SS3.19 Role of Benthic Communities in the Cycling and Balance of Nitrogen in Bays and Estuaries
Date: Friday, June 14, 2002
Time: 10:15:00 AM
Location: Oak Bay
 
LehrterJC, Dauphin Island Sea Lab/University of Alabama, Dauphin Island, USA, john.lehrter@mail.ua.edu
Pennock, J, R, Dauphin Island Sea Lab/University of Alabama, Dauphin Island, USA, jpennock@disl.org
 
REGULATION OF NITROGEN CYCLING PROCESS RATES BY DEGREE OF FRESHWATER INFLUENCE
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To address the controls of estuarine sediment nitrogen cycling processes, sediment fluxes of O2, N2, NH4, and NO3 were measured at 18 stations six times over an annual cycle. In conjunction with these experiments sediment nitrogen, carbon, and chlorophyll, water-column primary production, nutrients, and hydrographic profiles were measured at each site. Nitrogen cycling rates were lowest at stations experiencing the largest degree of freshwater influence. Generally, at these locations the water column was strongly stratified with bottom waters often having O2 concentrations < 0.5 mg/L and the sediment organic material contained a large terrestrial component, mainly woody and leaf debris. Additionally, these stations were riverine in nature with deep narrow channels and forested shorelines. Stations located in more typical open water estuarine environments had higher sediment nitrogen cycling process rates. Denitrification rates at stations with high freshwater influence were low despite high bottom water NO3 concentrations and may have been inhibited by low O2 and/or high sulfide concentrations. N2, O2, and NH4 flux were highest in the open estuarine environments and rates were positively correlated with water-column primary production rates.