BOSTON, Aug. 20 (UPI) -- Boston's Charles River used to be one of the most polluted in the country. In recent years it's been heralded as an environmental success story, but a recent outbreak of cyanobacteria threatens to undermine the accolades.
Cyanobacteria, also known as blue-green algae, is a prokaryotic bacteria that derives energy from the sun via photosynthesis. Blooms are common in the summer, fueled by a combination of high temperatures, sunny days and fertilizer runoff.
Some types of cyanobacteria can be toxic, and though the kind that's recently invaded the Charles River is not, it can cause skin irritation, vomiting and other mild symptoms.
Health officials have warned Bostonians against swimming in the Charles, and suggested boaters and dog-walkers limit contact with the water. Earlier this month, officials closed a local pond popular for swimming.
Though they have a rough idea, scientists don't fully understand the catalysts involved in cyanobacteria blooms, which makes thwarting them difficult. Experts say reducing fertilizer runoff is a positive goal for a variety of economic and environmental reasons. But the problem of cyanobacteria is more complicated.
"The problem is scientific -- we simply don't know what makes them bloom," Ferdi Hellweger, a water quality expert and an associate professor of civil and environmental engineering at Northeastern University, explained in a press release. "This highlights the need for more basic research into the ecology of cyanobacteria and a cautious approach when considering massive and costly management actions."
Hellweger is one of many conservationists working hard to make the Charles River swimmable once again.
"These blooms are threatening our vision of a swimmable Charles and are impacting other recreational activities around the river, including dog walking," he said. "The Charles River is not alone in this regard."
Blue-green algae blooms are approaching all-time highs in the Great Lakes this summer. Similar blooms are happening in the Gulf of Mexico. Last year, officials in Toledo, Ohio, were forced to shut down the local drinking water plant after an algae bloom turned toxic. Bottled water had to be trucked in for residents.
Some experts say the recent outbreak is less a story about the Charles specifically, and more a sign of the times -- of global warming. Warming temperatures seem to be an inextricable part of the story of growing algae blooms.
"I don't think it necessarily speaks to anything about the health of the Charles," Marc Nascarella, director of the Environmental Toxicology Program at Massachusetts' public health department, told the Boston Globe.