HR: 09:00h
AN: OS11B-05 INVITED     [Abstracts]
TI: Mississippi River Plume and Adjacent Continental Shelf
AU: * Rabalais, N N
EM: nrabalais@lumcon.edu
AB: The Mississippi River system dominates the flux of fresh water and associated dissolved and particulate materials on the central northern Gulf of Mexico shelf. The waters of the continental shelf adjacent to the Mississippi River are affected on varying spatial and temporal scales by a discharge that integrates runoff from 41 percent of the lower 48 United States. The Mississippi and Atchafalaya rivers combined contribute 580 km$^{3}$ per yr of fresh water to the Gulf of Mexico along with sediment yields of 210\times10$^{6}$ t per yr, 1.6\times10$^{6}$ t per yr nitrogen, of which 0.95\times10$^{6}$ t is nitrate and 0.58\times10$^{6}$ t is organic nitrogen, 0.1\times10$^{6}$ t per yr phosphorus and 2.1\times10$^{6}$ t per yr silica. The ecosystem adjacent to the discharges of the Mississippi River system, unlike many estuaries and confined seas, is an open continental shelf system. There is daily, weekly and seasonal variability in currents and stratification on the shelf and, therefore, no simple description of the couplings between nutrient delivery, carbon production in surface waters and delivery to and cycling in bottom waters. There are, however, multiple lines of evidence to implicate changes in riverine nutrient loads with overall primary and secondary production, carbon accumulation at the seabed, and low oxygen conditions on the shelf. The seasonally severe hypoxic zone that develops at the terminus of the Mississippi River system is the largest in the world's coastal ocean, reaching up to 20,000 km$^{2}$ of bottom water in mid-summer.
DE: 4805 Biogeochemical cycles (1615)
DE: 4815 Ecosystems, structure and dynamics
DE: 4863 Sedimentation
DE: 4219 Continental shelf processes
DE: 4235 Estuarine processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting