Planet ocean: could the vast ocean, which covers more than 70 percent of Earth's surface, be immune to human threat? Don't bet on it!

Could the vast ocean, which covers more than 70 percent of Earth's surface, be immune to human threat? Don't bet on it!

The symptoms are hard to ignore: dead marine animals washing up on beaches; toxic microbes proliferating along coastlines; fewer fish piling up in nets. Diagnosis: an ocean in crisis.

The Earth's billions of inhabitants rely heavily on the ocean. This enormous body of water provides humans with food, fossil fuels, climate control, and recreation.

"There are very few global issues, even poverty, that are not linked to the oceans," says Geoffrey Holland of the United Nations Educational, Scientific, and Cultural Organization (UNESCO).

So when scientists detected early signs of ocean distress, they dove into action. This year, which has been designated the International Year of the Ocean by the United Nations, policy makers from around the world plan to tackle several major marine issues. Among them: overfishing and water pollution.

WHERE ARE THE FISH?

Around the world, some species of fish are in danger of dying out due to overfishing (see map). That's bleaks news, considering that 5 percent of the total protein in the human diet comes from seafood. Last year, each American on average ate 6.8 kg (15 lb) of seafood.

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To meet the public's huge demand for seafood, commercial fishers cast their nets and trawl (drag nets along the seafloor) the oceans to extremes. Problems arise when fishers catch too many "young" fish from a particular species, explains Gordon Helm of the National Marine Fisheries Service (NMFS). With fewer juvenile fish in the ocean, the chance of species to reproduce themselves decreases.

Some sharks, for example, take 7 to 11 years to mature and give birth to only one or two pups every few years. The popularity of sharks as a delicacy in Asia drives fishers to nab numerous sharks before they can reproduce. Result: Some shark species have lost 80 percent of their populations over the past 10 years.

Equally in danger are cod, flounder, and red snapper. These fish are currently overfished in some parts of the U.S., thanks to high-tech fishing methods. Sonar arrays on commercial trawlers, for instance, use sound waves to track fish in water. These sonars alert onboard computers, which steer ships to follow large schools of fish. Then, a fishing net big enough to swallow the Statue of Liberty herds in the fish. "Better gear makes it possible to catch more fish more easily," Helm explains.

How can scientists tell if a stock is overfished? They count fish. Of course, counting fish that swim in the ocean isn't as easy as counting cattle that graze in a field. So the NMFS relies on reports of catches made by commercial and recreational fishers, as well as by scientists who trawl for fish stocks. The NMFS then compares these numbers with those from previous years to determine if the populations of certain species have declined.

Overfishing a stock is now illegal in the U.S., thanks to a law passed in 1996. To restore depleted stocks, the NMFS restricts the kind of fishing gear that can be used, imposes quotas on the number of fish that can be caught, and even closes fisheries during spawning seasons (when fish lay their eggs) to allow stocks to reproduce. The U.S. can enforce the overfishing law only in waters within 322 km (200 mi) of U.S. shores. Since fish inevitably travel into international waters, several countries are now negotiating treaties to protect migrating species, like the swordfish.

DIRTY WATER

While overfishing is one reason for the decline in fish populations, experts also point the finger at another culprit: polluted runoff, or non-point-source pollution.

Unlike point-source pollution, which can be traced directly to a single source like a sewage treatment plant, non-point-source pollution may come from sources that are not easily identified, explains Peyton Robertson of the National Ocean Service in Maryland.

All over the country, for example, people spray farms, lawns, and gardens with fertilizer. When it rains, chemicals from those fertilizer run off into rivers and streams. Next stop: the ocean.

Just as nitrogen in fertilizers spurs the growth of plants on land, it fuels the growth of small plants, called algae, in the ocean. When algae blooms die and sink to the ocean floor, they decay and rob the water of oxygen. Result: fish can die.

Fish aren't the only victims. If you love to frolic on the beach, runoff is a problem for you, too. In the past few years, some beaches across the country, including those in Long Island, New York, and San Diego, California, were shut down for days because non-point-source pollution made the ocean unsafe for swimming. Several tributaries in Chesapeake Bay, Maryland, were also placed off-limits because a deadly microbe called Pfiesteria piscicida (pronounced FEAST-ihr-yuh pes-kee-SEE-duh), which kills fish and causes health problems in humans, multiplied in the nitrogen-rich waters (see SW 10/20/97, p. 4).

Recently, President Clinton announced plans to combat non-point-source pollution by reducing runoff from farms and city streets. One plan is to compensate farmers for planting protective forests and grasslands that will absorb runoff before it reaches rivers, streams, and, ultimately, the ocean.