The post-spill meiofauna samples from station 20 are similar in 

 many aspects to the meiofauna community found after several months of 

 oil addition (190 ppb average of No. 2 fuel oil) to MERL experimental 

 ecosystems (MERL = Marine Ecosystems Research Laboratory, Graduate 

 School of Oceanography, University of Rhode Island, USA. In press by 

 Elmgren et al., also Grassle et al., 1978). Similarities include almost 

 total dominance by nematodes after prolonged oil exposure and very rapid 

 and drastic reduction in ostracod numbers following exposure. A detailed 

 comparison of the two data sets will help in evaluating the usefulness 

 of experimental ecosystems for studying and predicting the effects of 

 oil and other pollutants in the marine environment. 



6.5 Summary and conclusions 



Considerable amounts of oil reached the sediment within a week at 

 the most heavily affected stations, as shown by sediment trap data (see 

 Section 4). After one month, oil analyses of Ha coma balthica showed 

 contamination with oil at several, widely separated stations. The 

 macrofauna community responded drastically at station 20, and probable 

 short-term effects were seen also at station 21. The vagile macrofauna, 

 especially the amphipods died at or emigrated from the most affected 

 station (No. 20). The few remaining gravid amphipods showed an increased 

 frequency of abnormal eggs. No reduction in abundance or biomass was 

 found in Macoma balthica or Halicryptus spinulosus . All meiofauna 

 except the nematodes was drastically reduced at station 20 and a large 

 kill of ostracods seems to have taken place relatively soon after the 

 spill. In spite of these clear ecological effects, no Tsesis oil hydro- 

 carbons could be conclusively demonstrated in the sediments, probably 

 due to inadequate sampling methods. Neither the affected macrofauna, 

 nor the meiofauna showed any evidence of recovering within the 9-10 

 month period alter the spill so far studied. 



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