An unusually large outbreak of toxic algae in the Ross Island lagoon is troubling scientists who say the cyanobacteria bloom could have lasting effects.
Cyanobacteria blooms in the lagoon have been a fixture of Portland summers over the last decade, with the combination of heat and stagnant water creating optimal conditions for algae, but this year’s outbreak has been atypical.
“These are the worst water quality conditions I’ve ever seen out at the lagoon,” Desirée Tullos, a professor at Oregon State University, said. “I’ve sent these images to these world experts on cyanobacteria, and they are amazed and shocked by it. One of them, his response was ‘Wow, that’s wild.’”
The images show golf ball-sized, deep-green clusters or colonies of cyanobacteria material floating on the lagoon and through the river—an outbreak beyond what Tullos has seen in her years of taking samples at the lagoon.
Tullos said the reasons for the intensity of the current outbreak are clear: a warmer-than-average spring led to low water levels and saw the river reach its standard July temperature in May.
That was an auspicious development for the cyanobacteria. Then, there was another development that may inadvertently have strengthened the bloom.
In late July, Ross Island Sand & Gravel, which mined gravel from the lagoon until 2001 and still owns much of the island, put up a silt curtain to try to trap cyanobacteria material in the lagoon—a decision that may have blocked off some of the potentially hazardous material from reaching the river, but that also may have further reduced local water flow.
The Ross Island lagoon has been under a state-managed reclamation plan since 2002, with Ross Island Sand & Gravel required to fill the site with sediment, soil and other materials.
Tullos said it’s hard to know whether or how much the installation of the curtain may have exacerbated the outbreak, but it’s an important point to study for the state to shape its management policy for the coming years.
Ross Island Sand & Gravel is currently required by the terms of its water quality permit to install the curtain once toxin levels in the lagoon reach a certain level, but Tullos said that policy may need to be revisited. This summer, Ross Island Sand & Gravel deployed the curtain preemptively in what Tullos took to be an effort to be a responsible steward of the lagoon.
“What we’re doing is we’re trading off the mainstem river for the lagoon, so then it becomes an industrial wasteland—and there are sturgeon in there, there are bald eagles that are fishing, there’s so much wildlife that uses that lagoon, and I feel uneasy with that tradeoff,” she said.
As debates continue over the future of Ross Island, one of the leading proposals for the site is to bury material from the Portland Harbor Superfund site in the lagoon, a project which could save taxpayers millions of dollars but would be expected to take between 10 and 20 years to complete.
If the superfund material transfer project does go forward, Tullos said a silt curtain or some similar mechanism may be required for its duration to ensure that material being transferred to the lagoon does not contaminate the rest of the river. That, she said, could conceivably lead to bigger algae blooms.
“The more movement of water we get in there, the less suitable that habitat is for cyanobacteria,” Tullos said. “That curtain is isolating the tide, it’s not letting the tide come in and do the little flushing it can, and the bloom got worse.”
In the meantime, the intensity of the cyanobacteria outbreak in the lagoon has threatened river access across the city. Part of the Holgate Channel, which is the conduit for water from the lagoon flowing toward the Willamette River, turned green late last week.
Officials from the Department of Environmental Quality (DEQ) collected samples from the lagoon last Wednesday, and a DEQ spokesperson told the Mercury they expected the results of those samples early this week. The Oregon Health Authority (OHA) will then review the results and determine whether to issue a health advisory.
Late last week, the state directed Portland Parks & Recreation to put up signage alerting visitors about the water quality in the river at five different sites including Waterfront Park, Sellwood Riverfront Park, and Cathedral Park.
The toxic algae also caused river-based events to be canceled. The Human Access Project, an advocacy group that has worked for years to improve water quality and public access at the Willamette River, canceled two riverfront events last weekend over “due to extreme concern for river health affecting the ecosystem, human and pet health,” according to Scott Fogarty, the organization’s executive director.
In an email, Susan Mills, the DEQ spokesperson, confirmed to the Mercury that Ross Island Sand & Gravel set up the silt curtain independent of any OHA directive.
“At this point, DEQ can’t speculate as to if deploying the silt curtain as a containment measure has contributed to the bloom strength,” Mills wrote.
A cool start to September may conceivably help hasten the end of the outbreak, but Tullos said the end of the bloom could present its own issues when the bacteria clusters begin to break down, release toxins, and take in oxygen.
“What’s going to happen when this megabloom crashes? Is it going to suck all the oxygen out of the water? It’s just worse than anything we’ve ever seen,” Tullos said.
The bloom may have longer-lasting consequences, too.
“The cyanobacteria leave behind these resting, or dormant, cells,” Tullos. “They’re these dormant cells that are suited to survive harsh environments, like over winter, so the more we leave these remnants of cyanobacteria cells … essentially we’re just supplying the lagoon with more material to make more bloom next year.”
As climate change continues to create warmer water conditions and the effects of those conditions compound, Tullos reiterated that the simplest way to deal with the blooms is clear: opening up a channel to the lagoon to allow fresh water to flow in.
“We know what the solution is,” Tullos said. “It’s going to take a big community effort—people coming together, people not turning their back on the river—to deal with this issue.”
