2. To gain information on which arctic plant and microorganism species may be able to adapt 

 to the presence of a hydrocarbon-saturated rhizosphere. 



Seep A was chosen for the terrestrial seep studies for several reasons: 



1. There was a minimum of disturbance by man which occurred elsewhere in the area during 

 the period of the PET 4 activities. 



2. There appeared to be a difference between the vegetation immediately adjacent to the 

 seep and that several meters away. 



3. There were two distinct plant communities intersected by the seep. 



This seep consisted primarily of asphaltic material flowing down a slope which ended at the 

 shore of a small lake. New seepages of fresh oil were most obvious in the center of the asphaltic 

 area, but fresh oil could also occasionally be seen in the peripheral ground. Large areas to the 

 sides of this flow showed sparse vegetation covering a weU-oxidized asphaltic soil. This indi- 

 cated that major active seeps and flows were once in a position different from the present flow. 

 The fresh oil and tar flowed along frost cracks in the ground at the periphery of the seep and thus 

 formed finger-like projections into the tundra. This was especially noticeable at the lower part of 

 the slope where fresh flows could be seen advancing over the vegetation. Figure 31 is an overall 

 view o[ the Simpson seep. Figure 32 is a close-up of an active flow. 



The area seemed to be a good example of the successive stages in the natural oxidation and 

 degradation of oil. The freshly exuded oil was quite fluid but eventually formed a tar, probably 

 because of the evaporation of volatiles. After weathering, an asphalt was formed which was quite 

 resistant to further changes. However, when oil, tar, or asphalt came into contact with free water, 

 either at the edge of the lake or in pools of water collected on the seep, degradation into a gummy 

 light-brown material and finally into a loose brownish humus-type material occurred. The degrada- 

 tion in water was probably due to microbiolc^ical attack. Literature from temperate climate studies 

 also indicates that the microbial oxidation of hydrocarbons occurs faster under high water content 

 conditions. 



Plants were found growing in close association with the asphalt and oil, both at the periphery 

 and when entrapped by the flows. The plants surrounded by the seeps had their root systems em- 

 bedded in the tar. In places, plant shoots could be seen advancing into the asphalt. In those areas 

 where the flows contacted water, the plant growth was lush and mae advanced phenologically than 

 in the surrounding tundra. Only when the foliage became covered with an oil deposit was injury 

 visually noticeable. 



Two communities of vegetation were evident in the area of the seep. On the lower, wetter 

 portion of the slope, a community with Carex aquatilis as the dominant species was present. A 

 sharp change occurred farther up the slope with the beginning of a community dominant in Arcta- 

 groslis latUolia. Along the east side of the seep, the Carex community lined the periphery; in no 

 other place was this community seen at this elevation on the slope. 



Three transects were established running 4 meters in length from the east side of the seep, 

 into the surrounding tundra. The transects were placed so that they intersected changes in vege- 

 tation, which generally meant that 2 meters of the transect were in the Carex community and 2 

 meters were in the Arctagrostis community. 



1. Transect 1 was located near the top of the slope. Much of the top of the slope showed 

 asphalt outcroppings. This was the driest of the transects. The transect did not intersect the 

 major seep, but began about four meters away from its edge. 



2. Transect 2 was located further down the slope and extended from the edge of the seep. 



81 



