Drifting plastic debris as a potential vector for dispersing Harmful Algal Bloom (HAB) species

Macroscopic observations of floating plastic debris collected at several places along the Catalan coast (northwestern Mediterranean) showed conspicuous green-yellow patches adhered to them. The microscopic examination of these patches showed that they were constituted mainly of benthic diatoms and small flagellates (<20 mum). Potential harmful dinoflagellates such as Ostreopsis sp. and Coolia sp., resting cysts of unidentified dinoflagellates and both temporary cysts and vegetative cells of Alexandrium taylori were also found. Plastic debris is considered to be one of the most serious problems affecting the marine environment. We suggest drifting plastic debris as a potential vector for microalgae dispersal.