t .4. 2 Method s 



Part of the communities were enclosed in plastic bags (0 = 0.5 m, 

 volume 30-70 litres, Fig. 7.4.1, details see Guterstom, 1977) using 

 SCUBA diving. The oxygen consumption was measured with a YSI oxygen 

 electrode on several occasions over a 24 hr. period. 



Experiments were run at the most contaminated stations and at a 

 similarly exposed, "unpolluted" reference station. Further data from 

 these stations are presented in sections 7.2 and 7.3. Due to failure of 

 the Mytilus experiment at the reference locality, these results were 

 compared with results from laboratory experiments. 



7.4.3 Results and discussion 



The results from the three communities investigated show a typical 

 picture with relatively low respiration at this time of the year (Novem- 

 ber, Table 7.4.1). Only the Fucus communities at two oil polluted 

 localities showed higher respiration than similar unpolluted localities 

 (.Table 7.4.1). An increased respiration due to exposure to oil at 

 increasing concentrations was found in outdoor experiments with F. 

 vesiculosus from the northern Baltic (Canning and Billing, 1974). The 

 shallow soft bottoms showed the same respiration at both localities. 

 The same was found with Mytilus from oil polluted localities compared 

 with mussels from unpolluted areas. 



At the oil polluted localities oil could be seen in the plastic 

 bags after the incubation periods as it had floated up as small drops 

 under the plexiglass covers of the plastic bags in all experiments. In 

 June 1978 oil was still leaching out of the investigated sediments. 



Due to the low biological activity during the winter and the few 

 replicates in each experiment, no significant difference in respiration 

 could be found. As shown in Chapter 11 (Tables 11.1-11.4) and discussed 

 in section 7.2.4, the "unpolluted" reference station was later found 

 also to have been contaminated by the oil, even though not by visible 

 slicks. Any effects which might influence the community respiration 

 through changes in animal populations would therefore be expected to be 

 found during the following summer and autumn. Notim (1978) found lower 

 macrofauna populations at oil polluted Fucus communities of the northern 

 Baltic compared to unpolluted communities. 



162 



