Development of a reference coastal wetland set in Southern New England (USA)

Abstract

Various measures of plants, soils, and invertebrates were described for a reference set of tidal coastal wetlands in Southern New England in order to provide a framework for assessing the condition of other similar wetlands in the region. The condition of the ten coastal wetlands with similar hydrology and geomorphology were ranked from least altered to highly altered using a combination of statistical methods and best professional judgment. Variables of plants, soils, and invertebrates were examined separately using principal component analysis to reduce the multidimensional variables to principal component scores. The first principal component scores of each set of variables (i.e., plants, soil, invertebrates) significantly (p < 0.05) correlated with both residential land use and watershed nitrogen (N) loads. Using cumulative frequency diagrams, the first principal component scores of each plant, soil, and invertebrate data set were plotted, and natural breaks and best professional judgment were used to rank the first principal component scores among the sites. We weighted all three ranked components equally and calculated an overall salt marsh condition index by summing the three ranks and then transforming the index to a 0-1 scale. The overall salt marsh condition index for the reference coastal wetland set significantly correlated with the residential land use (R = -0.87, p = 0.001) and watershed N loads (R = -0.86, p = 0.001). Overall, condition deteriorated in salt marshes and their associated discharge streams when subjected to increasing watershed residential land use and N loads.

Local-scale characteristics of high-marsh communities next to developed and undeveloped shorelines in an ocean-dominated estuary, Murrells Inlet, SC

“…Based on salt marsh restoration studies, plant biomass (Broome et al 1986;Roman et al 2002), genetic diversity (Travis et al 2002), fish utilization (Roman et al 2002;Able et al 2004), and sediment salinities (Walters 2009) can change rapidly within newly planted marshes, while changes in sediment organic content (Craft et al 1999), nutrient cycling (Thompson et al 1995;Craft et al 1999), infauna (Sacco et al 1994;Levin et al 1996), and plant canopy (Zedler 1993) tend to require significant time if not decades. Ecological changes in Narragansett Bay salt marshes only were detected after two decades of urbanization (Wigand et al 2010). The developed shoreline we studied, OMD1, consisted of recently built (\5 years) and ongoing building and therefore was a newly developed shoreline along which high-marsh changes may not have been expected to have occurred.…”

“…Differences in tidal creek sediment characteristics (Sanger et al 1999a, b;Van Dolah et al 2008) and benthic faunal communities (Lerberg et al 2000;Bilkovic et al 2006) also have been correlated to landscape-scale change resulting from suburban, urban and industrial alterations of coastal watersheds. Although less studied, local development of the terrestrial-marine boundary also can affect adjacent marine habitats (Wigand et al 2001;Bertness et al 2002;Pennings et al 2002;Silliman and Bertness 2004;Bertness and Silliman 2008;Gedan et al 2009;Wigand et al 2010). In the rapidly developing Southeastern USA coastal region, both unknown local-and wellstudied landscape-scale changes (e.g., Lerberg et al 2000;Holland et al 2004;Lewitus et al 2004) are likely to have major affects on the terrestrial-marine boundary and adjacent marsh habitats.…”

Development and validation of rapid assessment indices of condition for coastal tidal wetlands in southern New England, USA

“…The finer scale measures of plant species and soil characteristics (i.e., resistance to penetration, surface macroorganic matter) were sometimes aggregated into a single VSS index to simplify the analyses. The statistical PCA and ranking approach was previously described to develop an intensive assessment condition index for a reference set of wetlands (Wigand et al 2010). When necessary, the signs of the eigenvectors and first principal component (PC1) scores were transformed with the expected best in the positive direction.…”

“…Wetland condition can be defined as the quality of the wetland as a function of physical, chemical, and biological parameters (Brooks et al 2004). Incorporating a reference set of wetlands (i.e., from low to high levels of anthropogenic alteration) or a reference standard (e.g., least disturbed) into the sampling design for the rapid assessment can help validate the method, and help provide a benchmark to compare stressor effects, biotic responses, and condition scores (Smith et al 1995;Brinson and Rheinhardt 1996;Wigand et al 2010). Assessment indices can be structured to provide an estimate of how much a wetland has diverged from a reference standard, or can be used to describe the relative rank of a wetland when its condition is compared to other sites in a regional reference set of wetlands.…”

“…Nested within the 81-site data set is a reference set of ten coastal tidal wetlands which spanned low to high watershed development and nitrogen loadings (Wigand et al 2003(Wigand et al , 2010. This reference set of coastal wetlands had previously been used to determine overall wetland condition based on time-consuming and labor-intensive studies of vegetation, invertebrates, and soils, hereafter referred to as the intensive assessment index.…”