On Shenandoah River, algae and bacteria continue to plague recreation — and human health

On the rolling river of old song, new growth is troubling the waters. 

When summer temperatures rise and waters slow, long strands of algae emerge in many parts of the Shenandoah and its North and South Forks. Thick and dense enough to form floating mats, they catch kayakers’ paddles and fishermen’s rods and deter swimmers and waders. 

This so-called filamentous algae isn’t just unsightly. One report from Shenandoah Riverkeeper Mark Frondorf this July described an outbreak in the North Fork near Mine Mountain as resembling “purple jelly” and smelling bad. 

“People will say, you know, ‘I brought my friends, I go here all the time through the years, but it was so nasty this time or these two months or this summer that I’m not coming back,’” said David Sligh, conservation director for environmental nonprofit Wild Virginia during a meeting on the Shenandoah this spring. “You’ve got testimony from outfitters and fishing guides that say, ‘After I take somebody there and it’s really horrible, I can’t take them back there. They don’t want to go.’” 

For more than a decade, filamentous algae problems have been mounting. In 2016, the Potomac Riverkeeper Network, which includes the Shenandoah Riverkeeper, sued the EPA over its approval of DEQ’s decision to not list the Shenandoah as impaired due to algae. The distinction would have required Virginia to enforce pollution limits for the waterway, but the group lost its suit in D.C. Circuit Court. 

Complaints have continued. In 2019 alone, the Virginia Department of Environmental Quality received 53 complaints about nuisance algae on the Shenandoah and its two forks. In 2020, there were 30 complaints. As of mid-August this year, there had been 20. 

“The vast majority of them are from just a few constituents, but with the level of attention and scrutiny on the North Fork of the Shenandoah … we are receiving more calls, more reports,” said Tara Wyrick, a water monitoring and assessment manager with DEQ’s Valley Region office. “We generally see algae growing all the way through the end of October.” 

At the same time, the appearance of a different phenomenon known as a harmful algal bloom has also left health and environmental officials concerned. Despite their name, these blooms — often called HABs — result from an overgrowth not of algae, but of cyanobacteria, an aquatic type of bacteria that relies on photosynthesis to survive. 

Cyanobacteria are not inherently bad and occur naturally in fresh and salt waters worldwide. But some types such as Microcystis are capable of producing “cyanotoxins” that can cause liver and kidney damage in humans and animals. In one high-profile 2019 incident, three dogs in Wilmington, N.C. died after swimming in pond waters where a HAB was occurring. 

HABs aren’t abnormal in Virginia, but this summer marked the first official occurrence on the Shenandoah. On July 23 the Virginia Department of Health issued an advisory for a portion of the North Fork that was later expanded twice to cover a roughly 53-mile stretch of the waterway. (The agency did note that although cyanobacteria mats were widespread at specific sites along the length, “they are not wide-spread throughout the entire ~53 mile stretch.”) 

“It’s very concerning for sure,” Secretary of Natural Resources Matt Strickler told the Mercury. And while both VDH and DEQ have been monitoring the problem, he noted, “I think both our agencies are understaffed and underfunded.” 

Phillip Musegaas of the Potomac Riverkeeper Network, which monitors the Shenandoah regularly through people such as Frondorf, fretted that as filamentous and other algal blooms become more common, river users will begin to see them as part of the river’s normal condition. 

“Our vision is not of a Shenandoah River that never has a single algal bloom in it,” he said. “But there’s a huge difference between occasional algal blooms on the river and what we’ve been seeing the past 10 years.” 

A tangled web

What causes explosions of filamentous algae as well as harmful algal blooms isn’t fully understood. Water temperature makes a difference, as does flow. Blooms of both are more common when rivers are hot, slow and shallow — conditions increasingly frequent as climate change makes weather both hotter and more unpredictable. 

Where disagreements arise is over how big a role nitrogen and phosphorus pollution play in driving the blooms. 

These nutrients, which lie at the heart of the problems that have plagued the Chesapeake Bay and its watershed for decades, come from a range of sources. Wastewater treatment plants and septic systems discharge them into waterways, as does stormwater runoff from developed areas. 

