In Penobscot Bay, Normandeau Associates (1975) report that considerable 

 variation exists in community composition. They think that the variation is 

 related to location and substratum variability, rather than season. Of the 

 221 species and 20,000 individuals collected, the following eight species were 

 dominant (i.e., most abundant; Normandeau Associates 1975): 



Strongylocentrotus droebachiensis sea urchin 



Echinarachnius parma sand dollar 



Thyasira f lexuosa bivalve 



Acmaea testudinalis limpet 



Alvania sp . gastropod 



Cerastoderma pinnulatum bivalve 



Astarte undata bivalve 



Leptocheirus pinguis amphipod 



Since some of the species listed above are infaunal (live in the bottom 

 sediment) the hard substrate must have contained pockets of sediments. 



High local abundances of sea urchins were reported in Penobscot Bay 

 (Normandeau Associates 1975). High densities of sea urchins also have been 

 observed in Cobscook Bay and at the mouth of the Sheepscot estuary (personal 

 communication from L. F. Doggett, Bigelow Laboratory, West Boothbay Harbor, 

 ME; June, 1977). Individuals of this species can pave the bottom and graze 

 everything in their path, thereby modifying the nature of the bottom for 

 several years. Subtidal rock bottom habitats are preferred feeding areas for 

 eider ducks, other seaducks, loons, and grebes where they feed on benthic 

 invertebrates . 



Subtidal rock bottom habitat (and intertidal rocky shore areas at high tide) 

 are preferred habitat for a number of fish species, including American eel, 

 sea raven, sea snails, snakeblenny, rock gunnel, tautog, redfish, and ocean 

 pout. Fishes are discussed in detail in chapter 11, "Fishes." 



The Intertidal Subsystem 



The physical intertidal zone is the area between extreme high and low tide 

 marks (see "Hydrography" above). This zone is ecologically different from the 

 subtidal zone, because of the alternative submersion and exposure of the 

 substratum. 



Eleven habitats occur in the intertidal zone of coastal Maine. They are mud 

 flat, sand flat, sand beach, gravel beach, cobble beach, boulder beach, 

 protected rocky shore, exposed rocky shore, emergent wetland, stream bed, and 

 reef. Only those habitats that are specific to the marine system are 

 discussed below. They are sand beach, exposed rocky shore, and boulder beach. 

 The other habitats are discussed in chapter 5, "The Estuarine System," because 

 the estuarine intertidal subsystem and marine intertidal subsystem are 

 ecologically similar in coastal Maine. 



The area of the intertidal marine subsystem in the characterization area is 

 60,576 acres (24,525 ha) and 71% of that acreage is in the eastern regions of 

 the characterization area (4, 5, and 6). Regions 4, 5, and 6 have 26% (15,895 

 acres; 6435 ha), 22% (13,297 acres; 5383 ha), and 24% (14,795 acres; 5990 ha) 

 of the total area, respectively. These regions have higher acreages because 



4-75 



10-80 



