Western Washington University graduate student Jefferson Emm and Professor of Environmental Science David Wallin are using a pair of unmanned aerial vehicles to complete a census of the eelgrass beds in Skagit County’s Padilla Bay.
Healthy eelgrass beds are vital nursery habitat for a variety of ecologically and commercially important fish and shellfish species such as herring, salmon and Dungeness crab. Padilla Bay, one of 29 waterways in the country’s National Estuarine Research Reserve system, is the largest contiguous eelgrass meadow in the country south of Alaska and the second-largest on the entire West Coast.
Mapping eelgrass beds has largely in the past been done by aerial imagery taken from manned aircraft or via satellites, but this project is the first to use unmanned aircraft systems (also called UAVs or “drones”) to conduct an eelgrass census, and Emm said part of the draw to attempt this project wasn’t just the importance of the data, but it was the novel way being employed to get that information.
“UAS (unmanned aircraft systems) and camera technology have rapidly improved in recent years while becoming more affordable and available, so it opened a window for us to try it. Each of the two vehicles has a type of camera that tells us different things about the eelgrass cover below it,” he said. “The cameras use spectral signatures unique to each cover type, like a fingerprint. We hope to use the imagery to delineate the invasive eelgrass, Zostera japonica, from the native eelgrass, Zostera marina.”
Understanding how the invasive eelgrass species is competing with – or coexisting with – the native species is a huge part of what they hope to find out, said Wallin.
“The invasive species, japonica, tends to live in shallower water than its native cousin,” he said. “But there is some overlap, and we are trying to understand how the two are working together.”
Wallin’s research has heretofore been as a terrestrial ecologist, but he is trying to find more applications for UAS to do remote sensing of populations that might not be as easily discoverable or accurately counted without the eyes in the sky. He worked with the U.S. Geological Survey using a UAS to seek out and count the Skagit County elk herd, for example, but this is the first time he has literally set up his office in knee-deep water more than a mile out into a bay.
“I am eager to find new applications for this technology and want to help introduce it to other researchers, because there is so much you can do with it that you simply can’t do through other traditional means,” Wallin said.
Each day during the data-gathering phase, Emm, Wallin, and a host of student and community volunteers pull sleds out into the bay from the dike near Samish Island. The sleds hold everything needed for an afternoon of research: dry bags with laptops, cameras, extra batteries, spare parts, and a pair of small tables. Once at the survey area – as far as 2500 meters from shore, but at the lowest lunar tides, the water is still only shin deep – the tables are set up, the vehicles unpacked and charged, and flights begin.
Each flight is preprogrammed into the vehicles, which weave back and forth across a grid, taking images with its camera. Once it is done and lands in the waiting arms of a researcher, the next vehicle uses its different camera to shoot the same grid. This is repeated on as many grid locations as possible before the tide begins to come back in.
“There is a bit of a ‘perfect storm’ which makes Padilla Bay a great place for this research. It’s quite shallow, with a relatively solid bottom, which allows us to access the vast expanses of eelgrass, by foot, during extremely low tides in summer months during daylight hours,” said Emm.
Emm arrived at Western after graduating from Northwest Indian College as part of a National Science Foundation grant to matriculate more Native American students into graduate schools to study science, and he said the summer field work in Padilla Bay towards his thesis has been incredibly rewarding.
“It’s been an amazing project, and I feel so lucky to have gotten the chance to work on it,” he said.
Wallin echoed those thoughts.
“The most rewarding part of my job is working with students on research projects. Students obviously learn quite a bit from their coursework. But it is involvement in research that really turns them into scientists,” he said. “With graduate students like Jefferson, I get the opportunity to guide them through the entire research process, from framing a research question, to figuring out methods, analysis of data and, finally, to writing up their results for a thesis and publication in a scientific journal.”
Emm and Wallin will share their data with the Padilla Bay Foundation, and will work over the course of the upcoming school year to prepare and submit it for publication. Funding for this project was provided by the Padilla Bay Foundation, and the vehicles were acquired through help from the Western Foundation via a grant from the Whatcom Community Foundation.
See a video of a drone launch here.
See a gallery of over 100 images of this research here.