For some of Jeff Tepper’s geology students, the lakes around Puget Sound offer fertile ground for summer research.
On a Tuesday morning in mid-July, Nancy Hollis ’22 was sitting on the deck of a 20-foot pontoon boat on Spanaway Lake, a cashew-shaped body of water in the middle of a residential neighborhood south of downtown Tacoma. Some half a million people visit the lake each year to swim, fish, paddle, and motorboat. But Hollis wasn’t there to play.
Off the edge of the deck, she was lowering a cylindrical device—a bit longer than a rolling pin—via a long cable. The boat was owned by shoreside resident and lake advocate Sandy Williamson, who stood at the helm as Hollis captured water-quality information, such as temperature and pH, at different depths. The information provided a snapshot of the lake’s conditions on that July day. But the impact of those data could be much larger.
Spanaway Lake, like many bodies of water worldwide, is experiencing an explosion of toxic algae—what scientists call hazardous algal blooms, or HABs. A warming climate and an influx of nutrients from sewage, fertilizers, and other human-generated sources trigger the blooms, which kill fish, birds, dogs, and even people, and regularly close recreation spots like Spanaway. Williamson, a retired hydrologist and chair of Friends of Spanaway Lake, has lived on the lake for 16 years; in that time, he’s seen a dramatic increase in the number of HABs, “with no end in sight,” he says.
Nancy Hollis ’22 spent part of her summer trying to understand the source of harmful algal blooms on Spanaway Lake in Tacoma.
Hollis is one of two Puget Sound students who studied area lakes this summer under the direction of geology professor Jeff Tepper; the other was Colin Glaze ’22, who did research at Waughop Lake and Wapato Lake. Both Hollis and Glaze were funded through the university’s summer research program.
Hollis’ work at Spanaway Lake picked up where another former student, Jack Lindauer ’18, left off. His research in the summer of 2019 upended the conclusions of a $400,000 study that Pierce County had previously commissioned, revealing that, contrary to the study’s report, sediments at the bottom of Spanaway Lake were not the main source of high levels of phosphorous, the primary nutrient that prompts the HABs. This meant that the $2 million solution that an outside firm proposed to the county wouldn’t work. Hollis is working to figure out what would work.
Hollis got interested in the research after taking an intro geology course with Tepper. Trained as an igneous petrologist—someone who studies volcanic rocks—Tepper previously worked at Valdosta State University in Georgia. But there were no rocks there, he says. “It was just mud, sand, and snakes.” So Tepper took analytical techniques he’d been using to study rocks and applied them to studying lakes instead. When he came to Puget Sound in 2001, he dove into research on lakes in the Pacific Northwest, and got his students involved, as well. Over the past two decades, more than 100 of Tepper’s students have studied 14 different lakes in the region, either for their theses or as part of Tepper’s environmental geochemistry class.
Through hands-on fieldwork, often in partnership with local landowners who lend boats and roll up their sleeves to help, Tepper and his students profile the lakes and examine human impacts. And, by taking core samples of lake sediments that include materials as much as 14,000 years old, they recreate the history of each body of water. A clay-rich section at the oldest part of the core marks a lake’s birth during glacial retreat. An inch-thick white line is ash from the eruption of Mount Mazama, the collapse of which created Oregon’s Crater Lake 7,600 years ago. And a layer of mud heavy in lead, copper, and zinc is the fingerprint of the 1895 opening of a copper smelter in Tacoma.
Those histories help shape the future of a body of water. Once Tepper and Lindauer ruled out sediments as the main source of algae-growing phosphorous at Spanaway Lake, that left groundwater as the likely culprit. Groundwater moves below the soil’s surface, picking up contaminants and carrying them downstream. Residential development around the lake over the years has left a legacy of phosphorous from thousands of septic systems, and the pollution streams into the lake through depressions, or “vents,” in the muck.
This summer, Hollis and Tepper cordoned off groundwater as it entered the lake using plastic curtains suspended over the vents. They treated some of the groundwater with iron to see whether it could bind to phosphorous in the water, starving the algae. Iron doesn’t produce the destructive side effects seen with alum, a more common algal treatment and the one proposed in Pierce County’s study. And it could prove to be the solution for Spanaway.
County officials, meanwhile, find the research Tepper and his students have carried out valuable, not only because it aids their own monitoring efforts, but because it provides new insights. “Like any good research,” says Tom Kantz, the county’s watershed services supervisor, “it raises important questions.”
Hollis plans to work in environmental geology after graduation, and she hopes to address chemical imbalances—like Spanaway’s phosphorous problem—to solve environmental problems. Hands-on research has not only solidified her interest in the field; it’s shown her how studying a neighborhood lake can help solve global challenges.
By Miranda Weiss Photo by Sy Bean Published Oct. 12, 2020