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CORVALLIS, Ore. - Researchers at Oregon State University have developed new ways to genetically analyze the cyanobacteria that cause harmful toxic blooms in lakes and reservoirs around the world, and found that one strain can rapidly replace another, with huge implications for their toxicity.

The bacteria, which are an ongoing concern because they can cause liver damage and neurotoxicity, are much more complex than commonly understood, scientists say, and long-term efforts to monitor or even manage them will be improved through a deeper understanding of their genetics.

"Something that looks very uniform under a microscope is actually far more complex," said Theo Dreher, a professor of microbiology. "As one strain of microcystis is replaced by another, there can be an increase or decrease in toxicity. And this can happen fairly quickly in one season."

A recent study, published in the journal Applied and Environmental Microbiology, outlines some of these genetic changes, using as a model the shifts in toxic bacterial blooms on the Copco Reservoir of the Klamath River, a place where they have been a major problem in recent years. In this analysis, a strain of microcystis that was very toxic was replaced rather abruptly by one that was far less of a concern, during one blooming season of spring through fall.

Dreher said that approaches to identifying the bacteria typically use a microscope to identify and count the number of cells that may contribute to toxicity. But that doesn't accurately predict how toxic they might be, he added, and assays to measure the toxicity can be both time-consuming and costly.

A complete understanding of the genetics and ecology of these bacteria, he said, could open the door to faster and less expensive monitoring, better protection of public health around the world, and even ways to improve management to reduce the growth of bacteria that are most toxic.