'Mahogany tide' algae hits Va. rivers

A burst of brown algae bloomed over portions of the Elizabeth and Lafayette rivers in the Hampton Roads region _ a so-called "mahogany tide" that can have lethal consequences for fish and shellfish.

Algal blooms have become common in the Chesapeake Bay watershed, the result of excessive nutrient pollution _ mostly nitrogen and phosphorus _ from too much fertilizer, vehicle exhaust, stormwater runoff and development activity.

All major tributaries of the bay in Virginia have had blooms of various algae species this summer, Christy Everett, Hampton Roads regional director of the Chesapeake Bay Foundation, said Monday.

Everett spotted the brown algal bloom last Wednesday, near Old Dominion University in Norfolk. On Thursday, during a flight over the region, she saw the bloom had spread to the Western Branch of the Elizabeth River, in Portsmouth and Chesapeake, and up into the Lafayette River in Norfolk.

ODU scientists examined samples and confirmed that a brown-colored species of algae had bloomed locally.

Such blooms usually last several days, Everett said. Chesapeake Bay Foundation scientists plan to fly over various Virginia rivers this Thursday to monitor the condition of the mahogany tide and check for other algal blooms, she said.

The algae soak up oxygen from waterways, and that can suffocate fish, crabs, oysters and clams. Nutrient enrichment also clouds the water, making it difficult for sunlight to reach the bottom so vital underwater grasses can grow and shelter bay creatures.

"They're completely preventable," Everett said of the blooms. "When we reduce the nutrients, there won't be these algal blooms."

Virginia lawmakers this year approved spending $250 million to upgrade sewage treatment plants, including several in Hampton Roads, to curb nutrients.

Algal blooms typically occur in summer and early fall because hot temperatures hasten plant growth. The dense patches of plant life, grow and move with the currents.

The mahogany tide in Hampton Roads is not believed to be toxic, though experts cautioned against swimming in waters with blooms.

"Common sense should tell anyone to avoid them," said Harold Marshall, an aquatic plants expert and professor emeritus at Old Dominion University.

Marshall said the species in question has increased in Virginia over the past decade.

He traced the beginning of this trend to 1992, when a massive mahogany tide swept from the Rappahannock River south to lower James River, out into the Atlantic Ocean and down to the North Carolina coast.

That event "seeded" local waters with the species so that, almost every summer, it multiplies when conditions are right, he said.

The blooms dissipate with a strong tidal exchange or wash into the open bay, he said.

The Chesapeake Bay Foundation has started a "Bad Water Hotline," [phone], for residents to report algae blooms and fish kills.

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