Each year, more than 100 oil tankers offload oil in Portland, Maine. If a ship leaked or spilled while unloading or while navigating through the harbor, oil would wash up, become trapped, and coat everything on the shores of Casco Bay-shoreline, plants, and birds. Winds and currents intensify the severity of the spill, especially if they drive the spill onto shore. Today, many agencies cooperate in oil spill drills so they'll be ready to respond quickly in an emergency. By identifying color and temperature changes of the sea surface, satellites can spot oil spills as small as those left by a ship pumping its bilge.
Much of the damage from an oil spill occurs within the first ten days. After that, it may persist for several years. Over a long period of time, oil may:
Many different methods are used to clean up oil spills. Some absorb or collect the oil (oil-absorbent pads or pompoms, suctioning devices, skimmers, or buckets); some disperse or settle the oil to the bottom (sand or detergents, pressurized hot water to wash the rocks): some (such as booms) contain the oil. Many of these methods don't actually clean up the oil, they just move it somewhere else where its effect may be less catastrophic. Bioremediation uses fertilizers to increase the number of oil-eating bacteria that can break down oil.
Thick oil smothers animals such as birds and sea otters. It clogs the feeding and breathing mechanisms of filter-feeders. It can also poison animals who swallow it. Over the long term, oil can cause cancer in marine life, destroy the skin and gill tissues of fishes, upset their equilibrium, and disrupt the chemical receptors in lobsters and fish that are necessary for attracting mates.
Scientists, particularly from island nations like those in the Caribbean Basin, are quite concerned about erosion and submergence of their countries by rapid sea level rise. Sea level rise over the next 100 years could also interfere with the wave-buffering capacity of shallow coral reefs. Scientists are trying to determine if Caribbean coral growth will keep pace with a rising sea level.
Ozone is a greenhouse gas in the upper atmosphere-an important one for shielding us from harmful ultraviolet rays. In small quantities, ultraviolet rays give us a tan; in large quantities they can cause skin cancer, eye damage, and other health problems in humans and animals.
To their surprise, scientists discovered a hole in the ozone layer in Antarctica in the early 1980s. The size of the hole varies from year to year, but it tends to be growing larger. They also found a smaller hole over the Arctic, and then found that the ozone layer had thinned somewhat over the entire globe. The chief cause is chlorofluorocarbons (CFCs)-gases made up of chlorine, fluorine, and carbon, that "gobble up" the ozone. They are used in refrigerants, solvents, and propellants in industrialized societies.
As ships have become faster and able to cross oceans in days rather than months, the animals they carry with them have become a problem. As far back as Columbus, sailors have had to contend with rats on board ships. Today's stowaways from Europe, zebra mussels, are more of a problem. Zebra mussels are well adapted to life in the Great Lakes and have rapidly become unwanted visitors.
