09/13/1999 SELECT BOARD Minutes - Laserfiche WebLink

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UPDATE (September 13, 1999): Nutrient Management of the Popponesset Bay System: Quantitative Assessment of the Nitrogen Loading Tolerances of Component Sub-Embayments Brian L. Howes, Ph.D. Center for Marine Science and Technology University of Massachusetts—Dartmouth Focus: The overall goal of this project is to manage nitrogen inputs into the Popponesset Bay System to restore the ecological health of the bay environments. At present, the Mashpee River, Shoestring Bay,Ockway Bay and inner Popponesset Bay are showing nutrient related stress. The nutrient over- loading of this estuarine system has resulted in the loss of eelgrass, enhancement of macro-algal mats (some areas with floating mats:Mashpee River& Shoestring Bay), reduced animal communities and bottom-water oxygen depletion. Restoration of each of these sub-systems requires identification of their specific tolerance level for nitrogen loading, identification of nitrogen sources contributing to present overloading,and implementation of management options to reduce loading to"healthy"levels. Overview: The on-going Water Quality Study focuses on a unified environmental assessment of the current health of the Popponesset Bay system, a determination of the sensitivity of Bay systems to changing levels of man-induced nutrient inputs, and identifying the primary ecological and anthropogenic processes affecting these conditions. The study is specifically designed to provide the quantitative information on nitrogen loading tolerances of the sub-embayments. Nitrogen tolerances are necessary for developing wastewater treatment(or other) plans aimed toward protecting future potential degradation of the Popponesset Bay System and/or ameliorating current nitrogen based degradation. Through this ecosystem wide approach, current and potential impacts and/or recovery of the ecological health of Popponesset Bay Systems can be determined. All parts of the study are required in order to provide the integrated environmental assessment needed for the development of a sound watershed/embayment nutrient management. Update on Study Findings: It is clear that a significant portion of the Popponesset Bay System is experiencing nutrient related water quality decline. The results of the Water Quality Study(to date) indicate that different areas within the system are showing different levels of environmental health. In general,areas with potentially lower circulation appear to have lower water quality and are more sensitive to impacts from nutrient loading. Not surprisingly, these are also most likely the areas with the most significant nutrient inputs. The Mashpee River is severely impacted by nutrient overload, showing poor water quality, algal blooms and frequent low oxygen conditions. Ockway Bay and Shoestring Bay experience periods of low oxygen and appear to be subject to occasional algal blooms indicative of nutrient related impacts. Upper Popponesset Bay (central) is also showing clear indications of nutrient related ecological stress, showing periodic low oxygen conditions and depauperate animal communities. This portion of the Bay system was originally thought to be relatively healthy,but measurements collected during 1998 and 1999 indicate that the zone of nutrient j impact has reached at least mid-way into the central Bay region. The CMAST Popponesset Bay Study has focused (to date) on determining the level and causes of