Abstract
Marine ecosystems are threatened by the invasion of exotic species which are aggressive and opportunistic colonizers of sensitive marine communities. These species can unbalance ecosystems to the point of causing algal blooms, depleting fisheries, cover beaches, and interfer with shipping operations. Their effects are often persistent and irreversible, and occur at exponential rates. These species can enter marine environments naturally, but their introduction has been amplified by human activities, particularly through shipping hulls and ballasts. Other sources of introduction include the aquarium trade, research, private stocking operations, and aquaculture.