Novel microbial community composition and carbon biogeochemistry emerge over time following saltwater intrusion in wetlands. (9th December 2018)

• Record Type: Journal Article
• Authors: Dang, Chansotheary; Morrissey, Ember M.; Neubauer, Scott C.; Franklin, Rima B.
• Is Part Of: Global change biology. Volume 25:Number 2(2019)
• Page Start: 549
• Page End: 561
• Publication Date: 2018-12-09
• Subjects: carbon biogeochemistry -- methanogenesis -- microbial community composition -- saltwater intrusion -- soil -- succession -- sulfate‐reducing bacteria; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.14486
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Sea level rise and changes in precipitation can cause saltwater intrusion into historically freshwater wetlands, leading to shifts in microbial metabolism that alter greenhouse gas emissions and soil carbon sequestration. Saltwater intrusion modifies soil physicochemistry and can immediately affect microbial metabolism, but further alterations to biogeochemical processing can occur over time as microbial communities adapt to the changed environmental conditions. To assess temporal changes in microbial community composition and biogeochemical activity due to saltwater intrusion, soil cores were transplanted from a tidal freshwater marsh to a downstream mesohaline marsh and periodically sampled over 1 year. This experimental saltwater intrusion produced immediate changes in carbon mineralization rates, whereas shifts in the community composition developed more gradually. Salinity affected the composition of the prokaryotic community but did not exert a strong influence on the community composition of fungi. After only 1 week of saltwater exposure, carbon dioxide production doubled and methane production decreased by three orders of magnitude. By 1 month, carbon dioxide production in the transplant was comparable to the saltwater controls. Over time, we observed a partial recovery in methane production which strongly correlated with an increase in the relative abundance of three orders of hydrogenotrophic methanogens. Taken together, our results suggest that ecosystem responses to saltwater intrusion are dynamic over time as complex interactions develop between microbial communities and the soil organic carbon pool. The gradual changes in microbial community structure we observed suggest that previously freshwater wetlands may not experience an equilibration of ecosystem function until long after initial saltwater intrusion. Our results suggest that during this transitional period, likely lasting years to decades, these ecosystems may exhibit enhanced greenhouse gas production through greater soil respiration and continued methanogenesis. Abstract : Sea level rise is expected to cause saltwater intrusion into historically freshwater wetlands, leading to shifts in microbial metabolism that alter greenhouse gas emissions and soil carbon sequestration. Here, we aimed to understand the temporal changes in microbial community composition and biogeochemical activity following saltwater intrusion in a 1‐year field manipulation experiment. Our results suggest the development of a unique successional microbial community may underpin methane production following saltwater intrusion. Further, the gradual changes composition and function we observed may indicate that previously freshwater wetlands may not experience an equilibration of ecosystem function until long after initial saltwater intrusion.