Controls on marsh carbon storage

Salt marshes act as major sinks for atmospheric carbon through high productivity and the ability to trap both organic and inorganic sediment. However, their future role in carbon storage under global climate change and increased nitrogen inputs remains uncertain, partly because we don’t yet have a full understanding of the in situ dynamics of deep sediment microbial communities responsible for metabolic processes that deplete organic carbon stores.

This research, conducted by graduate student Ashley Bulseco-McKim, in collaboration with Thomas Mozdzer and Don Barber of Bryn Mawr College and Jon Sanderman of Woods Hole Research Center, aims to characterize the microbial community structure and activity of deep marsh sediments (~2500 years old), while concurrently studying carbon quality of organic peat, thus enhancing our understanding of how these microorganisms influence important carbon pools and fluxes.

We collected sediments ranging from 10 cm to ~3 m in Spartina patens (saltmeadow cordgrass) habitat from the fertilized and paired reference creek of the TIDE project. In addition to preserving sediments for DNA extraction to look at microbial community diversity, we also collected samples to measure organic carbon quality. Through the use of Fourier Transform Infrared Spectroscopy (FTIR), which provides rapid, low cost identification of the building blocks of organic material, we can gather information on what kind of carbon exists at certain depths, and how it might relate to the microbial community.

These results will contribute critical information regarding patterns of distribution and activity of deep microbial life in a detritus based system, and how that microbial life relates to the critical ecosystem service of carbon sequestration. This project is funded by a grant to Jennifer Bowen from the National Science Foundation (DEB 1353140). 

We also received FICUS funding to push this analysis further!  We will work with the Environmental Molecular Science Laboratory at the Pacific Northwest National Laboratory and with the Joint Genome Institute to apply NMR Spectroscopy, metagenomics, and metatranscriptomics to further understand how the structure of carbon and the metabolic potential of microbial communities covary with depth in marsh sediments.