HSIAsia >>Marine Mammals >>

Marine Pollution and Habitat Degradation

Pollution poses a threat to marine mammals in many forms. Plastic debris, including the ubiquitous beverage six-pack rings, can become entangled around the snouts and necks of seals and sea lions, preventing proper breathing and feeding. Razor-thin nylon fishing lines slice off flukes and fins of whales and dolphins who have become entangled in them.

Oil spills, such as the horrific 1989 Exxon Valdez spill in Prince William Sound, Alaska, and the even more massive 2002 Prestige spill off the coast of Spain, may kill and injure hundreds or even thousands of marine mammals and birds. Direct damage includes the oiling of fur and feathers, which destroys their insulating properties; injury to internal organs through ingesting oil, especially as a result of cleaning it off fur or feathers; and pneumonia from inhaling it, especially in the case of whales and dolphins, who may inhale air through the oil slick at the surface of the water. Finally, a frequently overlooked threat to marine mammal populations is habitat destruction from oil spills that occur as side effects of other events; for example, acres of sea-grass beds vital to dugongs (relatives of the manatee) were destroyed in the Persian Gulf after the United States military operation Desert Storm.

Bottlenose dolphins, beluga whales, manatees, polar bears, and other marine mammals are threatened by industrial pollution (from sources such as heavy metals, PCBs and other organic pollutants) and the destruction of coastal habitats by agricultural runoff and other forms of environmental degradation. The large-scale die-off of bottlenose dolphins along the mid-Atlantic coast of the United States in the mid-1980s may have been the direct or indirect result of increasing levels of toxic waste from industrial sources in these waters. Such pollutants can depress the immune system of marine mammals, making the animals susceptible to diseases they could normally fight off. Polar bears in Svalbard, Norway, are exhibiting serious congenital abnormalities, the result of exposure to toxic pollutants in their otherwise pristine environment. These pollutants have apparently circulated to the Arctic from distant sources in Europe.

Marine mammals are also threatened by increasing vessel traffic. A prime example is the threat facing manatees in Florida as growing numbers of high-speed boats take to coastal waterways. These vessels often strike these slow-moving, surface-dwelling herbivores, scarring them for life or killing them. Right whales, the most endangered great whale species in the ocean, are also threatened by ship strikes. Their slow, surface-foraging behavior makes them highly susceptible to collisions in the busy shipping lanes of the North American Atlantic coast, their preferred habitat.