Red Tide Returns in 2006
Beginning in August 2006 and continuing to the present, a persistent bloom of the red-tide alga, Karenia brevis, has been present in Sarasota Bay and surrounding waters. Cell concentrations have reached levels of several million cells per liter of seawater, indicating a severe red tide event. As point of reference, cell 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 previous red tide event that occurred in Sarasota Bay waters persisted from February 2005 to January 2006 and cell concentrations reached a maximum of 300 million cells per liter. During the 2006 red tide bloom there have been significant increases in sea turtles stranding. Since 1 August 2006, Mote has responded to 84 sick or dead sea turtles in the Sarasota Bay region. On average, Mote responds to 50-60 sea turtle strandings per year. This increase in sea turtle strandings was also seen last summer during the prolonged red tide event in which over 92 sea turtles stranded between August and November 2005. Lastly, dolphin strandings do not appear to have increased during the current red tide event, with only 3 dolphins stranding since August 2006. This is in contrast to last year’s event when over 20 dolphins stranded between August and November 2005, and Sarasota Bay was included in the region identified as part of a Florida West Coast Unusual Mortality Event. Blood samples tested from the live sea turtles stranding during this year’s event have been positive for the red tide toxin. The scope of this year’s red tide event is currently smaller in magnitude and severity than last year’s year-long red tide bloom, but the cumulative effects of these continued red tide events on the Sarasota Bay ecosystem are unknown and currently under investigation.
