from which the clays were originally derived (Hathaway 1972) . These deposits 

 are subject to modification by waves and currents. 



Except for an occasional large stone, unconsolidated bottoms do not provide 

 suitable substrata for the development of large macroalgae. Hence, organic 

 matter flux is largely determined by phytoplankton production and the inflow 

 of detrital material. Microbial transformation of organic material depends 

 upon the degree of anaerobiosis in the sediments, which, in turn, is related 

 to the magnitude of organic deposition. 



Subtidai unconsolidated bottoms often support a large number of animal species 

 in varying densities. Since these animals are dependent on the influx of 

 detritus and phytoplankton productivity, the density of individuals below the 

 photic zone usually decreases with depth. At the same time diversity, or 

 numbers of species, usually increases with depth, because of the increasing 

 environmental constancy, which, over time, has allowed the species present to 

 partition the environment more finely through evolution (Gray 1974). 



Sediment type and particle size influences the structure of benthic 

 communities. Unstable sediments are suitable only for those species that can 

 burrow quickly and thereby maintain a proper contact with the sediment 

 surface. Fine sediments are often dominated by deposit feeders, which glean 

 organic matter from the substratum, and, in so doing, may prevent the 

 establishment of suspension-feeding populations (Rhoads and Young 1970). Fine 

 sand has the highest species richness, followed by a lowered number of species 

 in coarse sand or gravel. Sediments that have high percentages of silt and 

 clay appear to be generally poor in numbers of species. Sediments that have a 

 high silt-clay content also often have very high percentages (over 85%) of 

 polychaetes, often with high abundances of one or two species (Normandeau 

 Associates 1974) . 



Information on the benthic communities of unconsolidated bottoms in the marine 

 system in Maine is sparse relative to what is available in other geographic 

 areas. The principal qualitative surveys include Verrill (1874) and Kingsley 

 (1901) in Casco Bay (region 1), Procter (1933) in the Mt. Desert area (region 

 5), Webster and Benedict (1887) and Verrill (1872) in the Eastport area 

 (region 6). Quantitative studies in the characterization area are largely the 

 result of impact-related surveys. Normandeau Associates (1974), Rowe (1972 to 

 1973), and the U.S. Environmental Protection Agency (EPA; 1975) surveyed in 

 Casco Bay (region 1). Dean (1977) studied a site off the mouth of the 

 Kennebec River (region 2). Penobscot Bay sites were examined by Kyte (1974), 

 Normandeau Associates (1975), and Dean and Schnitker (1971) (region 4). 

 Larsen and Doggett ( unpublished ) sampled a few stations in Cobscook Bay 

 (region 6), and Bilyard (1974) did research near Damariscove Island (region 

 2). 



Cobscook Bay, the only place in region 6 where unconsolidated bottoms have 

 been sampled, seems to be particularly diverse. Larsen and Doggett 

 ( unpublished ) found the mean number of species per station (0.2m ) to be 50 

 (range 28 to 70). The mean density in Cobscook Bay, 3788 individuals (m~ ) 

 (range 880 to 12,970) is also relatively high for a nonenriched, boreal 

 coastal area. Both the diversity and density of Cobscook Bay, and presumably 

 eastern Maine in general, are a reflection of the unique hydrographic features 



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