Pattagansett Lake, East Lyme

2025 Aquatic Plant Survey Map of Pattagansett Lake

Transect Data | Water Data

      Pattagansett Lake is a public, 128-acre waterbody in East Lyme, CT. The lake has an average depth of 14 feet and a maximum depth of 33 feet. The lake is a bass management area and holds fishing tournaments at the state boat launch, which is located at the southern end of the lake. The shoreline consists of residential development, forest, and some farmland. Camp Pattagansett, a camp for Girl Scouts, is located at the northern end of the lake and has a designated beach and swim area. A campground featuring RV sites and cottage rentals is located on the southeast peninsula with their own beach/swim access. Regular crew practices by the East Lyme High School are also held on the lake throughout the week.

     CAES OAIS conducted its third aquatic vegetation survey of Pattagansett Lake in 2025. The previous surveys were conducted in 2013 and 2006. The 2025 survey documented 39 plant species, compared to 32 in 2013, and 25 in 2006. The dominant native vegetation included Robbins’ pondweed (Potamogeton robbinsii), which grew almost continuously around the lake in up to 4 meters of water, white water lily (Nymphaea odorata), and pickerelweed (Pontederia cordata), an emergent species found growing on the shoreline.

     Our 2025 survey also recorded five invasive plant species: fanwort (Cabomba caroliniana), swollen bladderwort (Utricularia inflata), variable-leaf watermilfoil (Myriophyllum heterophyllum), purple loosestrife (Lythrum salicaria), and phragmites (Phragmites australis). Variable-leaf watermilfoil significantly decreased in abundance from 2013 with only five patches located at the northern end, which is a significant difference from the large continuous patch around the whole lake in 2013. Fanwort was found growing in a few patches in the southwest cove and in two small patches at the northern end of the lake. Swollen bladderwort was found mostly on the western side of the lake in large patches. Purple loosestrife and phragmites, both invasive wetland species, were found in a few small patches throughout the lake.

     Rush (Juncas species) and swamp loosestrife (Decadon verticillatus), native wetland species, were both found growing at the shoreline around the entire lake. Yellow water lily (Nuphar variegata), eelgrass (Vallisneria americana), humped bladderwort (Utricularia gibba) and purple bladderwort (Utricularia purpurea) were found growing together around the whole lake in large patches.

     The northwest arm and southernmost portion of the lake are difficult to navigate as they are extremely shallow (less than 1 meter of water) and have become filled with plants and floating mounds of sediment. Oakes’ pondweed (Potamogeton oakesianus) and Robbins’ pondweed are the main plants that dominate these areas. A narrow channel appears to have been raked down the center of both locations so that the lake residents there may still use their boats to access the rest of the lake.

     Other species that occurred in the lake in a few small patches were small pondweed (Potamogeton pusillus), spotted pondweed (Potamogeton pulcher), slender naiad (Najas flexilis), sevenangle pipewort (Eriocaulon aquaticum), western waterweed (Elodea nuttallii), common bladderwort (Utricularia vulgaris), spineless hornwort (Ceratophyllum echinatum), quillwort (Isoetes species), Slender watermilfoil (Myriophyllum tenellum), common duckweed (Lemna minor), water starwort (Callitriche species), flat-leaf bladderwort (Utricularia intermedia), ribbon-leaf pondweed (Potamogeton epihydrus), watershield (Brasenia schreberi), cattail (Typha species), and snailseed pondweed (Potamogeton bicupulatus), spiral pondweed (Potamogeton spirillus), waterwort (Elatine species), an unidentified sedge, primrose-willow (Ludwigia species), great duckweed (Spirodela polyrhiza), arrowhead (Sagittaria species), and spikerush (Eleocharis species).

Other survey years: 2013, 2006