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LIGHT DEPENDENCE OF SEDIMENT-WATER NUTRIENT EXCHANGE IN A GULF OF MEXICO
Citation:
Hagy, J.D., III, J., Caffrey, J G. Campbell, AND M C. Murrell. LIGHT DEPENDENCE OF SEDIMENT-WATER NUTRIENT EXCHANGE IN A GULF OF MEXICO. Presented at ASLO Conference, Savannah, GA, 6/13-18/04.
Description:
The flux of dissolved nutrients between sediments and overlying water is an important component of nutrient processing in estuaries. These fluxes can be linked to sediment metabolism, which in shallow estuaries can be affected by light. Sediment cores were collected at sight stations in the Pensacola Bay System during July-August 2003. Cores were incubated in the dark and at three light treatments using layers of neutral density screening. Nutrient and benthic oxygen fluxes were measured. Most nutrient fluxes were not light dependent, even at stations where oxygen flux was light dependent. Ammonium fluxes ranged from +20 to +50 umol/m2/hr, lower than many estuarine summer rates, but higher than previously measured in Pensacola Bay. Nitrate plus nitrite fluxes were not detectable at four of the sites, and ranged from +15 to +37 umol/ms/hr at the remaining sites. Phosphate fluxes were negligible and much lower than expected from the corresponding N fluxes (assuming N:P=16:1). Dissolved silicate fluxes ranged from +69 to +379 umol/m2/hr, within the expected summer range for estuaries. The lack of strong light dependent nutrient fluxes was an unexpected result.