In the Larsen and Doggett study (in preparation ) no relationship between 

 sediment parameters (including interstitial salinity) and biotic parameters 

 could be discerned, with the exception of the Mt. Desert site. The beach at 

 Mt. Desert is most similar to the one at Reid State Park in terms of exposure 

 and sediment grain size, while in terms of density and species diversity the 

 two are dissimilar. The difference is that the sediments at Mt. Desert are 

 composed largely of shell fragments, which limit faunal development (Stephen 

 1930, and Hedgpeth 1957). 



The degree of wave exposure is a major ecological factor on sand beaches (Seed 

 and Lowry 1973) . The fauna of extremely exposed beaches is limited (Stephen 

 1930; and Scott 1960). With decreasing exposure, amphipods become abundant, 

 followed by polychaetes, and finally molluscs on the most sheltered beaches. 

 Increasing shelter cannot explain the distribution of fauna observed by Larsen 

 and Doggett (in preparation ) . An example of the faunal differences between an 

 exposed and neighboring less-exposed sand beach is presented in table 4-13. 

 The exposed beach is dominated by amphipods, while in the less-exposed 

 location polychaetes and molluscs are more abundant. The number of species 

 and biomass also increase with decreasing exposure (Mclntyre 1970). 



Sand beaches exhibit a high degree of variability in faunal density, as is 

 shown by the large ranges in density in table 4-14. The highest densities 

 recorded by Larsen and Doggett (in press ) occurred at the lower intertidal 

 regions of amphipod-dominated western beaches composing site group A. The 

 more eastern beaches in site groups B and C, which are dominated by 

 polychaetes, have much lower faunal densities. In general, the mean densities 

 on sand beaches are not exceptionally high, as has been stated often (Hedgpeth 

 1957). Indeed, of the nine intertidal habitats sampled in Maine (Larsen and 

 Doggett, in press ) sand beaches had the lowest mean species density. 



Sand beaches are populated by very few species relative to other marine 

 habitats. This is because of the stress associated with the constantly 

 shifting sediments. The range of species found at individual sites (table 4- 

 14) is fairly typical for boreal and temperate sand beaches. The high total 

 number of species reported by Larsen and Doggett (in preparation ) from the 

 western site-group A beaches largely confirms the summer zonation pattern 

 presented by Croker and coworkers (1975). The lower intertidal zone was 

 dominated by the haustorid amphipod Amphiporeia virginiana , the mid-intertidal 

 regions at these sites were inhabited by other haustorid amphipods, such as 

 Acanthohaustorius millsi and Haustorius canadensis, and the polychaete 

 Scolelepis squamata , while the amphipod Talorchestia megalophthalma , a species 

 related to Orchestia platensis , was the most abundant animal in the upper 

 intertidal area. This pattern is similar to that proposed by Dahl (1953) and 

 modified by Fincham (1971) for the north temperate regions with the exception 

 that no cirolanid isopod belt was found in the mid-intertidal region of the 

 beaches, a situation previously reported by Colman and Segrove (1955). 



A different pattern of zonation was observed by Larsen and Doggett (in 

 preparation ) at the eastern Maine beaches sampled. In each case, the lower 

 intertidal zone contained the polychaetes Nephtys caeca, Paraonis fulgens 

 and/or the amphipod Psammonyx nobilis . Croker and coworkers (1975) found the 

 latter species intertidally only in the winter in western Maine. Apparently, 

 sununer water temperatures are cool enough in the eastern part of the study 

 area for the species to survive on the beaches in this season. Polychaetes, 



4-92 



