The vast majority of the nation's estuarine waters suffer from excess nutrients, and most are predicted to worsen by 2020 as populations in coastal areas continue to swell, according to a recent report.
The report from the National Oceanic and Atmospheric Administration also showed that the mid-Atlantic region-including the Chesapeake Bay-was the most impacted area of the nation's coastline.
It was an update of a 1999 assessment, and while it found relatively little change in conditions over the last decade, it predicted coastal conditions will worsen in the future.
"What these results show is that we are just holding the line against nutrient-related degradation," said Suzanne Bricker, of NOAA's Center for Coastal Monitoring and Assessment, and the report's lead author. "Holding the line in the future is a daunting task in light of continued increases in coastal population that are expected."
For the systems with enough information to make future projections, the report acknowledged a "bleak outlook," predicting eutrophic conditions would worsen in 48 systems, stay the same in 11, and improve in only 14 systems by 2020.
The report illustrates that the problems that plague the Bay-excess nitrogen and phosphorus-are becoming more widespread among the nation's estuaries. Estuaries are highly productive ecosystems where fresh and salt waters meet. Their condition is considered a key indicator of overall coastal water quality.
(A recently completed analysis for the World Resources Institutes by Robert Diaz, of the Virginia Institute of Marine Science found worsening low-oxygen conditions near coasts globally.)
The NOAA report said that two thirds of the 141 systems assessed, representing 78 percent of the total area covered by the assessment, had moderate to high levels of eutrophication.
Overall, the top sources of pollution were agriculture, wastewater treatment plants, urban runoff and atmospheric deposition.
Symptoms of eutrophication included high concentrations of chlorophyll a, (a measure of algae growth); loss of underwater grasses; frequent nuisance or toxic algal blooms; macroalgae; and low levels of dissolved oxygen.
Eutrophication takes a toll in many ways. It leads to fish kills, nuisance algae blooms and reduced fishery landings. Declines in tourism may result when floating algal mats ruin the aesthetics of an area, or when toxins from algal blooms accumulate in fish and shellfish.
The mid-Atlantic region, which stretches from the Chesapeake Bay through Cape Cod, was the most severely impacted region. The reasons were high nutrient inputs and that estuaries in the region tend to be highly effective at trapping nutrients.
The prognosis of the Bay was mixed.
Of nine areas of the Bay that were assessed, four were considered worse than they were in 1999: the Chester, Choptank, Rappahannock and James rivers. Five others were unchanged: the Patuxent, York and Potomac rivers, as well as Tangier/Pocomoke sounds and the Bay's mainstem.
Looking to the future, the report predicted small improvements in the Chester and Choptank rivers and the mainstem of the Chesapeake. It predicted small deterioration in the Potomac and Patuxent rivers and the Pocomoke/Tangier sound. It predicted no change for the Rappahannock, York and James rivers.
Nationwide, few systems have significantly improved, the report said. All of the improvements came in places where discharges were aggressively controlled, such as Tampa Bay and Boston Harbor.
Areas where pollution sources were dominated by runoff from agriculture or development have generally remained unchanged or worsened.
Mark Rey, undersecretary for natural resources and environment at the U.S. Department of Agriculture, said progress is being made to reduce nutrient pollution on farms throughout the nation, but that it takes years for actions on the land to be felt far downstream.
"The good news is that nitrogen loss from farmers' fields is falling so we are making progress," he said. "The bad news is that this nitrogen reduction from the field has not yet translated into an immediate reduction in nitrogen loads reaching many estuaries. We know that Farm Bill programs are making a difference, but that difference will take more time to manifest."
Donald Boesch, president of the University of Maryland Center for Environmental Science, which cooperated on the report, said stepped-up monitoring is needed in watersheds to verify that actions taken on the ground are having intended results.
"We need to verify," he said. "We need to know whether the fact that we don't yet see results in the river and down in the coasts is due to the lag time, or that the [conservation] practices are not as effective as we thought they were."
