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Massachusetts Estuary Project(MEP) <br /> __------- _ Linked Watershed Embayment Model Peer Revietiv <br /> about the overall condition of the systems,not necessarily any specific sentinel station. It is not possible <br /> for an expert to critically evaluate the strength and reliability of the sentinel stations as a quantitative <br /> threshold without understanding what specific data are being used and how it was collected and analyzed <br /> by MEP(e.g.,shoot density, areal coverage,biomass,water depth,etc.). <br /> Determining how to establish nitrogen threshold concentrations in embayments where eelgrass is either <br /> completely absent or in very low abundance is another uncertainty(e.g.,Buttermilk Bay and Waquoit <br /> Bay). In these embayments it is not feasible to designate"in situ"sentinel stations. As each embayment <br /> in the MEP program is being treated as a separate entity with unique model parameters and threshold <br /> characteristics,it is very difficult to specify a level of confidence in transferring and applying threshold <br /> values from other embayment systems, A simple dose-response relationship between nitrogen <br /> concentration and eelgrass decline in an individual embayment may be reasonable in explaining long- <br /> term declines;however,modeling and empirical studies suggest that the sensitivity of vegetation <br /> (eelgrass;macroalgae and phytoplankton)to eutrophication can vary widely across systems(Havens et al. <br /> 2001,Krause-Jensen et al. 2008,Latimer and Rego,2010). In some cases there maybe no relationship at <br /> all and systems with low nitrogen loading do not support eelgrass for reasons other than nitrogen <br /> enrichment(e.g. light limitation,sediment conditions or recruitment limitations). <br /> Moving forward,the Panel recommends that the MEP adopt a more comprehensive approach for <br /> assessing the environmental conditions and status of eelgrass at sentinel sites. Predicting the level of <br /> certainty and the overall extent for eelgrass expansion into unvegetated and formerly impaired conditions <br /> where eelgrass is competing with other primary producers can be improved by incorporating more <br /> comprehensive monitoring and assessment of factors which affect eelgrass growth,reproduction and <br /> dispersal including optical water quality,substrate condition and water depth. The MDEP has a <br /> calibrated optical water quality model for eelgrass in southeastern Massachusetts embayments that could <br /> be used by the MEP program to expand the scope of understanding for the status of factors which affect <br /> eelgrass distribution, abundance and survival beyond nitrogen(Biber et al. 2008,Gallegos et al. 2010). <br /> The MEP also has an extensive bathyrmetry data set for each of the modeled embayments that can be used <br /> with the bio-optical model to conduct a more comprehensive environmental monitoring and assessment of <br /> threshold stations as well as making better predictions of the suitability of unpaired embayments for <br /> eelgrass growth when nitrogen reniediation and embayment restoration are implemented. <br /> The Panel further recommends that the MEP consider using standard methods for quantitatively assessing <br /> and reporting the health and condition of eelgrass at sentinel stations(see for example, Short and Coles, <br /> 2001,Neckles et al. 2011). Where feasible,categorical variables should be avoided and the sampling <br /> methods should provide numerical results(metrics)with measures of spatial and temporal variation that <br /> can be statistically compared with reference station criteria to ensure that the sentinel sites represent <br /> equilibrium conditions for eelgrass. <br /> Key Issue 3-Establishing Realistic Eelgrass Restoration Goals with Nitrogen Thresholds <br /> The expectation that eelgrass recovery in Massachusetts embayments will occur following nitrogen <br /> reductions is supported by empirical studies and observations at locations where point source discharges <br /> were modified(e.g.,Mumford Cove, CT;New Bedford Harbor,MA; and Boston Harbor,MA)(Vaudry <br /> et al. 2010,Leschen et al. 2010, Costello and Kenworthy,2011). Where viable reproductive populations <br /> are present,natural recovery of eelgrass can proceed by dispersal of flowers and seeds to unvegetated <br /> areas with suitable substrate and favorable environmental conditions(Greeve et al. 2005, Orth et al. <br /> 2006b Orth et al. 2006c,Vaudry et al. 2010). In contrast to natural recruitment, eelgrass restoration <br /> using adult transplants that depend on clonal growth is much slower than seed dispersal. Transplanting <br /> adult plants is an unpredictable process because success depends on several biological and physical <br /> factors and not just the concentration of nitrogen(Fonseca et al. 1998, Short et al. 2002,Paling et al. <br /> 2009, Orth et al. 2010). There is a large variation in the success rate and sustainability of seagrass <br /> December 30,2011 <br />