SS3.19 Role of Benthic Communities in the Cycling and Balance of Nitrogen in Bays and Estuaries
Date: Friday, June 14, 2002
Time: 9:15:00 AM
Location: Oak Bay
Ralph, E, A, University of Minnesota, Duluth, USA,
Heinan, E, , University of Minnesota, Duluth, USA, 
McManus, J, , University of Minnesota, Duluth, USA,
Sterner, R, , University of Minnesota, St. Paul, USA, 
Coupled Physical and Geochemical dynamics in a coastal freshwater system: Western Lake Superior
Between September 1998 and September 2001 we measured a number of physical, chemical, and biological parameters to characterize the cycling of organic carbon and associated nutrients in the coastal zone of western Lake Superior. This region frequently undergoes large amplitude upwellings. Temperature recorders, acoustic Doppler current profilers, and sediment traps were deployed on two moorings; this presentation will focus on the physical dynamics as well as their influence on biogeochemical processes. We have captured high frequency internal wave dynamics from periods that include stratification maxima and minima. We have also examined the influence of longer-time scale physical processes on sediment distribution patterns. The temporal pattern of particle export suggests two productivity maximums during the year that correspond to periods of water column stratification minima. The composition and flux of biogenic material imply that production in Lake Superior is tightly coupled to both light and nutrient availability-essentially, during periods of low nutrient availability, but high light, carbon production can be twice that expected based on available phosphorus (high C:P and Si:P ratios). Benthic carbon and nitrogen remineralization rates are generally higher at our near shore sites than offshore suggesting spatial variations in carbon export. We are exploring the role of interannual variability (caused by climatic variations) in determining nutrient dynamics.