Red tide impacts Sarasota Bay through most of 2005
By Spencer Fire, PhD candidate, University of California, Santa Cruz

Beginning in January 2005 and continuing to the time of this writing (October), a persistent bloom of the red-tide alga, Karenia brevis, has been present in Sarasota Bay and surrounding waters. Cell concentrations have reached levels approaching 300 million cells per liter of seawater, indicating a severe red tide event. As point of reference, concentrations of 1,000 cells per liter or less are considered background levels, and 100,000 cells per liter or more typically cause respiratory irritation in humans and fish kills. The 2004 red tide event occurring in Sarasota Bay waters lasted from January to March, and concentrations reached a maximum of 2 millions cells per liter. During the 2005 red tide bloom there have been significant increases in sea turtle and seabird strandings. Sea turtle strandings have increased 2-fold over the previous 10-year average with over 160 sea turtles stranding in the region since January. Live cormorants, brown pelicans and great blue herons with neurological signs consistent with red tide intoxication have been admitted to local wildlife rehabilitation centers in increasing numbers. Lastly, dolphin strandings have been above average for the summer months, with 19 dolphins stranding during July through October. Tissue samples tested from some of the sea turtles and dolphins have been positive for the red tide toxin. The scope of this red tide event is much greater in magnitude of severity and spatial distribution than many previous events, and several aspects of its effects on the biota of Sarasota Bay are currently under investigation.