only 8-10% of the pre-spill situation at stations A and C. Station B 

 between these two stations was probably affected in the same way (.Fig. 

 7.2.3.1). During the same period no such decrease occurred at the 

 "reference" Station G. Station D, which was hit by the oil four days 

 later, showed a possible decrease in magnitude of 40-50% although the 

 variations in the samples were high. Samples from stations F and E have 

 not been sorted yet, but observations during diving operations in the 

 area indicated less acute damage compared to stations A, B and C. 



In spite of the initially heavy degree of oil pollution, a sig- 

 nificant recolonization of the Fucus fauna had already started in the 

 middle of December 1977 at Stations A and C. At Station C the total 

 number of macrofauna specimens in October 1978 was of the same order as 

 in October 1977 before the oil hit the station. At Station G also, the 

 "reference" station, the situation in October 1977 and 1978, respective- 

 ly, was very much the same. The process of recolonization seemed to be 

 slower at Station B and possibly at Station D. 



The crustaceans Gammarus spp., Idotea spp . and Iaera spp . (Fig. 

 7.2.3.2, 7.2.3.3 and 7.2.3.4, respectively) were all drastically reduced 

 by the oil. The specimens of the amphipod Gammarus spp. were sorted 

 into two length classes, > 10 mm and < 10 mm (Fig. 7.2.3.2). The pre- 

 liminary results show no differences in the effect of the oil on these 

 two groups. In November 1977 Gammarus spp. was totally missing or 

 significantly reduced at all examined stations hit by the oil (Stations 

 A, B, C and D) compared to the pre-spill situation in October. But a 

 recolonization had already started in December 1977 at stations A and D. 

 The isopods Idotea spp. and Iaera spp. (Fig. 7.2.3.3 and 7.2.3.4) were 

 not totally missing in the November samples, but individuals remaining 

 were very few. At station B Iaera spp. was completely missing both in 

 December and in May, half a year after the accident. Recolonization by 

 Idotea spp. at the same station seemed likewise to be a slow process. 

 However, in October 1978, one year after the Tsesis ran aground, a 

 considerable recolonization of both species had taken place at station B. 



134 



