Exercise 7. Read and translate text

Effects of Oil Pollution

The effects of oil spills are difficult to predict because they depend on a number of factors, including the type of oil spilled (crude or refined), amount, distance of the spill from shore, time of a year, weather conditions, and ocean and tidal currents. Crude oil. refined oil are collections of hundreds of substances with widely different properties. After an oil spill, low-boiling aromatic hydrocarbons are the primary causes of the immediate killing of a number of aquatic organisms, especially in their larval forms. Fotunately, most of these toxic chemicals evaporate into the atmosphere within a day or two. Some other chemicals remain on the surface and form small, floating, tarlike globs. These floating subxtances are gradually broken down by bacteria over several weeks or months, although they persist much longer in cold polar waters.

Floating oil can coat the feathers of marine birds, especially diving birds, and the fur of marine mammal such as seals and sea otters. This oily coating destroys the animals natural insulation and buoyancy, and most of them drown or die of exposure from loss of body heat. It is estimated that nearly 150,000 - 450,000 marine birds in the North Sea and the North Atlantic regions are killed each year by chronic oil pollution, mostly from routine tanker releases.

Heavy oil components that sink to the ocean floor or wash into estuaries are believed to have the greatest long-term impact on marine ecosystems. These components can kill bottom-dwelling organisms such as crabs, oysters, mussels and clams or make them unfit for human consumption because of their oily taste and smell.

Oil slicks that wash onto beaches can have serious economic effects on coastal residents, who lose income from fishing and tourist activities. Oil-polluted beaches washed by strong waves or currents are cleaned up fairly, but beaches in sheltered areas remain contaminated for several years. Oil clean-up is very expensive for oil companies and coastal communities.

Studies of the effects of several crude oil spills in the open sea between 1989 and 1998 found that most forms of marine life recovered nearly completely within 3 years. In contrast, spills of oil, especially refined oil, near shore or in estuarine zones, where sea life is most abundant, have much more damaging and long-lasting effects. For example, damage to estuarine species from 1989 spill of refined oil at West Falmouth, Massachusetts, was still being detected 10 years later.