Research Product

Spiraling releases of pesticides in coastal watersheds have impacted our Gulf estuaries. Baldwin County, Alabama, is dominated by agricultural activities. Fish and Magnolia Rivers drain the watershed that empties into Weeks Bay National Estuarine Research Reserve, located in Baldwin County. This study was designed to trace the transport of pesticides through the watershed, measure loads, and assess fate and impact of these pesticides on Weeks Bay. Sixty-seven sites were chosen within Fish and Magnolia Rivers, Weeks Bay and Mobile Bay for sampling water, sediment and macrophytes. Samples were collected at certain sites both routinely as well as after heavy rain events. Pesticides measured in highest concentrations within Weeks Bay were simazine, atrazine, and 2,4 D. Results of this three year study showed that transport of pesticides was pronounced near the source and that each river had pesticide profiles that were unique to the agricultural practices in those drainage regions. Once riverine input reached Weeks Bay, the high flushing rates within the shallow estuary homogenized Bay sediments, losing the distinctive fingerprints of each of the river inputs. Whole sediment and sediment pore water were used for toxicity testing. Results indicated a minimal impact within the Bay while some sites within the rivers showed slightly higher toxicity. High suspended sediment loads possibly transport pesticides into Mobile Bay where they are dispersed.