Red tide strikes again. Manatee residents find dead shark, thousands of fish floating behind their homes in Bowlees Creek
Anna Maria Island, Longboat Key and the Bradenton area are not alone in feeling economic and environmental pain from red tide.
Many areas of the United States and around the world deal with what researchers call HABs, shorthand for Harmful Algal Blooms.
Restaurateur Ed Chiles recently vented his frustration over repeated red tide invasions, particularly this year’s persistent and pervasive bloom.
“We need to bang on the table,” Chiles said at a Manatee County Tourist Development Council meeting in November. “Enough is enough. We have to address what is coming out of Lake Okeechobee, cesspools, agriculture, shoreline restoration, sea grass and sewer treatment plants.
“We need to do everything we can to back away from the tipping point. That is Florida’s economy,” Chiles said.
Karenia brevis, the type of bloom found in the Gulf of Mexico, is the only one in the United States thought to produce a respiratory impact, and one of the few that directly kills fish, Rick Stumpf, a red tide expert for the National Ocean Service, said in an email this week.
Other ecosystem problems caused by Karenia brevis include lack of oxygen in waters near the bottom, partially because of the variety of decomposing dead sea animals. Sea turtles, manatees, dolphin and fish are affected. Red tide also causes closures of shellfish beds.
But there are other kinds of blooms found globally in environments as diverse as Greenland, Asia, Australia and New Zealand.
Rather than working in isolation, researchers often look at what scientists are doing elsewhere.
One example is Korea and China, where finely crumbled clay has been effectively used to control, or mitigate, algal blooms in aquaculture.
While the long-term effects of using clay on the environment are still not completely understood, it is a strategy that Mote Marine Laboratory in Sarasota will be looking into over the next year.
At a Sept. 24 press conference at Mote Marine, Eric Sutton, executive director of the Florida Fish and Wildlife Conservation Commission, announced that Gov. Rick Scott had directed a $2.2 million investment to test red tide mitigation technologies, including specialized clay field experiments and expansion of Mote’s ozone treatment system.
Mote’s patented ozone system was originally developed to remove red tide and its toxins from water entering Mote Aquarium.
The ozone system not only kills the red tide cells but removes its toxins, said Vincent Lovko, Phytoplankton Ecology Program manager at Mote Marine.
Mote will be evaluating a modified clay that does a better job in a smaller quantity to bind to red tide toxins and cells, Lovko said.
Mote is working in conjunction with Woods Hole Oceanographic Institution in Massachusetts, which has taken the lead on the clay mitigation research.
“There is not one magic bullet that will work on every HAB around the world,” Lovko said.
Example: “Mahogany tide,” caused by Karlodinium algae, occasionally appears in Chesapeake Bay and kills fish with a toxin.
On the U.S. west coast, domoic acid events — one of the few HABs caused by a diatom — have a big impact on local harvests of seafood and on sea birds and mammals.
The 2015 domoic acid event caused closures of harvests for Dungeness crabs, as well as a variety of shellfish from Washington to Southern California, Stumpf said.
Sea birds, seals, sea lions and sea otters were sickened and some died. Smaller domoic acid events occur within regions of the states, but not every year.
There is also another harmful algae called Alexandrium catenella that occurs on both the west coast and in the Gulf of Maine called “red tide” and produces a toxin (saxitoxin) that is picked up by shellfish, which can lead to paralytic shellfish poisoning in people.
This is an annual event starting in late spring and ending in the summer. It does not cause fish kills, and rarely kills other animals, Stumpf said.
Another harmful algae on the west coast, Akashiwo sanguinea, produces a foam that clumps the down in seabird feathers, causing death by hypothermia.
Red tide blooms appear to be occurring in more places and with more severity than in the past.
Normally, red tide appears off Southwest Florida in the fall, which is the start of dry season. For a bloom like this year, land-based nutrients, especially nitrogen from several sources, including run-off, fertilizers, and septic systems may have been a factor in increasing the size of this bloom, Stumpf said.
There is also a school of thought that iron-rich dust blown from the Sahara Desert could play a role in red tide blooms.
University of South Florida researchers reported in 2001 that they had tracked a dust cloud from north Africa to an area between Tampa and Fort Myers, where, fed by iron in the dust, a bloom of red tide erupted.
As with many HABs and their locations around the world, it can be difficult to neatly sum up any hypothesis.
“There are many different HABs so generalizations are difficult. K. brevis does benefit from dust but indirectly,” Bob Weisburg, distinguished university professor of physical oceanography at the University of South Florida, said of the Sahara dust theory.
“The biology is complex, but only half the story. If the water properties are not conducive for a bloom then one will not happen. These properties are determined by the ocean circulation so the ocean physics are as important for a bloom to occur as is the biology,” Weisburg said in an email.
Reducing nutrients in some estuaries, while not targeting the HABs, may help reduce them, Stumpf said.
In freshwater, there is more of a direct relationship between nutrients and the blooms. Ohio and U.S. Environmental Protection Agency are funding research into ways to reduce nutrient loads in Lake Erie that cause the cyanobacteria bloom there.
Locally, Mote’s ozone mitigation might make more sense for smaller areas, such as residential canals, while the modified clay technique would be better suited for larger blooms.
At its largest, this year’s Gulf of Mexico bloom, as measured by satellite imagery, measured about 150 miles along the Southwest Florida coast. It was about 15 to 20 miles wide.
The severity of red tide impacts, with the exception of recent flares at Robinson Preserve and in Palma Sola Bay, have been decreasing..