Using Submerged Aquatic Vegetation to Assess Riverfront Areas and Ecological Condition
Abstract
Current regulations dictating development on the banks of river systems found throughout Massachusetts are scientifically incomplete and result in unproductive arguments between landowners and local governments. According to the Massachusetts Wetlands Protection Act and Rivers Protection Act, a 25-foot or 200-foot riverfront area (depending on the density of the surrounding municipality) is established to protect the critical habitat bordering these freshwater systems. While this law restricts development along the banks of streams and rivers within the riverfront area, not only is it still permissible to develop on that land if approved by a local Conservation Commission, but also there seems to be no scientific data supporting 25-foot or 200-foot areas as adequate barriers for development.In this study, I developed a procedure to rapidly assess the ecological condition of the Swift River in central Massachusetts by testing to determine if either submerged aquatic plant species richness or percent cover can act as an indicator of impact due to development in a riverfront area. I hypothesized that samples near developed riverfront areas would exhibit both lower species richness and vegetative percent cover, as well as lower cover of Vallisneria americana, a common plant found in a variety of freshwater systems. An undeveloped and a developed section of the Swift River were sampled once in September and once in October using 15 randomized throws of a one-square-meter quadrat over 100-meter distance following the flow of the river. Comparing the undeveloped sample site to the developed revealed a statistical difference in the number of species present for both September (n=15; t=-2.346; p=0.03) and October (n=15; t=-4.012; p=0.001), though there was no statistical difference in percent cover for either September. Percent cover of V. Americana showed a difference between undeveloped and developed sample site for September (n=15; t=-2.317; p=0.04), but not for October (n=15; t=-1.623; p=0.13).
Current Massachusetts regulations and development decisions in the area sampled have therefore impacted species diversity in the riverbeds near the developed sample site. This is the first step in quantitatively addressing the riverfront areas outlined by the Rivers Protection Act, but further analyses are needed of other river systems in Massachusetts to corroborate these results. This could result in the need to readdress current Massachusetts regulations allowing for development within a riverfront area and whether there is adequate distance to prevent sediment and/or nutrient runoff from entering a river and negatively impacting its ecological health. If a Conservation Commission has access to a rapid assessment, conflicts between developers and their neighbors can be quickly settled.
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