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PHYSICAL AND BIOLOGICAL CONTROLS ON DISSOLVED OXYGEN DYNAMICS IN PENSACOLA BAY, FL
Citation:
Hagy, J.D., III, J., M C. Murrell, AND J G. Campbell. PHYSICAL AND BIOLOGICAL CONTROLS ON DISSOLVED OXYGEN DYNAMICS IN PENSACOLA BAY, FL. Presented at SWS/GERS Joint Society Meeting, Pensacola Beach, FL, March 30 - April 02, 2005.
Impact/Purpose:
Conference abstract
Description:
Nutrient enrichment of estuaries and coastal waters can contribute to hypoxia (low dissolved oxygen) by increasing primary production and biological oxygen demand. Other factors, however, contribute to hypoxia and affect the susceptibility of coastal waters to hypoxia. Hypoxia formation requires net biological oxygen consumption and a physical environment that limits oxygen inputs. We examined oxygen dynamics in Pensacola Bay, FL using salt-and-water balance "box" models of water and oxygen transport during 2002-2003. We directly measured benthic and planktonic metabolic rates in summer 2003. Unusually extensive hypoxia occurred in summer 2003 during a period of high freshwater inflow. Vertical diffusive exchange became negligible (exchange velocity <10cm/d) in lower estuary areas that became more stratified. Subtidal advective transport decreased from 3 to 5 cm/s. Measured bottom layer respiration (avg: 19 mmol/m2/d) was similar to estimates derived from the box model and lower than estimates for many estuaries. Water clarity affected oxygen dynamics by allowing oxygen production below the pycnocline, which offset oxygen demand on some dates. Thus, hypoxia occurred when strong stratification co-occurred with high turbidity.