Based on field observations by divers, the disappearance of the Fucus 

 belt macrofauna was due to death and/or narcosis. Along the shores of 

 Toro and parts of Liso, mass mortality occurred among littoral crusta- 

 ceans. After 12 months, considerable recovery had taken place, presum- 

 ably through immigration of amphipods and isopods from refuge areas. 

 Isopods of the genus Iaera were, however, an exception. In several 

 places, no recovery at all of Iaera could be observed. This could 

 probably be explained by the fact that these animals are extremely 

 thigmotactic, and are never found swimming in the free water. The re- 

 covery process of the littoral zone faunal composition was one of both 

 migration and multiplication of surviving individuals. The gammarids 

 were, for instance, totally lacking at a contaminated station in Novem- 

 ber. In June, they showed high abundance in all belts, but only 8% of 

 the samples contained adult individuals (corresponding frequency for 

 reference stations was 75-80%) . The isopods Idothea remained in the 

 area in low frequency in November, but reproduced in June and were 

 subsequently found in higher frequency, especially in the Cladophora 

 belt. 



The molluscs of the littoral zone do not appear to have suffered 

 drastic mortality. Instead, bivalves and gastropods seem to have re- 

 entered the algal zones after some time of immobilization on the bottom. 



Even if the recovery of the littoral fauna is incomplete, the 

 results obtained so far would indicate that a complete recovery of all 

 fauna representatives can be predicted within 2 to 3 years. In addition 

 to results of the Tsesis investigations, this statement is supported by 

 the findings of Notini (1978) when studying the recovery of an oil 

 polluted bay in the Stockholm archipelago. Here, the recovery took 3 to 

 4 years after the spill, which occurred under much the same conditions 

 as the Tsesis spill. 



The metabolism studies of the Fucus community did not reveal any 

 definite effects on community metabolism in the affected area. This may 

 have been due to the considerable variation of the background values. 



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