In the Lab
Researcher Probes Dead Zone, Mysterious Loss of Marine Life
Lurking in the water near the Mississippi River delta area, where the United States' largest river empties into the Gulf Coast, is death. And while it has the same name as a Stephen King novel, this dead zone offers a different brand of horror.
In its oceanic context, a dead zone is an aptly named, oxygen-starved area of water where almost nothing can live, where all fish, clams, lobsters, oysters, and other inhabitants suffer death by suffocation, and where future marine life may never have a chance. The zones range in size from just a few square miles to more than 45,000 square miles. And they are spreading.
Scientists say there are more dead zones being created now than ever before. In its global overview statement issued March 29, the United Nations Environment Program (UNEP) reported that dead zones top the list of the planet's emerging environmental challenges, warning that they pose as big a threat to fish stocks as overfishing.
The dead zone near the Mississippi River delta area stretches for some 7,000 square miles off the coast of Louisiana and is one of almost 150 dead zones around the globe, twice as many as there were in 1990. The main cause of these often vast expanses of ocean devoid of life, it is believed, is excess nitrogen and phosphorus runoff from farm fertilizers, sewage, and industrial pollutants. The chemicals trigger blooms of microscopic algae, or phytoplankton. Some studies have shown that as little as one pound of phosphorous can cause 500 pounds of algae. As the algae die and rot, they consume oxygen, thereby suffocating the marine life unable to flee the zone's grasp.
Dr. Antonietta Quigg of Texas A&M University at Galveston is testing that theory, basing her research on the dead zone that starts where the Mississippi empties into the Gulf of Mexico and studying a combination of biological, chemical, and physical interactions there that may or may not be triggered by fertilizer runoffs. Her work is part of two three-year studies funded by the National Oceanic and Atmospheric Administration.
"Levels of nitrogen in Gulf waters are especially high in the spring and summer, when fertilizers are most frequently used," Quigg said. "We sill have a lot of work to do, but it looks like fertilizer runoffs remain the culprit in helping create this large dead zone."
Quigg will closely examine bacteria found in the area to see if the suspected agents found in fertilizers are currently there. Because spring is peak fertilizing time for many farmers and ranchers all along the Mississippi River, which drains 40 percent of the country?s land area, the suspected runoff of the chemicals into the Gulf Coast area should be reaching a climax right about now.
"We will look at the nutrients in the water in the dead zone area, look at the water color, and examine the bacterial communities," Quigg said. "We want to determine what specific biological activities are going on there -- and their interactions with the chemical and physical environment. Whatever is happening is causing a large amount of marine life to die."
Because it has created a quick-acting dead zone, the Mississippi River delta area has become one of the most famous dead zones in the world, but other recent ones have occurred in South America, Japan, China, and Australia, according to the UNEP report.
"Dead zones seem to have one thing in common, and it's that they're getting bigger," Quigg said. "In our study, we hope to find some definitive answers on what is causing the dead zone in the Mississippi River delta area."
For more information, visit www.tamug.edu or www.unep.org .
Scientists Confirm That Air Pollution Contributes to Heart Disease
The very air we breathe may be killing us. Some scientists have long suspected that air pollution is dangerous for the human heart, but previous studies on the issue have been flawed, according to the American Heart Association (AHA). However, in a scientific statement released June 1, AHA asserts that air pollution is indeed a heart disease risk factor.
"The increase in relative risk for heart disease due to air pollution for one person is small compared with the impact of the established cardiovascular risk factors, such as high blood pressure or high cholesterol. However, this is a serious public health problem due to the enormous number of people affected and because exposure to air pollution occurs over an entire lifetime," said Robert D. Brook, M.D., lead author of the statement published in Circulation: Journal of the American Heart Association and assistant professor of medicine at the University of Michigan in Ann Arbor.
The association's experts conducted a comprehensive review of the literature on air pollution and cardiovascular disease and drew several conclusions:
1. Prolonged exposure to elevated levels of particle pollution is a factor in reducing overall life expectancy by a few years.
2. Short-term exposure to elevated levels of particle pollution is associated with an increased risk of death due to a cardiovascular event.
3. Hospital admissions for several cardiovascular and pulmonary diseases are increased in response to higher concentrations of particle pollution.
The panel recommends that people with heart disease or cardiovascular risk factors, diabetes, or pulmonary diseases limit outdoor activities when pollution is high, per U.S. Environmental Protection Agency Air Quality Index recommendations.
The AHA statement notes that more research is needed to determine the biological factors that may contribute to heart disease and identify the toxicities of various air pollutants.
"In addition, we hope that these conclusions will provide further support to the importance of the present-day air quality standards," Brook said.
For more information, visit www.americanheart.org.
This news item originally appeared in the July/August 2004 issue Environmental Protection, Vol. 15, No.7.
This article originally appeared in the 07/01/2004 issue of Environmental Protection.