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Modern Shelf Anoxia |
1 Center for Environmental and Estuarine Studies, University of Maryland System, Cambridge, Maryland 21613, USA
2 Louisiana Universities Marine Consortium, Chauvin, Louisiana 70344, USA
Depletion of dissolved oxygen to a point inducing mortality of bottom dwelling organisms (hypoxia) occurs in several continental shelf environments in Europe and North America and may have increased as a result of nutrient overenrichment due to human activities. Hypoxia in coastal waters results from plankton decomposition combined with a density stratification of the water column that hinders the oxygenation of bottom waters. Mass mortalities of benthic organisms have occurred as a result of extensive hypoxia on the inner continental shelves of the New York Bight and the northern Gulf of Mexico off Louisiana and Texas. Extensive hypoxia is rare in the New York Bight, and following catastrophic hypoxia in 1976, recovery of the benthic communities took more than two years. On the Louisiana-Texas shelf, large-scale hypoxia occurs virtually every year and recovery from this disturbance is rapid, because the community is kept in an early successional state by the annually recurring hypoxia.
