Is the distribution of the toxic dinoflagellate Alexandrium catenella expanding along the NW Mediterranean coast?

Abstract

The toxic dinoflagellate Alexandrium catenella is usually known as a cold waters species; however, during the summer of 1996 a bloom was observed in the Barcelona harbour (water temperatures above 20°C). This was the first time that an A. catenella bloom occurred in Catalan waters. Recurrent blooms have been observed annually from 1996 to 1999 during the warm season in this harbour. Since its first detection A. catenella has been recorded at an increasing number of stations along the coast, suggesting a progressive areal expansion. Two toxic, widespread events of this species occurred in non-confined coastal waters along 100 km of coastline during the summers of 1998 and 1999. We argue that the newly constructed harbours, serving as confined habitats for the development and maintenance of A. catenella, have contributed to the expansion of the dinoflagellate on the NW Mediterranean coast.