Surface Biomass Flux across the Coastal Mississippi Shelf

The exchange of water masses across the Mississippi shelf was used to determine the chlorophyll flux for an eight month period in 2013 through the major Mississippi River discharge period in Spring and Fall. Circulation models (NCOM and HYCOM) and SNPP satellite chlorophyll products were used to monitor the changes in the shelf transport and surface biological impact. The physical and biological response of cross shelf exchange was observed in rapidly changing dynamic movements of river plumes across the shelf as identified by the models and satellite products. Six sections on the shelf identified exchange corridors of transport and biomass chlorophyll flux of surface waters between the coast and offshore waters. During the eight month period, the nearshore waters show high carbon chlorophyll flux, averaging -60x10(3) kg chl extending to offshore waters. However, at the outer shelf break, a significant carbon flux was observed moving shoreward onto the shelf from offshore waters, averaging +100x10(3) kg chl, which is attributed to the dynamic Mississippi River plume. Results indicate a significant amount of offshore surface waters containing biological carbon can exchange across the shelf, clearly demonstrated through the combination of biological satellite products and physical models.