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What Lies Beneath

07/02/03
A USC biological sciences professor has partnered with the School of Engineering to develop a fleet of seaworthy robots that will monitor the growth of harmful algal blooms. Unchecked, the blooms can threaten or even kill humans and marine species such as birds and sea lions.
By Eva Emerson
Dave Caron, a professor in the USC College of Letters, Arts & Sciences.

Each year, some of the ocean’s tiniest denizens form massive blooms that threaten human and marine life as they tint coastal waters shades of brown, green, red and gold.

Harmful algal blooms can lead to toxic shellfish poisoning in humans that, depending on the algal species, causes stomach flu-like symptoms, temporary amnesia, disorientation, paralysis or, in the worst cases, death.

The blooms also have been linked to deaths in birds, sea lions and other marine species. Over a decade, the economic cost of these unpredictable blooms has added up to nearly $1 billion, according to the U.S. Environmental Protection Agency.

“From a human impact point of view and from an ecological point of view, it’s essential to figure out what gives these particular organisms this enormous step-up on the competition and leads to a bloom,” said Dave Caron, a biological sciences professor in the USC College of Letters, Arts & Sciences.

“Many species can form algal blooms,” he said. “But not all do, and most don’t most of the time. I’m interested in why blooms occur in a particular place and time. What are the triggers?

By combining new scientific understanding with novel environmental monitoring systems, Caron hopes to create new methods to rapidly detect harmful algal blooms, enabling public-health agencies to issue earlier warnings to reduce toxic shellfish poisoning cases.

His scientific goal is to identify all of the factors that influence the grown of bloom-forming algae.

“These basic ecological issues have been well-studied in macroscopic animals, but have been difficult to do in microbes because of their small size,” he said.

For example, ecologists in the Serengeti studying Cape buffalo populations looked at the availability of water holes, the abundance of grasses the buffalo eat and how disease and predators affect the population size.

Although current methods are not sensitive enough to detect it, Caron said that nutrients may not be uniformly distributed in the ocean. They may be more like the water holes in the grasslands of the Serengeti, with concentrations of nutrients separated by large distances, at least from the point of view of a tiny alga.

No one knows for sure, said Caron, who has focused much of his research on the brown tides in the bays of Long Island, N.Y., that repeatedly have affected bivalve populations such as bay scallops.

Caron is taking part in a Nature Conservancy study testing the idea that the depleted clam populations themselves are adding to the brown-tide problem. The team is looking at whether a denser population of clams might stave off a brown tide.

Caron recently devised a more efficient way to test water samples for the single-celled alga responsible for brown tides called Aureococcus anophagefferens.

Adapting an approach used in medicine, he developed an immunological assay for the algae that can be completed within a day. Although he said that even faster tests are still needed, the new test is an improvement over the time-consuming method of manually counting the alga through a microscope.

Similar tests have been created for the bloom-forming alga Pseudo-nitzschia. A problem along the West Coast, Pseudo-nitzschia blooms release a toxin called domoic acid, which causes amnesia in humans and can be fatal to marine life.

Caron has applied for grants to support regular monitoring of the algae using the new tests.

As a partner with scientists in the USC School of Engineering, Caron is part of an interdisciplinary team led by computer science professor Ari Requicha that aims to build a fleet of miniature, smart biosensors to monitor the growth of toxic algae in the ocean.

In the project’s first step, a miniaturized version of the immunological test – or other sensing technique – may be fitted into small seaworthy robots to sense a forming bloom.

The team’s long-term goal is to develop an autonomous network of free-swimming nanobots, each about the size of a microbe, that automatically would alert agencies and researchers to a harmful algal bloom.

Bob Calverley contributed to this story.

Contact Eva Emerson at (213) 821-2480.