Aquatic plants are essential components of healthy ecosystems in freshwater lakes and ponds. Invasive plants, however, are non-native species that are harmful to the environment. The ability of invasive plants to reproduce quickly, usually unhindered by native pests and pathogens, allows them to quickly displace native species. Studies suggest invasive species are the second leading cause of species extinction and responsible for billions of dollars in economic losses each year in the United States. Invasive aquatic plants reduce aesthetic and recreational value of water bodies, which negatively affects tourism and real estate values.
Prior to the Connecticut Agricultural Experiment Station Invasive Aquatic Plant Program (CAES IAPP), there was little baseline data on the existing plant communities in Connecticut lakes and ponds. Consequently, it was difficult to determine the extent of aquatic plant invasions and the impact these invasions were having on aquatic ecosystems. To resolve this lack of information, The Connecticut Agricultural Experiment Station, with funding from the U.S. Department of Agriculture, initiated the Invasive Aquatic Plant Program. Its purpose was to quantify the geographical distribution of invasive aquatic plants and study novel management techniques.
The surveillance and monitoring portion of the program has currently completed aquatic vegetation surveys on over 180 lakes and ponds. We now have enough baseline information to begin to asses the extent and nature of ecological change resulting from plant invasions. For instance, approximately 60 percent of the surveyed water bodies contained one or more invasive species. Even though the surveys are intended to provide information on the presence of invasive species, they also generate information on native aquatic plants. We have documented nearly 100 native species during our surveys including many that are listed by Connecticut as rare, threatened or endangered. It is noteworthy that many of the invading species are from tropical climates. The role of changing climate in the successful invasion and dominance of these exotic species in our water bodies is another topic of investigation.
When we survey each lake, we combine mapping of the general locations of the native and invasive aquatic plants with quantitative information on species abundance. Sampling for abundance is done on geo-referenced transects that start at the shoreline (0 meters) and continue out at distances of 5, 10, 20, 30, 40, 50, 60, 70 and 80 meters. At each sampling location, the abundance of all aquatic plants is determined along with the depth and sediment type. Abundance is estimated on a scale of 1 – 5 (1 = present but rare, 2 = occasional, 3 = common, 4 = abundant, 5 = dominant). We also use an underwater camera linked to a global positioning system, which provides details on the aquatic plants in deep water. The surveys allow us to monitor changes in plant communities, resulting from plant invasions or other causes. Finally, we gather information on water quality and other conditions to determine the factors that influence why an invasive aquatic plant is present and what may be encouraging it's growth.
We identify the plants either by morphological characteristics or molecular diagnostics. Our herbarium specimens of aquatic plants can be studied as a part of future research projects. Our molecular techniques require extraction, amplification and sequencing of DNA from three separate genomic regions of the plant in question. Upon definitive molecular identification, individual sequences are then archived in our own database. (Follow this link for more information on molecular identification of invasive aquatic plants.)
CAES IAPP’s survey data compliments our invasive aquatic plant control studies by identifying suitable test sites and monitoring the effects of treatments. CAES IAPP’s invasive aquatic plant control research focuses on methods such as herbicides, winter drawdown and biological control. Currently, experiments using US EPA approved herbicides are underway in Bashan Lake, East Haddam, and Crystal Lake, Middletown. In 2006, CAES IAPP started research on biological control agents as a possible invasive aquatic plant control option. This research includes biological control agents for Eurasian watermilfoil (Myriophyllum spicatum), particularly the milfoil weevil (Euhrychiopsis lecontei). We have introduced this weevil into Candlewood Lake, Danbury and Indian Lake, Sharon and we are monitoring it's effects. A study of the plant eating fish grass carp (Ctenopharyngodon idella) is underway in Grannis Lake, East Haven. We also are investigating the use of integrated pest management (IPM) for invasive plant control in Connecticut water bodies. (Follow this link for more information on control studies.)
Ultimately, CAES IAPP's work can help support a proposed statewide early detection and rapid response protocol aimed at eradicating new introductions of invasive aquatic plants before they become difficult, large-scale problems.