Global Occurrence of Hypoxic Zones
| Analytical Overview |
| This map was created based on the inventory of known hypoxic areas around the world. It should not be considered a complete description of hypoxia occurrence, but rather a subset of the areas where hypoxia occurs. Such mapping is inevitably biased towards areas with better reporting mechanisms. Consequently, most observations take place in industrialized countries. |
Map Projection
Geographic
Map Description
Dissolved oxygen levels in water column below 2 mg/liter is a condition called hypoxia, where a majority of the marine organisms cannot survive. This map presents observations of hypoxic zones around the world. Nutrient pollution, especially from nitrates and phosphates, has increased dramatically this century largely because of increased use of agricultural fertilizers and growing discharge of domestic and industrial sewage. Significant changes in ecosystem condition are often detected when a coastal system exceeds its capacity to absorb additional nutrients. Although historical information on hypoxia is limited, experts believe that the prevalence and extent of hypoxic zones have increased in recent decades.
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Citation:
World Resources Institute - PAGE, 2000
Sources:
- NOAA (National Oceanic and Atmospheric Administration). 1997, The 1995 National Shellfish Register. Silver Spring, MD:NOAA.
- Diaz, R.J. and R. Rosenberg. 1995. Marine Benthic Hypoxia: A Review of its Ecological Effects and the Behavioural Responses of Benthic Macrofauna.Oceanography and Marine Biology: an Annual Review1995 33:
- Diaz, R.J.. Virginia Institute of Marine Science, School of Marine Science, College of William and Mary, Gloucester Point, VA. 1999. Personal Communication. November 28.