The contribution of archaea and bacteria to nitrification in sulfide-rich marsh sediment

A common limiting source of nitrogen for plants is nitrate and nitrite, generated by the process of nitrification by sediment microbial communities. In marsh ecosystems, there can be clear distinctions in sediment chemistry depending on local plant species and their associated microbial communities, even for plants in close proximity. Spartina alterniflora and Juncus roemerianus are two different marsh plants species that can grow directly adjacent to each other. In this project we went to a Louisiana salt marsh and took sediment cores from the root systems of each plant species and measured potential nitrification rates in the sediment over three days. We separated the sediment cores into 30 soil samples and treated each with either a control, sulfide, or the inhibitors PTIO and sulfathiazole. With this method we were able to look at the inhibitory effect of sulfide on nitrification and isolate either archaea or bacteria to identify their contribution to the potential nitrification rate. Analyzing nitrification in this manner shows how microbial community dynamics can change depending on the plant biota and geochemistry, even at distances within a few meters. Therefore, as plant populations shift due to sea level changes and coastal development, there may be drastic impacts on the nitrogen cycle and the availability of key nutrients for primary producers. It will be important to monitor these plant-microbe associations to analyze whether changes in plant biota, microbial communities or geochemistry have far-reaching impacts on water quality and overall ecosystem health.

Primary Presenter: Nicole Lyons, University of Miami (njl84@miami.edu)

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