PRITCHARD ISLAND BEACH — Facing the glassy surface of Lake Washington, environmental lab scientist Wyatt Klepac with King County dipped sterile plastic containers into the water.
These samples would be taken to a lab, spread on a plate and then examined for bacterial growth.
That’s one of two tiny things, along with toxic algae, scientists will be keeping an eye out for this summer that could force a beach closure and roil your swimming plans.
It’s unclear how climate change might affect closures in the region. But generally algae thrives in warmer water and bacteria is commonly washed into waterways, mostly from animal feces. As summers get hotter, access to cold bodies of water will become more important for people who don’t have a place to cool down.
In the past five years, toxic algae closed King County beaches an average of nine times each swimming season. Bacteria from feces closed beaches 15 times on average each season, though testing and reopening protocols have changed over time.
The Rainier Beach park Klepac sampled last week is one of 27 locations where King County scientists test for dangerous microbes during warmer months.
Here’s what we can expect this summer and beyond.
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Prepare yourself for a little lesson on microbiology.
Toxic algae are specific types of cyanobacteria (also called blue-green algae) that can produce toxins. There are thousands of cyanobacteria species and they are some of the oldest organisms on earth. These single-celled organisms are thought to have created the oxygen we breathe today.
Then there’s ordinary green algae, which is a group of plant-like organisms, and does not pose a toxic threat.
Both cyanobacteria and green algae are parts of a healthy lake ecosystem. But an algae bloom can happen when either grows in excess of what the lake can handle.
In summer, officials test for the toxins and intestinal bacteria, typically E. coli, at swim beaches. Officials will also test a beach if there is a report of a cyanobacteria bloom. Beaches can reopen after one week of testing showing low bacteria or two weeks of low toxins.
Scientists don’t know what makes cyanobacteria produce toxins and guess it is a byproduct of their natural processes, said University of Missouri professor Rebecca North, who studies freshwater toxic algae.
North said scientists also don’t know what triggers the production of toxins among cyanobacteria, but if they do, they might be able to find a way to turn it off, she said.
Only a few types of cyanobacteria produce toxins and even if that strain is blooming, it doesn’t mean it is producing toxins, King County limnologist Rachael Gravon said. Toxins take time to degrade and can stick around after the bloom is gone, North said.
Cyanobacteria blooms look like a paint spill, slimy scum, foam or clumps on the water and can be blue-green, red, brown or pea. (The state has a helpful gallery of examples online.)
If you see one, officials advise keeping your pets away from the water. Officials say an easy way to test for what kind of algae you’re seeing is to dip a stick into the water. If the algae looks like hair or has filaments, it’s green algae. If the stick looks like it’s been dipped in paint, that’s cyanobacteria that could be toxic.
Scientists are unsure how climate change will affect cyanobacteria blooms and their toxicity.
Warm and sunny weather is expected to promote algae growth in general, which will increase the risk for toxic algae, Gravon said. However, that relationship is complicated.
“Likely we will see algae growth increase with increasing favorable conditions,” Gravon said. “We’re still not going to know if its always toxic without testing it.”
North said while nutrients and temperature play a role in toxic blooms, there is no “universal relationship” between temperature, nutrients and algae toxicity across all lakes.
Scientists also are not able to say whether toxic algae has increased in the last few decades of warming. Toxic algae testing is often done after a bloom has already been spotted, and the research is relatively new, North said. Education around algae blooms has also increased, leading to more reports, and most places including King County only test during the warmer months, which presents a limited set of data, Gravon said.
Toxic algae is most common during the fall in Seattle when windstorms and runoffs from rain recirculate nutrients into the water. Although, it has also been detected in winter, Gravon said.
Climate change could result in more bacteria-related closures due to more frequent and intense rainstorms, but those effects are likely to be minor, King County ecologist Daniel Nidzgorski said.
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