The orders found were: Insecta: Thysanoptera , Collembola, Orthop- 

 tera, Hemiptera, Coleoptera, Hymenoptera and Diptera. Crustacea: 

 Isopoda (P orcellio scaber ) and Amphipoda ( Orchestia gamma re llus ) . 

 Arachnoidea: Araneae, Arcarina and Opiliones. Myriapoda : Diplopoda 

 and Chilopoda. Oligochaeta: Plesiopora and Gastropoda: Stylommato- 

 phora . 



The genera Pachydrilus and Enchytraeus (Oligochaeta) have not been 

 taken into consideration and were left out in all calculations. This 

 was due to the difficulty of obtaining reliable abundance estimates for 

 these highly contagiously distributed animals. The estimated numbers 

 are given in Table 8.2.4 and percent distribution in Table 8.2.5. 



8.2.3 Description of the stations 



At station B and D there was a small belt of totally dry wrack only 

 a couple of centimeters deep and 15 cm wide, which, according to Backlund 

 (1945), could be characterized as a wrack string. The wrack consisted 

 almost exclusively of Fucus vesiculosus with some Cladophora . At these 

 two stations a few oil slicks could be seen on some stones but not in 

 the wrack. Station B, one of the most heavily contaminated stations, 

 was subject to cleanup in the middle of June 1978, during which time 

 parts of the ground were dug up and turned over. 



At station C, also heavily contaminated, a rather large slick of 

 oil was found in one of the quantitative samples. Here, the wrack 

 accumulation was much larger, about 10-15 cm deep and 50 cm wide, con- 

 sisting of decaying wet wrack. 



At station G, the reference station, the wrack bed was similar in 

 size to that at C and consisted of decaying wet wrack. At this station 

 there was a bed of reed adjacent to the sampling area, and as a result 

 the wrack contained much material from Phragmites australiensis . 



8.2.4 Results 



8.2.4.1 Pitfall traps 



At station G there were more individuals and systematic groups in 

 each trap as well as a higher total number of systematic groups found 



178 



