Scientists Learn More About Harmful Algae Blooms

These are the Aureococcus anophagefferens cells of a harmful algal bloom brown tide. Photo/Chris Gobler, Stony Brook University

New York Sea Grant reports that scientists from several institutions are studying the genome of a harmful alga that causes so-called “brown tide” in Long Island Sound every summer. The alga is not toxic to humans, but can block sunlight from reaching underwater vegetation and destroying critical shellfish habitat.

Here’s an excerpt: [The scientists] analyzed the complete genome of the brown tide alga Aureococcus anophagefferens, the first harmful alga genome ever to be sequenced, and found that the alga has unique genes that may allow it to outcompete other marine phytoplankton in conditions that have been altered by human activities.

Specifically, A. anophagefferens has more genes than its competitors for metabolizing high levels of organic matter and toxic heavy metals from fertilizers and wastes found along heavily populated coastlines. It also has more genes to harvest light so it can survive for longer periods in murky estuaries clogged with organic matter.

A. anophagefferens produces opaque brown tides in U.S. East Coast estuaries and in South Africa. Unlike other harmful algae, they are not toxic to people, but they are environmentally devastating, blocking sunlight and killing seagrass beds and commercial shellfish. No A. anophagefferens blooms were recorded before 1985. Now they are annual summer events that cause severe losses to shellfisheries, especially in Long Island, N.Y. In 2007, the Department of Energy’s Joint Genome Institute sequenced A. anophagefferens’s genome from cultured Long Island cells.

“It’s really exciting to be able to apply these new tools and a molecular approach to old questions about how organisms are functioning and interacting with their environment,” Dyhrman said. “By looking at when the genes are transcribed through a bloom, we’re hoping to provide the next piece in the puzzle—understanding what is fueling and causing the demise of blooms.”

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Sea Grant

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