56 



BIOLOGICAL REPORT 31 



since the effects of salt marsh organic matter pro- 

 duction on the open waters of the bay are based on 

 detrital food chains. Periphyton, eelgrass epiphytes, 

 and macroalgae are estimated from other systems 

 and adjusted to approximate distribution within 

 Buzzards Bay (Costa 1 988a). 



Although macrophytes have higher rates of pro- 

 duction. Buzzards Bay supports essentially a phy- 

 toplankton-based (89%) carbon cycle. Although 

 macrophyte production is more concentrated, phy- 

 toplankton photosynthesize throughout most of the 

 water column of the bay and its embayments (Table 

 4.5). In addition, the areal extent of phytoplankton 

 habitat is more than seven times that for all benthic 

 floral types. Historically this distribution has not 

 changed significantly given the relatively small con- 

 tributions from wetlands and eelgrass beds. These 

 latter plant communities, however, contribute more 

 than organic matter. Eelgrass beds and tidal wet- 

 lands provide habitats with ecological processes and 

 niches very different from those of the open bay. 

 The concentration of organic matter production in 

 these systems and the physical environment they 

 create give them a disproportionate role in the 

 secondary production of Buzzards Bay. 



Phytoplankton and Zooplankton. Buzzards 

 Bay phytoplankton populations are generally re- 

 ported as being dominated by Skeletonema 

 costatum, Leptocylindrus minimus, and species 

 of Rhizosolenia. Zooplankton are dominated by 

 the copepods Acartia spp. and Paracalanus 

 crassirostris. Most of the phytoplankton produc- 

 tivity in Buzzards Bay is attributed to diatoms, with 

 dominant species consisting of a mix of estuarine 

 and coastal species commonly found in New En- 

 gland. Red tide blooms have not been significant in 

 Buzzards Bay to date. Brown tides (Casper et al. 

 1 987), so detrimental to filter-feeding communities 

 and certain fish populations, have not been observed, 

 although these phytoplankton have been reported 

 in nearby Narragansett Bay. 



Macroalgae. The distribution of macroalgae 

 in Buzzards Bay appears to be controlled by tem- 

 perature (lower bay waters are colder than those in 

 the shallow embayments and upper bay), substrate. 



light, and nutrient availability. The temperature ef- 

 fect is particularly noticeable in the shallow regions, 

 which exhibit distinct seasonal floras of winter and 

 early spring versus midsummer and fall (Davis 

 1913). 



Within the Buzzards Bay system there is a wide 

 range of macroalgal habitats, each habitat contain- 

 ing a diversity of algal species. The shallow, high- 

 light, nutrient-rich regions support the most laxuri- 

 ous growth. Brackish pools and intertidal areas 

 within salt marshes have algal mats dominated by 

 Lyngbya and Microcoleus, floating or loosely at- 

 tached growths of Enteromorpha species, and 

 patches of Ascophyllum along creek banks. The 

 shallow embayments and nearshore zone of the 

 open bay support green algae. Cladophora, with 

 C. flexuosa and C. arcta abundant on hard sub- 

 strates (rocks, piers) in spring and summer and C. 

 gracilis forming dense accumulations in embayments 

 in summer. 



Those areas of rock or cobble shores (south- 

 eastern shore) support the most impressive 

 macroalgal growth. The rockweeds, As'cop/7v//»A?7 

 nodosum and Fucus vesiculosus, abound on rocks 

 in the littoral zone. Other hard-bottom (sand, shells, 

 or rock) species of note are Laminaria spp., 

 Condrus crispus and Polysiphonia (8 spp.) in 

 deeper water and Sargassum and Codium in the 

 shallower areas of the bay. Phyllophora is notable 

 as being found at the lower depths on substrate 

 ranging from rock to sand to mud and is distributed 

 throughout the bay (Davis 1913). 



Macroalgae are of concern to resource manag- 

 ers because dense accumulations can result from 

 excessive nutrient loading to shallow coastal water 

 bodies (Valielaetal. 1990; Costa etal. 1992). When 

 they occur, these accumulations may have detrimen- 

 tal impacts on benthic communities, both infauna 

 and fish. At the more modest levels of production 

 generally found in Buzzards Bay, attached 

 macroalgae can have the opposite effect, providing 

 habitat for animals and increasing secondary 

 productivity. 



Eelgrass. Eelgrass, or Zostera marina, is a 

 rooted subtidal macrophyte that forms extensive 



