Startling Increase in Number of Ocean Dead Zones

The United Nations released a report Thursday saying that scientists have discovered that the number of "dead zones" in the world’s oceans has increased dramatically in the last two years. These zones are places in the deep seas where pollution threatens fish and other marine life, as well as the people who depend on them for food.

A team of researchers led by Robert Diaz, a marine scientist at the College of William and Mary in Williamsburg, VA, found new dead zones at numerous locations, including the Fosu Lagoon in Ghana; the Mersey River estuary in Britain; the Archipelago Sea in Finland; the Pearl River estuary and Changjiang River in China; the Aegean Sea in Greece; the Montevideo Bay in Uruguay; and in the western Indian Ocean. The number of zones found shows a 34% jump in the total number of dead zones in just the past two years.

"It seems like a big jump in two years," said Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium. She said that an important factor has been the increase in pollution from countries around the world that have been developing rapidly and becoming more industrialized in recent years.

Rabalais was not part of the UN’s research effort, but she has studied the Gulf of Mexico’s dead zone, a tremendous area about the size of New Jersey. Rabalais said that marine creatures can usually escape from the perils of a dead zone if they can swim fast enough. "The things that are left behind are the ones that usually can’t survive," she said. "When you consider the size of some of these areas, it's removing what's considered the essential habitat for fishes and crustaceans."

Most of the world’s dead zones are caused by pollution-fed algae, because it deprives living marine life of oxygen. Scientists blame pollutants such as fertilizer, farm run-off, sewage, and the burning of fossil fuels for most of the world’s dead zones, which cover tens of thousands of square miles of water throughout the world. Pollutants contain excessive amounts of phosphorous and nitrogen, and such nutrients cause explosive blooms of tiny plants called phytoplankton. When those tiny plants die, they sink to the bottom of the sea, where they are eaten up by bacteria, which use up the oxygen in the water.

The UN’s marine experts said that the number and size of oxygen-deprived zones in the oceans has grown each decade since the 1970s. "The low levels of oxygen in the water make it difficult for fish, oysters and other marine creatures to survive as well as important habitats such as sea grass beds," UN officials said. "These areas are fast becoming major threats to fish stocks and thus to the people who depend upon fisheries for food and livelihoods."

One tiny bit of good news contained in the UN’s report was that there is some hope for the recovery of damaged coral reefs, which act like nurseries for the creatures in the ocean. UN scientists determined that reefs bleached in the late 1990s by high surface sea temperatures are affected by how polluted the waters are. "Coral reefs recovering faster are generally those living in marine protected areas and coastal waters where the levels of pollution, dredging and other kinds of human-induced disturbance are considered low," the UN said.

So if pollution control efforts continue, those coral reefs will continue to recover. However, the dead zones will most surely continue to expand. UN research has determined that by 2030, the world’s rivers will be pumping 14% more nitrogen into seas and oceans than that found in the mid-1990s.