Researchers have determined that red tides are not random, but instead have patterns that can be predicted in order to alert officials to the dangers.

The Scripps Institution of Oceanography and University of California San Diego scientist George Sugihara and his colleagues developed a new technique that explains what causes red tides to form in coastal areas seemingly out of nowhere.

"Even with vast improvements in 'ecosystem forecasting' over the past few decades, it remains a major challenge for scientists," said Alan Tessier, deputy director of the National Science Foundation's Division of Environmental Biology, said in a release from the Scripps Institution of Oceanography. "This research shows that the challenge is being overcome using innovative techniques that offer us information such as how to predict red tides. That's important for knowing when to close fisheries and swimming areas, and for the health of residents who live along affected waters."

In Southern California, red tides can produce nighttime light shows with illuminating breaking waves that create eerie blue trails behind surf fish.

But in other areas, including off Florida and in the the Great Lakes, the blooms can be toxic. They cause die-offs, shellfish poisoning, and respiratory problems in humans and marine mammals.

"Red tides were a mystery for so many years because we were looking at the ecosystem as if it was in equilibrium and unchanging and therefore could be studied a piece at a time," said Sugihara, a distinguished professor of natural science at UC San Diego and a senior author on the study. "It was a mystery only because we were looking at it the wrong way. Looking for things that simply 'correlate' with red tides will fail."

A student-led Scripps research team analyzed data from the primary pigment in algae -- chlorophyll-a -- and nutrient concentrations and various physical aspects of the ocean collected off Scripps Pier in La Jolla, Calif. Now in its 100th year, Scripps Pier is one of the oldest continuous monitoring programs of ocean temperature and salinity in the world.

By feeding ecological data into Sugihara's equation-free models, known as empirical dynamic modeling, the researchers identified patterns, as detailed in a study published in the journal Ecology.

The EDM method is studied as a whole system over a 30-year archive rather than as separate pieces.

"The approach allowed us to find factors that come together as a perfect storm to produce a red tide," said Sugihara. "These factors include having a stable water column and low nutrient levels in surface waters."

With model improvements and real-time observations, Sugihara and team believe the blooms could be predicted as part of an early warning system for future red-tide events.

The blooms affect power and desalinization plants, and create oxygen-depleted zones in the waters.

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