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The Honolulu Advertiser
Posted on: Sunday, August 25, 2002

Growing algae blooms raise fear of ocean change

 •  Waikiki volunteers skim invasive limu

By Carl Weiser
Gannett News Service

WASHINGTON — Along the coast of Kenya this spring, a deadly red tide of algae killed so many sharks, tuna and eels that fishermen had trouble pushing their boats through the water.

Volunteer divers and snorkelers removed hundreds of pounds of alien algae yesterday off Waikiki, where the seaweed covers the reef, blocks sunlight and threatens native plants and animals.

Cory Lum • The Honolulu Advertiser

In the Mediterranean, fernlike algae blanket hundreds of miles of sea floor, replacing most other life forms and creating a marine desert.

Off the coast of Florida this spring, 27 manatees died as a result of exposure to "red tide," an algae blooms that turned the water red.

And last fall, Pfiesteria — the mysterious, potentially toxic microbe that once invaded Chesapeake Bay tributaries — was discovered in an Australian river.

Scientists fear that something odd is happening in the world's waters, specifically to one of the world's most ubiquitous organisms: algae.

Giant masses of algae, called blooms, are bigger and more frequent. They're appearing in places they've never been and staying longer.

No one is sure of the cause, but scientists offer several suspects: shipping, which carries algae to new homes in ballast water; global warming, which creates a more nurturing environment for them; and pollution draining into the oceans from coastal development and farmland, which provides nutrients.

"People assumed oceans were so vast they would dilute whatever impacts we had on them," said Donald Scavia, chief scientist for the federal government's National Ocean Service. "They're finding out that's not the case."

Algae, the plants of the ocean, are vital to life. They are the chief food source for fish and produce 30 to 50 percent of the planet's oxygen. Most of the 25,000 species are harmless. Some are used as thickeners and colorants.

But some emit poisons. And in massive blooms, many species can harm plants, animals and people.

Algae-produced toxins can trigger breathing difficulties and damage skin. The most comprehensive report yet from the world's top ocean scientists, the April 2001 GEOHAB report, concluded that algae had poisoned at least 2,000 people and killed "several hundred" around the world. Most deaths are from eating algae-contaminated shellfish.

Algae has its biggest impact on the fishing and tourism industries. It can kill fish and the underwater grasses that shelter them. When an algae bloom dies after a few days or weeks, the algae sink to the bottom. The bacteria that feed on it then use up most or all of the available oxygen.

Reports of algae-caused fish kills, such as the one in summer 2000 in a canal in Rehoboth Beach, Del., have become more common.

Gannett News Service

A 2000 study from the Woods Hole Oceanographic Institution estimated the cost to the U.S. economy from harmful algal blooms at $49 million a year in lost tourism, fishing, and health costs.

Algae blooms are nothing new. Capt. James Cook complained in a 1770 log entry of "brown scum" on the sea.

But scientists have seen the bizarre blooms, fish deaths and algae-caused shellfish poisonings escalating worldwide. A 1999 conference of U.S. and Canadian health officials, scientists and fisheries experts centered on "Harmful Algal Blooms: The Encroaching Menace."

Many scientists suspect the primary cause to be pollution from farm animals, fertilizer and increased coastal development. Such waste is a smorgasbord to algae — and they've had quite a buffet in recent years.

In the 15 years from 1985 to 2000, the amount of inorganic nitrogen fertilizer applied to crops was equivalent to the amount used on the planet until then, according to the National Research Council, an independent group of scientists who advise the government. Examining 139 coastal areas, the council found 44 with "severely" high levels of nitrogen and phosphorus that algae feed on, including the Gulf of Mexico and the Mid-Atlantic coast.

Several California university scientists found that urea, which is in urine and urban runoff, may have helped spur a 1995 algae bloom that stretched 500 miles, from Mexico's Baja peninsula north to Monterey Bay in northern California.

But algae outbreaks also have occurred in places where pollution is minimal. And blooms thought to be pollution-related turned out to be the result of coastal currents carrying algae from one spot to another. Satellite photos have tracked Saharan dust clouds to the West Florida coast, where the iron-rich particles spurred blooms of Trichodesmium, a red tide algae.

Some types of algae are simply being discovered — or once rare forms have "found their day in the sun," said Donald M. Anderson, who runs the National Office for Marine Biotoxins and Harmful Algal Blooms at Woods Hole.

Other explanations:

  • Global warming. Climate change moves warmer water, and algae, farther north. Severe storms caused by climate change also can replant algae around the world.
  • Global shipping. Ships take in water as ballast in their home port and release it, with thousands of organisms, at their destination.
  • Natural selection. Like all species, algae are evolving and adapting. Mutations cause new forms of algae to multiply.

Scientists are generally pessimistic about controlling the blooms, since coastal development is increasing, pollutants continue to flow into estuaries, and governments are slow to take action to curb pollution.

In the aftermath of the Pfiesteria outbreak in the Mid-Atlantic, Congress in 1998 passed the Harmful Algal Bloom and Hypoxia Research and Control Act, which essentially calls for a series of studies and strategic plans.

An October 2000 report required by the law contained the usual dire warnings — that blooms were found in almost every coastal state, are increasing and causing ecological and economic havoc and sometimes death. The report also noted there were virtually no studies on how to prevent or control blooms.

"I'm afraid I see them increasing," Anderson said. "It's very likely we will keep discovering new toxic species."