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Local researchers examine blue carbon from Salish Sea to Arabian Gulf

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Scientists here and worldwide are trying to answer the question of how much blue carbon various kinds of shoreline habitats can store.

Stored blue carbon — primarily in the form of plant matter that gets buried under wet sediment, where oxygen can’t reach it to start the decomposition process — reduces the amount of climate change-inducing carbon dioxide that gets into the atmosphere.

For Oregon State University researcher Chris Janousek, learning more about such areas as a wetland habitat around a slough that connects to Padilla Bay could help prioritize land management practices along the West Coast.

“This information can help us think about which wetlands are most important to conserve from a carbon perspective,” Janousek said. “It can also help us guide restoration efforts ... as we’re looking at which sites make the most sense to restore.”

As Janousek walked the south Padilla Bay wetland Aug. 10, he took GPS measurements to compare to the tides and help determine the role that saltwater plays in how much carbon accumulates over time. He also checked groundwater depth, temperature and salinity near the slough.

Janousek is part of a regional research team that is looking for correlations between groundwater conditions and the rates of carbon capture across study sites.

“We think the water table plays a big role, but what exactly it’s doing, that’s to be determined,” he said.

Other members of the research team are monitoring greenhouse gas levels in the air above the soil, and taking soil samples in order to measure long-term carbon capture.

Previous local research has shown that Padilla Bay’s eelgrass meadows could hold the equivalent of about 1 million metric tons of carbon dioxide within the top 1.5 feet of sediment; that local salt marsh and distant mangrove habitats are likely to hold even more carbon; and that a salt marsh reopened to the tides is now locking up carbon twice as fast as adjacent lands.

The current project — of which the local slough is one of many study sites throughout the Pacific Northwest — aims to build off of those previous findings and influence change.

“We’re hoping that (the study) will be very informative not only for researchers, but also for land managers, policymakers, and those interested in restoration,” Janousek said.

Janousek and scientists from groups including the Padilla Bay National Estuarine Research Reserve and Pacific Northwest National Laboratory are collecting data at eight sites in Skagit County. Some of those sites are along the Padilla Bay shoreline, and others are in the Skagit River delta.

COURTESY P4211168 Milltown Isl Skagit tidal marsh.JPG

Grassy marsh gives way to forest at Milltown Island in the Skagit River delta, a site where blue carbon is being studied. 

Data is also being collected at dozens of other sites, including near the mouth of the Columbia River and along the Oregon coast.

Jude Apple of the Padilla Bay National Estuarine Research Reserve said it’s the third such project for which the reserve has received funding. With each subsequent project, he said scientists are “digging deeper and deeper into understanding blue carbon.”

“As we emit more and more carbon into the atmosphere, we have to find ways to capture it and put it back into the ecosystems ... This is an opportunity for us to work together answering important questions like ‘How do we remove carbon from the atmosphere?’ and ‘Where do we keep it?’” Apple said.

The current research began this spring and will continue for a year, with data collected every six to eight weeks.

At the end of the year, an additional piece of data will be collected: the amount of sediment accumulated over a white clay marker placed on the ground at each site at the start of the project.

Blue Carbon

Christopher Janousek of Oregon State University points out a patch of white clay placed near Big Indian Slough south of Padilla Bay. How much sediment covers the clay over the course of a year will help determine how much of what is called blue carbon can be stored in the slough. 

“Then we can estimate, every year, how much carbon is coming into the site,” Janousek said. “That’s one piece of the puzzle.”

As the data comes in, Apple said it will become possible to put a monetary value on future restoration work when it comes to locking up carbon.

“What restoration projects have the highest bang for their buck if you think about it in terms of carbon capture?” he said. “People are interested in investing in carbon offsets, and we are poised to give information to let that happen.”

Those working on the project are part of the Pacific Northwest Blue Carbon Working Group, which has been compiling data from various studies throughout the region.

“We’re collecting data from Baja, California, to Alaska,” Janousek said.

The increasing interest in blue carbon had one local expert heading across the globe to gather samples.

Western Washington University’s Katrina Poppe went to the United Arab Emirates in September 2019 to sample mangroves, a kind of tropical coastal forest, and to teach locals the method of sediment coring she has used for blue carbon research.

COURTESY Sherif_Steve_Katrina5.JPG

Western Washington University Research Associate Katrina Poppe, center, works will project partners in the United Arab Emirates in September 2019 to cap a sediment core from a mangrove forest. 

"Sometimes it's a precarious moment when you pull a core out of the ground and before you put the cap on," she said of the team effort to keep the sample contained. 

“It was very interesting for me because I haven’t worked in a mangrove system before, and especially not a system where a lot of the sediment is built of like old shell material,” Poppe said. “Some of the samples looked just like chalk instead of mud or sand, so the results looked different than the kind of results I’m used to seeing here in the Northwest.”

Poppe, a research associate at Western Washington University, worked in the United Arab Emirates with blue carbon expert Steve Crooks of Silverstrum Climate Associates.

The two set out with a team from the Abu Dhabi Global Environmental Data Initiative and the UAE Ministry of Climate Change & the Environment to collect sediment core samples from lagoons.

After four grueling days, the group had pulled 10 core samples, sliced them into rounds Poppe calls “little mud cookies,” and shipped them to Washington state.

COURTESY IMG6.jpg
Segments of core samples taken from mangrove forests in the United Arab Emirates dry on Katrina Poppe's hotel balcony in September 2019. "The really dark brown ones are the ones that have a lot of carbon in them, and some are pretty white with not so much carbon. There was quite a range," she said. 

Poppe then used a gamma spectrometer at Western Washington University to figure out the carbon content of each sample.

Western Washington University’s gamma spectrometer is in high demand these days. Poppe’s lab has also been recruited to process core samples from a project in British Columbia and from work being done in Northwest Washington.

In partnership with Janousek and the regional project team, Poppe and colleague John Rybczyk are collecting two core samples from each of 15 sites throughout Washington, including those in Skagit County.

“Within the Skagit we have several sites to try to get a look at the differences,” Poppe said.

In order to compare which kinds of sites best capture carbon, they include natural, undisturbed marsh; disturbed, diked and farmed land; and recently restored marsh.

Blue Carbon

Big Indian Slough cuts through the grassy marsh south of Padilla Bay, where how much blue carbon accumulates is being studied. 

— Reporter Kimberly Cauvel: 360-416-2199, kcauvel@skagitpublishing.com, Twitter: @Kimberly_SVH, Facebook.com/bykimberlycauvel

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