Chesapeake Bay nitrogen fluxes derived from a land-estuarine ocean biogeochemical modeling system: Model description, evaluation, and nitrogen budgets.
The Chesapeake Bay plays an important role in transforming riverine nutrients before they are exported to the adjacent continental shelf. Although the mean nitrogen budget of the Chesapeake Bay has been previously estimated from observations, uncertainties associated with interannually varying hydrological conditions remain. In this study, a land-estuarine-ocean biogeochemical modeling system is developed to quantify Chesapeake riverine nitrogen inputs, within-estuary nitrogen transformation processes and the ultimate export of nitrogen to the coastal ocean. Model skill was evaluated using extensive in situ and satellite-derived data, and a simulation using environmental conditions for 2001-2005 was conducted to quantify the Chesapeake Bay nitrogen budget. The 5 year simulation was characterized by large riverine inputs of nitrogen (154 × 109g N yr-1) split roughly 60:40 between inorganic:organic components. Much of this was denitrified (34 × 109g N yr-1) and buried (46 × 109g N yr-1) within the estuarine system. A positive net annual ecosystem production for the bay further contributed to a large advective export of organic nitrogen to the shelf (91 × 109g N yr-1) and negligible inorganic nitrogen export. Interannual variability was strong, particularly for the riverine nitrogen fluxes. In years with higher than average riverine nitrogen inputs, most of this excess nitrogen (50-60%) was exported from the bay as organic nitrogen, with the remaining split between burial, denitrification, and inorganic export to the coastal ocean. In comparison to previous simulations using generic shelf biogeochemical model formulations inside the estuary, the estuarine biogeochemical model described here produced more realistic and significantly greater exports of organic nitrogen and lower exports of inorganic nitrogen to the shelf.
Virginia Institute of Marine Science College of William & Mary Gloucester Point Virginia USA.
Yang
Y
Feng
Virginia Institute of Marine Science College of William & Mary Gloucester Point Virginia USA.
Marjorie A M
MA
Friedrichs
Department of Marine and Coastal Sciences, Rutgers The State University of New Jersey New Brunswick New Jersey USA.
John
J
Wilkin
International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences Auburn University Auburn Alabama USA.
Hanqin
H
Tian
International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences Auburn University Auburn Alabama USA.
Qichun
Q
Yang
Center for Coastal Physical Oceanography Old Dominion University Norfolk Virginia USA.
Eileen E
EE
Hofmann
Department of Marine Science University of Southern Mississippi, Stennis Space Center Mississippi USA.
Jerry D
JD
Wiggert
Horn Point Laboratory University of Maryland Center for Environmental Science Cambridge Maryland USA.
Raleigh R
RR
Hood
Chesapeake Bay; interannual variability; modeling study; nitrogen budget
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