UT researchers crack code to harmful brown tides

A team involving University of Tennessee, Knoxville, researchers has conducted the first-ever genetic sequencing of a harmful algal bloom (HAB) species, cracking the genome of the micro-organism responsible for the Eastern Seaboard's notorious brown tides.

Brown tides decimated the scallop industries of New York and New Jersey in the 1980s and 1990s and continue to plague the waters off North America and South Africa. The tides are not poisonous to humans, but the chronic blooms are toxic to marine life and block sunlight from reaching undersea vegetation, reducing the food available to fish and shellfish. Indeed, they have decimated sea grass beds and shellfisheries leading to billions of dollars in economic losses.

Steven Wilhelm, microbiology professor; Gary LeCleir, research associate in microbiology; Nathan VerBerkmoes, adjunct assistant professor of microbiology at UT Knoxville and Oak Ridge National Laboratory; and Manesh Shah, senior research associate at the School of Genome Science and Technology, in collaboration with other researchers were able to solve the mystery as to why HABs continue to bloom when there are so many other competing species in the water with them.

Their findings are published in the current online edition of the Proceedings of the National Academy of Sciences.

The researchers discovered that the algae's unique genetic structure allows them to thrive in polluted ecosystems, providing clues to why certain species have experienced explosive growth in water around the globe in recent decades.

They found there are certain functions HABs can perform that other algae cannot. For instance, they are able to survive for long periods in no light. They are able to metabolize in organic matter and handle what would normally be toxic amounts of metals like copper. The HABs also have a larger number of selenoproteins, which use the trace element selenium to perform essential cell functions illustrating a concordance between the genome and the ecosystem where it's blooming. The takeaway is that the organism thrives in human-impacted conditions.

“We now know that this organism is genetically predisposed to exploit certain characteristics of coastal ecosystems,” said the authors. “But we also know the characteristics are there because of activities of man. If we continue to increase, for example, organic matter in coastal waters, then it's going to continue to favor brown tides since it's genetically predisposed to thrive in these conditions.”

The research team was led by Christopher Gobler of Stony Brook University's School of Marine and Atmospheric Sciences. Brian Dill, a postdoctoral fellow from Oak Ridge National Laboratory, along with scientists from the Woods Hole Oceanographic Institution, Brigham and Women's Hospital, Harvard Medical School, Rutgers University, Macquarie University, University of Delaware, Stanford University and Massachusetts Institute of Technology also contributed to this study.

Funding for the research was provided by New York Sea Grant, U.S. Department of Energy, National Oceanic and Atmospheric Administration, National Institutes of Health and National Science Foundation.