To all red-tides watchers! Posted July 15, 1998 to Phycotoxins listserver

The St. Lawrence estuary on the canadian east coast is one of the hottest spots in the world for PSP. The causative organisms are Alexandrium tamarense, and occasionally A. ostenfeldii. Each year, shellfish from hundreds of kilometers of coast become toxic for several weeks. Usually, cell concentrations remain below 50,000 cells per liter, with shellfish becoming toxic (> 80 µg STX/100 g meat) when cell concentrations reach only 1,000 cells per liter.

Last week, a huge red tide (150 km long by 2-3 km wide of discolored water) developed along the south shore with cell concentrations reaching 4 million cells per liters! Several ship and helicopter surveys showed that Alexandrium was present in high concentrations all over the Estuary.

Although most of the coastal zone was already closed for shellfish harvesting, the Department of Fisheries and Oceans, in collaboration with the Canadian agency for Food Inspection sent a warning to the media to advise people that the shellfish may be extremely toxic this year. So far, there is no report of fish or seabird mortallity.

A research project on the determination of the variation in the in situ growth rate of Alexandrium spp. was on its way in our lab when the red tide occured. It thus represents a great opportunity to determine the importance of this parameter on the dynamics of Alexandrium blooms in the St. Lawrence.

Maurice Levasseur, for the Toxic Algal Research Team of Maurice Lamontagne Institute

Department of Fisheries and Ocean Canada

Maurice Lamontagne Institute

Mont-Joli, Quebec

Canada G5H 3Z4

levasseurm@dfo-mpo.gc.ca

Fax:(418) 775-0546

Tel: (418) 775-0608