The percentage of abundance and biomass of dominating and vagile 

 species is shown in Tables 7.3.5a and b. Gamma rus spp. and Iaera spp . 

 had a very low share of the abundance in November. In many vegetation 

 belts they were totally absent, for example at station B. In June, 

 Iaera was still missing at that station, except in the Ceramium + Mytilus 

 belt, where a single individual was found. 



In June, gammarids occurred in high abundance at all stations 

 (Table 7.3.3 and 7.3.5a). Most of the gammarids were juveniles. Only 

 8%"-of the samples contained adult individuals at Station B. Correspond- 

 ing frequencies for stations D and G were 75% and 80%, respectively. 



7.3.2.3 Comparison with data from oil analysis of Mytilus edulis 



The oil content of Mytilus edulis at different times of the year 

 is given in section 11.3.1 and Tables 11.1 and 11.2. The analyses 

 showed a low level of oil before the contamination (10/27/77), and a 

 drastic increase after the spill. The oil content then decreased during 

 the year as shown by successive analyses. The high mortality/absence of 

 all vagile forms mentioned above at the contaminated stations in Novem- 

 ber corresponds well with the high oil content analyzed in Mytilus . The 

 return of vagile forms indicates a healthier environment. This is also 

 indicated by the decreasing oil content analyzed in Mytilus . 



7.3.3 Discussion 



The vegetation, animal diversity and biomass for each vegetation 

 belt usually showed higher values at the reference Station G, especially 

 in November but also in June (Tables 7.3.1, 7.3.2, and 7.3.3). Station 

 G may be considered to be a typical station for the area. No previous 

 investigations in the surrounding area indicate that it would be extreme 

 in any way (Haage, 1975, 1976; Jansson, 1974; Jansson and Kautsky, 1977, 

 Kautsky, 1974; Wallentinus, 1976). The parallel work of Notini also 

 corroborates this (section 7.2). 



No effect of the oil spill on the benthic macrovegetation was 

 observed. The same observations were made in the Baltic by Notini 

 (1978) and Ravanko (1972). They investigated accidents which happened 

 at the same season, before the spring growth. 



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