By Balachander Suriyanarayanan: Subscribe to Balachander's RSS feed
September 6, 2010 12:51 PM EDT
The number of hypoxic or ‘dead zones’ in U.S. coastal waters have been rising rapidly over the last 50 years, threatening ecosystems and fisheries nationwide, according to a report.
The report by environmental and scientific federal agencies said incidents of hypoxia — a condition in which oxygen levels drop so low that fish and other animals are stressed or killed — have increased nearly 30-fold since 1960 mainly due to human activities that create excess nutrients that run off into coastal waters.
“These growing dead zones endanger fragile ecosystems and potentially jeopardize billions of dollars in economic activity,” said Environmental Protection Agency administrator Lisa Jackson.
The presence of excess nutrients in water is thought to lead to reduced oxygen concentrations. Hypoxic waters generally do not have enough oxygen to support fish and other aquatic animals, and are sometimes called dead zones because the only organisms that can live there are microbes such as bacteria.
Over 300 of the 647 U.S. coastal water bodies were assessed for the new report, including the Gulf of Mexico, home to one of the largest such zones in the world. 307 of the 647 ecosystems now experience stressful or lethal oxygen levels, threatening commercial and recreational fisheries, the report said. There were just 12 hypoxic regions in US coastal waters prior to 1960.
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Unnatural levels of hypoxia, which occur mostly in the summer, are mainly because of human activities that deliver nutrients such as nitrogen and phosphorous into waterways. Fertilizer runoff from agricultural, urban and suburban landscapes, sewage discharges, and air pollution are major contributors.
The new report also noted that climate change may be causing or aggravating the problem. The expected long-term ecological changes favor progressively earlier onset of hypoxia each year and, possibly, longer overall duration. Higher rainfall can be expected to promote increased runoff of nutrients to coastal ecosystems, causing more severe oxygen depletion.
Also, the expansion of agriculture for production of crops to be used for food and biofuels will result in increased nutrient loading to coastal waters, the report said.
The impact of the BP Deepwater Horizon oil spill on oxygen levels in the Gulf of Mexico was not considered in this report because the spill had not yet occurred at the time the report was completed.
Scientists at the National Oceanic and Atmospheric Administration (NOAA) and Princeton University had said last month that the ocean hypoxia or toxic concentrations of dissolved oil arising from the Deepwater Horizon blowout are likely to be “locally significant but regionally confined to the northern Gulf of Mexico.”
Research on biofuel life cycles has shown less environmental impacts if cellulosic feedstocks are used instead of corn. Higher production of corn-based ethanol biofuel is projected to exacerbate hypoxia in the Gulf of Mexico and other coastal areas. There were questions over the growth of hypoxic in the Gulf of Mexico as U.S. corn and ethanol production increases.
However, recent data from university researchers and government agencies shows that the Gulf hypoxic zone in 2009 was the smallest in 10 years and the second smallest in the last 20 years at 3,000 square miles. This data showed that there is absolutely no correlation between the size of the annual Gulf hypoxic zone and yearly corn and ethanol production, according to a USGS official.
Effective nutrient reduction will not only reduce the incidence and severity of hypoxia but will also mitigate other habitat impacts such as algal blooms, the report from the Committee on Environment and Natural Resources said.
Widespread implementation of nutrient removal technologies in wastewater and storm water management also offers opportunities for reducing nutrient inputs to coastal waters, the report concluded.
The report was compiled by the National Oceanic and Atmospheric Administration and had significant inputs from the Environmental Protection Agency, the Department of Agriculture, the U.S. Geological Survey (USGS), and the Virginia Institute of Marine Science.
According to NOAA, the dockside value of commercial fisheries was $659 million in 2008 and the 24 million fishing trips taken in the year by more than three million recreational fishers further contributed well more than $1 billion to the Gulf economy.
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