The ignored stowaways: worldwide dispersion of exotic microalgae species through the biofouling recovering the ships underwater body

Abstract

Invasion by introduced species cause huge environmental damage and economic (estimated in $138 billion in USA). Marine ecosystems are specially affected by introduced species of toxin-producing microalgae. Ships ballast water has been considered the major vector in dispersion of phytoplankton. However, most ships do not use ballast water. Alternatively, we propose that the biofouling recovering the underwater body of ships is the main cause of microalgal dispersion. Antifouling paints (containing tributyltin, TBT or other toxics) are used to coat the bottoms of ships to prevent biofouling. After sampling biofouling recovering the underwater body of ships we demonstrate that numerous coastal, oceanic and toxin-producing microalgae species proliferates attached on bottoms of ships directly on TBT antifouling paint. These microalgae species should be resistant variants because antifouling paints rapidly destroy sensitive wild type microalgae. Consequently, the key to explain microalgae species transport via ships biofouling is know the mechanisms that allow to these species to survive long time attached to antifouling paint. A fluctuation analysis demonstrate that genetic adaptation by rare spontaneous mutation, which occurs by chance prior to antifouling exposure is the mechanism allowing adaptation of microalgae to antifoulig paints and their dispersion in the ships biofouling. Around 3 TBT-resistant mutants per each 10-4 wild type sensitive cells occurs in microalgal population. This assures a rapid colonization of ships bottoms to travel long-distances