Abstract
The occurrence and abundance of Pseudo-nitzschia species in the Bay of Banyuls-sur-Mer, northwestern Mediterranean Sea, were studied from 2002 to 2003 and during spring 2004. Pseudo-nitzschia is a frequent component of the microplankton in this area (more than 58%of the samples) with its highest abundance (104-106 cells L−1) during springtime (from April to May). Shorter blooms (for only one week in August) were detected in summers of 2002 and 2003. These periods are associated with warmer temperatures and relatively nutrient-rich waters. SEM and TEM observations showed the causative organism responsible for the blooms to be the potentially toxic diatom P. calliantha. A listing of the 29 described Pseudonitzchia species is provided as well as the list of 11 potentially toxic species.