
Photo: Eurasian watermilfoil (Myriophyllum spicatum). Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Animals
(insects, reptiles, mollusks, crustaceans, and amphibians)

Photo: Rusty crayfish (Faxonius rusticus).
Credit: United States Geological Survey (USGS) , US Geological Survey, Bugwood.org

Photo: Round goby (Neogobius melanostomus). Credit: Eric Engbretson, US Fish and Wildlife Service, Bugwood.org
Pathogens and Diseases
(disease-causing molds, fungi, bacteria, and viruses)

Photo: Whirling disease (Myxobolus cerebralis). Credit: Alberta Environment and Parks , Bugwood.org