SS3.15 Physical Forcing and Pelagic-Benthic Interactions in Aquatic Systems
Date: Thursday, June 13, 2002
Time: 2:30:00 PM
Location: Oak Bay
 
PetersonBJ, Marine Biological Laboratory, Woods Hole, USA, peterson@mbl.edu
Deegan, L, A, Marine Biological Laboratory, Woods Hole, USA, ldeegan@mbl.edu
Vallino, J, J, Marine Biological Laboratory, Woods Hole, USA, jvallino@mbl.edu
Tobias, C, , Marine Biological Laboratory, Woods Hole, USA, ctobias@mbl.edu
Hughes, J, E, Marine Biological Laboratory, Woods Hole, USA, jhughes@mbl.edu
Cieri, M, , Maine Department of Marine Resources, West Boothbay Harbor, USA, Matthew.Cieri@state.me.us
 
IMPACT OF HYDROLOGIC FORCING ON BENTHIC-PELAGIC COUPLING OF NITROGEN FLOW IN TWO TIDAL RIVERS
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The fate of watershed-derived nitrogen in tidal rivers is determined by interactions between geomorphology, hydrology, biogeochemistry and food web structure. To study these interactions, we performed two Nitrogen ISOtope TRacer EXperiments (NISOTREX) at the Plum Island Sound in northeastern Massachusetts. The experiments compared N cycling in tidal rivers with low versus high flushing. In the Parker River the residence time of water was 5 to 15 days whereas in the Rowley River it was 1 to 3 days. In the Parker under slow flushing a bloom of planktonic diatoms developed and assimilated all available nitrate. The diatoms supported a highly productive planktonic community of zooplankton and fishes and, via sinking, a highly productive benthic community of amphipods, crabs and fishes. Very little N was exported downstream. In the Rowley rapid flushing limited the development of the phytoplankton. The nitrate was instead taken up by benthic diatoms. Benthic invertebrates became labeled by feeding on benthic diatoms rather than on a rain of planktonic diatoms. Because of the rapid flushing, most of the nitrate was exported to Plum Island Sound.