Recent research details potential solutions to Ross Island Lagoon’s cyanobacteria blooms

The Ross Island Lagoon, which sits in the center of the four-island complex known as Ross Island, is a byproduct of decades of mining. In addition to industrial purposes, the lagoon also has a long history of being used recreationally and provides habitat for a variety of vulnerable plant and animal species.

In 2015, researchers began to see cyanobacterial blooms in the lagoon. Cyanobacteria is a type of bacteria that can pose a serious threat to the health of animals and people who come into close contact with the water. When present, it gives the water a bright green appearance.

Because the lagoon is a warm, stagnant pool, it’s an ideal breeding ground for cyanobacteria. And it’s only getting warmer due to climate change. The tide from the Willamette River pulls the cyanobacteria out into the river’s main flow, contaminating the rest of the water. The Oregon Health Authority routinely releases warnings urging against recreational river use during warmer seasons because of this.

Since 2017, Oregon State University and the Willamette River group the Human Access Project have been working on reducing these lagoon blooms. There is work being done by different groups to address the cyanobacterial blooms in the Ross Island Lagoon. Desirée Tullos, professor of water resources engineering at Oregon State University, joins us to share more.

This transcript was created by a computer and edited by a volunteer.

Dave Miller:  This is Think Out Loud on OPB. I’m Dave Miller. In 2015, researchers started finding harmful cyanobacteria blooms in the Ross Island Lagoon in Portland. Toxins from these blooms can flow out of the lagoon into the main stem of the Willamette River, making it dangerous to swim in at times. In the nearly 10 years since that first discovery, scientists, engineers and engaged Portlanders have been working together to solve this issue and to improve the river’s overall health. We’re going to get an update on their work right now. Desirée Tullos is the lead researcher on this project. She is a professor of water resources engineering at Oregon State University and she joins us now. It’s great to have you on the show.

Desirée Tullos:  Thanks, Dave. Happy to be here.

Miller:  What is cyanobacteria?

Tullos:  Well, cyanobacteria are naturally occurring. They’ve actually been around a really long time, around three and a half billion years, and they produce a lot of the oxygen that’s in our atmosphere that we depend on. That’s sort of the bright side. The darker side is that while they are naturally occurring, they’re occurring in places and in numbers where they can harm human and ecological health. So as humans, we’ve impacted rivers in a lot of ways. We’ve created warm stagnant waters that have a lot of nutrients in them. And those are conditions where these cyanobacteria can thrive and outcompete these other more desirable algae bacteria in rivers. And that’s when we start to see these harmful blooms that turn the river green.

Miller:  So just to be clear, would these cyanobacteria, in small numbers, naturally occur in Northwest rivers like the Willamette?

Tullos:  Yeah, they do. The USGS was out in the lower Willamette in 1973 and 1974, and they were detecting one of the attacks that we see out there today. But they’re in much smaller numbers than what we see today because we have modified the system so much.

Miller: In what ways? What’s the perfect recipe for making a bloom? If that’s what you wanted to do, what would you do?

Tullos:  Yeah, so that recipe has three main ingredients. The first is nutrients. Nutrients are definitely elevated in the Willamette, and that’s been the case for quite a while. The second is temperature. The data clearly show that the lower river is getting warmer and has been over the past decade or so. But the third is the stagnant water. So we need nutrients, warmer temperatures and stagnant water because the cyanobacteria have these really cool gas vesicles that allow them to migrate [and] move around to essentially find the sweet spot wherever they want to be in terms of sunlight and nutrients. And so it’s those three things that we’ve created in the lower Willamette that allow ‘em to really thrive.

Miller:  This seems like a good time to talk about the Ross Island Lagoon, in particular. For folks who maybe are not aware of Portland’s geography, first of all, just where is it and what is it like, this lagoon?

Tullos:  The Ross Island Lagoon is located in the lower Willamette River, just downstream of Ross Island Bridge. It used to be a set of islands. Back in the ‘20s though, the [U.S. Army] Corps of Engineers came in and they created this embankment at the upper end to help connect the islands for access, but it shut off flow through the lagoon. And then over time, a private gravel operator removed a lot of gravel. In fact, a lot of the concrete in downtown Portland includes gravel that came from the Ross Island Lagoon. But that created a stagnant pool in the middle of a flowing river where those cyanobacteria really can thrive.

Miller: So it seems like we have inadvertently, in terms of changing the hydrology and also with climate change, made the perfect breeding ground for this cyanobacteria?

Tullos:  Exactly, yeah. Again, under natural conditions, where they occur, they’re not a problem. But they can be harmful when they bloom because they produce toxins that can make people and dogs and wildlife sick. They also can change the quality of the water, elevating pH, depleting oxygen that’s in the water, and that can kill fish and other aquatic organisms.

Miller:  How serious are these toxins? You said that they could be harmful for humans, for animals, for fish, but how serious is it? I guess I’m just wondering about the severity of toxic exposure?

