Effects on the Water
Oil spills affect water in a variety of ways. When oil is released into water, it does not blend with the water. Oil floats on the surface of salt and fresh water. Over a very short period of time, the oil spreads out into a very thin layer across the surface of the water. This layer, called a slick, expands until the oil layer is extremely thin. It then thins even more. This layer is called a sheen and is usually less than 0.01 mm thick.
Oil spills on the surface of the water are subjected to the whims of weather, waves and currents. All these natural forces move slicks across the surface of the water. In addition, these forces stir up the oil slick and also control the direction the slick moves in. An oil spill far out at sea can be carried ashore by wave and current action. Rough seas can split an oil slick apart, carrying some oil in one direction and more in another. In contrast, a near shore oil spill can be totally controlled by currents and wave action that causes the oil to come ashore, damaging marine shoreline habitat.
Different types of oil react differently when spilled. Some evaporate in small amounts, while others break down quicker. After the sheen breaks down, a moderate amount of oil will break down and be deposited on the bottom of the ocean. This usually happens in shallow water. Certain types of microbes will break apart and consume the oil, but this in no way makes up for the damage done during the spill. In addition, when oil breaks apart and sinks to the ocean floor, it contaminates the underwater habitat, too.
Effects on the Coastline
Perhaps the most visual part of an oil spill is the harsh effects oil has on the coastline. Pictures of oil covered birds and sea mammals are common. Oil is thick and sticks to everything it touches. While the most visual part of the damage might be the birds and wildlife you see on TV, consider that the oil covers everything right down to a grain of sand. Every rock, piece of driftwood, saw grass, sand, soil, and microscopic habitat is destroyed or affected by the thick oil that washes ashore after a spill. Oil spills affect the coastal habitat from the smallest shells up to the largest boulders.
Unless there is a concerted effort to clean the shoreline, oil will basically stay on shore until weather and time break the oil down. The process is extremely slow, which is why so many environmentalists work diligently to clean beach areas, rocks, and shoreline that have been contaminated. The gooey mass that makes up an oil slick litters the shoreline with ugly black tar. What makes it so very dangerous is that the coastline is where so much marine life is concentrated. Typically, shore areas are the nurseries for fish and marine life, in addition to being the home of many young marine mammals. Contaminated shorelines are not only unsightly, but also extremely dangerous to any wildlife in the area.
Effects on Marine Life and Wildlife
When oil floats on the water surface, a marine mammal that surfaces in the center of the slick ingests the oil. If this marine mammal is miles from the oil spill but happens to ingest a fish that swam through it, he is poisoned. The effects are far reaching. Marine and coastal life can be contaminated in a number of ways, through poison by ingestion, destruction of habitat and direct contact with oil.
Ingesting oil can cause any number of problems. Death is the obvious one. However, if an animal ingests oil-saturated food, the effects might be longer reaching that simply making the animal ill. People are not aware of the immediate impact to an animal's ability to mate and have viable offspring after being exposed to oil contamination. Fish ingest oil suspended in the water through their gills. It is known that this affects their ability to reproduce.
Habitat destruction is all too obvious with an oil spill. The most visible would be seen on shore, but beneath the water there is a very delicate balance in the reefs and shallow water habitats. Plankton, the smallest organisms, are affected by oil spills. This effect moves right on up the food chain. Of particular concern are the very delicate sea animals, such as clams and mussels that feed on plankton.
Direct contact with oil harms any animal that comes in contact with the oil. Bird's feathers are designed to repel water to protect the animal from the elements, and they allow many birds to float on the water when resting or searching for food. When oil cakes the feathers of a bird, it keeps the feather from repelling water. Oil also weighs down the bird, keeping it from flying. If a bird isn't cleaned of the oil, it's a sure license to death. Many birds ingest deadly amounts of oil trying to clean their feathers. The same holds true for marine mammals. Marine mammal fur acts as an insulator to keep the animal warm in the coldest waters. When oil saturates the fur, it ruins the ability of the fur to retain heat. Again, marine mammals can ingest the oil when trying to clean their fur.