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 C sat 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 C sat and integral chlorophyll normally encountered in the coastal waters of the northern Gulf of Mexico.ψ * varies between 0.054 and 0.063 m 2 (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. The overall 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.