SS3.15 Physical Forcing and Pelagic-Benthic Interactions in Aquatic Systems
Date: Thursday, June 13, 2002
Time: 2:15:00 PM
Location: Oak Bay
 
TobiasCR, Ecosystems Center / Marine Biological Laboratory, Woods Hole, USA, ctobias@mbl.edu
Giblin, A, E, Ecosystems Center / Marine Biological Laboratory, Woods Hole, USA, agiblin@mbl.edu
Tucker, J, , Ecosystems Center / Marine Biological Laboratory, Woods Hole, USA, jtucker@mbl.edu
McClelland, J, , Ecosystems Center / Marine Biological Laboratory, Woods Hole, USA, jmcclelland@mbl.edu
Peterson, B, J, Ecosystems Center / Marine Biological Laboratory, Woods Hole, USA, peterson@mbl.edu
 
SEDIMENT SINKS FOR DIN, AND PREFERENTIAL RECYCLING OF BENTHIC MICROALGAL NITROGEN IN A SHALLOW MACROTIDAL ESTUARY DURING HIGH RIVER DISCHARGE
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Hydrodynamics and ecosystem structure are two underlying controls that partition nitrogen processing between the water column and benthos in estuaries. The fate and transport of watershed-derived nitrogen in a New England estuary was investigated during high river discharge using a whole-estuary 15N isotope enrichment. Benthic processes dominated N cycling under these conditions. High river discharge supplied a large flux of NO3- rich water to the estuary and decreased water residence times below that of phytoplankton generation times. Without phytoplankton demand, high NO3- concentrations prevailed and fueled benthic autotrophy and denitrification. Benthic microalgae represented only a partial sink for N since 15% of the N assimilated was preferentially recycled by sediment bacteria and released to the water column as NH4+. At high discharge the percent attenuation of the watershed-derived N in the estuary was smaller than the relative N removal during periods of low discharge, long residence time, and high water column productivity. However because high discharge dominates annually, the total mass of watershed N removed by the estuarine benthos was greater than that removed by water column phytoplankton.