Damage from oil accidents is most severe in narrow fjords and inlets without strong
wave activity. Up to now no research reports are available about the long-term effects
of the oil of the "Amoco Cadiz" on the fjords of Britanny. Immediate damage was
specially severe close to the high water mark in the area which is preferred by the
young bottom stages of lugworms and clams. In some salt marsh areas the oiled sediment had to be exchanged completely, which means a total devastation of the area.
Salt marshes are known to be specially vulnerable (Table 18), and sometimes the
effect of oil ist most severe after as long as 2 years. In Chedabucto Bay, Canada, the
salt marsh recovered only 6-7 years after an oil spill (Vandermeulen and Ross 1977).
Oil trapped in the clay sediment can exert its toxic effect for many years and prevent recolonization. It seems that terrestrial plants, including salt marsh vegetation,
is much more sensitive to oil than algae, because oil components immediately penetrate their tissues (CowellI978).
On rocky shores, which have been cleaned with detergents after an oil spill, recolonization is comparable to the recolonization one observes on a nude rock. The first
organisms which appeared on the Cornwall shore after the "Torrey Canyon" accident
in 1967 were green algae of the genera Ulva and Enteromorpha. They covered the
entire region because the limpets and periwinkles which usually eat away all algae
seeds had been killed by the oil and by the subsequent cleaning procedures. In the
autumn of 1967 brown seaweed (Fucus) settled and grew to such an extent that the
barnacles, which up to this period had survived successfully, perished under the seaweed carpet. In 1968 limpets started to immigrate from the low water level to the
higher zones and by their grazing activity prevented further settlement of algae seedlings. From 1970 to 1972 the carpet of brown seaweed became thinner and thinner
and finally disappeared, because any new settlement was prevented by enormous
numbers of limpets. When finally the limpets could not find enough food, their
population declined to normal numbers, and barnacles had a chance to settle. Since
1975 they have dominated the region, as they did before the oil accident (A.l. and
E.C. Southward 1978).
At Cornwall there was a small cove oiled from the "Torrey Canyon" accident, which
was left without cleaning operations. Rock and organisms were covered with a
1-2 mm oil layer, but one month after the oiling some barnacles had managed to
clean an opening through the oil, and took up filter feeding activity. Mussels (Mytilus
edulis) seemed to survive, but limpets were gone. In 1968 about half of the barnacles
were dead, some limpets had returned. After 2 years all oil had gone without any
treatment, and there was never an algal bloom on the rocks.
If one cleans a rocky coast after an oil spill the result is dubious: one gets a carpet of
slippery green algae. It can therefore be good advice to leave the oiled coast alone
and to restrict cleaning operations to such coastal areas where tourists would be
molested by the oil.
Sandy beaches sometimes have a good capacity of natural self-cleaning. When on
May 12, 1976, the tanker "Monte Urquiola" stranded a few miles from La Coruna,
Northern Spain, and 30,000 t of crude oil spoiled the coast, some sandy beaches
were covered with a 30 mm layer of oil which persisted for weeks. The meiofauna,
consisting of microscopical worms and crustacea living in the pores between the sand
grains, was nearly completely killed. One year later, however, the beaches appeared
95
wave activity. Up to now no research reports are available about the long-term effects
of the oil of the "Amoco Cadiz" on the fjords of Britanny. Immediate damage was
specially severe close to the high water mark in the area which is preferred by the
young bottom stages of lugworms and clams. In some salt marsh areas the oiled sediment had to be exchanged completely, which means a total devastation of the area.
Salt marshes are known to be specially vulnerable (Table 18), and sometimes the
effect of oil ist most severe after as long as 2 years. In Chedabucto Bay, Canada, the
salt marsh recovered only 6-7 years after an oil spill (Vandermeulen and Ross 1977).
Oil trapped in the clay sediment can exert its toxic effect for many years and prevent recolonization. It seems that terrestrial plants, including salt marsh vegetation,
is much more sensitive to oil than algae, because oil components immediately penetrate their tissues (CowellI978).
On rocky shores, which have been cleaned with detergents after an oil spill, recolonization is comparable to the recolonization one observes on a nude rock. The first
organisms which appeared on the Cornwall shore after the "Torrey Canyon" accident
in 1967 were green algae of the genera Ulva and Enteromorpha. They covered the
entire region because the limpets and periwinkles which usually eat away all algae
seeds had been killed by the oil and by the subsequent cleaning procedures. In the
autumn of 1967 brown seaweed (Fucus) settled and grew to such an extent that the
barnacles, which up to this period had survived successfully, perished under the seaweed carpet. In 1968 limpets started to immigrate from the low water level to the
higher zones and by their grazing activity prevented further settlement of algae seedlings. From 1970 to 1972 the carpet of brown seaweed became thinner and thinner
and finally disappeared, because any new settlement was prevented by enormous
numbers of limpets. When finally the limpets could not find enough food, their
population declined to normal numbers, and barnacles had a chance to settle. Since
1975 they have dominated the region, as they did before the oil accident (A.l. and
E.C. Southward 1978).
At Cornwall there was a small cove oiled from the "Torrey Canyon" accident, which
was left without cleaning operations. Rock and organisms were covered with a
1-2 mm oil layer, but one month after the oiling some barnacles had managed to
clean an opening through the oil, and took up filter feeding activity. Mussels (Mytilus
edulis) seemed to survive, but limpets were gone. In 1968 about half of the barnacles
were dead, some limpets had returned. After 2 years all oil had gone without any
treatment, and there was never an algal bloom on the rocks.
If one cleans a rocky coast after an oil spill the result is dubious: one gets a carpet of
slippery green algae. It can therefore be good advice to leave the oiled coast alone
and to restrict cleaning operations to such coastal areas where tourists would be
molested by the oil.
Sandy beaches sometimes have a good capacity of natural self-cleaning. When on
May 12, 1976, the tanker "Monte Urquiola" stranded a few miles from La Coruna,
Northern Spain, and 30,000 t of crude oil spoiled the coast, some sandy beaches
were covered with a 30 mm layer of oil which persisted for weeks. The meiofauna,
consisting of microscopical worms and crustacea living in the pores between the sand
grains, was nearly completely killed. One year later, however, the beaches appeared
95