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Algae blooming on Buffalo River, but ecologists say it’s just a nuisance for now

Natural occurrences common, harmless, but could worsen, they say by Bill Bowden | July 25, 2022 at 7:14 a.m.
Bluffs cradle the Buffalo National River, which runs for 135 miles from Ponca to the White River, in this undated file photo. (NWA Democrat-Gazette/Flip Putthoff)

With Arkansas' July heat wave, algae has been blooming on the Buffalo National River.

Lucas Driver of Little Rock, an ecologist with the U.S. Geological Survey's Lower Mississippi Gulf Water Science Center, said the filamentous algae blooms are naturally occurring in just about all fresh waters, but they can reach nuisance levels under certain conditions.

"If these blooms get worse, then you might start seeing negative impacts on visitors to the state's crown jewel of the Buffalo River," he said.

The national park attracts about a million visitors a year. Most of them don't go there for the algae.

"Bloom" refers to colonies of algae growing out of control.

What most people see on the Buffalo River is non-toxic algae of the genus Spirogyra, Driver said. "Lime green, slimy, hairlike filaments that can grow to be several feet long under certain conditions," he said.

Sometimes they grow from the riverbed to the surface, where they are called mats.

"That's when people start getting upset," Driver said. "It can be a real deterrent to people who are out there trying to swim or fish."

After a storm, the algae can become detached from rocks, pebbles or bedrock and float downstream like "little river tumbleweeds," Driver said.

Buffalo River algal blooms have been documented in field notebooks over the past several decades as well as in earlier historical reports.

According to a 1978 report on the Buffalo River, "Copious blooms of Spirogyra are associated with deep pools with large rocks and a sand-silt base. ... Cattle access at Tyler Bend appears to be directly related to localized and extremely heavy Spirogyra bloom."

According to a 2018 news release from the national park, "Some algae is important to a healthy ecosystem and most species are harmless, although a nuisance to paddlers, swimmers and fishers."

"Most of our blooms are just nuisance algae," said Shawn Hodges, an ecologist with the Buffalo National River. "It's unsightly. It's not aesthetically pleasing, but it's there. ... I'm not surprised to hear reports of algal blooms this time of year, especially when we're having 100-degree days."

"Especially in the height of the summer, you're going to find algae at some places, and a little bit of algae is not a big deal," Driver said. "Algae blooms to some extent are not a big deal. It's a naturally occurring thing. It's unpleasant for people to be around. It can turn into an ecological stressor as we call it under certain conditions."

If the algae blooms on the river continue to grow, they could rob fish, frogs and invertebrates of oxygen. Driver said algae could displace organisms or disrupt their ability to access required habitats for feeding, reproduction or refuge from predators.

"We see blooms that can flare up in the late summer and fall," Driver said. "Typically, when it gets cooler, those blooms start to die off in the late fall and winter."

Hodges said he has worked at the national park since 2004. He saw algae blooms that year and the next, but says they're more extensive now. Hodges said he's never seen an algae bloom on the Buffalo that killed fish.

WATER STUDY

After anecdotal reports of large algae blooms on the river in 2016, 2017 and 2018, the Geological Survey -- working with the National Park Service -- began monitoring river water at regular intervals and checking for algae. Volunteers from state agencies also assist.

As part of the study, water quality is checked for nutrients every four to eight weeks at two dozen sites along a 70-mile stretch of the river from the Hasty bridge to Rush, Driver said. A visual assessment for algae is made for about 500 meters of the river at 12 of those testing sites. A detailed survey is done in areas when filamentous algae is present.

"It's not a perfect snapshot," Driver said. "It gives us a representation of the spatial extent of the algae. This is just kind of one snapshot, one avenue, one piece of the puzzle. There's lots of work to be done."

He said suspected causes of algae blooms include heat, excessive sunlight, low-flow hydrology and nutrients in the water. Nutrients include elements such as nitrogen and phosphorus.

"The watershed in general has lots of different nutrient sources, from agriculture, humans -- there's septics, there's chicken houses, there's pasture, there's hayfields that get fertilized," Driver said.

He said the area's karst terrain could allow nutrients to enter the river from underground sources such as sinkholes, caves and springs.

Hodges said algae provides food for fish.

"We have fish that just feed on algae," he said. "There's always algae present all year long. It's always there, but sometimes conditions are perfect for a bloom to occur. At this point, we're still trying to figure out what the main cause is."

In general, the Buffalo River is considered a very low-nutrient watershed, Driver said.

