Control of invasive seaweeds

Seaweeds have invaded ecosystems along the coasts of many countries where they can displace native algae and seagrasses, reduce biodiversity and impair habitat of fish and invertebrates. The most widespread and notorious cases have been introductions of Caulerpa taxifolia, which now infests over 20,000 ha of Mediterranean subtidal zones. Few attempts to control seaweed invasions have been successful, due to often harsh and highly variable physical conditions in marine environments, and the lack of efficacious methods. Use of heat, copper, chlorine, salt, freshwater and various mechanical (removal) approaches have been successful in reducing or eradicating some infestations. Biological control by herbivorous mollusks and sea urchins has been investigated, but has yet to result in any operational programs. Nutrient inputs from near-shore sources have exacerbated the spread of some species (e.g., off the Florida coast). To counter the increase in seaweed introductions and the spread of these species, it will be useful to adapt, where feasible, methods that have proven successful in controlling freshwater weeds. New methods will need to be developed as well. This will require better communication among researchers and managers working to reduce introductions and negative impacts of these seaweeds.