Rivers to reservoirs: hydrological drivers control reservoir function by affecting the abundance of submerged and floating macrophytes
Lakes and reservoirs are important sites for biogeochemical cycling on both regional and global scales. Shallow lakes often have higher coverage of submerged aquatic vegetation (SAV) because of increased light penetration to the sediment as well as stronger interactions between the sediment and the water column. These biotic and abiotic interactions can strongly affect nutrient cycling. This study evaluated how hydrologically driven changes in SAV coverage affected nutrient processing within a relatively shallow reservoir. To assess these effects, a comprehensive water quality sampling network was established that quantified nutrient concentrations in the inflows and outflow of the lake. Annual vegetation surveys quantified the spatial coverage of SAV. Annual inflow was significantly lower in the first year of the study compared to the following 2 years. Consequently, SAV coverage was also highest during the lowest flows in the first year and was lower in the following 2 years when flows were greater. NO3-N concentrations were also lowest within Hydrilla beds and in the outflow during the growing season of the first year. Our results suggest that hydrological variation was the main driving variable of SAV coverage, and that the extent of SAV coverage strongly controlled nutrient processing at the whole-reservoir scale.
KeywordsHydrilla verticillata Reservoir Nutrient processing SAV spatial coverage Hydrology
We thank Brian Clayton, Bryan Cloninger, Nathalie Smith, and the Golladay lab for assistance in the field and the laboratory. We thank Jean Brock for assistance with ArcGIS. We also thank André Padial and two anonymous reviewers for their insightful comments on an earlier version of this manuscript. Funding for this project was provided by the National Science Foundation (DEB 1404160), the Joseph W. Jones Ecological Research Center, and the University of Georgia Graduate School.
- Brown, S. J. & M. J. Maceina, 2002. The influence of disparate levels of submersed aquatic vegetation on largemouth bass population characteristics in a Georgia reservoir. Journal of Aquatic Plant Management 40: 28–35.Google Scholar
- Greig-Smith, P., 1983. Quantitative Plant Ecology. Blackwell Scientific Publications, Oxford.Google Scholar
- Hobbs, R. J., S. Arico, J. Aronson, J. S. Baron, P. Bridgewater, V. A. Cramer, P. R. Epstein, J. J. Ewel, C. A. Klink, A. E. Lugo, D. Norton, D. Ojima, D. M. Richardson, E. W. Sanderson, F. Valladares, M. Vilá, R. Zamora & M. Zobel, 2006. Novel ecosystems: theoretical and management aspects of the new ecological world order. Global Ecology and Biogeography 15: 1–7.CrossRefGoogle Scholar
- Hutchinson, G., 1977. A Treatise on Limnology: Vol. I. Geography, Physics and Chemistry. Wiley, New York.Google Scholar
- Langeland, K. A., 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), “The Perfect Aquatic Weed”. Castanea 61: 293–304.Google Scholar
- Li, L., W. Li & Y. Deng, 2013. Summer rainfall variability over the Southeastern United States and its intensification in the 21st century as assessed by CMIP5 models. Journal of Geophysical Research: Atmospheres 118: 340–354.Google Scholar
- NOAA/NCEI, 2017: Climate Data Online. NOAA National Centers for Environmental Information, accessed 24 October 2017 [available online at https://www.ncdc.noaa.gov/cdo-web].
- Pace, M. L., R. D. Batt, C. D. Buelo, S. R. Carpenter, J. J. Cole, J. T. Kurtzweil & G. M. Wilkinson, 2016. Reversal of a cyanobacterial bloom in response to early warnings. Proceedings of the National Academy of Sciences of the United States of America 114: 352–357.CrossRefPubMedCentralPubMedGoogle Scholar
- Peterson, R. N., W. C. Burnett, S. P. Opsahl, I. R. Santos, S. Misra & P. N. Froelich, 2013. Tracking suspended particle transport via radium isotopes (226Ra and 228Ra) through the Apalachicola-Chattahoochee-Flint River system. Journal of Environmental Radioactivity 116: 65–75.CrossRefPubMedGoogle Scholar
- Scheffer, M., 2009. Critical Transitions in Nature and Society. Princeton University Press, Princeton.Google Scholar
- Simberloff, D., J.-L. Martin, P. Genovesi, V. Maris, D. A. Wardle, J. Aronson, F. Courchamp, B. Galil, E. García-Berthou, M. Pascal, P. Pyšek, R. Sousa, E. Tabacchi & M. Vilà, 2013. Impacts of biological invasions: what’s what and the way forward. Trends in Ecology & Evolution 28: 58–66.CrossRefGoogle Scholar
- Torak, L. J., D. M. Crilley & A. J. A. Painter, 2006. Physical and hydrochemical evidence of lake leakage near Jim Woodruff Lock and Dam and ground-water inflow to Lake Seminole, and an assessment of karst features in and near the lake, southwestern Georgia and northwestern Florida. Scientific Investigations Report 2005–5084: 1–93.Google Scholar