The bacterium that causes cholera, Vibrio cholerae, has a known association with a crustacean (called a copepod) which lives on zooplankton, a type of plankton. Cholera outbreaks have been linked with environmental factors, including sea surface temperature, ocean height, and biomass (this is estimated by measuring chlorophyll produced by plankton).
Professor Rita R. Colwell and her team at the
Scanning electron microscope image of Vibrio cholerae bacteria, which infect the digestive system. Wikimedia Commons, via T.J. Kirn, M.J. Lafferty, C.M.P Sandoe and R.K. Taylor, 2000, "Delineation of pilin domains required for bacterial association into microcolonies and intestinal colonization", Molecular Microbiology, Vol. 35(4):896-910