Scoloplos sp . , Ophelia bicornis , and oligochaetes are dominant at mid- 

 intertidal heights at Pemaquid (region 3), Jonesport (region 6), and Roque 

 Bluffs (region 6), respectively. The sparsely populated Lincolnville (region 

 4) and Mt. Desert (region 5) beaches have no clear dominants in the mid- 

 intertidal region of the beach. Talitrid amphipods remain present at high 

 intertidal heights with Orchestia platensis at Lincolnville and Mt. Desert and 

 Talorchestia megalophthalma at the two most eastern beaches. 



Very few species are present above mean tidal level (MTL) in the winter 

 (figure 4-30). By moving seaward during the fall and winter, the animals are 

 able to decrease the exposure time and stabilize the temperatures to which 

 they must be exposed during low tide. The dominant amphipod on western Maine 

 beaches, Amphiporeia virginiana , does not exhibit this seasonal shift (Croker 

 et al. 1975). 



Croker and coworkers (1975) found that the haustorid amphipod, Amphiporeia 

 virginiana, made up more than 50% of the biomass at more exposed sandy beaches 

 in southern Maine. Because A. virginiana does not migrate appreciably on a 

 seasonal basis (Croker et al. 1975), there would be only minor differences in 

 seasonal biomass. As Croker and coworkers (1975) pointed out, seasonal 

 differences in biomass and abundance may become more pronounced on beaches 

 that are more sheltered and not dominated by A. virginiana . 



Energy flow through a sand beach system is less complex than in other 

 intertidal habitats. The sand beach is completely dependent on imported 

 energy for the maintenance of its resident populations; that is, the sand 

 beach fauna utilize the primary production of other systems as supplied by 

 waves and currents. Odum and coworkers (1974) describe the sand beach system 

 as follows: 



The beach, with its sand fauna, forms an extensive 

 food filtering system taking from the rushing water 

 nutrients in the form of detritus, possibly dissolved 

 materials, and plantonic or larger organisms. 



Odum and coworkers (1974) divide the fauna of a sand beach into three 

 components: epipsammon, endopsammon, and mesopsammon. The epipsammon are 

 those species that occur above the sand surface and usually prey on the 

 endopsammon, or those species that live in the sand. Epipsammon is composed 

 principally of shorebirds and fish; whereas, in the characterization area, the 

 edopsammon is dominated by haustorid amphipods, especially Amphiporeia 

 virginiana . This species of amphipod is known to be preyed upon by shorebirds 

 (Croker 1972). 



The mesopsammon group is defined as those flora and fauna that live between 

 sand grains. Figure 4-31 illustrates the relations of these components to 

 each other and the oceanic system. Imported material is used by the infaunal 

 constituents, which either export directly to the marine system or provide 

 energy to the next highest trophic level. 



Gulls, terns, shorebirds, and waterfowl are the dominant birds using beaches. 

 Most birds using sand and gravel beaches, bars, and spits use them more for 

 resting than for feeding. Least terns and piping plovers use beaches for 

 nesting and are the major exception to this usage pattern. Sand beaches are 



4-95 



10-80 



