The Role of Land-Use/Land-Cover and River/River-Margin Denitrification in the Regulation of Nitrogen Delivery to the Mobile Bay Ecosystem

Nutrient over-enrichment (eutrophication) has become a critical management issue in coastal environments as a result of the negative effect that it has on the production of aquatic food webs, commercial fishing harvest, recreational use and the aesthetic value of these ecosystems. Like most other large watersheds, the Mobile Bay watershed has been highly altered. Problems associated with land-use and land-cover change, e.g. increased use of fertilizer, deforestation, and destruction of wetlands and riparian vegetation, are the primary sources of increased non-point source N pollution to estuaries. To understand the effects of these changes on coastal ecosystems, it is necessary to examine the relationship between land-use/land-cover and N dynamics in watersheds that are undergoing rapid change. It is also imperative that we understand how the major biogeochemical removal processes such as denitrification and storage in plant biomass, serve to modify anthropogenic nutrient loads to these systems.

There are two primary goals in this study:
1) To produce N mass balance models, based on the linkage between land-use/land-cover and hydrology, for three characteristic sub-watersheds of Mobile Bay; a predominately agricultural watershed, a predominately urban watershed, and a predominately pristine watershed located in the Mobile/Tensaw River delta.
2) To use the relationships between basin land-use/land-cover and N dynamics gleaned from the study of these linkages at the finest spatial resolution possible to quantify N flux over an annual cycle from the lower Mobile Bay watershed, the portion of the watershed below the confluence of the Alabama and Tombigbee Rivers, to the Mobile Bay estuary.