The Tampa Tribune


Study finds link between bacteria, red tide blooms

By Neil Johnson

November23, 2009

Researchers have found a link between bacteria and the algae that causes the red tide outbreaks that leave beachgoers wheezing and shorelines strewn with dead fish.

The findings may allow scientists to better predict when the population of algae will explode to create a bloom, said William Sunda, a National Oceanic and Atmospheric Administration scientist who co-wrote a report on the study.

And in the distant future, the discovery may point to a way to stop a bloom or diminish its effects, he said.

A red tide occurs in Florida waters when tiny algae grow into such prodigious numbers they turn the water a reddish color. They secrete toxins that kill fish and other marine creatures and can cause respiratory problems for people.

The algae constantly inhabit the waters around Florida but are normally in numbers too low to cause problems.

The NOAA research found that a type of bacteria provides a necessary element for the algae to blast into a frenzy of reproduction.

The bacteria and algae work together in a symbiotic relationship.

Scientists found that the bacteria release a compound that lets the algae absorb iron, something essential for photosynthesis in all plants but also difficult for the algae to get from seawater.

"The algae need a lot of iron," Sunda said.

Without the extra iron, there would be no algae blooms, he said.

In return, the algae produce nutrients for the bacteria so its population can expand and produce more iron for the algae.

"The whole process feeds on itself," he said.

Experiments that eliminated the bacteria either killed the algae or kept it from growing, Sunda said.

"We always knew the bacteria was there," he said. But scientists did not know its role in boosting the red tide blooms.

None of the current computer models used to predict red tide considers the bacteria populations as a factor in the forecasts.

"The next generation of models could include this," Sunda said.

If scientists can figure out a way to safely control the bacteria, it might reveal a method to control the red tide outbreaks.

"These particular algae and bacteria need each other," Sunda said.