More than 180 aquatic nuisance species now exist in the Great Lakes. Enhanced prevention and control efforts are critical to halting new invasive (non-native) aquatic, wetland, and terrestrial species from becoming established in the Great Lakes. By rapidly reproducing and spreading, invasive species can degrade habitat, harm native species and alter food webs. Prevention is the most cost-effective approach to dealing with organisms that have not yet arrived and could potentially threaten the Great Lakes. Once invasive species establish a foothold, they are virtually impossible to eradicate; however, invasive species still need to be controlled to maintain the health of the Great Lakes ecosystem. The GLRI is supporting efforts to prevent and control invasive species. As a part of this effort, the USGS is working with others to help prevent and/or control invasive carp, Phragmites australis (common reed), Zebra and Quagga mussels.