AQUATIC VEGETATION ASSESSMENT AT PORTUGUÉS AND CERRILLOS RESERVOIRS, PUERTO RICO

Abstract

Waterbodies in Puerto Rico are constantly threatened by the introduction, establishment and spread of aquatic weeds. Their introduction is promoted by the aquarium and horticultural trade, as well as by travel and commerce via air and marine transportation. Once introduced, their dominance limits recreational use of waterbodies, and management operations in reservoirs used for potable water and flood control deteriorate. In Puerto Rico, the problem has worsened because of limited citizen awareness, wrong public perception of available management techniques and eutrophic man-made water bodies serving as suitable habitat for aquatic weeds. Currently the most troublesome aquatic weeds in Puerto Rico are waterhyacinth (Eichhornia crassipes), waterlettuce (Pistia stratiotes), alligatorweed (Alternanthera philoxeroides), hydrilla (Hydrilla verticillata) and giant salvinia (Salvinia molesta) (Robles, 2011). During the 1970s, botanists from the US Army Corps of Engineers (USACE) recognized the problem that waterhyacinth, waterlettuce and alligatorweed represented to several waterbodies in Puerto Rico (Gangstad, 1977; Rushing, 1974). Waterhyacinth and waterlettuce are free-floating aquatic weeds well established in such reservoirs as La Plata, Guayabal and Carraízo, and Cartagena Wildlife Refuge in Puerto Rico (Robles, 2011). Alligatorweed has been observed in many water bodies and drainage canals; however, its area of infestation has decreased due to successful biocontrol agents (Robles, 2011). Recent introductions of the submersed aquatic weed, hydrilla, and the aquatic floating fern, giant salvinia, are limited to a few locations in northern Puerto Rico (Robles, 2011). All five aquatic weeds cause negative ecological and economic impacts to water supply reservoirs, irrigation and drainage canals, private ponds, as well as estuaries and freshwater wetlands used as wildlife refuges (Robles and González, 2010). Specifically, waterhyacinth causes problems in the operation of hydroelectric plants, clogging dams and pumping facilities of aqueducts and sewer operations (Rushing, 1974; Gangstad, 1977). Other troublesome weeds like the facultative wetland species catclaw mimosa (Mimosa pigra) are wide-