Responses of Tidal Freshwater and Brackish Marsh Macrophytes to Pulses of Saline Water Simulating Sea Level Rise and Reduced Discharge

Abstract

Coastal low-salinity marshes are increasingly experiencing periodic to extended periods of elevated salinities due to the combined effects of sea level rise and altered hydrological and climatic conditions. However, we lack the ability to predict detailed vegetation responses, especially for saline pulses that are more realistic in nature than permanent saline presses. In this study, we exposed common freshwater and brackish plants to different durations (1–31 days per month for 3 months) of saline water (salinity of 5). We found that Zizaniopsis miliacea was more tolerant to salinity than the other two freshwater species, Polygonum hydropiperoides and Pontederia cordata. We also found that Zizaniopsis miliacea belowground and total biomass appeared to increase with salinity pulses up to 16 days in length, although this relationship was quite variable. Brackish plants, Spartina cynosuroides, Schoenoplectus americanus and Juncus roemerianus, were unaffected by the experimental treatments. Our experiment did not evaluate how competitive interactions would further affect responses to salinity but our results suggest the hypothesis that short pulses of saline water will increase the cover of Zizaniopsis miliacea and decrease the cover of Polygonum hydropiperoides and Pontederia cordata in tidal freshwater marshes, thereby reducing diversity without necessarily affecting total plant biomass.

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Acknowledgements

This material is based upon work supported by the National Science Foundation through the Georgia Coastal Ecosystems Long-Term Ecological Research program under Grant No. OCE- 1237140. We thank Huy Vu, Wei-Ting Lin, Jacob Shalack, Caroline Reddy, Tim Montgomery, Zachary Chejanovski, Carolyn Kilgore and George Wheeler for help with this project. We thank Wade Sheldon for assistance with the salinity data. This is contribution number 1068 of the University of Georgia Marine Institute.

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Correspondence to Fan Li.

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Li, F., Pennings, S.C. Responses of Tidal Freshwater and Brackish Marsh Macrophytes to Pulses of Saline Water Simulating Sea Level Rise and Reduced Discharge. Wetlands 38, 885–891 (2018). https://doi.org/10.1007/s13157-018-1037-2

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Keywords

  • Saline intrusion
  • Freshwater marsh
  • Brackish marsh
  • Zizaniopsis miliacea
  • Polygonum hydropiperoides
  • Pontederia cordata