Past and future of the marine bioinvasions along the Southwestern Atlantic

The first comprehensive survey of marine bioinvasions in the southern Southwest Atlantic Ocean (SWA, ca. 33 degrees 45'-ca. 54 degrees 50'S) published in 2002 reported 31 introduced and 46 cryptogenic species. In this assessment, we update this work by providing a deep historical perspective of marine biological invasions as well as a full new review of introductions that have occurred over the past nearly two decades. We reviewed a variety of sources including peer-reviewed journals and monographs, government reports, and museum databases, among others. The previous survey was re-evaluated and taxonomic experts were also consulted. For each species, the possible status as introduced or cryptogenic, likely vector, likely native region, first collection date if known, and the first authoritative reference of its SWA occurrence were determined. Species were categorized by biogeographical provinces. Our reevaluation of species status lowered the 2002 survey to 29 introduced and 29 cryptogenic species. The result of our analyses added 100 new introduced and 43 new cryptogenic species, making a total of 129 introduced and 72 cryptogenic marine species for the SWA. Of these 100 species, 67 were found in the literature older than the 2002 survey, and 33 were found as new invasions that occurred since 2002, averaging one new invasion every 178 days. Ships are the most likely vector of invasions with an additional few species introduced with aquaculture, for ornamental purposes or for stabilizing coastal dunes. Most species are native to either the North Pacific or North Atlantic Oceans. Most introduced species (51%) occur in the warm temperate SWA marine ecoregion, while fewer (16%) occur in the cold temperate Magellanic marine ecoregion. Since ships are the main vectors in the region, we forecast that new introductions will continue until regional and international regulations to control ballast water and hull fouling begin to be effective. Our results urge the creation of long-term assessment programs focused on marine coastal biodiversity as a way to avoid inefficient environmental management based on deficient baseline information.