Description of toxigenic species of the genus Pseudo-nitzschia in coastal waters of Uruguay: Morphology and distribution

Pseudo-nitzschia is a genus of marine diatoms, widely distributed from tropical to polar regions. Over 35 species have been described, some of which produce domoic acid (DA). This neurotoxin is responsible for the intoxication syndrome in humans and marine animals called Amnesic Shellfish Poisoning (ASP). Most of these toxigenic species are an important component of phytoplankton and have been recorded in the Southern Cone of South America (Argentina, Brasil, Chile and Uruguay).The Dirección Nacional de Recursos Acuáticos (DINARA) conducted a long-term monitoring program along the Uruguayan coast, beginning with the first toxic algal event reported in 1980. Six species of Pseudo-nitzschia: P. australis, P. delicatissima, P. fraudulenta, P. multiseries, P. multistriata and P. pungens were reported in Uruguayan waters. Until recently, the only event with detected levels of DA (9.9 μgDA/g), as determined by the HPLC standard method, was caused by P. multiseries in December 2001 with values reaching 1200 cells l−1. This record represents the first DA report associated with this species in Western Atlantic waters. In February 2009 P. multistriata was detected for the first time in Uruguayan waters, with a density of 2 × 106 cells l−1. This report suggests that Uruguay is the southern limit of its biogeographic distribution in the Southwest Atlantic. During this study, analysis by optical and scanning electron microscopy confirmed the presence of four species of Pseudo-nitzschia in Uruguayan waters: P. fraudulenta, P. multiseries, P. multistriata and P. pungens which are potentially producers of DA. We also include information on the trends in Pseudo-nitzschia abundance with water temperature and salinity.

► Pseudo-nitzschia species from Uruguayan waters are documented by electron microscopy.
► Most of Pseudo-nitzschia blooms >5000 cells l−1 (71%) occur during austral spring and summer, between October and April.
► The most abundant Pseudo-nitzschia blooms (>20.000 cells l−1) occur at salinity >30.