Recent hurricanes Helene and Milton have stirred up what some are calling a “blob of death” and scientists with NOAA are concerned about impacts it will create for Florida in the days and weeks ahead. The blob is really a bloom, but this bloom doesn’t consist of pretty flowers. Instead, it’s a bloom of a microscopic algae species named Karenia brevis also known simply as “red tide.” These blooms can cause respiratory illness and eye irritation in humans; they can also kill marine life, and lead to shellfish closures. Blooms are often patchy, so impacts vary by beach and throughout the day.
According to NOAA scientists and their Ocean Land Color Imager (OLCI), a significant bloom in the shape of a blob has formed off the central west coast of Florida’s panhandle. Known as a harmful algal bloom or HAB for short, this blob is far enough off-shore now not to directly impact people on the coast. But as the blob drifts closer to the coast, more significant human impacts can be expected. And regardless of human impacts, harmful impacts on marine life are happening right now. According to NOAA, red tides, caused by Karenia brevis algae, produce toxins that can cause fish kills, respiratory irritation, and mortality of sea turtles, manatees, birds, and dolphins.
The duration of a bloom in nearshore Florida waters depends on physical and biological conditions that influence its growth and persistence, including sunlight, nutrients, and salinity, as well as the speed and direction of wind and water currents. Researchers are watching oceanographic conditions in the region carefully and using forecasting tools similar to seasonal weather forecasts to predict how long this bloom will last and where it may move to next. The National Centers for Coastal Ocean Science (NCCOS) monitors conditions daily and issues regular forecasts for red tide blooms in the Gulf of Mexico and East Coast of Florida.
Hurricanes Helene and Milton’s high winds and rough surf have stirred-up nitrogen rich cool waters through cool water upwelling, helping feed into the ongoing widespread blooms of this algae which releases neurotoxins into the water. The heavy rains of from the hurricanes have also helped wash pollution into the Gulf, including nitrogen used as fertilizer in Florida’s agricultural industry.
These HABs aren’t uncommon after tropical cyclones. In 2005, Hurricane Katrina carried a harmful algal bloom up to the Florida Panhandle. In 2018, Tropical Storm Gordon intensified and spread an algal bloom to the Florida Panhandle too. It is too soon to know how large this “blob of death” will become and what its final impacts on Florida will be; but knowing how large and impactful Helene and Milton were, it’s likely the HAB will be significant too.
