A team of researchers at Colby College and the Bigelow Laboratory for Ocean Sciences has been awarded a $600,000 four-year grant from the North Pacific Research Board to investigate the role of volcanic ash in supporting the marine ecosystem of the northeastern Pacific Ocean.
Led by Bess Koffman, assistant professor of geology at Colby, and Catherine Mitchell, a senior research scientist at Bigelow, the project will assess the impacts of volcanic ash using satellite remote sensing, ship-based experiments, and laboratory geochemical analyses. The grant will also support up to eight Colby undergraduate researchers, who, starting this fall, will have opportunities to participate in the science in world-class labs at Colby and at Bigelow over the next four years.
The interdisciplinary team also includes Benjamin Twining, Bigelow’s Henry L. & Grace Doherty Vice President for Education and a senior research scientist at the lab, and Karen Stamieszkin, a postdoctoral associate at the Virginia Institute of Marine Science and an adjunct scientist at Bigelow.
“The northeastern Pacific is a large, fascinating region because it’s an incredibly productive fishery,” Koffman said. “But the organisms at the base of the marine food web, phytoplankton, are limited by a lack of iron, which is a key nutrient. We’re hoping to learn more about the role of volcanoes in supporting the marine ecosystem by supplying iron and other nutrients. In particular, we’re interested in understanding the role of resuspended volcanic ash—ash that was deposited during an eruption and then, months to years or even decades later, blown by the winds out over the ocean.”
In this region, off the west coast of North America, materials derived from soil and rock, such as dust and freshly erupted volcanic ash, supply iron, supporting not only phytoplankton growth but also fish further up the food web. Native Alaskan communities and a multi-billion-dollar fishing industry, depend on these fisheries for survival.
Previous studies highlight particular volcanic eruptions as a source of iron and stimulant of phytoplankton growth, but it isn’t yet known how effective or important this source might be compared to other known sources of iron, over a longer time scale. Satellites provide one of the best ways to observe the impacts of ash on phytoplankton growth over time, but it is challenging to separate the satellite signals of phytoplankton biomass from ash in the water or air. The team will develop an improved satellite algorithm for accurately separating phytoplankton optical signals from dust and ash particles in the air and water to address this issue. This improved algorithm will help determine basin-scale impacts of ash deposition events on phytoplankton biomass.
Using existing satellite imagery, the research will identify both freshly erupted and remobilized ash plumes over the past 22 years, and then will apply the improved algorithm (developed through laboratory experiments and modeling) to determine the impacts of ash deposition on primary production.
The project also will evaluate the significance of previously erupted volcanic ash that is resuspended after months to decades of sitting where it fell after the original eruption. Koffman’s research has shown that the properties of this so-called “aged ash” change through time, making its nutrient content more accessible to phytoplankton than that in fresh ash.
“As climate change continues to impact this region, the relative importance of different nutrient sources may change,” Koffman said. “This is one reason why we are really excited to have the chance to study these processes.”
The team will also participate in two research cruises in the Gulf of Alaska to conduct at-sea experiments. Ship-based incubation experiments will illuminate the effects of added ash (both fresh and aged) on natural phytoplankton communities. Finally, geochemical characterization of ash, including the amount and form of its nutrient content, will help link geological processes to ocean productivity. Through this multifaceted approach, the researchers will determine the impacts of fresh and aged ash on phytoplankton communities and will be able to scale from shipboard experiments to basin-scale phytoplankton blooms measured with satellites.
The researchers have partnered with the Aleut Community of St. Paul Island to learn from and document traditional knowledge, including myths, legends, and personal observations of volcano-ocean ecosystem interactions. The traditional knowledge will be incorporated into the scientific approach and data interpretation, opening the door for new, unexpected insights into the ecosystem. In parallel, the researchers will share their science with Aleut youth each year through outreach activities during local environment-focused festivals over the course of the four-year project. Through these community-based knowledge-sharing approaches, the team will engage with and respectfully learn from people who have lived in this region for millennia, a place where volcanic eruptions are an inextricable part of the landscape and ecosystem.
Colby students will be involved in everything from lab experiments to analysis of satellite “big data” to modeling. They will assess the optical effects of dust and ash in seawater, and then model the influence on ocean color. They also will analyze the geochemistry and physical properties of ash particles. Using satellite data, they will learn to identify freshly erupted and remobilized ash plumes. Students will then apply the improved algorithm to measure the impact of ash deposition on primary production.