Co-Creating Climate Solutions: Designing Carbon Monitoring Tools for Salt Marshes

Summary

The webinar described a collaborative project to develop affordable, portable tools for measuring carbon dioxide fluxes in New England salt marshes. The work addresses a lack of spatially detailed, year-round greenhouse-gas measurements, which limits understanding of marsh carbon storage and the effects of restoration and climate change.

Scientific context and motivation

Salt marshes and other coastal vegetated ecosystems store “blue carbon.” Their high productivity captures carbon, while vegetation and sediment trap and retain it. Much of this stored carbon is in the soil.

These ecosystems also release greenhouse gases through plant, animal, and microbial respiration and decomposition. The balance between carbon uptake and release is important for assessing their overall climate-mitigation value. As presented in the webinar, blue-carbon ecosystems cover less than 1% of the ocean’s surface area but hold 50% or more of the carbon stored in marine sediments.

Carbon fluxes may vary with vegetation, weather, season, marsh location, and human impacts. Sea-level rise, altered water flow, ditching, infrastructure, invasive-species management, and restoration may all affect marsh function.

Existing measurement approaches have trade-offs. Flux towers are expensive and have a variable measurement footprint, while instruments such as Picarro or LGR analyzers can be costly and labor-intensive. More accessible tools could support monitoring and help evaluate restoration locations and outcomes.

Methane and nitrous oxide are also relevant greenhouse gases, but this project focused on carbon dioxide measurements. The team tried measuring methane with the sensor package but was unsuccessful during this project phase.

Sensor development and project approach

The team developed small, lightweight sensor packages using off-the-shelf components. Each package was approximately five inches by five inches, weighed less than two pounds, and cost roughly $600 or less. The sensors measured carbon dioxide, air temperature, humidity, and time.

Measurements used a closed-chamber setup: a collar was placed in the marsh sediment, a chamber was fitted over it, and a sensor was placed inside. The team used the Epicollect5 app to record measurements and associated metadata.

Sensors were calibrated using three standard gases and checked against a backpack Picarro analyzer. The project worked with all five New England National Estuarine Research Reserves (NERRs). Training, field trials, surveys, and follow-up discussions provided repeated user feedback that informed revisions to the sensor, chamber, deployment steps, and written protocol.

The protocol covers field deployment, metadata collection, calibration, validation, and data processing. Field experience suggested that two people are needed to operate two sensor-and-chamber setups. Two sensors could be deployed simultaneously in an average of about 16.5 minutes, and teams could collect up to 32 flux measurements in a day when focusing on that work.

The team collected 483 flux measurements with help from 26 people, including people new to carbon-flux sampling. Each reserve met the project’s target of at least 40 measurements during the late-summer loan period. Sampling took place in December, February, May, July, August, and September.

Preliminary findings

In the data plots, positive flux values indicate carbon released to the atmosphere; negative values indicate carbon uptake from the atmosphere.

Fluxes varied substantially within marshes and among reserves. Even two measurements taken close together could differ, and spatial patterns appeared patchy rather than following a simple upland-to-water gradient.

The preliminary year-round data showed some carbon release during the dormant winter season. This release was smaller than summer uptake in many cases, but the team emphasized that winter fluxes may matter to annual carbon budgets and have been understudied in the region.

Seasonal patterns differed among sites. Some southern marshes showed growing-season uptake and slight winter release. Great Bay showed a pronounced seasonal change, including strong uptake in July, while nearby Wells showed a more consistent pattern across seasons.

Fluxes also differed among plots dominated by different plant species. The team observed greater uptake in low-marsh plots, often dominated by Spartina alterniflora, and slight release in plots dominated by high-marsh Spartina patens. These patterns are preliminary and may reflect several environmental factors integrated by vegetation.

When averaged across sites, the more southern marshes were carbon sinks, while the more northern sites showed a small average release. The presenters noted that this comparison also reflects differences in growing-season length and sampling.

Across the whole year, carbon fluxes showed weak relationships with air temperature and light. Fluxes still varied widely within a single season, suggesting that weather alone does not explain the observed patterns.

The work creates a basis for pairing flux data with existing reserve records, including vegetation and weather monitoring, and for assessing carbon fluxes before and after restoration. The project also collected baseline measurements at a Connecticut site scheduled for restoration.

Implications and limitations

The sensors and protocol may help reserves monitor blue-carbon services, compare locations for restoration, and track changes associated with climate change, vegetation shifts, and changing winters. The technology could also be adapted to other settings, including other marsh regions, forests, farms, and urban lawns.

The project’s analysis was preliminary. The team had not measured nighttime fluxes or soil-water-table conditions, and methane sensing remained a goal for future development. The presenters also discussed possible future adaptations, such as chambers for taller vegetation and a floating sensor design.

Researchers and sources featured

• Robinson W. (Wally) Fulweiler — Boston University; project speaker and Coastal Ecology and Biogeochemistry Laboratory lead.
• Lena Champlin — Boston University; project speaker and postdoctoral fellow.
• Nick Soberal — NERRS Science Collaborative; webinar host and introduction.
• Jennifer West and Kenny Raposo — Narragansett Bay Reserve collaborators.
• Amanda Villard — credited by Fulweiler with helping begin work on an earlier sensor version.
• Holly Emery — previous PhD student whose marsh CO₂-flux work was discussed.
• Amanda Fuller — named in the Q&A as lead author of a related paper in Frontiers.

Sources, programs, and tools mentioned: National Estuarine Research Reserve System (NERRS); NERRS Science Collaborative; Centralized Data Management Office (CDMO); Epicollect5; backpack Picarro analyzer; Frontiers.