the earliest colonizers may be Balanus ; barnacles have a major settlement 

 period around April - May. As the barnacles grow, they provide surface 

 heterogeneity that allows attachment and survival of Fucus germlings; as 

 the Fucus canopy develops, it provides protection for other elements of 

 the recolonization community. If the rock is cleared in June, subsequent 

 to the major barnacle set, Fucus germlings that settle in summer are 

 more vulnerable to grazing; recovery is usually delayed until the following 

 year. If grazers are excluded from the cleared areas (e.g., by the wire 

 cages), Fucus may grow without prior establishment of a barnacle population. 

 Sometimes, however, exclusion of grazers can actually retard Fucus 

 development; if sufficient moisture is available, ephemeral algae (e.g., 

 Enter omorpha , Porphyra ) may grow so densely that they reduce the settlement 

 of other organisms beneath them (Menge 1975; NUSCo 1982). Once barnacles 

 are established, in the absence of predation they may crowd themselves 

 into 'hummocks' and become detached (Grant 1977). Alternatively, mussels 

 may settle into a barnacle patch; particularly in the low intertidal, 

 given protection from predation, they may grow so rapidly that they out- 

 compete the barnacles for attachment space. 



The above discussion was included to describe some of the many 

 possible stages an intertidal community might go through in recovering 

 from a severe perturbation. The same stages may be found in unperturbed 

 communities as well; the denudation that I called 'severe' is actually a 

 commonly occurring process throughout the intertidal. Biological and 

 physical factors (e.g., grazing, predation, storms, ice-scouring) may 

 clear substrata at almost any time of the year. Therefore, recolonization 

 cannot be regarded as a precise series of successional stages; rather, 

 the intertidal community is continually undergoing dynamic processes. 



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