"Arguably the most challenging problem is the reduction of nutrient pollution from agriculture," said Boesch, who has been heavily involved in coastal issues both in the Bay and in the Gulf of Mexico.
What is Eutrophication?
Eutrophication is a process in which the addition of nutrients (nitrogen and phosphorus) to waterbodies stimulates algal growth. Excessive nutrient inputs lead to serious problems.
When the excess algae die, they are decomposed by bacteria in a process that removes oxygen from the water, creating conditions harmful or lethal to aquatic life.
Algal blooms also cloud the water, causing the loss of underwater grasses that provide important habitat for fish, shellfish and waterfowl. Some algal blooms can consist of species that are toxic to fish and harmful to humans.
In recent decades, human activities such as sewage discharges and agriculture have greatly increased nutrient inputs, which is further exacerbated by rapid population growth in coastal areas.
Eutrophic conditions are worsened in estuarine systems, such as the Chesapeake, which effectively trap nutrients, preventing them from being easily diluted or flushed out of the system.
Low-oxygen conditions affecting coasts around the world
Nutrient pollution is leading to increasing numbers of coastal areas suffering from low-oxygen conditions worldwide, a trend likely to take an increasing toll on coastal ecosystems, according to a Virginia Institute of Marine Science researcher.
Robert Diaz, a professor of marine science at VIMS, reported in a 2003 paper that nearly 150 coastal areas around the globe suffered from hypoxia-oxygen conditions low enough to harm aquatic life.
In a recently completed analysis for the World Resources Institute, Diaz identified more than 300 areas-nearly double the 2003 number-that either definitely, or likely, suffer from low-oxygen conditions.
"That is something to be concerned about," said Diaz, who noted that many of the problems were in highly productive areas for fish.
Diaz's analysis comes as a new report from the National Oceanic and Atmospheric Administration warned of increasing eutrophic conditions in the nation's estuaries.
In addition, a team of researchers led by Nancy Rabalais, chief scientist for the Louisiana University Marine Consortium, reported finding a record 9,650 square miles of "dead zones" in the Gulf of Mexico this summer, the largest observed since scientists began tracking low-oxygen levels in the Gulf in 1985.
The primary cause is considered to be nutrient pollution from the Mississippi River basin.
Diaz's review shows nutrient problems are far from limited to the United States, or the Chesapeake Bay, where improving dissolved oxygen levels is a major focus of cleanup strategies.
His new report of studies worldwide found 161 areas where hypoxic conditions were documented, and another 175 "areas of concern" which likely have low-oxygen problems, but where data is limited.
"My guess is that the vast majority of the areas of concern are probably hypoxic," Diaz said.
The increase, he said, likely stemmed both from worsening conditions and the fact that more scientists are examining the condition of coastal waters and reporting their findings.
But even 300 is certainly an undercount-huge areas of the map he has compiled are blank, including almost all of India and Southeast Asia, where there is little or no information.
"There are probably a lot of bad areas, but the [governments there often don't] allow the reporting of bad things," Diaz said.
In contrast, he found only 13 areas that had improved, mostly in areas dominated by point source dischargers that have been brought under control.
"The common threat in all of these improved systems is the management of nutrients getting into the system," Diaz said.
"The other common thing is they are all highly urbanized estuaries where control of these point sources makes a big difference."
The only clear example of water quality improving as the result of reductions from runoff-or nonpoint sources-is in the Black Sea. The collapse of the Soviet Union-and its subsidized use of fertilizers-led to a dramatic nutrient reduction.
Diaz said that while overfishing was the "keystone" impact on oceanic ecosystems in the 20th century, he expects that oxygen depletion will be the main source of human disturbance to those systems this century because it can affect large amounts of habitat used by demersal fish-those that live near the bottom areas, which are most affected by low dissolved oxygen.
"The best way you can erode vast areas of habitat for demersal fish, and maybe even some water column species, is to make the place hypoxic," he said. "You can clearly get thousands of square kilometers on Earth to become hypoxic with the current strategies that municipalities and everybody else has of just allowing nitrogen to run into the sea."