Proliferation of small docks and piers in salt marsh habitats poses potential cumulative impacts through shading and displacement of marsh vegetation. Environmental permitting guidelines provide construction recommendations regarding various dock characteristics (e.g., height, orientation, deck spacing, deck materials), but few quantitative data exist to substantiate these guidelines. In a project funded through a 2013 MassBays Research and Planning Grant , the MA Division of Marine Fisheries constructed an experimental dock matrix to specifically address the effect of dock height on underlying marsh vegetation. These results provided useful information on this particular dock characteristic and data on short-term (i.e., 1-3 years) shading effects.
To further build on this controlled, short-term study, MarineFisheries will conduct a large scale sampling of vegetation characteristics under existing private docks and piers across the Massachusetts coast using the same sampling approach employed in the dock matrix study. Specifically, clip plot samples of marsh vegetation aboveground biomass will be collected under docks and from adjacent unshaded control locations to quantify any changes in marsh stem density, height, biomass, and elemental composition a) in relation to unshaded areas and b) in relation to different dock designs.
Data generated from this project, combined with data being generated from the 2013 Study, will provide managers with information on dock shading impacts for use in future planning and regulation of coastal development. These data may be used to assess whether existing regulations are effectively minimizing impacts to marsh vegetation and if not, may point to revised guidelines to achieve minimization and ideally avoidance of impacts. Such data will help coastal towns with future management decisions pertaining to dock and pier proliferation across existing salt marsh habitats.