Freshwater wetlands of the temperate north are exposed to a range of pollutants that may alter their function, including nitrogen (N)-rich agricultural and urban runoff, seawater intrusion, and road salt contamination, though it is largely unknown how these drivers of change interact with the vegetation to affect wetland carbon (C) fluxes and microbial communities. We implemented a full factorial mesocosm (378.5 L tanks) experiment investigating C-related responses to three common wetland plants of eastern North America (Phragmites australis, Spartina pectinata, Typha latifolia), and four water quality treatments (fresh water control, N, road salt, sea salt). During the 2017 growing season, we quantified carbon dioxide (CO₂) and methane (CH₄) fluxes, above- and below-ground biomass, root porosity, light penetration, pore water chemistry (NH₄⁺, NO₃^-, SO₄^-², Cl^-, DOC), soil C mineralization, as well as sediment microbial communities via 16S rRNA gene sequencing. Relative to freshwater controls, N enrichment stimulated plant biomass, which in turn increased CO₂ uptake and reduced light penetration, especially in Spartina stands. Root porosity was not affected by water quality, but was positively correlated with CH₄ emissions, suggesting that plants can be important conduits for CH₄ from anoxic sediment to the atmosphere. Sediment microbial composition was largely unaffected by N addition, whereas salt amendments induced structural shifts, reduced sediment community diversity, and reduced C mineralization rates, presumably due to osmotic stress. Methane emissions were suppressed by sea salt, but not road salt, providing evidence for the additional chemical control (SO₄^-2 availability) on this microbial-mediated process. Thus, N may have stimulated plant activity while salting treatments preferentially enriched specific microbial populations. Together our findings underpin the utility of combining plant and microbial responses, and highlight the need for more integrative studies to predict the consequences of a changing environment on freshwater wetlands.  

We conducted a wetland mesocosm experiment during the 2016-2017 growing seasons to test how traits (i.e., biomass, root porosity) of three common wetland plants (Phragmites australis, Spartina pectinata, Typha latifolia, hereafter Phragmites, Spartina, Typha, respectively) and four water quality treatments (freshwater control, N, road salt, sea salt) interact to alter C gas fluxes (CO₂, CH₄, C mineralization) and sediment microbial communities. Raw data associated with plant, pore water, and carbon flux responses are provided here. All raw sequence datasets are available in the NCBI Short Read Archive (SRA) under the BioProject ID PRJNA604015. Please see associated manuscript for details on data collection.

2017 plant, pore water, and carbon response metrics are in associated CSV file titled "Donatoetal_data."  Responses with "NA" indicate that no data are available, either due to sample processing error or concentrations below the instuments detection limit. A brief description of the response metric headers and their associated units can be found in the CSV file titled "Donatoetal_metadata." Please see associated manuscript for details on data collection and analysis.