HR: 09:45h
AN: OS11B-07 INVITED     [Abstracts]
TI: Phosphorus Limitation of Phytoplankton Growth in the Mississippi River Plume: A Case for Dual Nutrient Control?
AU: * Ammerman, J W
EM: ammerman@imcs.rutgers.edu
AF: Rutgers University, Institute of Marine and Coastal Sciences, New Brunswick, NJ 08901 United States
AU: Sylvan, J B
EM: sylvan@imcs.rutgers.edu
AF: Rutgers University, Institute of Marine and Coastal Sciences, New Brunswick, NJ 08901 United States
AB: The Action Plan agreed to in 2001 by federal, state and tribal agencies calls for reducing the area of the Mississippi plume hypoxic zone to less than 5,000 square kilometers by 2015, to be achieved by a 30 percent reduction in the dissolved inorganic nitrogen entering the Gulf of Mexico. Evidence collected over that last fifteen years suggests that seasonal phosphorus limitation of phytoplankton growth on the Louisiana shelf coincides with the periods of both highest river flow and maximum primary productivity in the spring. The phosphorus limitation documented here almost certainly results from increased nitrogen input from the Mississippi River over the past fifty years. This phosphorus-limited productivity is most likely responsible for the summer hypoxia, though the detailed mechanism of hypoxia generation is unclear. If the Mississippi River is the major source of phosphorus as well as nitrogen to this system, then it may be time to recommend reductions in phosphorus as well as nitrogen. This would be consistent with recent recommendations for control of both nitrogen and phosphorus inputs to estuarine systems, as well as with the partial recovery of parts of the Black Sea since the major declines in nitrogen and phosphorus inputs began in the early 1990s. Though unanswered questions about the sources and supply rate of phosphorus to the Mississippi plume system remain, the need for phosphorus reductions should be thoroughly evaluated.
DE: 4834 Hypoxic environments
DE: 4845 Nutrients and nutrient cycling
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting