ECOLOGY OF BUZZARDS BAY: An Estuarine Profile 1 25 



grouped into two types: permanent and variable. 

 Permanent closures are long-term restrictions with 

 no immediate prospect for opening; variable clo- 

 sures are periodically closed and reopened. About 

 60% of the closures are permanent. Variable clo- 

 sures are generally related to weather (warmer tem- 

 peratures increase bacterial activity and therefore 

 often increase coliform populations) and sewage 

 treatment facility malfunctions. In both cases, how- 

 ever, shellfish can be transferred to clean areas for 

 growth and spawning purposes. 



Fecal coliforms are the most common bacterial 

 group used as indicators for potentially dangerous 

 human viruses, which are the real public health con- 

 cern involved in shellfish bed closures. Identifica- 

 tion and quantification of coliform bacteria in coastal 

 waters are relatively simple; this is not the case for 

 viruses, however, and to date no routine methods 

 are available for viral monitoring without great ex- 

 pense and specialized laboratories. Several prob- 

 lems surround the use of coliform bacteria as a 

 monitoring tool. As intestinal bacteria, they are only 

 indicators of pathogen inputs. This method gives no 

 indication of toxic inputs or nutrient or oxygen con- 

 ditions, which ultimately structure the ecological 

 health of an environment and the viability of benthic 

 communities and economic species offish and shell- 

 fish. More importantly from a monitoring standpoint, 

 the presence of coliform bacteria does not mean 

 that viruses are present or even that human wastes 

 are involved. Attempts to identify more specific 

 bacterial indicators have as yet been unsuccessful, 

 with no organism determined to be specific to hu- 

 man sources nor as easily measured as fecal 

 coliforms and as cost effective as coliform monitor- 

 ing. At least for the near future, regulators and man- 

 agers have decided to remain conservative in pro- 

 tecting Buzzards Bay's residents and visitors, main- 

 taining the use of fecal coliforms to identify poten- 

 tial threats to the public health. 



High levels of coliform bacteria usually result in 

 two regulatory actions: first closure of shellfish beds 

 to harvesting to minimize threats to public health 

 through consumption; and second, closure of wa- 

 ters to swimming to minimize direct contact with 

 contaminated waters. Shellfish depuration is 



occasionally undertaken when beds are closed, 

 whereby the shellfish arc removed from bacterially 

 contaminated regions to clean areas and allowed to 

 filter for a specified period ( from days to weeks), 

 subsequently ridding themselves of the temporary 

 bacterial associates. After suitable testing, these 

 shellfish are then evaluated for consumption. 



There are several sources of pathogens and bac- 

 teria to Buzzards Bay, including sewer outfalls, 

 poorly functioning on-site septic systems, 

 stormwater runoff", wildlife, waterfowl, and domes- 

 tic animals. Sewage treatment facilities utilizing 

 outfalls are required to disinfect wastes before dis- 

 charge; however, occasionally failures occur and 

 wastes enter untreated. Bacteria from animal wastes 

 can be introduced to Buzzards Bay waters both 

 directly (primarily waterfowl) and indirectly through 

 incorporation into stream and stormwater flows. 

 Coliform contamination from storm runoff has been 

 identified as the primary cause of shellfish closures 

 in Massachusetts (Heufelder 1 988; Weiskel et al. 

 1 996), and apparently in Buzzards Bay as well. It 

 appears that bacteria associated with animal wastes 

 are washed from impermeable surfaces (roads), 

 which frequently drain directly into the surface wa- 

 ters of an embayment. This helps to explain the re- 

 lationship between increasing nonurban population 

 (Fig. 6. 1 ) and area of shellfish closures because the 

 amount of impermeable land surface is related to 

 development. 



While potential coliform contamination from hu- 

 man wastes is also related to development, the only 

 mechanism for transport involves breakout and sur- 

 face flow from septic tanks since coliforms appear 

 to migrate less than 2 m from residential subsurface 

 disposal sites even if discharge is directly to the 

 water table (Weiskel et al. 1996). In addition, 

 coliform closures occur in areas already served with 

 sewers as well as in areas of on-site disposal. Re- 

 cent studies that compare the ratio of fecal coliform 

 to fecal streptococci may be useful as fecal strep- 

 tococci are often considered better indicators for 

 human wastes. Case studies characterizing the 

 sources of fecal coliform in storm water for the wa- 

 tershed of Bourne showed these ratios to be quite 

 low, indicating only very limited instances of 



