Eelgrass from the Air: WWU grad student studying vital ecosystem using drones
Western Washington University graduate student Hannah Hein studied the vast rolling prairies of her native Minnesota as an undergrad at St. Olaf College – and she has now shifted her research focus to a vital underwater grassland, the critically important eelgrass meadows of the Pacific Northwest, and specifically those found 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. The beds also perform important roles in helping to filter the water column and stabilize nearshore sediment. 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.
“Being from Minnesota, I had never worked in a marine environment before – all my work to date has been done in forests and grasslands,” Hein said. “So this was an opportunity to work on a project and a thesis choice that I couldn’t pass up.”
Mapping eelgrass beds has largely in the past been done by aerial imagery taken from manned aircraft or via satellites, but Hein’s project is among the first to use unmanned aerial vehicles (also called UAVs or “drones”) to conduct an eelgrass census. Hein said part of the draw to attempt this project wasn’t just the importance of the data, but it was the novel way being used to gather that information.
Padilla Bay’s extensive eelgrass meadows are made up of two species of the plant, one native (Zostera marina), and one introduced and invasive (Zostera japonica). 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.
“The invasive species, japonica, tends to live in shallower water than its native cousin,” she said. “But there is some overlap, and researchers are trying to understand how the two are working together, how they compete, and if the two types of eelgrass can live together.”
Hein flies the drones from a portable helipad on the dike above Padilla Bay, with the drone’s special cameras shooting the eelgrass meadows from above. The imagery is then analyzed by Hein to show the density of the beds as well as differentiate between the two species.
The actual days of shooting the images need to be reasonably sunny and coincide with the lowest tides of the season. Using a series of permanent monitoring transects put in place by the Padilla Bay National Estuarine Research Reserve, markers for each of the grids need to be walked by volunteers hundreds of yards out into the bay and placed at the corner of each grid square. Each flight is preprogrammed into the vehicles, which weave back and forth across the day’s sampling grid. This is repeated across the entire study area before the tide begins to come back in.
Hein said that just as important as the data from her survey is the plugging of that data into an equation to predict eelgrass growth and biomass.
This was an opportunity to work on a project and a thesis choice that I couldn’t pass up.
“This way, other researchers can use my work as a template for researching eelgrass meadows elsewhere quite easily – but also the fundamentals of building this equation would allow it to be easily transferred and used for almost any type of shallow aquatic ecosystems,” she said.
Hein’s faculty advisor, WWU Professor of Environmental Science David Wallin, worked with Hein to get her up to speed on the drones and how to fly them.
“Hannah has really embraced the use of this technology and how it could be used in a novel way to do this work,” he said.
Hein will share her data with the Padilla Bay Foundation, and will continue to work 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 Pitts Sportsmen’s Fund of the Whatcom Community Foundation.
For more information about Hein’s research, contact her at email@example.com; find out more about Western’s graduate-degree programs in the sciences at https://gradschool.wwu.edu/.