|Effects of Variation in River Discharge and Wind-Driven Resuspension on Higher Trophic
Levels in the Mobile Bay Ecosystem
|James H. Cowan, Jr.1, John F.
Valentine2 and William M. Graham2
1 Department of Marine Sciences, University of South Alabama, Mobile, AL 36688
2 Dauphin Island Sea Lab, 101 Bienville Boulevard, Dauphin Island AL 36528
|Proper management of the Mobile Bay estuary and its living resources requires a fundamental
understanding of current ecosystem structure and function. In addition, knowledge of how the
ecosystem responds to natural and human-induced perturbations is necessary for predicting
ecosystem health in the future. Among the most important aspects of how estuarine ecosystems
function are the linkages between nutrient delivery, primary production and secondary
production. More specifically, we do not fully understand how these linkages are
modulated by variability in freshwater discharge in an adjacent estuary--estuarine
plume/shelf ecosystem. We argue that understanding is lacking because adjacent
systems have seldom been studied at appropriate temporal and spatial scales, due
largely to difficulty in finding a location where study is logistically feasible.
Mobile Bay and vicinity offers such a location. The information collected during
this study will provide insight as to how pulsed delivery of freshwater to
estuaries acts to regulate production because we will be able to investigate
trophic linkages across a spatial scale that has been heretofore impracticable.
In this initial phase, efforts will be focused on characterization of the biological and biogeochemical patterns and pathways within the study area. Three major research questions guide this work: 1) What are the nutrient stocks, and what is the size of the biomass pool at each trophic level (e.g. microbial, phytoplankton, zooplankton, benthos, and forage fishes), and how do they change in space with each season?; 2) At what rate is biomass (carbon) transfered between pools; and, 3) Do transfer rates and transfer pathways between biomass pools differ withvarying levels of freshwater inflow, during wind driven resuspension events, and with season?