Big Sioux River is South Dakota's latest failure in containing zebra mussel spread

The countdown until an aquatic infestation arrives on the doorstep of Sioux Falls began yesterday.

Buried within a South Dakota Game, Fish and Parks press release, the agency responsible for slowing the spread of zebra mussels reported said stripy specimens now infest the Big Sioux River.

Zebra mussels are an aquatic invasive species that can significantly disrupt the ecosystems it inhabits and, per U.S. Forest Service research, can cause hundreds of millions of dollars to city infrastructure on an annual basis

According to GFP's release, the infestation extends from "the Big Sioux River from Lake Kampeska to the confluence of the Big Sioux and Missouri River." This includes the river's hairpin bend running through Sioux Falls and inclusive of Falls Park.

GFP staff, the release states, discovered the mollusks at two separate locations while conducting river otter surveys along the river.

"The zebra mussels were detected roughly five miles south of Watertown, and downstream of the connected zebra mussel positive waterbody of Lake Kampeska," GFP Aquatic Invasive Species Coordinator Tanner Davis wrote in the release.

This is not the first zebra mussel infestation in South Dakota. It's not even the first reported detection of the mollusk this year. The state has been dealing with the invasive species since the first shelled invader was found in Lewis and Clark Lake in 2015, and the Thursday announcement comes on the heels of another infestation reported Friday in Marshall County's Roy Lake.

Similarly, discounting portions of the Missouri River, the Big Sioux River is now the second major stream to be considered infested, after zebra mussels were found in James River earlier this year.

More: Zebra mussels invade James River, Sand Lake National refuge in first South Dakota incident of 2023

Zebra mussels will soon make Sioux Falls its new home, GFP confirms

The fact of the latest infestation, though, should be cause for concern to the City of Sioux Falls, said Jay Gilbertson, treasurer of the East Dakota Water Development District, a quasi-governmental subdivision of the state.

Previously, this growing epidemic limited itself to festooning docks and boats near lakes and streams meant for recreation, such as Pickerel Lake and Enemy Swim Lake.

At this point, 17 lakes are considered infested with zebra mussels, as well as the James River and, now, the Big Sioux River — both are tributaries to the Missouri River, of which a portion is also considered infested — according to data from the South Dakota Lakes & Streams Association.

The effect on these waters, most of which are in rural areas, is as significant as the impact on urban lakes and streams, Gilbertson said.

But in terms of pure numbers, the AIS footprint is now multiplied with this latest development, Gilbertson continued.

"The number of people who are going to be potentially impacted by this occurrence has jumped up dramatically, if only because the City of Sioux Falls, which draws water from the river, will now need to start planning. And there, you're talking north of 200,000 people," Gilbertson told the Argus Leader on Thursday. "All of those folks now have a stake in the game, whereas the 200 homeowners at Cochran — Well, it's a beautiful lake and there's certainly public access, but it's now impacting a much bigger group of people."

To one who asks the question of whether the City of Sioux Falls itself will be impacted, the answer is "yes," based on GFP's response to an e-mail from Argus Leader.

While there's nothing indicating the physical manifestation of zebra mussels in Sioux Falls, the city and other municipalities downstream of the infestation sites may see "small areas of colonization where suitable habitat is present," according to Nick Harrington, GFP's communications manager.

Just as well, Sioux Falls now has the economic problem associated with the mussels to consider.

"Potential costs associated with infestations could come from maintenance of infrastructure, such as for irrigation use of the river, as zebra mussels can effect [sic] associated pipes and screens," Harrington wrote.

South Dakota, unlike other states, has not drafted an economic impact study to estimate the cost of damages to infrastructure that could result from an infestation. But zebra mussels are well-known for ringing in multi-million dollar repairs to affected structures, like power stations and water treatment plants, by clogging intake pipes.

Pat Starr, a Sioux Falls City Council Member, told the Argus Leader the mussels should present a "huge concern" to the city from an economic perspective.

At the same time, this development touches many things that could impact Sioux Falls residents, from water usage to recreation and even public safety, Starr said.

"It's a huge concern because they're such an invasive species that once they do get into the system, they reproduce so quickly and they take over," Starr said. "It contributes to just a lot of really nasty things that make the river even more polluted and … it makes it more expensive to move forward."

In a word, State Rep. Linda Duba, whose district includes northern Sioux Falls and a portion of the Big Sioux therein, summed up the discovery as "frustrating."

"We've got to find a way to just knock this down because it can be — it will be — devastating to our state from a tourism and wildlife perspective," Duba told the Argus Leader. "If that revenue drops considerably, now you've reduced your tourism footprint, the value of your homes around these lakes. This all impacts people in general and … our economy."

Latest infestations should be ringing alarm bells

As serious as the detection of zebra mussels in the Big Sioux River comes across for its many economic and ecological implications to the city, it's not well understood what the city plans to do once the mollusks inevitably inhabit Sioux Falls.

In response to a request to comment, City Public Relations and Communications Officer Vanessa Gomez said the city will refer to the GFP for guidance on the spreading species as it makes its way to and through Sioux Falls. She then directed the request to GFP.

