Water lettuce

Invasion

Water lettuce is among the world's most productive freshwater aquatic plants and is considered an invasive species. The species can be introduced to new areas by water dispersal, fragmentation, and hitchhiking on marine transportation or fishing equipment. The invasion of Pistia stratiotes in the ecosystem can lead to environmental and socio-economic ramifications to the community it serves. In waters with high nutrient content, particularly those that have been contaminated with human loading of sewage or fertilizers, water lettuce can exhibit weedy overgrowth. It may also become invasive in hydrologically altered systems such as flood control canals and reservoirs. The severe overgrowth of water lettuce can block gas exchange in the surface water, creating hypoxic conditions and eliminating or disrupting various native marine organisms. Blocking access to sunlight, large mats of water lettuce can shade native submerged plants and alter communities relying on these native plants as a source of food. The growth of these mats can also get tangled in boat propellers and create challenges for boaters or recreational fishermen.