post-spill but pre-exposure , as was done after the Tsesis grounding, the 

 study is of course, most ideal. This requires rapid response and ac- 

 curate trajectory predictions. 



3. The deep soft bottoms : Since the Tsesis study showed that oil 

 can reach the benthos within days, immediate sampling is necessary as an 

 indication of pre-spill conditions (see section 1.6). The amphipods and 

 the ostracods, both crustacean groups, were especially sensitive to oil. 

 The amphipods probably emigrated from the affected area, while most of 

 the ostracods probably died. Repeated sampling soon after the spill 

 would be necessary to confirm such conclusions. 



The oil analysis proved invaluable in the interpretation of the 

 biological responses, and for this the sediment trap data and the Macoma 

 balthica samples were particularly useful. Macoma have been suggested 

 as ideal indicators of oil pollution and the Tsesis study supports this 

 idea. The most reliable indicator of the insult was the contamination 

 of Macoma by oil. The second most reliable were changes in macro- and 

 meiofauna community composition. Whereas Macoma are well suited for 

 registering an oil insult to the area, other species are far more sen- 

 sitive for registering ecological effects. Therefore, a well balanced 

 (ideally holistic) study of the macro- and meiofauna is required to give 

 a totally accurate picture. 



The oil distribution seems to have been quite patchy, and at least 

 a rough mapping of the affected area would have been highly desirable. 

 It may not be feasible, however, to perform such a mapping in a statis- 

 tically reliable way. For this reason, the importance of patchiness and 

 possible "refugia" is difficult to study, although it is likely that 

 recovery rates depend strongly on the proximity of source areas for 

 recolonization. Areal extent of the affected area can be established by 

 sampling a grid of stations, taking one sample per station. Such a 

 survey would require expensive analyses, but would, perhaps, permit 

 greater economy in later analyses by identifying the most desirable 

 sites for the more detailed studies. The location of areas of poor 

 degradation should receive attention as possible reservoirs for 

 pollutants . 



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