The dominating bivalve in the area, Mytilus edulis , showed great 

 fluctuations in the Furus samples, both within a sample set and between 



the sets (Fig. 7.2.3.5J. However, a decrease in density figures in 

 November compared to October due to oil was found. During the same 

 period no such decrease occurred at Station G. The • ffects are there 

 but closer analysis of the collected data is needed. When the My til u s 

 edulis from stations C and G are sorted into tw y o groups (> 5 mm and 

 5 mm), comparison of these size groups strongly indicates a mortality of 

 small individuals (< 5 mm) at Station C (Table 7.2.3.1). 



The abundance of Theodoxus f luviatilis , the dominating gastropod i n 

 the area, also decreased significantly during the first months following 

 the spill (Fig. 7.2.3.6), but at station C recolonization was very slow. 

 In October 1978 the mean density figures were still significantly Lower 

 than in October 1977. 



7.2.4 Discussion 



Unfortunately, sorting and examination of F ucus samples is very 

 time consuming. At present 49% of the collected Fucus samples have been 

 inspected. In spite of this the available data presented here strongly 

 indicate drastic effects on the Fucus macrofauna in the area. The 

 abundance of all macrofauna species, with the possible exception of the 

 barnacles Balanus improvisus, decreased during the acute phase at sta- 

 tions affected by the oil. Comparison with the reference station G on 

 the island of Fifong shows no such decrease there during the same period. 



The degree and duration of the damage varied at the different 

 stations. From the results available, station B and C were probably the 

 stations most affected, followed by station A. Station D showed a 

 smaller degree of acute effect and a preliminary look at the samples 

 from station E shows the same type of results. This may be explained by 

 the fact that the oil reached these locations 5 to 10 days after the oil 

 spill occurred. Therefore, this oil had been weathered for a longer 

 period of time compared to that at stations B, C and A. Both these 

 stations (D and E) are situated in shallow bays with low water exchange. 

 They are the most protected of the stations studied here. Therefore the 



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