INTRODUCTION 



Rocky shores of northeastern North America and the communities that 

 have developed on them are important components of the marine ecosystem. 

 Per unit area, the intertidal zone and near-shore waters are among the 

 most highly productive regions of the world (Mann 1973). Intertidal 

 algae provide food directly and indirectly, to snails, crabs, and other 

 benthic invertebrates, as well as fish, shore-birds, and man (Bold and 

 Wynne 1978; Edwards et al. 1982; Menge 1982). Many plants release over 

 50% of their annual biomass as detritus and dissolved nutrients (Josselyn 

 and Mathieson 1978) . The larger perennial algae in particular contribute 

 to the intertidal community's physical structure by providing shade and 

 protection to plants and animals living beneath them, and attachment 

 space for epiphytes growing upon them (Stephenson and Stephenson 1972; 

 Menge 1975) . 



In addition to their intrinsic values, rocky intertidal communities 

 have attributes that are important to a biological monitoring program. 

 Some of the organisms that make up the community are long-lived, and 

 capable of integrating effects of environmental conditions over many 

 years. Other species are ephemeral, and in their presence and abundance 

 respond very quickly to changing conditions. Some species are sessile 

 or slow-moving, and continuously exposed to potential impacts; others 

 are motile, and their abundance and distribution at' any locality are an 

 indication of the suitability of the environment at that time. Many 

 intertidal organisms show precise seasonal patterns in their occurrence, 

 abundance, and reproductive status; these patterns allow comparisons 

 between sites and between years. Finally, the accessibility and stability 

 of the rocky shore itself permit establishment of permanent sampling 



