Cape Cod Salt Marsh Monitoring

Over the last several years, CCS has been studying the specific ecology of salt marsh chemistry and plant species distribution on Cape Cod with help from The Boston Foundation, New England Natural Areas Wildlife Grants Program, and Sweet Water Trust. This support has led to a great deal of valuable data and the development of a directed research and monitoring program designed to work with state agencies and land management groups to improve coastal wetland restoration. The project hypotheses, goals, and preliminary findings are detailed below:
 

The Center for Coastal Studies has recently completed the first year of a three-year comprehensive ecological assessment of a series of tidally restricted salt marshes within Cape Cod. The study is designed to examine the significance of marsh age, soil texture and soil biogeochemistry between native (cord grass [Spartina]) and invasive (reed grass [Phragmites]) plant communities occurring within Cape Cod’s salt marsh habitat. These data will be considered as they relate to conservation, restoration and management of these valuable ecosystems. Specifically, the data gathered will aid in the development of site-specific restoration strategies designed to promote native plant species and discourage invasive plant communities that detract from wetland functions and values and associated wildlife habitat. This project is based upon CCS’s on-going ecological assessment salt marsh restoration and ecology within the Cape Cod Bay and our Coastal Solutions initiative to link rigorous scientific study with existing land management and policy towards improving coastal wetland restoration.

To insure the applicability of this study to timely restoration issues in the state of Massachusetts, CCS focused upon salt marshes cited in the Atlas of Tidally Restricted Salt Marshes of Cape Cod, produced by the Cape Cod Commission in conjunction with the Massachusetts Wetland Restoration Program. The rationale is simple – to provide a scientific basis to support and improve coastal wetland restoration success. CCS scientists plan to continue to record plant community structure, pore water chemistry, and soil characteristics using standard, reproducible methods within these Cape Cod salt marsh ecosystems towards the improvement of restoration planning and implementation. This continuing project seeks to achieve this through two components: 1) an on-going ecological monitoring component, including measurement of several biological and biogeochemical parameters, designed to classify general coastal marsh types; and 2) a modeling component to apply results towards the development of more effective site-specific management decisions within presently identified systems suggested for future restoration.

Based upon data collection from the 2003 growing season, CCS has compiled a preliminary profile of a selection of Cape Cod salt marshes, highlighting the relationships between soil types, interstitial biogeochemistry, and the dominant plant community. In short, the data demonstrate potentially significant differences between the soil and chemistry between restricted and natural marshes that may be exploited to promote effective plant community restoration. Through continued monitoring, the data can direct the pre-restoration planning process by providing a site-specific understanding of existing conditions, and aid in the prediction of desired outcomes. Meanwhile, these data can contribute to a Cape wide data base valuable to scientists and land managers. Presently CCS is in the process of creating a web-based system of reporting these data, so that they will be immediately available to the public.

Given the great expense of wetlands restoration and the large number of potential projects, it is essential to establish rational, scientifically-proven methods to measure results and determine the success of such ventures. CCS believes this continued project will help both managers and funders in setting their own priorities for selecting restoration projects in the future. Through the implementation of our ongoing study, CCS has developed stronger working relationships and pending collaborations with local and state agencies, actively working towards improving wetlands management and restoration as well as data exchange within and between interest groups.

While preliminary at this stage, the data reflect the well-documented trend where tidally restricted salt marsh sites maintain significantly lower salinity than natural, unrestricted sites within the same system. With reduced tidal exchange comes a decreases in oxygen-rich water flushing the systems, thus, tidally restricted sites tend to be more anaerobic (lacking oxygen). Again, overall, the sites sampled reflected this predicted pattern (Table 1). Despite this trend, when restricted and unrestricted portions of salt marsh systems were compared at individual sites, CCS data suggests that the strength of this prediction breaks down. At many sites, significant difference did not exist, questioning the potential effectiveness of tidal restoration strategies for these systems. In fact, highlighting site-specific differences is one of the goals this study attempts to demonstrate, as shown in Table 2. At these sites, novel, site-specific management strategies may be required to achieve restoration goals.

Table 1: Mean values for selected pore water biogeochemical parameters between tidally restricted and unrestricted salt marshes within Cape Cod Bay. Standard deviation is shown in parentheses. Significant differences are denoted by differing lowercase letter (a, b).

Table 2: Site-specific comparison of two individual salt marsh systems within Cape Cod Bay. Mean values of selected pore water biogeochemical parameters are shown between restricted and natural portions each system. Differing lower case letters represent significant differences between matched pairs at each site.

Perhaps the most exciting preliminary outcome of this broad sampling protocol, however, is documentation of the pore water biogeochemistry occurring in the three main plant communities observed throughout the 13 sites within 8 salt marsh systems studied; natural low marsh (Spartina-dominated), transitional (Spartina-Phragmites), and invasive mid- to high-marsh (Phragmites-dominated). The preliminary data suggest that of the five biogeochemical parameters sampled within each of these dominant plant communities, only salinity appears to differ significantly (Table 3). More unexpected is that the range of salinity observed is relatively low and easily tolerated by native plant species as well as invasive Phragmites, suggesting that dramatic salinities may be required in natural and tidally restricted sites to effectively utilize salinity stress as a restoration strategy within many of the sites examined.

Table 3: Comparison of selected biogeochemical parameters for three dominant plant community types within salt mashes of Cape Cod Bay. “Spartina” dominated by Spartina alterniflora, “Phragmites” dominated by Phragmites australis, and Transition” comprises elements of the former two.

While there remains considerable work and data analysis left to do, the project is advancing steadily as we work towards completing another season of data collection, summary conclusions and management implications. This project has received funding from Sweet Water Trust, The Boston Foundation, New England Natural Areas Wildlife Grants Program, William P. Wharton Foundation, Community Foundation of Cape Cod , Grace W. Allsop Foundation, and the CCS General Fund.