In terms of preparedness, some Sioux Falls city councilors acknowledged they did not receive direct notice from the agency that the infestation was discovered in the city's main waterbody and source of drinking water. Council Member Greg Neitzert, who oversees Sioux Falls northwest district, first learned of the zebra mussels' detection in the Big Sioux when Argus Leader reached out to him for this article, while Starr, whose municipal demesne is the city's northeast district, found out about the event from GFP's Thursday morning press release.

"The Big Sioux River was determined to be infested on Wednesday, Sept. 27. Per our Zebra Mussel Rapid Response Plan, notification was made via press release within 24 hours of this infestation," Harrington said. "Notifications to potentially impacted user groups begin as soon as the infestation is confirmed, and continues while the press release and other information is shared to the public."

More importantly, however, the press releases themselves reveal how GFP responds to new detections, Gilbertson said.

The Thursday mussel infestation, Gilbertson noted, was not detected as part of standard monitoring but, in a separate capacity, while GFP staff were surveying the stream's river otters.

"The other way to look at it is, 'We were making absolutely no effort to see if they were there … Luckily, we happened to be out in the river doing something else and found these things while looking at river otters,'" Gilbertson said. "It's like, 'Well, great … but what are you doing to protect us or what are you doing to protect the resource or what are you doing to keep anyone who pulls water out of the river from having to spend extra money because of what's in the river and dealing with it?' And the answer is precious little other than saying, 'Oh yeah, hey, we found it.'"

This points to the ongoing philosophy within the agency that zebra mussels are considered to be an "inevitable" plague on South Dakota's lakes and streams, hence why GFP's messaging includes "slow the spread" and not "stop the spread."

Such a mindset comes from GFP Secretary Kevin Robling himself, who described the zebra mussel spread as "an inevitable thing" during an annual South Dakota Wildlife Federation conference in Brookings on Aug. 4, according to a column published in the Watertown Public Opinion by Brad Johnson.

More: State is content to be benchwarmer in invasive species battle

The philosophy was spelled out even further back in Robling's letter in response to an inquiry from the state Government Operations and Audit Committee, which noted the "current philosophy and comments from GF&P consistently speak to being unable to stop the spread of zebra mussels."

GFP, for their part, has sent 1,997,000 emails containing AIS messaging and allocated $62,000 to outreach and communications expenditures, more than double the number of emails sent and a $20,000 increase from 2021, according to Robling's written reply to the 12-page information request from GOAC.

Their messaging has some degree of success, based on GFP's watercraft inspection data, which indicated 96% of boaters complied with boat plug removal regulations in 2022.

But other states have found success where South Dakota has ailed in its response.

After a minor scare in 2016, when zebra mussel veligers — the microscopic, larval form of the mollusk — was detected in Montana's Tiber and Canyon Ferry Reservoirs, the state has invested about $5 million annually in water sampling and boat check stations, according to Missoula-based KPAX News.

Since then, Montana's lakes have not tested positive for the invasive species, even after a record-number of mussel-infested boats passed through the state in 2022.

Evidence of the unstoppable nature of the rapidly-reproducing, ever-spreading invasive mussels, including the quagga variety, does hold water. The Columbia River Basin was the final holdout as the last remaining mussel-free region in the U.S. until the Idaho Department of Agriculture announced on Sept. 18 and later confirmed through DNA testing that quagga mussel veligers had been sampled in the Snake River, according to Boise State Public Radio.

In response to this discovery, the state shut down public access to part of the Snake River as well as nearby lakes. Idaho Gov. Brad Little told reporters on Sept. 19 the mussel represented a "potential crisis" but added the state is resolved to "aggressively" fight the invasive species.

Meanwhile, South Dakota's go-to response continues to focus on "prevention" first and foremost, followed by "containment" and "mitigation," according to GFP's latest strategic plans. "Eradication" is labeled as one of GFP's "key components" of managing aquatic invasive species, but this is generally considered "costly, largely ineffective, and … likely infeasible" by the department.

Right now, the department currently touts its Rapid Response Team, an intergovernmental group comprised of various South Dakota agencies that work together to coordinate a sub-24-hour announcement on the infestation, as a major piece in its prevention efforts. This includes posting "conspicuous" signage warning boaters of a lake's infested status and to "Clean. Drain. Dry."

But now that three of South Dakota's major rivers are under threat of an ecosystem-destroying shellfish, Duba wonders if delaying the inevitable truly was — and is — a step in the right direction.

"Maybe they could slow migration from 'lake A' to 'lake B' by putting up a few more signs, but, at some point, I mean, we've had signs for out there for a very long time," Duba said. "Anyone who's the least bit concerned or worried has read the signs and they've either they've made the decision to either pay attention or they're just going to ignore it. And so adding more signs to the mix, I'm not sure whether that's much of a response."

Dominik Dausch is the agriculture and environment reporter for the Argus Leader and editor of Farm Forum. Follow him on Twitter and Facebook @DomDNP and send news tips to ddausch@gannett.com.

This article originally appeared on Sioux Falls Argus Leader: Zebra mussels may cost Sioux Falls in the long run