Water Resources Research Act Program

Details for Project ID 2020GA170B

Assessing drought effects on consumer-mediated ecosystem processes using experimental wetlands

Institute: Georgia
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $18,000 Total Non-Federal Funds: $36,127

Principal Investigators: Jose C. Colon-Gaud

Abstract: Freshwater wetlands are important harbors of biodiversity and support an abundance of ecosystem functions. Yet these ecosystems are increasingly threatened by human’s demand for freshwater resources, changes to land use, and changing climates. Many of the functions provided by wetlands are facilitated by macroinvertebrate consumers, thus understanding the factors that shape these consumer communities provides critical information about the fate of ecosystem services given the potential for change. For example, many wetland macroinvertebrates receive a vast amount of energy from detrital pathways and, in doing so, function as mediators of organic matter processing which ultimately impacts carbon storage. As wetland ecosystems are exposed to natural and anthropogenic changes, macroinvertebrate detritivore communities will be impacted, thus affecting the rates of material turnover. One such change is the predicted increase in drought conditions that will impact the hydrology of many inland wetlands. Furthermore, the increasing demand for freshwater during droughts will result in permanently flooded sites becoming temporary wetlands or drying entirely. These conditions are certain to affect consumer communities in wetlands and ultimately ecosystem processes. Our proposed study examines macroinvertebrate community structure and leaf decomposition in permanently vs. temporarily flooded wetlands to understand the effects of climate change on ecosystems of the southeastern US. To do so, leaf packs will be deployed in experimental ponds at the former USFWS Bo Ginn National Fish Hatchery in Jenkins County, GA and allowed to be colonized by macroinvertebrates. A series of replicate ponds will be exposed to two treatments, flooded temporarily (~60-90d) or flooded permanently in order to simulate the effects of drought disturbance in depositional wetland ecosystems. We hypothesize that stable (i.e., less disturbed), permanently flooded wetlands provide suitable conditions more favorable to organic matter decomposition, thus resulting in faster turnover rates of detrital materials that transfer energy to higher trophic levels. We also predict that macroinvertebrate communities in temporary ponds will be less diverse as these are susceptible to harsher conditions (e.g., lower dissolved oxygen, higher water temperature, and reduced habitat) resulting in higher rates of predation and competition. Whereas permanently flooded wetlands will provide stable conditions and increased habitat leading to higher macroinvertebrate diversity. Lastly, we predict that these differences in consumer diversity will result in faster decomposition rates at permanently versus temporarily flooded wetlands.