MIAMI (Reuters) - A tidal wave of man-made trash is threatening world oceans, damaging wildlife, tourism and seafood industries and piling additional stress on seas already hit by climate change, conservationists said on Tuesday.

A report by U.S.-based Ocean Conservancy detailed what it called a “global snapshot of marine debris” based on itemized records of rubbish collected by nearly 400,000 volunteers in 104 countries and places in a single day in September 2008.

Close to 7 million pounds (3.2 million kg) of trash -- the weight of 18 blue whales -- was collected from oceans, lakes, rivers and waterways in the 2008 cleanup, the group said in its report “A Rising Tide of Ocean Debris and What We Can Do About It”.

It warned of a “tidal wave of ocean debris,” calling it a major pollution problem of the 21st century.

Topping the list of the 11.4 million items of trash collected were cigarette butts, plastic bags, and food wrappers and containers. In the Philippines alone, 11,077 diapers were picked up and 19,504 fishing nets were recovered in Britain.

“Our ocean is sick, and our actions have made it so,” Vikki Spruill, president and chief executive of Ocean Conservancy, said in a statement accompanying the report.

“We simply cannot continue to put our trash in the ocean. The evidence turns up every day in dead and injured marine life, littered beaches that discourage tourists, and choked ocean ecosystems,” she said.

“By changing behaviors and policies, individuals, companies, and governments can help improve the health of our ocean, the Earth’s life support system.”

The full report, including a country-by-country Marine Debris Index, was published at www.oceanconservancy.org.

ANIMALS KILLED, TOURISM HURT

Detailing how refuse poisoned oceans and waterways, the report said the waste entered the food chain, injured beachgoers and weakened economies by sapping precious dollars from tourism and seafood industries.

Thousands of animals, including marine mammals, sea turtles, seabirds and others, choked or were poisoned each year by eating trash, or drowned when they became entangled in bags, ropes and old fishing gear.

The 2008 cleanup volunteers found 443 animals entangled or trapped by marine debris, releasing 268 alive.

“Keeping our ocean free of trash is one of the easiest ways we can help improve the ocean’s resilience as it tries to adapt to the harmful effects of climate change such as melting ice, rising sea levels, and changing ocean chemistry,” Ocean Conservancy said.

It recommended public and private partnerships to monitor and reduce marine trash and increased funding for research on the problem. A policy of “reduce, reuse, recycle” would help lower trash levels, combined with technological solutions.

“Trash doesn’t fall from the sky, it falls from our hands,” Spruill said. “Humans have created the problem of marine debris, and humans should step up and solve it.”

Ocean Conservancy said its next International Coastal Cleanup would be held around the world on September 19.