Comprehensive studies on the long-term effects of oil in littoral 

 communities indicate that the damage can be very great and can persist 

 for prolonged periods of time. The thorough work of Southward and 

 Southward (1978) on the effects of the Torrey Canyon oil spill of 1967 

 shows that serious effects, manifested as absence of several faunal 

 species and abnormal and excessive growth of algae, were evident even 

 after 8 years. After 10 years, the situation was still not normal with 

 respect to the diversity of fauna. Evidence from Baja California during 

 the wreck of the Tampico Maru indicates that species were still absent 

 and the balance of the littoral community was not restored 16 years 

 after the accident (North, 1973). 



The most important differences between these spills and the Tsesis 

 spill, with respect to the effects in the littoral zone, are mainly 

 results of the quantity and composition of the spilled oil and the 

 technique used during the clean-up operations. The observations after 

 the Torrey Canyon spill indicate that the longest lasting effects could 

 be observed at the heavily oiled rocks, which received repeated appli- 

 cations of toxic dispersants (Southward and Southward, 1978). The 

 severe effects during the wreck of the Tampico Maru were caused by the 

 large amounts of highly toxic diesel oil (North, 1973). Also, at the 

 Tsesis site, the biological effects of the spill were minimized by low 

 biological activity and low temperature and by the decision not to use 

 oil dispersants. The oil spill happened at the start of a season with 

 low activity in the littoral zone. The low temperature and ice cover in 

 January and February minimized plant and animal activity, and many 

 individuals died in accordance with the natural seasonal pattern. 

 During these 3 to 4 months of low activity, before the spring growth 

 started, some of the remaining oil in the littoral zone may have been 

 washed out, and the toxic fractions may have been diluted. Thus, the 

 effect was less than it might have been if the oil spill had occurred in 

 the beginning of the growing season in April, May or June. 



The accumulation of petroleum hydrocarbons in littoral bivalves 

 ( Mytilus ) is a very rapid phenomenon. During large spills in coastal 

 areas, bivalves frequently demonstrate such accumulation (Blumer et al., 



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