Excess nutrient loading is a common feature of coastal environments, associated with urbanization, industrial animal production or fertilizer application to crops. In large river plume or estuarine systems, excess nutrients from the watershed result in widespread eutrophication that may be the source of recurring summer hypoxic conditions in subsurface waters, having detrimental effects on benthic organisms. Despite eutrophic conditions, the unbalanced supply of anthropogenic nitrogen (N) and phosphorus (P) relative to the Redfield ratio can lead to seasonal P limitation in surface coastal waters. Recent investigations in the Mississippi and the Changjiang River plumes, two of the world largest river systems, indicate that P limitation has a significant effect on the magnitude, and spatial and temporal distributions of primary production and respiration and, consequently, on hypoxia. Using simulations from two coupled physical-biogeochemical models of the northern Gulf of Mexico and the East China Sea we explore the similarities and differences between the two river systems with regards to P limitation and hypoxia. We draw general patterns that will help mitigating coastal hypoxia in large river systems.

Primary Presenter: Arnaud Laurent, Dalhousie University (arnaud.laurent@dal.ca)

Authors:

Arnaud Laurent, Dalhousie University  (arnaud.laurent@dal.ca)

Katja Fennel, Dalhousie University  (katja.fennel@dal.ca)