Sediment quality survey of the Choctawhatchee Bay system in the Florida panhandle

Abstract

Choctawhatchee Bay is located in the western Florida panhandle. The system was originally oligohaline with input primarily from Choctawhatchee River which terminates at the east end of the bay. The Choctawhatchee Bay and River watershed has a drainage area of 5349 square miles in Florida and Alabama (NWFWMD, 1996). Historically, marine waters entered the bay via only periodic breakthroughs to the Gulf of Mexico. A permanent pass to the Gulf of Mexico was opened in 1929 at the west end of the bay (Livingston, 1987). Marine waters from the Gulf of Mexico flowed through the western pass and combined with the freshwaters from the Choctawhatchee River creating an estuary in transition. Choctawhatchee Bay has an east to west longitudinal axis that stretches 27 miles long, but is only 4 miles wide. Average depth of the bay is 22 ft (US Department of Commerce and NOAA, 1997). Choctawhatchee Bay has several small tributaries on the northern shore. Eglin Air Force Base occupies the majority of the immediate drainage basin on the northern shore. While the northern shore has experienced some development, the southern shore of Choctawhatchee Bay has been the site of an exponential increase in urbanized growth over the last few decades (US Department of Commerce and NOAA, 1997). Previous studies have identified high metal concentrations and low dissolved oxygen in Choctawhatchee Bay and adjoining bayous (Livingston, 1987). Some have speculated that the low dissolved oxygen concentrations result from the unique nature of Choctawhatchee Bay, particularly the dramatic convergence of fresh and marine waters (US Department of Commerce and NOAA, 1997). Choctawhatchee Bay is stratified via a halocline separating freshwater at the surface from marine waters at the bottom. The lack of mixing and gas exchange between the marine and fresh waters creates a large anoxic zone in the marine (bottom) bay layer, resulting in low biotic integrity (Livingston, 1987). The literature has identified areas of concern in Choctawhatchee Bay and distinguished possible problem sources (Livingston, 1987; US Department of Commerce and NOAA, 1997; NWFWMD, 1996). Reportedly, stormwater runoff and residential development were responsible for increased nutrient loading to the bay. It was further suggested that these nonpoint source inputs were exacerbating problems in the bayous where water quality was often lower (CBA, 1998). Other Edited by Bruce J. Richardson