| |
Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Large Rivers 1
Nutrient concentrations and flux in the Mobile River system
A.K. Ward1, J.Y. Hodgson1, K.H. Pritchard1, M. Aaron2, and G.M. Ward1. 1Center for Freshwater Studies, University of Alabama, Tuscaloosa, AL 35487, 2Shelton State Community College, Tuscaloosa, AL 35405
The Mobile River system, southeastern U.S., empties into Mobile Bay with the fourth largest river discharge in North America. It includes 7 major rivers that with the Tennessee River contain the highest biological diversity of aquatic fauna in North America. This project examined water chemistry and phytoplankton composition throughout the lengths of the Sipsey and Cahaba rivers, two of the last free-flowing rivers in this system, with the goal of identifying hotspots of nutrient input. Samples from the mainstems and selected tributaries were collected from 12 sites on the Sipsey and 13 sites on the Cahaba over 13 months. Nutrient concentrations in areas associated with point source inputs from urbanized areas were highest in both rivers. The Sipsey generally had lower nutrient concentrations throughout the mainstem (e.g., nitrate–N levels of 200–300 µg/L) compared to the Cahaba (400–500 μg/L), but phytoplankton abundances increased more in the Sipsey in response to high nutrients (greater than two mg N/L). Although landuse in both river catchments is threatening pristine parts of these rivers, transport of nutrients to sensitive, down-gradient areas is not as critical as for some tributaries of the Mississippi River or some other southeastern rivers.
|
|
