42 



BIOLOGICAL REPORT 31 



Table 4.1. Dominant soft-bottom, hard-bottom, and rocky intertidal communities in Buzzards Bay Soft- 

 bottom species listed comprise 95% of the species present by number Hard-bottom species are listed when 

 found to comprise more than 1% of the population. Data on soft- and hard-bottom species from Sanders 

 (1958, 1960); rocky intertidal data from unpublished field surveys (Boston University Marine Program) 



•Phyla are listed for seaweeds, classes for other species 



'Because Cerastoderma populations are highly seasonal, it is not considered to be a good characterizing species for this community (Sanders 1958) 



and organic matter and oxygen that appears to be 

 structuring Buzzards Bay benthic communities 

 today. 



Sanders ( 1 958, 1 960) characterized the benthic 

 communities in Buzzards Bay into two faunal groups 

 or assemblages. The first is typified by deposit feed- 

 ers generally present in softer, muddier sediments 

 and dominated by the polychaete Nephthys incisa 

 and the lameMibranch Nuncula proxima. The weak 

 currents that allow organic matter to settle out in 

 these areas provide a source of food for large num- 

 bers of these deposit feeders (average Nuncula 

 densit) 30-40,000 m 2 ). Data from Sanders (1958. 

 1 960) also indicate that the distribution of deposit 

 feeders is strongly correlated to the percentage of 

 clay, with the smaller clay particles having more sur- 

 face area to bind organic matter. The second com- 

 munity is primarily found offshore in sandy bottoms 



and is made up mainly of filter feeders dominated 

 by amphipods (Ampelisca spp.). The primary de- 

 terminant for distribution of filter feeders is not fully 

 known, but their communities generally predomi- 

 nate in areas of well-sorted fine sands indicative of 

 moderate, relatively constant currents that provide 

 sufficient food via suspension in the water column. 

 Driscoll and Brandon ( 1 973 ) further divided 

 subtidal habitats within Buzzards Bay into four func- 

 tional groups: shallow protected, nearshore, open 

 bay, and offshore. The shallow protected, nearshore. 

 and offshore areas are generally characterized as 

 having fine-grained sediments (mean grain diameter 

 of less than 0. 1 8 mm), analogous to the Nuncula 

 proxima - Nephthys incisa communities identified 

 by Sanders ( 1 958, 1 960). These three habitats have 

 distinctly different sediment characteristics and fau- 

 nal assemblages than the open bay areas (mean grain 



