ECOLOGY OF BUZZARDS BAY An Estuanne Profile 41 



Buzzards Bay maintains a wide variety of habi- 

 tats within its environs, representative of most eco- 

 system types found along the mid- Atlantic coast of 

 the United States. Barrier beaches, tidal wetlands, 

 tidal flats, rocky intertidal zones, and hard and soft 

 sediment systems are found all along the perimeter 

 of the bay, as well as circulation-restricted coves 

 and embayments providing protected habitat for 

 many plant and animal species. 



The somewhat unique positioning of Cape Cod 

 along the Atlantic coast has made it a zoogeographic 

 barrier making Buzzards Bay the northern limit for 

 many marine species. North of Cape Cod to La- 

 brador (the American Atlantic Boreal Region ), the 

 biota is more arctic in species composition com- 

 pared with the more temperate species found from 

 the south of Cape Cod to Texas (the American At- 

 lantic Temperate Region). Cape Hatteras forms 

 another boundary to the south, and the region be- 

 tween Cape Cod and Cape Hatteras is known as 

 the Virginian Province. Because of the influence of 

 different currents (the Labrador and Maine currents 

 from the north and the Gulf Stream from the south), 

 water temperatures vary greatly between Cape Cod 

 Bay and Buzzards Bay, with many cold water spe- 

 cies ranging only as far south as Cape Cod, and 

 vice versa. The mixing of Cape Cod Bay water with 

 that of Buzzards Bay since the constaiction of the 

 Cape Cod Canal has stimulated interest regarding 

 potential changes in distribution of various species 

 as a result of this physical alteration. 



The shallow water areas within Buzzards Bay 

 are strongly influenced by meteorological conditions 

 and watershed inputs. Because they are shallow and 

 generally have limited tidal exchange, these areas 

 tend to have greater ranges of environmental con- 

 ditions than those in the central bay. For example, 

 embayment waters frequently warm more rapidly 

 than the bay with approaching summer months and 

 cool more rapidly with the onset of winter. In addi- 

 tion, as these nearshore waters are the immediate 

 recipient of freshwater inputs from terrestrial 

 sources, their salinity structure is more typical of 

 estuaries. Another ecological stress in these 

 embayments is ice rafting, which results from tidal 



fluctuations during winter months. Ice rafting often 

 leads to the scouring of many shallow water areas 

 including tidal wetlands and flats. This scouring of- 

 ten results in the disturbance of bottom-dwelling 

 communities or the dislocation and movement of 

 large sections of wetland peat. As a result of their 

 structure, circulation, and proximity to nutrient in- 

 puts from the adjacent watershed, these shallow 

 embayments tend to have higher rates of produc- 

 tivity than the central bay region on an areal basis 

 and are more susceptible to periodic hypoxic or 

 anoxic conditions in their bottom waters. The net 

 result is a relatively environmentally stable central 

 bay region, fringed with embayments presenting not 

 only a variety of physical habitats but also a greater 

 range in environmental conditions. In this chapter 

 we describe the major habitats within the Buzzards 

 Bay estuarine system and the dominant plant and 

 animal species that help to define them. 



4.1. Open Water and 

 Embayments 



4.1.1. Fauna 



Benthic. The composition and distribution of 

 benthic communities within Buzzards Bay are de- 

 termined primarily by the sediment characteristics 

 of the bay bottom (Table 4. 1 ). Composition and 

 grain size affect the ability of many benthic animals, 

 notably invertebrates and bivalves, to settle and 

 burrow. The benthic community that evolves is sec- 

 ondarily affected by the sediment organic content, 

 which represents a carbon source for benthic de- 

 posit feeders and heterotrophic microbial commu- 

 nities. For a benthic community under a vertically 

 well-mixed water column a high sediment organic 

 content is beneficial. In areas where periodic strati- 

 fication occurs, however, the concomitant high mi- 

 crobial respiration rates create low oxygen condi- 

 tions in bottom waters, which can result in lower 

 populations through reduced recruitment and larval 

 survival or even shifts in benthic community struc- 

 ture towards lower diversity and more opportunis- 

 tic species. It is the interaction between grain size 



