Aquatic vegetation and trophic condition of Cape Cod (Massachusetts, USA) kettle ponds

The species composition and relative abundance of aquatic macrophytes was e valuated in five Cape Cod, Massachusetts, freshwater kettle ponds, represen ting a range of trophic conditions from oligotrophic to eutrophic. At each pond, aquatic vegetation and environmental variables (slope, water depth, s ediment bulk density, sediment grain size, sediment organic content and por ewater inorganic nutrients) were measured along five transects extending pe rpendicular to the shoreline from the upland border into the pond. Based on a variety of multivariate methods, including Detrended Correspondence Anal ysis (DCA), an indirect gradient analysis technique, and Canonical Correspo ndence Analysis (CCA), a direct gradient approach, it was determined that t he eutrophic Herring Pond was dominated by floating aquatic vegetation (Bra senia schreberi, Nymphoides cordata, Nymphaea odorata), and the algal stone wort, Nitella. Partial CCA suggested that high porewater PO4-P concentratio ns and fine-grained sediments strongly influenced the vegetation of this eu trophic pond. In contrast, vegetation of the oligotrophic Duck Pond was spa rse, contained no floating aquatics, and was dominated by emergent plants. Low porewater nutrients, low sediment organic content, high water clarity a nd low pH (4.8) best defined the environmental characteristics of this olig otrophic pond. Gull Pond, with inorganic nitrogen-enriched sediments, also exhibited a flora quite different from the oligotrophic Duck Pond. The spec ies composition and relative abundance of aquatic macrophytes provide good indicators of the trophic status of freshwater ponds and should be incorpor ated into long-term monitoring programs aimed at detecting responses to ant hropogenically-derived nutrient loading.