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oF_f7c jl i�/( , zzd <br /> "Environmental processes are extremely complex and inherently uncertain, and even the best and most sophisticated <br /> models are only simplistic representations." <br /> ."the Panel recommends that they characterize validation as a process, not an end result, and point out that model <br /> validation cannot ensure acceptable predictions"... <br /> p.18 Peer Review <br /> Empirical and modeling studies demonstrate that eutrophication in southeastern Massachusetts is derived mostly from a <br /> combination of nitrogen enhanced chlorophyll abundance in the water column and excessive macroalgal growth(Valiela et <br /> al. 1997b, Hauxwell et al. 2001). The MEP program has not specifically identified nitrogen threshold values for either of <br /> these two components, so it is not possible to predict if the threshold concentrations would limit these primary producers <br /> from outcompeting eelgrass(Pedersen and Borum, 1996,McGlathry et al.2007). <br /> p.21 Peer Review <br /> It is not possible 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 by MEP (e.g., <br /> shoot density, areal coverage,biomass,water depth, etc.).....Moving forward,the Panel recommends that the MEP adopt a <br /> more comprehensive approach for assessing the environmental conditions and status of eelgrass at sentinel sites. ..... As <br /> per Short et al. (2002), an embayment restoration suitability index should be developed that incorporates a wider set of <br /> predictor variables than just the nitrogen concentrations at the sentinel stations. <br /> pp.23+24 Peer Review <br /> The nitrogen source distribution imbalance towards nonpoint sources will undoubtedly make attainment of the TMDL more <br /> challenging, and perhaps more costly. However, it may provide a better framework for phased implementation that could <br /> support a structured adaptive management approach. <br /> p.26 Peer Review <br /> A potential management outcome already identified in CWMPs is constructing sewers and centralized wastewater <br /> treatment facilities. Those actions would technically shift the nitrogen load from a nonpoint source load allocation to a <br /> point source wasteload allocation within the TMDL. That reallocation requires an update of the adopted TMDL, and <br /> reapproval by EPA,which would also provide an opportunity to apply the reassessment and adjustments that are learned in <br /> an adaptive management framework. <br /> ..the size and character of Cape Cod's watersheds, the high levels of nitrogen removal required to meet TMDLs, and the <br /> limited diversity of sources and management options may be obstacles-to watershed market mechanisms, like trading. <br /> Small watersheds with few sources responsible for most or all of the impairment have low market appeal because options <br /> for trading are so limited. Hence,nitrogen credits would likely be a scarce commodity in many Cape Cod watersheds and <br /> would become even more limited as attainment of the final TMDL nears. <br /> p.27 Peer Review <br /> each of the MEP studies should include a sensitivity analysis of key components and links in the nitrogen loading and <br /> transport chain. ....The Panel also recommends that the list of parameters evaluated in the sensitivity study for each estuary <br /> be expanded from that in Howes et al. (2002)to also include the concentration of nitrogen at the ocean boundary since this <br /> is known to be a sensitive parameter. <br /> p.29 Peer Review <br /> the Panel believes the uncertainties in these data-based linkages are conservative in the sense that the actual nitrogen <br /> concentrations required to achieve the eelgrass endpoints are probably lower than the threshold nitrogen concentrations in <br /> the TMDLs <br /> p.30 Peer Review <br />