SS3.19 Role of Benthic Communities in the Cycling and Balance of Nitrogen in Bays and Estuaries
Date: Friday, June 14, 2002
Time: 10:30:00 AM
Location: Oak Bay
 
KieneRP, University of South Alabama , Mobile, USA, rkiene@disl.org
Pennock, J, , Dauphin Island Sea Lab, Dauphin Island, USA, jpennock@disl.org
Cowan, J, L, Dauphin Island Sea Lab, Dauphin Island, USA, jcowan1@lsu.edu
Blythe, E, F, University of South Alabama, Mobile, USA, fennelb@hotmail.com
Axell, M, , University of South Alabama, Mobile, USA, maxell@disl.org
 
SPATIAL AND TEMPORAL VARIABILITY IN AUTOTROPHIC PRODUCTION AND HETEROTROPHIC CARBON UTILIZATION IN A LARGE GULF-COAST ESTUARY, MOBILE BAY, USA.
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We are studying trophic coupling in Mobile Bay, a large, shallow estuary located on the U.S. Gulf Coast. Here we report the annual cycle of primary production as well as water column and sediment microbial heterotrophic activity at three sites in the estuary. Primary production was low in spring, despite high freshwater flow and nutrient delivery. With diminishing freshwater flow, and seasonal advance toward summer, primary production increased and remained high (60-160 mmol C m-2 d-1) until fall when rates declined despite continued nutrient availability. Bacterioplankton secondary production was closely coupled with water column primary production and estimated bacterial carbon utilization approximately balanced primary production. Sediment respiration averaged 26% of the total annual carbon processing, but contributed up to 40-60% to total carbon flow during the fall-winter, when freshwater inflow and water column heterotrophic activity were low. Annual primary production ranged from 22-27 mol C m-2 but all stations displayed net-heterotrophy. The oligohaline station was the most heterotrophic, consuming 6.6 mol C m-2 y-1. Temporal patterns and the influence of physical forcing on these autotrophy/heterotrophy relationships will be discussed.