In images reminiscent of the biblical plague of blood from the Exodus story, Florida's coasts experience a concerning natural phenomenon every year that turns the sea red: "red tide." Now, in a new study, researchers from the University of South Florida have identified for the first time nearly a dozen viruses connected to this mysterious phenomenon, according to a report in The Independent.
Finally, Karenia brevis has been identified as the cause of 'red tide' as researchers identified nearly a dozen viruses associated with red tides that are harmful and costly https://t.co/DTZoaASsS7 pic.twitter.com/TujfH9dW5R
— Samer ✒ سامر (@sam6) March 23, 2025
The new research, published in the journal mSphere of the American Society for Microbiology, could help predict future "red tide" events and possibly even prevent some of their severe damages.
What is red tide – and why is it dangerous? Red tide is actually a massive bloom of Karenia brevis algae, a single-celled organism that produces neurotoxins. The algae bloom causes the death of fish, birds, and other marine creatures, and can cause respiratory problems in humans and even death.
The phenomenon is driven by environmental factors such as ocean currents, nutrients washed into the water, extreme weather events, and climate changes that lead to rising sea temperatures. The red tide occurs naturally in Florida almost every year, typically in late summer or early fall, and lasts between three and five months, according to data from the Florida Fish and Wildlife Conservation Service (FWC), which partnered in the research.
An aggressive toxic algal bloom called 'red tide' is killing ocean life in Florida, where there's now a state of emergency pic.twitter.com/idSykdABhI
— NowThis Impact (@nowthisimpact) August 18, 2018
The economic damages of the phenomenon are estimated in the millions of dollars, and it affects large areas. Just last month, a strip of red water in Florida stretched for more than 199 miles, from the Tampa Bay area to Key West. The phenomenon is not unique to Florida, and around the same period, Argentina's coasts also turned red.
With climate change and continued warming, the red tide phenomenon raises concern, as according to researchers, rising temperatures are one of the factors encouraging the phenomenon.
During "red tide" events, researchers collected samples of Karenia brevis blooms to analyze them in the laboratory. They used a method that determines the DNA composition of the sample to find the viruses. "We know that viruses play an important role in the dynamics of harmful algae blooms, but we didn't know which viruses might be associated with Karenia brevis blooms," said Jean Lim, the lead researcher of the study from the College of Marine Science at the University of South Florida. "Now that we've identified several viruses in the red tide bloom, we can work to determine which viruses might affect these events."
According to Lim, "There may be a connection between the abundance of viruses and the dynamics of the bloom. For example, an increase in the number of viruses found in a sample might indicate that a red tide bloom is about to begin, or that it is about to end."
The new findings could improve monitoring and prediction efforts for the phenomenon. Since viruses target specific organisms, they may provide an environmentally friendly way to manage the blooms. "There may be specific viruses that might only infect Karenia brevis," Lim added. "If we can identify and isolate these viruses, they could be used as a biological control agent."
