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Posts Tagged ‘nutrient pollution’

‘Dead Zone’ in Gulf of Mexico Largest Ever Measured

Posted by feww on August 6, 2017

Gulf of Mexico dead zone measured 22,720 km²

At 22,720 square kilometers (8,776 square miles), this year’s dead zone in the Gulf of Mexico is the largest ever measured, according to NOAA.

Image credit: N. Rabalais, LSU/LUMCON)

“Previously the largest Gulf of Mexico dead zone was measured in 2002, encompassing 8,497 square miles. The average size of the dead zone over the past five years has been about 5,806 square miles, three times larger than the Gulf Hypoxia Task Force target of 1,900 square miles.”

This large dead zone size shows that nutrient pollution, primarily from agriculture and developed land runoff in the Mississippi River watershed is continuing to affect the nation’s coastal resources and habitats in the Gulf.

These nutrients stimulate massive algal growth that eventually decomposes, which uses up the oxygen needed to support life in the Gulf. This loss of oxygen can cause the loss of fish habitat or force them to move to other areas to survive, decreased reproductive capabilities in fish species and a reduction in the average size of shrimp caught.

Additional graphics available from:

https://gulfhypoxia.net/

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Most U.S. Rivers, Streams in Poor Condition for Aquatic Life

Posted by feww on March 27, 2013

Thousands of stream and river miles across the country under ‘significant pressure’: EPA

In its first comprehensive survey looking at the health of thousands of stream and river miles across the country, the U.S. Environmental Protection Agency (EPA) has found more than half – 55 percent – in poor condition for aquatic life.

The 2008-2009 National Rivers and Stream Assessment reflects the most recent data available on the condition of the water resources, EPA said.

[Does that mean the significant degradations that have occurred in the past 5 years not yet taken into account? Moderator]

“The health of our Nation’s rivers, lakes, bays and coastal waters depends on the vast network of streams where they begin, and this new science shows that America’s streams and rivers are under significant pressure,” said Office of Water Acting Assistant Administrator.

The data was collected by EPA, state and tribal researchers from about 2,000 sites across the country.

biocon
National Rivers and Stream Assessment. Biological condition of the nation’s rivers and streams, based on the Macroinvertebrate Multimetric Index (EPA/NRSA).

Indicators Evaluated for NRSA

Biological Indicators

  • Benthic macroinvertebrates
  • Periphyton (algae)
  • Fish community

Chemical Indicators

  • Phosphorus
  • Nitrogen
  • Salinity
  • Acidity

Physical Indicators

  • Streambed sediments
  • In­stream fish habitat
  • Riparian vegetative cover
  • Riparian disturbance

Human Health Indicators

  • Enterococci (fecal indicator)
  • Mercury in fish tissue

The following are excerpts from EPA report:

Runoff Contaminated by Fertilizers

  • Nitrogen and phosphorus are at excessive levels. Twenty-seven percent of the nation’s rivers and streams have excessive levels of nitrogen, and 40 percent have high levels of phosphorus. Too much nitrogen and phosphorus in the water—known as nutrient pollution—causes significant increases in algae, which harms water quality, food resources and habitats, and decreases the oxygen that fish and other aquatic life need to survive. Nutrient pollution has impacted many streams, rivers, lakes, bays and coastal waters for the past several decades, resulting in serious environmental and human health issues, and impacting the economy.

Decreased Vegetation Cover and Increased Human Disturbance

  • Streams and rivers are at an increased risk due to decreased vegetation cover and increased human disturbance. These conditions can cause streams and rivers to be more vulnerable to flooding, erosion, and pollution. Vegetation along rivers and streams slows the flow of rainwater so it does not erode stream banks, removes pollutants carried by rainwater and helps maintain water temperatures that support healthy streams for aquatic life. Approximately 24 percent of the rivers and streams monitored were rated poor due to the loss of healthy vegetative cover.

[Whopping] Increase in Bacteria Levels.

  • Increased bacteria levels. High bacteria levels were found in nine percent of stream and river miles making those waters potentially unsafe for swimming and other recreation (samples exceed an enterococci threshold level for protecting human health.)

Increased Mercury Levels

  • Increased mercury levels. More than 13,144 miles of river lengths (streams were not evaluated) have fish with mercury levels that may be unsafe for human consumption. For most people, the health risk from mercury by eating fish and shellfish is not a health concern, but some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child’s developing nervous system.

NRSA Sample Sites

NRSA sample sites
National Rivers and Stream Assessment Sample Sites.

Related Links

water-pollution.JPG
“Troubled Waters” by U.S. PRIG

Posted in Global Disaster watch, global disasters, global disasters 2013, Significant Event Imagery, significant events | Tagged: , , , , , , , , , , , , , , , , | Leave a Comment »

Ocean Deserts Source of GHG

Posted by feww on March 12, 2010

Dead zones contribute to climate change

Hypoxic Waters Elevate Greenhouse Gasses in the Atmosphere

A University of Maryland Center for Environmental Science oceanographer says  that the increased amount of nitrous oxide (N2O) produced in aquatic dead zones, low-oxygen (hypoxic) waters, increases concentrations of the potent GHG in the atmosphere, worsening the impacts of global warming and contributing to the widening of ozone “holes” that allow harmful UV radiation through.

Eutrophication in the Sea of AzovEutrophication is caused by human activity. (Source: NASA).

“As the volume of hypoxic waters move towards the sea surface and expands along our coasts, their ability to produce the greenhouse gas nitrous oxide increases,” explains Dr. Codispoti of the UMCES Horn Point Laboratory. “With low-oxygen waters currently producing about half of the ocean’s net nitrous oxide, we could see an additional significant atmospheric increase if these ‘dead zones’ continue to expand.”

N2O, a highly potent greenhouse gas, is present in minute concentrations in Earth’s atmosphere, and is now a major factor in the destruction of the stratospheric ozone layer. “For the past 400,000 years, changes in atmospheric N2O appear to have roughly paralleled changes in carbon dioxide CO2 and have had modest impacts on climate, but this may change. Just as human activities may be causing an unprecedented rise in the terrestrial N2O sources, marine N2O production may also rise substantially as a result of nutrient pollution, warming waters and ocean acidification. Because the marine environment is a net producer of N2O, much of this production will be lost to the atmosphere, thus further intensifying its climatic impact,” a UMC news release said.

As dissolved oxygen levels decline in coastal waters, the N2O production increases. “Under well-oxygenated conditions, microbes produce N2O at low rates. But at oxygen concentrations decrease to hypoxic levels, these waters can increase their production of N2O.”

Shallow suboxic and hypoxic waters produce high rates of N2O “because respiration and biological turnover rates are higher near the sunlit waters where phytoplankton produce the fuel for respiration.”

“When suboxic waters (oxygen essentially absent) occur at depths of less than 300 feet, the combination of high respiration rates, and the peculiarities of a process called denitrification can cause N2O production rates to be 10,000 times higher than the average for the open ocean. The future of marine N2O production depends critically on what will happen to the roughly ten percent of the ocean volume that is hypoxic and suboxic.

“Nitrous oxide data from many coastal zones that contain low oxygen waters are sparse, including Chesapeake Bay,” said Dr. Codispoti. “We should intensify our observations of the relationship between low oxygen concentrations and nitrous oxide in coastal waters.”

The article “Interesting Times for Nitrous Oxide” appears in the March 12, 2010 edition of the journal Science.

University of Maryland Center for Environmental Science

Related Links:

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