Researchers predicting large Gulf of Mexico dead zone

19 June 2013 21:55  [Source: ICIS news]

HOUSTON (ICIS)--Researchers working with the National Oceanic and Atmospheric Administration (NOAA) said Wednesday that based on estimate models, the 2013 seasonal Gulf of Mexico hypoxic zone could be record-size. This "dead zone" is a result of the heavy rains and subsequent flooding in the Midwest.

The concern is that the excessive rains, which have hit a majority of the key corn-growing regions this spring, will cause an increase in nitrogen-based fertilizer to run off into the ocean waters. The released nitrogen encourages the rapid growth of algal blooms, which sink to the ocean floor where bacteria will decompose the organic matter.

At the same time, the bacteria consumes the oxygen and thereby results in hypoxic, which is low-oxygen, or anoxic, oxygen-free, conditions. The dead zone typically appears in the summer as there is less mixing of currents.

NOAA modelers at the University of Michigan, Louisiana State University, and the Louisiana Universities Marine Consortium are forecasting that this year's dead zone will be between 7,286 and 8,561 square miles (11,726 and 13,778 sq km), which could place it among the 10 largest recorded. The high estimate would exceed the largest ever reported, 8,481 square miles in 2002.

The forecast is based on the assumption that there would be no significant tropical storm activity in the two weeks preceding or during the official measurement period scheduled from 25 July to 3 August. NOAA said a storm could drop the size of the zone to a low of 5,344 square miles.

First documented in 1985, the dead zone has consistently covered about 6,000 square miles off the coast of Louisiana and impacts sea life as it forces the populations of fish and other shellfish to relocate or die. The dead zone has had financial repercussions for the commercial fishing industry.

“Monitoring the health and vitality of our nation’s oceans, waterways and watersheds is critical as we work to preserve and protect coastal ecosystems,” said Kathryn D. Sullivan, acting NOAA Administrator.

Researchers have primarily placed the blame on farmland run-off, namely what they view as the overuse of fertilizers in the Corn Belt, as the main culprit with some fault for the size and severity allowed for weather conditions such as wind direction and water temperature.

According to the US Geological Survey it is estimated that 153,000 metric tons flowed into the Gulf during the month of May, which is a 16% increase in the annual nutrient load average.

"Long-term nutrient monitoring and modeling is key to tracking how nutrient conditions are changing in response to floods and droughts and nutrient management actions," said Lori Caramanian, deputy assistant secretary of the interior for water and science.

"Understanding the sources and transport of nutrients is key to developing effective nutrient management strategies needed to reduce the size of hypoxia zones in the gulf, bay and other U.S. waters where hypoxia is an ongoing problem."

Some critics of fertilizer practices in the US have urged farmers to discontinue fall applications and instead wait until spring plantings as well as devising means to control water spilling from the fields into the rivers that feed hundreds of miles downstream into the ocean.

According to research data, the amount of nitrogen entering the Gulf has increased by about 300% since the 1960’s with agricultural run-off suspected in increasing those levels as domestic production has been expanded over the years as well as the advancement of fertilizer applications.

A state and federal task force in 2008 released a goal to reduce the zone to less than 2,000 square miles by 2015, but significant progress has not yet been achieved. Since 1995, the zone has averaged 5,960 square miles.

“The size of the Gulf dead zone goes up and down depending on that particular year’s weather patterns. But the bottom line is that we will never reach the action plan’s goal of 1,950 square miles until more serious actions are taken to reduce the loss of Midwest fertilizers to the Mississippi river system, regardless of weather,” said Donald Scavia, University of Michigan aqua ecologist.

Because of the drought, NOAA said the 2012 zone was the fourth-smallest on record, approximately 2,889 square miles. The agency said the confirmation of the 2013 hypoxic zone will be released in August following its surveying operation.

By: Mark Milam
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