denudings in particular will add information on growth and mortality 

 rates to the data that have been collected in the Ascophyllum growth 

 studies. 



Because of the importance of Fucus vesiculosus in the structure and 

 function of the intertidal community, particular attention has been 

 given to the abundance and reco Ionization patterns of this alga in the 

 Rocky Shore Survey. The present sampling procedures are well designed 

 for detecting changes in abundance of intertidal organisms, in terms of 

 percent cover. More importantly, they allow us to identify long-term 

 trends, and to determine whether these trends can be attributed to 

 thermal impact or are part of a widespread natural cycle. As an example, 

 Figure 6 illustrates percent cover values for the fucoid canopy in Zone 

 2 of six rocky shore stations for the past three years (Bay Point was 

 omitted, due to consistently low coverage). 



There is a general tendency for the highest values to occur in late 

 summer (July-Aug.); coverage decreases as older plants are removed by 

 storms, and occasionally, by ice-scouring. Values generally begin to 

 increase around March, as the survivors resume growth, and new plants 

 settle and are recruited into the population. At all stations but 

 Seaside Exposed, there was a decrease in mean annual percent cover of 

 fucoids from spring 1979 to spring 1981, with minima occurring in April 

 of 1981. This decrease was attributed to natural mortality of Fucus . 



Fucus vesiculosus is a perennial alga; its lifespan is estimated at 

 2-4 years (Nienburg 1930; Knight and Parke 1950; Keser 1978). Older 

 plants are susceptible to epiphytism (Menge 1975), storm damage, and 

 ice-scouring (Vadas et al. 1977); their removal makes space available 

 for settlement and growth of new germlings to continue the cycle. The 



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