Which Are the Effects of an Oil Spill?

That was the greatest ecological disaster on the sea: in 1978 the tanker "Amoco-Cadiz" contaminated with 280,000 tonnes of crude oil the coasts off Bretagne (Western France).

More "famous" is the ecological catastrophe produced by Exon Valdez in 1989 on Alaska's shores. During the 1991 Gulf War, about one million oil tonnes blackened the Persian Gulf.

In 1992, The "Aegean See" got stuck in La Coruna (Northwestern Spain) and to the escape of 80,000 tonnes of oil, a giant cloud provoked by the partial combustion of the oil was added.

Fresher in our memory are two events: The 1999 "Erika" accident, off Bretagne coasts, when, beside the 12,000 tonnes of escape, other 18,000 tonnes of crude oil stored in the reservoirs had to be pumped out, plus the "Prestige" incident, in November 2002, off Galicia (Northwestern Spanish coasts), which poured 64,000 tonnes of contaminant material, reaching even the French coasts and being the greatest environmental catastrophe in Spain's history.

Which are the environmental and economic consequences of an oil spill? A large array of sea species, from marine mammals (cetaceans, seals, otters) to sea birds, turtles, fish, crustaceans, and mollusks lose their habitat.

But the petroleum acts directly on the animals and plants, physically and chemically. The life in the tidal area is erased.

Most animals die smeared by the oil or poisoned by the toxic compounds (including carcinogen) of the hydrocarbons. Clams and cockles have no chance of survival.

The fuel decomposes the natural oils of the sea birds' plumage. This fat is secreted by the uropygial gland (near the base of the tail) and is indispensable for the birds to isolate their body from the freezing waters and make them float on the water. Birds smeared in petroleum, if they don’t drown, they die of hypothermia, as their feathers lose the isolating role. The ones that get drowned are eaten by fishes and other birds, and the contamination spreads.

The most affected birds are the most bound to the sea, such as the guillemots, razorbills, puffins, shags and gannets.

Sea mammals, like seals, can get lung intoxications from the petroleum. Cetaceans, like dolphins, porpoises and false killer whales can get their breathing duct, mouth and genitalia obstructed by oil, but this can also get inside the stomach.

Bottom animals, like mussels, which feed by filtering the water, ingest very quickly the toxins and die. Mussels still can accumulate toxins from the water for long periods. Crabs eat the intoxicated corpses, and with them accumulate the toxins.

The most affected fish species are the bottom ones, like rays, congers, soles, and flounders.

Dune ecosystems can be affected, and in some cases even rare plants, located only in some coastal dunes, like Rumex alpestris in the case of "Prestige".

The effect of the oil spills is extremely severe as the shore areas represent breeding and refuge areas for many marine species. Oil mixed with sand can cover sea beds down to 30 m (100 ft) in depth, killing sea cucumbers, scallops, starfishes, sponges, sea snails, octopuses, cuttlefish, squids, spider crabs and velvet crabs.

Fishing and seafood harvesting are banned. Marine flora stops the photosynthesis, by not receiving light, and the oxygen disappears. After such a disaster, the ecosystems needs 6 to 10 years to recover.

So, how can an oil spill be stopped?
The most important thing is to stop the oil from spreading. To this end floating barriers are used, but they are effective only when the sea is calm. In the areas where crude oil accumulates, it can be sucked out by pumps. If it's very thick, some chemical compounds are added to turn it more fluid. Oil absorbing skimmers cleanse the crude oil while marching through it.

When the oil reaches the coast, the only option is to remove the sand or soil impregnated with oil. Sometimes heavy machinery is used. This oil is heavy, with low water solubility, and few gases, very persistent in the environment, and rich in sulfur, benzenes and benzopyrenes (highly toxic chemicals).

Heavy machinery can be employed. The workers must operate protected by plastic overall to avoid direct contact with the oil, as toxic chemicals can cross the skin and volatile toxins from the oil can be inhaled. Pressured water jets and biodegradable detergents can be used to cleanse small areas.

Recovered birds that have the plumage oiled are wrapped in cloths to avoid hypothermia. They are kept in dark cages to protect them for stress. A soft detergent is used for cleansing their plumage and they are forced to ingest food.

In the "Erika" event 100,000 birds died. 130,000 could have been affected by the Prestige event. Most had come from very far away, like Scotland, Ireland, and even Finland.

Marine mammal fur also loses its insulator feature and the mammals must be washed with serum outside and inside, in case of oil ingestion. Currently, satellites are used to track down tankers that escape oil. The specialists analyze the oil samples, check the tankers that passed the area, and the registers link the crude oil type to a specific refinery where the boat was charged.


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