Oil spill Effects 401 



enhancement of the nutrient cycling rate control the competition among 

 the various algal species. 



In other experiments with oil in the Arctic, green and blue-green algae 

 become abundant. For example, Hanna et al. (1975) and Snow and Scott 

 (1975) report that Oscillatoria increased after oil spills and some of our 

 experimental subponds followed the same pattern (Federle et al. 1979). 

 This change did not occur in the whole-pond experiments we performed 

 but did occur when experiments were run in subponds without sediment. It 

 is likely that the phosphorus in the natural ponds is kept low and relatively 

 unavailable because of adsorption by the sediment; in lakes and in 

 experimental vessels without sediment the phosphorus becomes more 

 available because of the elimination of zooplankton. 



Rooted Plants 



No damage to the vascular plants, especially the dominant Carex 

 aquatilis, was observed in the ponds during 1970, but growth was affected 

 during following years. Immediately after the spill much of the oil became 

 attached to the stems of this sedge along the shore of the pond. As long as 

 the oil touched only the stem there was no damage; some damage did 

 occur when the oil contacted leaves. In the same manner the new leaves of 

 Carex that appeared the next spring (1971) were killed in the area of the 

 pond where they had to actually push through the floating layer of oil. This 

 mechanical effect, therefore, could have been the cause of the low biomass 

 of Carex in the areas of heavy oil accumulation (Table 9-4). The area 

 covered with a light accumulation of oil had a lowered Carex biomass in 

 1971 but was back to normal in 1972. There was no evident effect on the 

 rooted plantsV)f the 10-fold smaller spill in 1975 in Pond Omega. 



TABLE 9-4 The Above-water Live Biomass of Carex aquatilis in Ponds E 

 and C in 1971 and 1972* 



Treatment 



8 July 1971 17 July 1972 



Heavy oil 



A (north transect, Pond E)** 



3 (15) 



6 (8) 



Light oil 



B (south transect. Pond E)** 



18 (9) 



34 (8) 



Control 

 (Pond C transect)** 



30 (8) 



27 (5) 



* Data are expressed in g dry wt m ; (n) = number of samples. 

 **Location of transects given in Figure 9-1. 



