Three Ways of Looking at the Lake
In Willsboro Bay, about nine miles out from Burlington Harbor, Tori Pinheiro hangs over the gunwale of the UVM research vessel Melosira and stares down into black water. Like the huge gray eye of a sea monster, a round concrete weight appears out of the depths. The steel cable from the boat's trawling winch keeps turning and the hundred-pound weight emerges into morning sunshine, dripping. From its underbelly, another line still dangles into the water. Pinheiro, a research technician, hauls the line, and pulls onto the deck a slimy-looking black canister the size of a large water bottle.
"This is it," she says, as she turns to a laptop computer sitting on a fish-dissecting table in the middle of the deck, "one of our twenty-seven receivers. There's months of data in there."
She activates the canister and soon it's downloading to the computer. What the receiver has been recording are pings bits of noise at 69 kilohertz that come from fish. The fish don't make the noise themselves neither they nor people can hear a pitch that high. Instead, the noise comes from transmitters, about the size of a AA battery, that have been surgically implanted into the fish some ninety lake trout and twenty walleye tagged by UVM scientists and seventeen lake sturgeon tagged by State of Vermont scientists. As the fish swim about, they each emit a unique pattern of pings, a kind of acoustical barcode of identity, and when they get close enough to one of the receivers it hears them. Tracking these pings over time lets scientists create a map of the fish moving and spawning.
"You can watch animals on land with binoculars or helicopters," says professor of fisheries Ellen Marsden, Ph.D., who has been leading the development of this new CATOS project for Champlain Acoustic Telemetry Observation System. "But with fish, it's incredibly difficult to know where they are and where they are going. What happens under the surface has largely been a mystery. But now we can ‘see' them."
And that helps the scientists ask fundamental questions about fish behavior and health. Like: what happened to the lake trout? By 1900, native lake trout had disappeared from Lake Champlain, perhaps due to land use change. "We don't know why," Marsden says. Since 1972, the state of Vermont has been stocking the lake with hatchery-raised trout. These fish find mates, lay eggs, produce fry, and the fry swim off to deep water. But then these young fish are never seen again. "All the trout in the lake are hatchery fish," Marsden says. At least that's what the story was until last year. Then, in 2015, Marsden and others began to find wild trout in their net surveys.
To better understand the mysterious absence of wild lake trout and the equally mysterious return of some of them Marsden and her students have been using the CATOS network to see what the trout do on their spawning grounds and elsewhere.
With receivers strategically positioned along the whole 125- mile length of the Lake Champlain and at key causeway openings, "we can keep track of fish for years," Marsden says. "Suddenly we have a new perspective on where fish are going" females moving in and out of spawning reefs, a male suddenly shooting eight miles down the lake, another spending 25 days seemingly searching for an opening through the causeway at Malletts Bay.
"A lot of what we're doing is filling in gaps in our knowledge about species that are experiencing difficulty," says Tori Pinheiro, who completed her master's degree studying with Ellen Marsden. "In lake trout, CATOS is helping us understand basic questions about their behavior. We can't solve any of these problems, or create restoration plans, without a better view of the whole story."
It's a blue-sky, scorching hot day in July at Burlington's North Beach. Just the kind of day to go swimming except nobody is in the water. The lake is deadly quiet. Near the boardwalk, signs warn people to stay away because of blue-green algae blooms. These toxic cyanobacteria foul beaches in Lake Champlain some summers, and they're becoming more frequent in parts of this lake and other lakes around the world. But, though algae end up on beaches, the root of the problem is not there. To find the sources of the problem and there are many a large team of Vermont scientists is following the water from beachside to lake bottom, out to inflowing brooks and rivers, and upstream to the parking lots, farm fields, forests, roads, towns, and mountains that drain the 8,234 square mile Lake Champlain Basin.
The team within the Vermont EPSCoR program, a National Science Foundation-funded effort to support research across the state is looking at the lake, its source rivers, and its surrounding human communities, "as a whole and complex system," says UVM hydrologist Arne Bomblies, Ph.D., an assistant professor of civil and environmental engineering and the associate director of EPSCoR.
In April of 2016, the work of EPSCoR was dramatically enhanced with a $20 million grant from the NSF, supported by U.S. Senator Patrick Leahy. The new five-year project, called BREE, for Basin Resilience to Extreme Events, is looking at how and why some parts of the lake are resilient to extreme weather events, while others face dramatic flood damage, runaway nutrient pollution, and ecological problems like unwanted algae.
