Operationalizing sustainability:: Management and risk assessment of land-derived nitrogen loads to estuaries

Sustainable coastal management requires that the goals and means of management be made operational and specific. We use Waquoit Bay, Massachusetts, as a case study, to suggest a decision-making process that brings updated scientific results forward while incorporating stakeholder concerns. Land-derived nitrogen loading is the major agent of change for receiving estuaries in the Waquoit Bay estuarine complex, so control of nitrogen loading rates is a principal goal of land management plans. We can establish the relationships of land use pattern to nitrogen loading rates, and of loading rates to mean annual concentrations of nitrogen in the estuaries. The latter, in turn, can be related quantitatively to mean annual production and biomass of phytoplankton, macroalgae, and eel-grass. We propose that phytoplankton, macroalgal, and eelgrass production and biomass are suitable end point measures that can be made meaningful to stakeholders. We define the relationship of agent of change vs. end point measure, and then have policy makers and stakeholders decide which critical end point is desirable or acceptable for the selected end point measures. Thus, science results and stakeholder opinion are merged to establish management goals. Having chosen a desired critical end point, we can use nitrogen loading models to assess the degree to which different management options can alter nitrogen loading rates to levels that meet the agreed-upon management goals. These modeled simulations will identify the effects on loading rates from each management action and, hence, permit an assessment of a suite of management actions that can be used to meet the management goals. These procedures incorporate ecological knowledge with cultural, political, and economical imperatives and force identification of what is acceptable as an end result. These strategies furnish one way to design reasonable, and ecologically and socially sustainable plans for the inevitable use and management of coastal watersheds.