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BENTHIC AND WATER COLUMN PROCESSES IN A SUBTROPICAL ESTUARY: EFFECTS OF LIGHT ON OXYGEN FLUXES
Citation:
Murrell, M C., J. Hagy, J.D., III, J G. Campbell, AND Caffrey. BENTHIC AND WATER COLUMN PROCESSES IN A SUBTROPICAL ESTUARY: EFFECTS OF LIGHT ON OXYGEN FLUXES. Presented at ASLO 2004 Summer Meeting, Savannah, GA, June 13 - 18, 2004.
Impact/Purpose:
Conference presentation
Description:
Murrell, M.C., J.D. Hagy, J.G. Campbell and J.M. Caffrey. In press. Benthic and Water Column Processes in a Subtropical Estuary: Effects of Light on Oxygen Fluxes (Abstract). To be presented at the ASLO 2004 Summer Meeting: The Changing Landscapes of Oceans and Freshwater, 13-18 June 2004, Savannah, GA. 1 p. (ERL,GB R982).
Eutrophication caused by excess nutrients can exacerbate hypoxia by increasing bottom water and sediment respiration. However, in shallow sub-tropical estuaries, the euphotic zone often extends below the pycnocline allowing oxygen production to offset respiration. We examined the effects of light on benthic and water column oxygen fluxes in Pensacola Bay, FL, USA. Measurements were made during summer 2003 at 8 sites distributed along depth and estuarine gradients. Sediment and water samples were exposed to several light levels ranging from 0 to 800 micro Einsteins/m2/s. Benthic and water column dark respiration average 7.5 and 42 mmol.m2/d, respectively. The benthos accounted for 18% (range: 1% to 45%) of total water column respiration and 33% (range: 4% to 76%) of below-pycnocline respiration, suggesting a minor role of the benthos in oxygen demand. Furthermore, six benthic stations and all water samples exhibited significant photosynthesis-irradiance responses, which tends to offset respiration in the euphotic zone. Pensacola Bay has a photic depth of ca. 5m and an average depth of 3 m suggesting that significant light reaches the bottom over much of the bay.