Biological communities and ecosystem function in restored and natural prairie wetlands

• Author / Creator

  Bortolotti, Lauren E

• Prairie wetlands provide many important ecosystem services including supporting biodiversity, improving water quality, preventing erosion, recharging groundwater, and attenuating floods. However, more than half of prairie wetlands in North America have been lost, primarily due to drainage for agriculture. Restoration may be able to reestablish lost services, although there remain substantial gaps in our understanding of the recovery of biodiversity and ecosystem function in restored prairie wetlands. Here, I present an investigation characterizing biological communities and ecosystem function in restored and natural prairie wetlands in southeastern Saskatchewan, Canada. My first objective was to assess recovery of the abiotic environment (water chemistry, sediment organic carbon [OC]) and various biological communities (phytoplankton, sediment diatoms, zooplankton, benthic macroinvertebrates, submersed aquatic vegetation [SAV]) after hydrological restoration. I used a space-for-time experimental design, surveying “recently restored” (restored 1-3 years before study), “older restored” (restored 7-14 years before study), and “natural” (never drained) prairie wetlands. Recently restored wetlands differed from older restored and natural wetlands in that they had higher total phosphorus (TP) and dissolved carbon dioxide (CO2) but lower specific conductance, pH, and sediment OC. Phytoplankton, diatom, and zooplankton communities showed little relationship to restoration state, but taxonomic composition of macroinvertebrate and SAV communities were different in recently restored wetlands. The consistent resemblance of older restored wetlands to natural wetlands suggests that recovery of the abiotic environment and many biological communities is possible within ~10 years of restoration, a result with direct implications for management. I quantified greenhouse gas (GHG) fluxes from the open water of three restored and natural prairie wetlands and used both CO2 fluxes and net ecosystem production (NEP; measured using the diel oxygen technique) to assess the metabolic status (i.e., net autotrophic or heterotrophic) of prairie wetlands. GHG emissions tended to be high, but variable. The recently restored wetland emitted more CO2 and methane than either the older restored or natural wetland, and only the latter showed extensive CO2 uptake. CO2 supersaturation was a less reliable indicator of wetland metabolic status than NEP, especially at daily timescales, owing to the confounding influence of geochemical processes on CO2 concentrations. I measured ecosystem metabolism, including NEP, gross primary production (GPP), and ecosystem respiration (ER) in three restored and natural prairie wetlands and identified the drivers of these rates. PAR, temperature, proxies of water column stratification, and SAV abundance were the main drivers of metabolism within wetlands. However, the recently restored wetland differed from the other sites in that chlorophyll a (chl a) and TP were also drivers of GPP and NEP. Among-wetland differences in NEP rates were determined by a combination of wetland state (i.e., clear water or turbid) and the degree to which emergent vegetation subsidized ER. GPP and ER were highest in the older restored wetland followed by the natural and recently restored wetlands. The GPP gradient across sites was explained by the abundance of SAV whereas the ER gradient by the abundance of substrates for microbial respiration (dissolved organic carbon, sediment OC). To date, this body of research represents one of the most comprehensive examinations of the recovery of biological communities after wetland restoration in the Canadian Prairie Pothole Region and is the first to look at ecosystem metabolism in this system. My work suggests that many attributes of prairie wetlands recover after restoration, though more work is needed to better characterize the effects of restoration on ecosystem metabolism and to understand how broadly applicable these findings are to the rest of the Prairie Pothole Region.

• Subjects / Keywords

  • Biodiversity
  • Ecosystem function
  • Prairie wetlands

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R31G0J539

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.