By Shelia Watson
Contributing Writer

A mystery killer lurked in the estuaries along the eastern United States throughout the 1990s.

Something in the water had killed millions of fish, costing the seafood and recreational fishing industries hundreds of millions of dollars and baffling marine biologists.

Scientists speculated that a strain of algae might be the culprit and even pointed a finger at a prime suspect: Pfiesteria piscicida.

Because of its rapid growth, which produces algae blooms in coastal water, the organism was implicated in several incidents of mass fish deaths from Delaware to Alabama, particularly in the Neuse River in North Carolina and the Chesapeake Bay.

But there was a glitch with that assumption: Lab tests on the normally inoffensive Pfiesteria could not duplicate a lethal form of the algae. Inconsistent test results evoked debate in academic circles, and, although research continued for nearly two decades, the cause of the fish deaths remained a mystery.

Last month, the mystery was solved by a team of researchers at the Hollings Marine Laboratory on James Island.

“What we learned is that copper was the metal of note and that it has to be in a certain state to be toxic,” said lead researcher Peter Moeller of the National Oceanic and Atmospheric Administration. “This is an important discovery for understanding environmental cues. It’s a whole new paradigm in toxicity.”

Moeller had long suspected that heavy metals might be a factor in Pfiesteria’s lethality. He brought together a research team from the agencies that share space and work cooperatively at the Hollings Marine Laboratory—NOAA’s National Centers for Coastal Ocean Science, the Medical University of South Carolina, the National Institute of Standards and Technology and the College of Charleston—to identify the actual toxin and the conditions under which it is produced.

The team determined that the Pfiesteria cell produced the toxin possibly as a mechanism to protect itself from copper in the environment. When exposed to certain environmental factors that can destabilize it, such as sunlight, the toxin quickly breaks down into the chemical species believed to be the actual lethal agents. The findings were published recently in several peer-review science journals.

Solving the Pfiesteria puzzle took about a decade, Moeller said.

“I was working on wet chemistry (specific lab conditions) for about seven years, but from a nature products perspective, that’s not that long when you consider we’re dealing with very small quantities of material from very large cultures,” he said. “We have lists of toxins here that took up to 70 years to discover, so this was relatively a fast discovery.”

The metal-containing organic toxins produced by the organism were characterized by corroborating data obtained from five distinct instrumental methods: nuclear magnetic resonance spectroscopy, inductively coupled plasma mass spectrometry, liquid chromatography particle beam glow discharge mass spectrometry, electron paramagnetic resonance spectroscopy and X-ray absorption spectroscopy.

Besides solving an intriguing scientific enigma, the discovery provides a new way to look at the toxicity of harmful algal blooms. Because the Pfiesteria’s blooms have increased globally in recent years, NOAA, an agency of the U.S. Commerce Department, is concerned about the organism’s potential threat to human and marine health as well any economic impacts.

The discovery has huge potential for environmental science and technology and could keep the Hollings Marine Laboratory busy for quite a while, Moeller said.

“This is going to be a very seminal issue,” he said. “From a monitoring perspective, with the seafood industry for instance, we can develop very specific monitoring tools to give predictive indices where toxicity will occur.

“Another thing we’d like to do is look at naturally occurring metals, which are much more important than we thought, as well as what helps the metals change naturally."

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