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Short-term effect of simulated salt marsh restoration by sand-amendment on sediment bacterial communities
Thomas, F., J. Morris, C. Wigand, AND S. Sievert. Short-term effect of simulated salt marsh restoration by sand-amendment on sediment bacterial communities. PLoS ONE . Public Library of Science, San Francisco, CA, 14(4):e0215767, (2019). https://doi.org/10.1371/journal.pone.0215767
Increased flooding of marshes associated with sea level rise can cause vegetation loss, erosion of creek and channel banks, and loss of habitat for some fish, shellfish, and wildlife. In the face of accelerated sea level rise, placing a layer of sediment or sand on marsh surfaces (a process called thin layer placement) is an increasingly important restoration practice to increase marsh elevation and optimize plant growth. In this study, we examined the effect of adding sand to marsh soils on the sediment bacterial communities. We found that the amount of flooding and soil characteristics largely determined the bacterial community composition, and that the bacterial community can stabilize after sand additions if the optimal flooding conditions are provided. High acid levels in the sediment of the experimental chambers with added sand may be due to the higher number of bacteria that utilize iron. These results will help inform resource managers and restoration practitioners carrying out marsh restoration practices using sand, sediment, or dredge materials to build coastal resiliency.
Coastal climate adaptation strategies are needed to build salt marsh resiliency and maintain critical ecosystem services in response to impacts caused by climate change. Although resident microbial communities perform crucial biogeochemical cycles for salt marsh functioning, their response to restoration practices is still understudied. One promising restoration strategy is the placement of sand or sediment onto the marsh platform to increase marsh resiliency. A previous study examined the above- and below-ground structure, soil carbon dioxide emissions, and pore water constituents in Spartina alterniflora-vegetated natural marsh sediments and sand-amended sediments at varying inundation regimes. Here, we analyzed samples from the same experiment to test the effect of sand-amendments on the microbial communities after 5 months. Along with the previously observed changes in biogeochemistry, sand amendments drastically modified the bacterial communities, decreasing richness and diversity. The dominant sulfur-cycling bacterial community found in natural sediments was replaced by one dominated by iron oxidizers and aerobic heterotrophs, the abundance of which correlated with higher CO2-flux. In particular, the relative abundance of iron-oxidizing Zetaproteobacteria increased in the sand-amended sediments, possibly contributing to acidification by the formation of iron oxyhydroxides. Our data suggest that the bacterial community structure can equilibrate if the inundation regime is maintained within the optimal range for S. alterniflora. While long-term effects of changes in bacterial community on the growth of S. alterniflora are not clear, our results suggest that analyzing the microbial community composition could be a useful tool to monitor climate adaptation and restoration efforts.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
ATLANTIC ECOLOGY DIVISION
HABITATS EFFECT BRANCH