Macrophytic Vegetation of the Freshwater Kettle Ponds of Cape Cod National Seashore

Coe, James; Soukup, Michael

Cape Cod National Seashore has twenty freshwater kettle ponds which currently exhibit a series of trophic states ranging from near-pristine oligotrophy (e.g., Duck, Dyer) to extreme eutrophy (e.g., Williams, Turtle). This study looked at the macrophytic vegetation in 17 of the 20 ponds in Wellfleet and Truro, Massachusetts, during the summer of 1978. Macrophytic pond vegetation is of primary interest to the Park Service management for two reasons. First, the pond flora at any time should provide a rough indication of the trophic state of the community. The dominant vegetative characters of a pond community wll evolve and change as the pond undergoes successional change. Secondly, and perhaps more urgently, macrophytic vegetation within and around the ponds often interferes with recreational use and enjoyment of the pond resources. The primary purpose of this study was to conduct an inventory of the plants growing within and bordering the kettle ponds, while collecting material for a reference herbarium collection of the flora. In addition, preliminary rough maps were sketched indicating potential problem sites of dense macrophytic growth. While previous National Park Service reports have commented on pond plant life (e.g. Hinds, 1966; Godfrey, 1976; Randal, 1976; Soukup, 1977), none have attempted an exhaustive inventory and mapping. Summary: A thorough inventory of pond-associated plant species and a permanent reference herbarium collection of aquatic macrophytes in Wellfleet, Massachusetts has been completed. In addition, the presence of significant patches of weedy pondweed growth has been sketched onto outline maps of the ponds. The distribution of plant species among various ponds was found to reflect the trophic state of the pond community, and changes over time of the composition of the flora should help indicate progress of successional phenomena. Moreover, growth of pond vegetation was noted to respond to "cultural eutrophication" and provides resource managers with a visible indicator of excessive nutrient input into pond ecosystems. Current locations of such enrichment worthy of management concern appear to be reflected in sites of dense weed growth, and are identified on the maps.