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.