The first detection happened in the Lafayette River near the Norfolk Yacht & Country Club in July.
Researchers at Old Dominion University sample water in the area several times a week during the summer, when algae blooms are most likely to develop, said Margie Mulholland, a professor in ocean and earth sciences.
On July 22, her team confirmed a bloom of the species Margalefidinium polykrikoides, nicknamed “Marge.” (No relation to Mulholland.)
Colleagues at the National Oceanic and Atmospheric Administration then tracked it via satellite imagery as it slowly moved through the region, carried by shifting currents.
The bloom has made it to parts of the James and York Rivers and even around the coast to the Oceanfront. It now seems to be dissipating, though a patch identified by satellite near Tangier Island may be connected, Mulholland said.
Algae are a crucial part of the ecosystem, “the base of the food web,” Mulholland said. Blooms become harmful when there is an overgrowth, “when you get too much of a good thing.”
They can be harmful in different ways.
Some produce toxins that can hurt people and marine life, Mulholland said. Others might not be inherently toxic, but as they decay, the bacteria consume oxygen, creating what are called “dead zones” in the water. The massive plumes also block sunlight from reaching underwater plants.
Blooms are often spurred by nutrient pollution such as fertilizer that runs off land and fuels algae growth. They also like heat, multiplying much faster in warmer waters.
But Mulholland said scientists don’t yet understand how exactly they form.
“That’s the million-dollar question,” she said.
“Marge” started appearing in the lower Chesapeake Bay in the early 1990s and has since bloomed nearly annually. But it was absent the past few summers.
“So this year, it’s caused quite a stir,” Mulholland said.
These blooms are called “mahogany tides” because they appear as muddy red underwater streaks.
The biggest complaint is often the smell, “like rotting organic matter,” Mulholland said.
But for the first time, she has also received reports of respiratory distress from people out on the water.
ODU is part of a broad coalition tracking and studying algal blooms in the bay, including the state, NOAA, the Virginia Institute of Marine Science and the Mid-Atlantic Regional Association Coastal Ocean Observing System.
They are trying to develop a real-time alert system to warn people when harmful algae is on the rise.
“Sort of like the flood alerts we get from the city when there's going to be flooding, but we want a bloom alert for people on the water that might want to avoid bloomy waters,” Mulholland said.
A hatchery might want to close its water intake so the algae doesn’t get in and contaminate shellfish, for example, or anglers could avoid affected areas.
Mulholland said researchers are still learning about species like “Marge” that have been around for a long time.
But in the meantime, new species seem to be emerging. And as the bay warms because of climate change, it’s causing marine heat waves and shifts in the ecosystem.
Flooding from more intense rainfall and rising sea levels also causes stormwater runoff that can fertilize blooms.
“We’re very concerned with them getting worse,” she said.
They are racing to answer the million-dollar question about when and why blooms form.
“If we can figure that out, then we stand a chance at stopping them.”
You can report sightings of local algal blooms on the Virginia Department of Health's website.