"With climate change, we're seeing increasing extreme weather events, longer rain storms, greater precipitation amounts," Bomblies says. "Understanding the changing nature of flood risk is a big outcome of this project," he says. And flood risk is not just about washed away bridges and lost crops. It's also about lake water quality larger and more frequent floods carry and circulate larger amounts of sediment and pollution in the lake including unwanted phosphorus, one of the key drivers of algae blooms.
In order for the team to better see the Lake Champlain Basin as a whole system, the scientists have deployed a network of advanced optical sensors in streams, soils, and on buoys in the lake itself. These sensors gather a wide range of information about water conditions like turbidity, pH, dissolved oxygen and chlorophyll "which is a tracer for total phytoplankton populations" says UVM's Peter Isles, Ph.D., a lake scientist who recently completed his doctoral degree within EPSCoR, "as well as specific variables which help us trace cyanobacteria populations."
The power of these sensors is not only the range of information that they gather, giving a rich portrait of changing water conditions, but also the high frequency with which they gather it. Some collect information every fifteen minutes, others every hour. Though climate change is a slow-moving master, storms and key changes to ecosystems can arrive rapidly. In 2012, the summer was very hot and dry, resulting in the strongest algae blooms Lake Champlain had seen in decades. Then September brought a huge storm, with more than four inches of rain, and, hour-by-hour, it "totally changed the composition of the phytoplankton and the concentration of nutrients in the lake and really shut down the bloom that year," said Isles. "We would've never seen the effects of that storm event if we didn't have highfrequency data because it comes through in a day or two."
At the heart of the BREE project is the development of a powerful computer simulation called an integrated assessment model that will test policy scenarios and help identify strategies for protecting the health of the lake, infrastructure in the surrounding watershed, and water quality during and following extreme weather events. This new assessment model will draw together three other EPSCoR modeling efforts: one that explores human dynamics such as plausible decisionmaking of farmers and other landowners in the Missisquoi River watershed in light of existing economic and land-use realities; another that has been building detailed physical models of watershed dynamics in a changing climate, including one that has been completed for Vermont's Mad River Valley; and a third that is modeling the hydrology of the lake itself.
At UVM's Rubenstein Ecosystem Science Laboratory on Burlington's waterfront, Jessica Griffin, a senior from the University of Connecticut, carefully opens a small jar of Mysis shrimp collected from the bottom of Lake Champlain and places one under a powerful dissecting microscope. On a nearby monitor, the fingernail-clipping-sized shrimp appears like a giant squid. "Dissecting the stomach of these guys take some real doing and skill," she says with matter-of-fact pride.
Griffin has come north to Vermont with nine other students from colleges across the country for a ten-week summer REU an intensive research experience for undergraduates supported by the National Science Foundation. "We see the lake and our facilities here at UVM as an outstanding place to cultivate and train the next generation of scientists," says professor Jason Stockwell, Ph.D. He's the director of the Rubenstein Lab and leads this summer program.
Under Stockwell's guidance, and with help from his graduate student, Brian O'Malley, Griffin is undertaking an independent research project sampling detritus from the bottom of Lake Champlain. She aims to understand better the eating patterns of Mysis shrimp and she's learning techniques for examining their stomach contents along the way. "The conventional thought indicates that the Mysis rise to the top waters of the lake at night in order to take advantage of better food sources, but studies recently have found that some of these organisms never leave the bottom," Griffin says, pointing at a large stack of scientific papers she has been reading. "They must be taking advantage of some kind of food source down there." She's working to find out what it is.
"If we care about sport fisheries or commercial fishing, if we don't want algal blooms, if we want to manage invasive species we have to understand food webs," Griffin says. The theme of this UVM summer program is to train students in interdisciplinary research on ecological and socioeconomic interactions in the Lake Champlain ecosystem. Or, as Griffin says: "We need to know who is eating what."
The next afternoon, Stockwell is leading Griffin and her fellow REU's in an exercise creating a lake. Well, not exactly, but the professor is having each student go to the whiteboard and add elements of an abstracted version of Lake Champlain. From their past courses and summer studies, the students make drawings of diatoms and cycling nitrogen, plants and clams and the sun, then sediment and copepods and an eel. A swimmer and a sailboat appear, then sewage and a "next generation" pollutant: pharmaceutical waste. The whiteboard fills with arrows and loops and labels like "thermocline" and "hypolimnetic." "What key chemistry is not up there yet? "Stockwell asks. "Oh, dissolved oxygen," one of the students says. "Yes, there you go," says Stockwell. He keeps pushing them to think about the many elements that make a lake. "How about bacteria? They're a huge driver in lake systems," Stockwell says. "There's a whole microbial food chain that is often overlooked."
A student adds some of that element to the whiteboard and, just like that, their picture of the lake grows yet more complex