SS3.19 Role of Benthic Communities in the Cycling and Balance of Nitrogen in Bays and Estuaries
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
BernhardAE, University of Washington, Seattle, USA, aeb5@u.washington.edu
Giblin, A, E, Marine Biological Laboratory, Woods Hole, USA, agiblin@mbl.edu
Tucker, J, , Marine Biological Laboratory, Woods Hole, USA, jtucker@mbl.edu
Waterbury, J, B, Woods Hole Oceanographic Institute, Woods Hole, USA, jwaterbury@whoi.edu
Stahl, D, A, University of Washington, Seattle, USA, dastahl@u.washington.edu
 
SALINITY EFFECTS ON COMMUNITY STRUCTURE AND NUMBERS OF AMMONIA-OXIDIZING BACTERIA AND NITRIFICATION RATES IN ESTUARINE SEDIMENT
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We investigated the effects of salinity on nitrification and ammonia-oxidizing bacteria (AOB) community structure in estuarine sediments. Sites were chosen to represent a range of salinities (low, mid, high) and varying sediment matrix (unvegetated sediment vs. vegetated marsh). Potential nitrification rates and Most Probable Numbers (MPNs) were measured at four salinities (0, 5, 10, 30). Community structure was assessed by real-time PCR using primers specific for the 16S rDNA of AOB. Overall, rates and total AOB DNA were higher in April than in August. Rates in the marsh, however, were higher in August than in April, coinciding with maximal Spartina growth. Rates and MPNs, in general, showed higher values near in situ salinities. AOB affiliated with the beta subdivision of the Proteobacteria were dominant at low salinity sites. Gamma subdivision members dominated at high salinity. These data indicated a seasonal cycle of nitrification, and a shift in AOB populations along the salinity gradient. By correlating changes in community structure with changes in process rates, we are beginning to resolve factors controlling nitrification in estuaries.