Dead Zones: A Common Symptom of Nutrient Pollution
At least 166 hypoxic dead zones attributable to human activities have been documented along our Nation’s coasts. Some estuaries experience very large dead zones every year such as the Chesapeake Bay, Long Island Sound, and the Gulf of Mexico.
Hypoxia in the Chesapeake Bay has worsened since the 1960’s and has been directly linked to nutrient pollution (Hagy et at., 2004). The map below (Figure 1) demonstrates the considerable extent of poor dissolved oxygen levels in the Bay in August, 2009 (Chesapeake EcoCheck, 2009 ).
Long Island Sound has episodes of hypoxia every summer and the problem has been worsening since the 1950’s. The map below (Figure 2) presents historic data showing conditions since 1991 (Connecticut Department of Environmental Protection, 2009).
The Gulf of Mexico dead zone threatens valuable commercial and recreational fisheries that generate about $2.8 billion annually in the region. The map below (Figure 3) shows the extent of this dead zone on July 27, 2009 (Louisiana Universities Marine Consortium, 2009).
The video below provides an overview of the dead zone phenomena, with a focus on the Gulf of Mexico.
Source: NOAA Satellites Environmental Visualizations Laboratory. Download video: Dead Zone (12 MB)
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For more information:
NOAA's National Estuarine Eutrophication Assessment
NOAA NCCOS Hypoxia and Nutrient Pollution Page
Mississippi River/Gulf of Mexico Watershed Nutrient Task Force