assumption that the observed decline is part of a natural cycle rather 

 than the result of a man-induced impact is supported by the fact that it 

 occurs throughout the study area, even at control stations beyond the 

 influence of MNPS . The cyclic nature is particularly clear at the Fox 

 Island-Sheltered station, where fucoid percent cover values of 11% in 

 April 1981 increased to 46% by the following spring (Fig. 6). In August 

 1982, Fucus cover at this station was up to 60%, a three year maximum. 



Figure 6 also presents Zone 2 Fucus canopy cover at the recolonization 

 stations, in the strips denuded in April 1979 (except for Fox Island- 

 Sheltered, where the recolonization transects were burned and cleared in 

 June 1978) . Further evidence that the loss of Fucus in the undisturbed 

 transects was natural mortality of older plants is seen in the fact that 

 over the same time span (1979-1981), coverage increased in the recolon- 

 ization transects. The recovery of Fucus populations (particularly 

 rapid at Fox Island-Exposed, potentially the most impacted site) indicates 

 that environmental conditions necessary for Fucus growth have not deteri- 

 orated over the past three years. 



The comparison of recolonization to undisturbed transects also 

 indicates one of the advantages of the present multi-faceted monitoring 

 program; data from one study can support hypotheses presented in another 

 facet. 



Ascophyllum growth studies - Ascophyllum nodosum is a particularly 

 effective monitoring tool, especially for studying thermal impacts 

 (Vadas et al. 1976; Keser and Foertch 1982). The abundance, longevity, 

 and mode of growth of this alga permit easy measurement of response to 

 changes in environmental conditions; the growth rate of Ascophyllum has 

 been shown to be particularly sensitive to temperature changes (Stromgren 

 1977; Vadas et al. 1978; Wilce et al. 1978). 



25 



