Pollution, urban sprawl and over-fishing are depleting marine life in U.S. coastal waters, according to a report released this month by the Pew Oceans Commission.

"For centuries we have viewed the oceans as beyond our ability to harm and their bounty beyond our ability to deplete," commission chief Leon Panetta, a former congressman and chief of staff to President Clinton, said. "We now know that this is not true."

How oceans are polluted

The largest threat to marine life, according to the report, stems from land runoff. Land runoff is a process in which contaminants, such as pesticides from farmland or chemicals from industrial areas, leak into the ground, flow into nearby rivers and streams and then wash into oceans.

Pollution from city streets and backyards also finds its way into coastal waters. Every eight months, more than 10 million gallons of oil from streets and driveways flows into U.S. oceans, the study says.

When toxic pollutants leak into the ocean they can damage the reproductive systems of fish.

For humans, polluted oceans can add up to contaminated seafood and fewer places to swim. More than 13,000 beaches were closed in 2001 because of pollution advisories.

The study cited urban sprawl -- or over-development of urban areas -- global warming, and over-fishing among its other areas of concern. About 50 percent of the U.S. population live within 50 miles of the coast, and widespread fishing methods such as bottom-scraping nets can damage marine habitats, the study says.

In the Gulf of Mexico off the coast of Florida, an area once abundant with fish species, lack of oxygen related to run-off pollution has created a "dead zone" the size of the state of Massachusetts, according to the report.

What the government can do

The commission -- made up of 18 scientists, environmentalists and government representatives -- studied 4.5 million square miles of ocean over three years. Members blamed the federal government for doing too little to protect the oceans and coastal areas.

The commission's members recommended that Congress revise and strengthen pollution laws, including regulations that limit the amount of fish commercial fishermen can catch.

It also suggested that the National Oceanic and Atmospheric Administration, or NOAA, an office of the U.S. Department of Commerce, become independent and open up more field offices.

The government has also created a panel, the U.S. Commission on Ocean Policy, which will examine the state of the nation's oceans. The panel is expected to release its own report with recommendations later this summer.