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Bournes Pond Systems, Popponesset Bay System, and the nearby Hamblin / Jehu Pond / <br /> Quashnet River analysis in eastern Waquoit Bay, among many other systems previously <br /> analyzed by the MEP. This is almost certainly going to be true for the other embayments within <br /> the MEP area, as well, inclusive of Waquoit Bay, Eel Pond and Childs River. <br /> The threshold nitrogen levels for the Waquoit Bay embayment system, shared by <br /> Falmouth and Mashpee,were determined as follows: <br /> Waquoit Bay Threshold Nitrogen Concentrations <br /> • Following the MEP protocol, the restoration target for the Waquoit Bay Embayment <br /> system should reflect both recent pre-degradation habitat quality and be reasonably <br /> achievable. The approach for determining nitrogen loading rates, which will maintain <br /> acceptable habitat quality throughout and embayment system, is to identify a sentinel <br /> location within the embayment or sub-embayment and second, to determine the nitrogen <br /> concentration within the water column which will restore that location to the desired <br /> habitat quality. Given the complex configuration and hydrodynamics of the Waquoit Bay <br /> Embayment System, multiple nitrogen thresholds locations were selected as to insure an <br /> accurate determination of estuarine response to reductions in watershed nitrogen <br /> loading and/or enhanced tidal flushing. <br /> • Within the main basin of Waquoit Bay, a sentinel station was selected at the long-term <br /> monitoring location (WB12) targeting restoration of eelgrass habitat within the basins <br /> northern and southern portions. Similarly, within the Childs River the long term <br /> monitoring within the main channel near the upper extent of the historic coverage as <br /> selected (CR02). Meeting the nitrogen target at both these stations will necessarily <br /> result in lower total nitrogen levels in the down gradient Eel Pond (east branch and Eel <br /> Pond lower basin) and southern portion of Waquoit Bay, to restore eelgrass habitat in <br /> these lower tidal reaches as well. Meeting the nitrogen threshold in upper Waquoit Bay <br /> will also lower nitrogen related impairments in Sage Lot Pond, which is presently <br /> supporting moderately impaired eelgrass habitat. As such, Sage Lot Pond is presently <br /> just over its nitrogen threshold, and only a moderate reduction in nitrogen levels is <br /> required to achieve restoration. Since Sage Lot Pond exchanges tidal waters with the <br /> lower portion of Waquoit Bay, as nitrogen levels are reduced in the main basin, Sage Lot <br /> Pond levels will decline as well. For these basins, the target nitrogen level to achieve <br /> restoration of eelgrass habitat is 0.38 mg TN L"', compared to the present tidally <br /> averaged TN levels of 0.40 mg TN L"'for Waquoit Bay and 0.63 mg TN L-'for the Childs <br /> River station <br /> • Although the nitrogen management target is restoration of eelgrass habitat (and <br /> associated water clarity, shellfish and fisheries resources), benthic infaunal habitat <br /> quality must also be supported as a secondary condition. This is the case for the <br /> western basin of Eel Pond which has not historically supported eelgrass beds, but <br /> presently has significantly impaired benthic animal habitat (and the Quashnet River). <br /> Benthic animals are more tolerant of nutrient and organic matter enrichment than <br /> eelgrass, which requires clear waters and high oxygen levels. At present, in the regions <br /> with moderately to significantly impaired infaunal habitat within upper Eel Pond, long <br /> term monitoring station ER01 has an average tidal total nitrogen (TN) level of 0.67 mg <br /> TN L"'. The observed impairments throughout this estuary are consistent with <br /> observations by the MEP Technical Team in other estuaries along Nantucket Sound <br /> (e.g. Perch Pond, Bournes Pond, Popponesset Bay). Based upon these observations <br /> Executive Summary 9 <br />