44 BIOLOGICAL REPORT 31 



Fig. 4.1. Method of feeding and reworking of sediments 

 by Yoldia limatula. From Rhoads (1963). 



The state of oxidation or reduction of the benthic 

 sediments at any one location is an integration of 

 the type of benthic community, rate of bioturbation, 

 and rate of delivery of organic-rich particles to the 

 sediments. In areas with low organic matter deliv- 

 ery or deep burrowing, deposit-feeding communi- 

 ties the sediments are generally oxidized, and con- 

 versely more reducing (sulfide) where high rates of 

 organic deposition and shallow burrowing commu- 

 nities occur. In Buzzards Bay physical disturbances 

 can affect benthic communities and hence 

 bioturbation by reducing the depth of bioturbation 

 and increasing the sulfitic zone of the sediments; with 

 sufficient time, the communities are reestablished. 

 Over the past 1 00 years, however, nutrient and or- 

 ganic discharges to Buzzards Bay waters (e.g.. New 

 Bedford) have led to increased organic delivery to 

 sediments in some areas, which appears to have 

 resulted in the alteration of benthic communities. 

 Whether the structuring factor is the rate of organic 

 matter delivery directly or secondary effects of water 

 column hypoxia or anoxia is unclear. The result is 

 declining diversity and shallowing of the depth of 

 bioturbation and therefore an increase in the sulfitic 

 zone in those areas. This general scheme of 



alterations (Rhoads and Germano 1986) in benthic 

 communities and sediment oxidation (Fig. 4.2) is 

 occurring in Buzzards Bay today; the difficulty for 

 ecologists and managers is to distinguish alterations 

 driven by natural or physical forces from those 

 driven by nutrients and organic matter. 



Buzzards Bay sediments also play an important 

 role in the life stages of many pelagic species. For 

 instance, studies of the eggs of marine planktonic 

 copepods in the bottom sediments of Buzzards Bay 

 indicate that sediments may be part of an important 

 pathway for recruitment of these organisms into the 

 plankton community. The eggs, which have the 

 ability to resist digestion when ingested by benthic 

 predators, overwinter in the sediments and hatch in 

 spring when water temperatures rise (Marcus 

 1 984). In shallow coastal waters such as Buzzards 

 Bay, storm events, current flow, and bioturbation 

 also influence the transport and hatching of these 

 eggs. Marcus (1984) and others (Dale 1976; 

 Anderson et al. 1 982 ) indicated this mechanism may 

 also be important for dinoflagellate bloom forma- 

 tion, whereby large numbers of cysts and fine- 

 grained sediment particles accumulate on the sea 

 floor and are resuspended on a large scale by cer- 

 tain physical disturbances such as coastal storms. 

 Marcus and Fuller (1989) later determined that 

 physical mechanisms affecting sedimentation and 

 transport can be used to predict the distribution and 

 abundance of recently spawned eggs on the bay 

 bottom. 



Meiofauna. Meiofauna represent infauna from 

 most marine phyla with the unifying trait that they 

 are animals, mostly metazoans, that can pass through 

 a 1 .0-0.5 mm screen. Their role in organic matter 

 cycling in coastal sediments is still an area of active 

 research, but it is clear that they play a role in sedi- 

 ment microbial food chains and are consumed by 

 deposit feeders. Meiofaunal populations in Buzzards 

 Bay are overwhelmingly dominated by nematodes 

 and kinorhynchs. composing between 89 and 99% 

 of the total numbers ( Wieser 1 960). Certain spe- 

 cies of nematodes appear to be restricted to par- 

 ticular sediment types; for instance Odontophora 

 and Leptonemella species dominate sandy 



