Invasive Aquatic Plants: A Threat to Mississippi Water Resources

Invasive aquatic plants are an ever-growing nuisance to water resources in Mississippi and the rest of the United States. These plants are generally introduced from other parts of the world, some for beneficial or horticultural uses. Once introduced, they can interfere with navigation, impede water flow, increase flood risk, reduce hydropower generation, and increase evapotranspirational losses from surface waters. Invasive species also pose direct threats to ecosystems processes and biodiversity. Although there are at least twenty different species of nonnative plants currently in Mississippi, with another eight perched on our doorstep, four species cause the bulk of nuisance problems in large surface waters: Eurasian watermilfoil (Myriophyllum spicatum), hydrilla (Hydrilla verticillata), waterhyacinth (Eichhornia crassipes), and water primrose (Ludwigia hexapetala). One additional species (giant salvinia (Salvinia molesta)) is a source of significant national concern. I will discuss general modes of introduction to the United States, dispersal to water resources, spread throughout a water resource once a plant is introduced to the system, and effects of large stands on water resource quality. General management approaches include prevention of infestation, and biological, chemical, mechanical, and physical control techniques of plant infestations. While many regulatory agencies oppose management for fear of potential adverse effects of the management techniques, in general the failure to prevent widespread growth of these species causes more harm to the resource than effective management.