Agriculture too is a major contributor: both the fertilizers used on fields and animal manure are significant producers of nutrient pollution. Over the past decade Virginia has made big strides in encouraging farmers to adopt nutrient management plans and fence off livestock, particularly cattle, from streams to stem the flow of nitrogen and phosphorus into state waterways. Still, officials have been forthright that the biggest pollution reductions Virginia needs to make between now and 2025 come from the agriculture sector. 

The U.S. Environmental Protection Agency has identified a link between nutrient pollution and algal blooms, noting that “too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle.” 

To many environmental groups, the root of the algae issue in the Shenandoah is clear: nutrient pollution, especially from agriculture. 

“Blooms in general are always exacerbated by nutrients,” said Joe Wood, a senior scientist with the Chesapeake Bay Foundation’s Virginia office. In the Shenandoah watershed, “it’s probably a combination of agricultural and wastewater sources.” 

Other factors are at play, Musegaas acknowledged: algal blooms do “very much depend” on water level, flow and temperature. But “the Shenandoah Valley and the river is very intensively used for industrial farming.”

“If there was not nutrient pollution in the river, from agriculture, from stormwater, from all these sources, yes, you would occasionally still have algae popping up,” he said. “But you would not have this massive extent of very large, very noxious blooms that happen every summer.” 

Martha Moore, the Virginia Farm Bureau Federation’s vice president for governmental relations, however, rejected the idea that agriculture is definitely a primary contributor to the blooms, pointing to other potential contributors such as increased development, an overabundance of wildlife accessing the Shenandoah’s waters and the close proximity of large national parks. 

“I just don’t know the science is completely there to determine what is the root cause,” she said. “There are a lot of people who want to draw conclusions just based on what they believe. I think it’s really important to look at what science has been done.” 

Virginia DEQ has adopted a similar stance. 

“The circumstances that lead to the development and persistence of algal blooms are complex and not well understood,” said Sandy Mueller, who along with Wyrick has led the agency’s efforts to grapple with filamentous algae in the Shenandoah. “While many factors can contribute or combine to create conditions leading to algal blooms, there is not a single factor that can be identified at this time that will result in a HAB or filamentous algae event.” 

Wyrick agreed: “There’s no smoking gun,” she said. “We wish that there were. There’s a lot of different factors at play.”

How much algae is too much algae? 

Instead, DEQ has focused on finding a way to measure how much algae is too much algae when it comes to the Shenandoah. 

For filamentous algae, defining what constitutes “nuisance algae” is a tricky task. The EPA doesn’t set specific thresholds for such algae, meaning Virginia didn’t have a framework on which to build its criteria. And, said Mueller, “there’s some subjectivity to what constitutes a nuisance condition.” 

This August, after several years of fieldwork and several months of debate by a work group convened to address the algae problem, DEQ proposed a new set of criteria for how much chlorophyll-a — a proxy for algal growth — can be present in the Shenandoah and its two forks over a three-year period. If concentrations of chlorophyll-a exceed those thresholds during the recreational season more than once during three years, the agency will declare that filamentous algae has reached nuisance levels. 

The criteria will need approval from the State Water Control Board before they can go into effect.

“We think this is a really good start in terms of having a standard to actually measure how much algae is out there and how much it is negatively affecting recreation,” said Musegaas. 

Sligh of Wild Virginia was less enthusiastic, saying that while the new criteria have “positive aspects,” they are “insufficient to ensure that nutrient-related problems in the Shenandoah are adequately prevented” because they only apply to filamentous algae and not other types that can impact waters. 

The filamentous algae standards notably also do not apply to cyanotoxins linked to harmful algal blooms. Although the EPA in 2019 issued standards that states can adopt as water quality or swimming advisory thresholds for two cyanotoxins known as microcystin and cylindrospermopsin, DEQ decided not to incorporate them into the state framework. Instead, the agency will continue to rely on Virginia Department of Health monitoring to make decisions. 

In a June meeting, Sligh questioned whether there was a downside to state adoption of the EPA standard.

“It is acknowledging that there’s been a problem and maybe trying to prevent that from happening again, which I think is the real intent of water quality standards,” he said. “It’s not just to react and document problems but to look ahead and keep them from happening.” 

DEQ Director of Water Planning Jutta Schneider said staff “just don’t see the need to add the criteria.”

“We have a process,” she said. “We think the process is working.”

This story has been corrected to reflect that Microcystis, and not microcystin, is a type of cyanobacteria. Microcystins are a type of cyanotoxin.