Date of Award
Master of Science
Natural Resource Ecology and Management
Michael J. Weber
Lakes constitute about 87% of the world’s freshwater and provide a number of valuable ecosystem services. However, changes in land use and the introduction of non-native fishes often results in lake degradation through changes in habitat, water quality, and biotic structure. . To counteract these threats and improve lake ecosystems, natural resource agencies often invest considerable effort by manipulating watershed and in-lake process responsible for lake degradation. For example, the Iowa Lake Restoration Program began in 2006 with the goal of improving water quality and biotic integrity across natural and constructed lakes. Since then, the Iowa Department of Natural Resources has worked with communities and other resource agencies to improve water quality and restore fish communities. Over the last decade, many improvements in water quality and fisheries have been observed due to these efforts. However, these observations are based largely on anecdotal evidence or individual water chemistry parameters that may provide inaccurate representations of overall lake condition and restoration success. Thus, to create a more holistic evaluation of previous restoration projects and inform future efforts, further analysis was needed on the interrelationships among water quality and the biological community before and after restoration. The objectives of this study were to evaluate water quality, phytoplankton, zooplankton and fish communities in 21 restored Iowa lakes pre- and post-restoration. A Before-After-Control-Impact (BACI) system design was used to account for natural change associated with the spatial and temporal variability across restored lakes. Water clarity, indexed by Secchi depth, turbidity, suspended solids, and phosphorus, improved 1 year post restoration for in-lake (natural) and both treatments, but not for other treatments. Additionally, restoration had no detectable effect on phytoplankton or zooplankton community composition, likely due to the myriad of other biotic and abiotic factors that can influence these populations. Changes in water clarity over post-restoration years were not correlated with the amount of sediment removed, shoreline riprapped, lake surface area, or the watershed: surface area ratio. However, water clarity was positively related to the change in largemouth bass abundance, but negatively related to the abundance of common carp and channel catfish. Results of this study begin to elucidate possible trends related to restoration measures and add to our current knowledge on the interrelationships among water quality, fish assemblage, watershed, and lake characteristics. Second, I evaluated factors regulating bluegill population characteristics (relative abundance, size structure, and condition) among Iowa lakes. Bluegill are ubiquitous in systems across Iowa but populations are of varying quality. Bluegill are positioned in the middle of lake food webs, and subsequently are influenced by a suite of biotic and abiotic factors. Thus, bluegill can be used as an indicator of lake health. Bluegill relative abundance increased with largemouth bass relative abundance, watershed:lake surface area, and N:P ratio and decreased with turbidity. Bluegill size structure increased with channel catfish relative abundance and zooplankton density. Bluegill condition increased with largemouth bass relative abundance and common carp relative abundance, but decreased with largemouth bass size structure and lake depth. Relationships among bluegill and environmental characteristics can provide insight to managers regarding parameters to manipulate in order to improve these important panfish populations. Together, results from these chapters can be of significant use to resource managers when considering implications of restoration on native fish communities in the future.
Matthew Christian Bevil
Bevil, Matthew Christian, "Ecosystem-level evaluation of Iowa's lake restoration program" (2016). Graduate Theses and Dissertations. 15667.