Red tide blooms are complex problems. A naturally occurring event not yet fully understood, they are driven – in part – by environmental factors such as ocean circulation, nutrient concentration, and climate change.

They can also be deadly for marine life, cause respiratory issues for beachgoers, and impact coastal economies based around tourism and fishing.

Understanding what makes them tick is, therefore, serious business. And a new study from researchers at the University of South Florida has gone some distance to shine a light on the kind of environmental factors that cause them.

Published in the American Society for Microbiology’s journal mSphere, the study is the first to identify the kind of viruses associated with something called Karenia brevis – the single-celled organism that causes red tide.

In fact, by testing water samples collected from red tide blooms off southwest Florida, the researchers found several viruses – including one new viral species – all present within the Karenia brevis blooms.

By identifying the viruses associated with red tide, researchers hope to be able to better forecast the development of blooms and better understand the environmental factors that can cause them to terminate. 

Where it could break new ground is in exploring these viruses as the biocontrol agents for red tide, providing an environmentally-friendly method for controlling them.

“We know that viruses play an important role in the dynamics of harmful algal blooms, but we haven’t known what viruses might be associated with Karenia brevis blooms,” said Jean Lim, the study’s lead author and a postdoctoral researcher at the USF College of Marine Science.

“Now that we’ve identified several viruses in red tide blooms, we can work to determine which viruses might have an influence on these events.”

To conduct the study, Lim and her team partnered with researchers from the harmful algal bloom monitoring and research programme at the Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute, who collects samples during red tide events.

In the lab, Lim used a technique known as viral metagenomics – a process of extracting genetic material from water samples – to identify the viruses present within samples containing red tide.

Current monitoring efforts rely on satellite images of chlorophyll concentrations and field samples. Ocean circulation models operated by researchers at the USF College of Marine Science can help forecast the movement of red tide blooms. 

It’s hoped that a better understanding of viruses that influence red tide could improve long-term monitoring and forecasting efforts by signalling that a bloom will develop or terminate.

Lim and her team are therefore looking for the signs of correlation between viral abundancies and bloom dynamics. 

“For example, an increase in the number of viruses found in a sample might suggest that a red tide bloom is about to begin, or that it is going to end,” said Lim. “Researchers could use information about viral abundancies to help predict bloom cycles.

Lim has even proffered the idea that there could be specific viruses that “may only infect Krenia brevis.”

“If we can identify and isolate those viruses, they may be used as a biocontrol agent that won’t have a broader negative impact on marine ecosystems.”

As a next step, Lim and her colleagues will attempt to determine whether viruses identified in the recent study have an influence on Karenia brevis or other species that co-occur with red tide blooms.

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