Tullos:  Well, in collaboration with the Oregon Department of Environmental Quality, we are working to sample the river to measure the toxin levels. Currently, we actually have a field crew out in the river today, right now, as we speak, collecting samples to understand the concentrations. But it really depends on how concentrated it is because in really high concentrations, it can be pretty dangerous. It can kill dogs. These toxins are liver toxins or neurotoxins. They can even create respiratory inflammation. But they have to be at high enough concentrations to really make people sick.

And small bodies are more vulnerable. So dogs and kids are more vulnerable than, say, adults. Ingestion is the primary way that people get sick. So simply contacting it might give you some irritation on your skin, but it’s ingesting it or inhaling it where you really start to get exposed. And so right now, the river’s safe as far as we know. We haven’t detected high concentrations of toxins. There is currently no advisory on the river in the lower Willamette. But as this river starts to turn green, you start to see that scum in the water. That’s when we start to get concerned about people getting exposed.

Miller:  And this is a season when you would assume there’d be the highest likelihood of toxic blooms?

Tullos:  Correct. Usually what we’ve been seeing over the last five or six years, since we’ve started studying it, is that the blooms tend to really start to peak late July. Then the worst of it really starts to happen the first week of August. So we’re not out of the woods yet, but we did have a wet spring. Spring seems to be really important in terms of how wet it is, how cold the river is – those two things really seem to drive the patterns that we see in the summer. We had that big heat wave a few weeks ago. We started to see signs of a bloom forming, but then we got this rain. In fact, we got some hail. The river’s cooled off, and our data suggests that cyanobacteria have slowed production too. So we’re going to keep watching it and, again, working with partners, continue setting the system to make sure that it’s safe for people to access.

Miller: There is a dark irony here that these blooms have become more common after the big pipe was put in to make sewage overflows much less common. And after a really concerted kind of social project of getting Portlanders to think about the Willamette as a safe, fun place for recreation, not to mention the fact that the exact times when these blooms are most likely are the hot times when Portlanders would be most interested in getting in the water. It’s a shame that that’s the way that the timing works.

So I want to turn to what you can do about this. The phrase I’ve seen is a flushing channel. What does that mean?

Tullos:  I want to take you back just a couple of steps about how we got started. I was living in Portland doing these open water swims with the Human Access Project. That’s when I first connected with Willie Levenson who leads the Human Access Project. And we’ve spent the last six years building the science, the partnerships and the funding to solve this issue. So I just really want to emphasize this is science-based. We’ve really spent a lot of time learning about the lagoon. It’s not just something we’ve just come up with. In fact, the idea of the flushing channels existed before I was working on this project. It’s been around for a long time. The justification for it is really based on understanding the current and local conditions that contribute to the bloom, and then figuring out how to reverse that using engineering and nature-based solutions.

I mentioned earlier that the Corps of Engineers had built that embankment on the southern end, the upstream end. So essentially what we’re talking about with the flushing channel is a resetting of those ecological processes, allowing flow to move through the lagoon again, restoring that flow through it. That existed historically, so essentially removing that competitive advantage that those cyanobacteria have [during] the hottest times of the year.

Miller:  It sounds sort of like breaching a dam?

Tullos:  I spent a lot of time thinking about breaching dams, Dave. And I can tell you that it’s actually pretty similar, in terms of restoring the movement of water, sediment and natural processes to a river.

Miller:  Are there engineering challenges or financial challenges? Lemme put it this way – what’s the bigger challenge, getting the money for this or figuring out the best way to do it technically?

Tullos:  This may reveal my biases, but I tend to think that the engineering part is actually quite straightforward. The engineers that I’m working with on this project are like, “This is no big deal.” Yes, there are contaminated buried sediments in that embankment. So it’s a complex project for a number of reasons, and that’s why we prioritized science from the very beginning. But for those of us who work in rivers, and are familiar with the engineering and movement of material and water, that part doesn’t keep me up at night.

The things that I don’t know about and feel more intractable to me is how we move towards getting the funding and moving the project forward, which is why partnering with people like Willie Levenson has been so helpful because there are people who know how to get things done. I know how to engineer the technical aspects of it, but the part of building the partnerships, building the capacity and the resources is something I find to be very challenging.

Miller: Your office, with these partners you’ve been talking about, put out a video just yesterday about this project that had some history, including photos from what the area looked like more than a hundred years ago. The Windemuth floating swim platform [was] in the same exact location, a place apparently that was just a beloved place for Portlanders to swim, this big floating place, almost like a pool except it was in the middle of a river. What are your hopes for what the area could be like in the future?

Tullos:  I think that my hope for the river is that we can knock this cyanobacteria bloom back to the point where salmon are more abundant and Portlanders aren’t afraid to get in the river. I think for me, those are the two big priorities. I have a young child. We swim in the river all the time. And I feel like this is one of those places where we can show the next generation that we are working to reverse the impacts of climate change, the impacts that we’ve created, to help create that sort of intergenerational equity for them. So they still have these resources in the future, both the fish and the recreational access.

Miller:  Desirée, thanks very much.

Tullos:  Thanks, Dave.

Miller: Desirée Tullos is a professor of water resources engineering at Oregon State University.

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