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CSCOR Sponsored Research Cruise Documents Low Oxygen and Animal Mortalities Associated with Florida Toxic Algal Bloom
Karenia brevis, sometimes called the “Florida Red Tide,” is a highly toxic alga that causes human respiratory distress, toxic shellfish, animal mortality, and water discoloration. Karenia brevis often blooms off of the west coast of Florida, generally in the late summer and fall. This year an unusual bloom started in January, resulting in a manatee mortality event in March, and persisted in localized areas through the summer. In early August, Florida 's Fish and Wildlife Research Institute (FWRI) received sudden reports of massive benthic mortalities (especially on coral reefs), fish kills, and a substantial increase in turtle strandings. During this same time period, ECOHAB / MERHAB -funded moored Breve Busters, instruments that can optically detect Karenia in the water, indicated a bloom in the area. Researchers found anoxic water at depth along a HAB monitoring cruise transect, and both the cruise data and MERHAB -funded moorings showed that the water column was stratified. Subsequent sampling by the State, with assistance from local divers, indicated that benthic mortalities, the Karenia brevis bloom, and anoxia were widespread. The last time such an event occurred in Florida, according to FWRI, was 1972.
On August 7, 2005, FWRI requested funds from CSCOR's Harmful Algal Bloom Event Response Program to assist the State of Florida in mapping the area with low oxygen and high Karenia brevis abundance. Researchers from FWRI and the University of South Florida mapped an area from the mouth of Tampa Bay north to Pasco County and found that the region of bottom oxygen depletion began about 10 miles offshore and extended at least 30 miles offshore. This area coincided with sites of reported bottom mortalities, which were confirmed at some stations by divers on the cruise. For detailed results from the cruise, see the Florida Fish & Wildlife Research Institute's website. Post-Katrina sampling by FWRI indicated the waters in this region were reoxygenated due to mixing caused by the passage of the hurricane. The bloom of Karenia brevis , however, persists in Southwest Florida . There is also a Karenia bloom along the Florida Panhandle, which has resulted in fish kills and closures of shellfish harvesting (see FWRI current status report for Northwest Florida). This bloom also spread to the west into Alabama and Mississippi waters.
The funds provided by NCCOS' CSCOR not only assist the State of Florida in the short-term, but also provide critical information for long-term HAB research efforts in the region. NOAA has invested more than $12 million since 1997 to assist Gulf of Mexico coastal managers in reducing the public health risks and economic impacts of Karenia brevis (click here for a list of projects).
In November 2005, NOAA Fisheries Service declared a multi-species Unusual Mortality Event (UME) related to the Karenia bloom. The multi-species UME includes manatees, sea turtles, dolphins, and seabirds and will allow for an ecosystem level investigation of bloom effects. For more about UME's, visit NOAA Fisheries Office of Protected Resources.