Modeling the impacts of decadal changes in riverine nutrient fluxes on coastal eutrophication near the Mississippi River Delta

Abstract

A mathematical model was used to link decadal changes in the Mississippi River nutrient flux to coastal eutrophication near the Mississippi River Delta. Model simulations suggest that bottom water hypoxia intensified about 30 years ago, as a probable consequence of increased net productivity and increased sedimentation of the organic material produced in situ in the upper water column. Model simulations also suggest that long-term increase in riverine nutrient fluxes has been responsible for this historical decrease in bottom layer oxygen concentrations. Importantly, model simulations are in good agreement with the available historical data from the northern Gulf of Mexico, and are additionally supported by the retrospective analyses of sedimentary records. Conclusively, this modeling study supports the hypothesis that riverine nutrient fluxes, via their influence on net productivity of the upper water column, play a major role in controlling the development of bottom water hypoxia and accumulation of organic carbon in coastal sediments.