"The Buffalo is pristine," he said. "That's one of the reasons it's a national park. Water quality historically has been very, very good. It's still considered a very low-nutrient system."

Driver said there's no real rule for what constitutes too much algae, and algae is more common in lakes than rivers.

After a public survey in 2012, West Virginia ecologists decided that 40% filamentous algae coverage of a streambed -- regardless of the bloom length -- is the point at which algae is interfering with the recreational use of the stream.

"We currently don't have that definition in place," Driver said of Arkansas.

Last week, during a survey of the Buffalo River, ecologists found less than 10% algae coverage at some of the 12 testing sites, Driver said. At other sites, algae covered more of the riverbed, but specific estimates of coverage hadn't been analyzed as of Friday.

"What we're seeing right now I wouldn't consider out of the ordinary, but the summer isn't over yet," Driver said.

He said the algae was generally more dense on the lower Buffalo River, where it's wider and more shallow, with some deep pools.

"Based on our experience, algae is typically more prevalent in the lower part of the river, downstream of Tyler Bend," he said.

Driver said he saw some filamentous algae that had grown to the extent that it was forming mats on top of the water.

"I didn't see any huge mats," he said. "I saw a couple of places along the edge of the river where the algae was starting to accumulate on the surface."

Driver said the current phase of the nutrient water-quality study is winding down, and they are exploring ways to continue the research.

While the water study has been underway for 4.5 years, Driver said more time is needed to gather data and explore relative trends.

Spirogyra is mostly a nuisance, but other algae is classified as harmful.

"Ranging from microscopic, single-celled organisms to large seaweeds, algae are simple plants that form the base of food webs," according to the National Oceanic and Atmospheric Administration. "Sometimes, however, their roles are more sinister. Under the right conditions, algae may grow out of control -- and a few of these 'blooms' produce toxins that can kill fish, mammals and birds and may cause human illness or even death in extreme cases. Other algae are nontoxic, but eat up all of the oxygen in the water as they decay, clog the gills of fish and invertebrates or smother corals and submerged aquatic vegetation. Still others discolor water, form huge, smelly piles on beaches or contaminate drinking water. Collectively, these events are called harmful algal blooms, or HABs."

While NOAA is talking mostly about the ocean there, some harmful algae can be found in freshwater streams.

Cyanobacteria, often called "blue-green algae," is naturally occurring in most freshwater streams, including the Buffalo River. It can produce toxins and is considered a harmful algae, and it caused problems on the Buffalo in 2018.

"... A species of blue-green algae (also called cyanobacteria) has been identified within the river," according to a July 27, 2018, news release citing Hodges. "This species has the potential to produce cyanotoxins, which can be harmful to humans and pets. Unfortunately, you cannot tell if the algae would produce cyanotoxins just by looking at it. A few visitors have reported illnesses after swimming in areas with algae this month."

HOG FARM

Environmentalists thought a large hog farm, which closed in January 2020, might be to blame for a spike in nutrients in the Buffalo River.

In 2012, the state permitted C&H Hog Farm to operate a farm near Big Creek, a tributary of the Buffalo River. The farm was allowed to house up to 6,503 hogs, although it normally operated with about 3,000.

After years of controversy, in 2018 the Arkansas Department of Environmental Quality denied C&H a permit to continue operating the farm.

The next year, Arkansas paid C&H $6.2 million for the farm land, which is being used as a conservation easement to protect the river.

From 2016-18, Driver participated in a study of Big Creek and the Buffalo River.

The study looked at monthly nutrient concentrations and the response of periphyton in the Buffalo River both upstream and downstream from its confluence with Big Creek. Periphyton refers to aquatic organisms including plants, algae and bacteria that live attached to underwater surfaces such as rocks on a riverbed.

"Basically, we went out and scraped algae off of rocks," Driver said. "It was standardized. There were a certain number of rocks we'd pick up from the streambed."

Some of what they found was to be expected.

"Nutrients in Big Creek were higher than in the main stem, but that is not surprising and that is not unusual for tributaries of the Buffalo River," Driver said.

And in the Buffalo River?

"There was no significant difference in nutrient concentrations upstream and downstream, but there appeared to be a slight difference in the periphyton communities downstream, which could indicate a response to even subtle changes in nutrient concentrations," Driver said.

Cassie Branstetter, a spokeswoman for the Buffalo National River, said she's received no complaints this year regarding algal blooms.

Branstetter said the park hasn't tried to remove any algae.

"Algae could be removed with algaecides, but in a natural environment that would be very detrimental to the ecosystem," she said. "These are typically used in fountains and other man-made water features to keep them looking pretty."


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