Evidence for a new regime shift between floating and submerged invasive plant dominance in South Africa
- 224 Downloads
Classical biological control for the management of floating invasive plants has been highly successful in South Africa. However, restoring ecosystem services has been compromised by a new suite of submerged invasive plants. This study proposes that biological control of floating invasive macrophytes acts as a catalyst in a regime shift between floating and submerged invasive plant dominance. Regime shifts are large and sudden changes in the structure and functioning of ecosystems. The proposed shift is driven by the rapid decomposition of floating plants and subsequent increase in availability of nutrients and light. A mesocosm experiment explored the effect of biological control on floating Pistia stratiotes L. (Araceae) upon the growth of invasive submerged Egeria densa Planch. (Hydrocharitaceae), and native submerged plant species of the same family; Lagarosiphon major (Ridl.) Moss (Hydrocharitaceae). The results revealed a cascade effect of biological control of P. stratiotes on the availability of nitrogen, resulting in increased relative growth rates and invasive capacity for E. densa. In contrast, the native L. major could not compete with healthy or damaged P. stratiotes. These findings highlight the vulnerability of South African freshwater systems to submerged plant invasions and demonstrate the importance of a more holistic approach to invasive plant management.
KeywordsMacrophyte Invasion Competition Alternate stable states Biological control
This research was funded through the Department of Environmental Affairs, Natural Resource Management Programme’s Working for Water programme. Further funding for this work was provided by the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation of South Africa. Thanks are extended to the staff of the Centre for Biological Control (South Africa) for their help in the building and maintenance of the experiments, particularly Rosie Mangan and Rosalie Smith for plant collection and care. The authors also thank Jordie Netten for her valuable and constructive comments on earlier drafts of this manuscript.
- Basson, M. S., P. H. Van Niekerk & J. A. Van Rooyen, 1997. Overview of Water Resources Availability and Utilization in South Africa. Department of Water Affairs and Forestry, Pretoria.Google Scholar
- Brix, H. & H. H. Shierup, 1989. The use of aquatic macrophytes in water pollution control. Ambio 18: 100–107.Google Scholar
- Center, T. D., 1994. Biological control of weeds: water hyacinth [Eichhornia crassipes] and water lettuce [Pistia stratiotes]. Food and Agriculture Organization of the United Nations. http://agris.fao.org/agris-search/search.do?recordID=GB9602237 [accessed July 12 2016].
- Champion, P. D., & R. D. Wells, 2014. Proactive management of aquatic weeds to protect the nationally important Northland dune lakes, New Zealand. Proceedings from: 19th Australasian Weeds Conference, 1–4 September 2014, Tasmania, Australia: 139–142.Google Scholar
- Coetzee, J. A., M. P. Hill, M. J. Byrne & A. Bownes, 2011. A review of the biological control programmes on Eichhornia crassipes (C.Mart.) Solms (Pontederiaceae), Salvinia molesta D.S.Mitch. (Salviniaceae), Pistia stratiotes L. (Araceae), Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae) and Azolla filiculoides Lam. (Azollaceae) in South Africa. African Entomology 19: 451–468.CrossRefGoogle Scholar
- De Wit, C. T. & J. P. Van den Bergh, 1965. Competition between herbage plants. Netherlands Journal of Agricultural Science 13: 212–221.Google Scholar
- Evans, G. C., 1972. Relative growth rate. In Anderson, D. J., P. Greig-Smith & F. A. Pitelka (eds), Studies in Ecology, Vol. 1., The quantitative analysis of plant growth University of California Press. Berkeley, California: 295–314.Google Scholar
- Hill, M. P. & J. Coetzee, 2017. The biological control of aquatic weeds in South Africa: current status and future challenges. Bothalia-African Biodiversity & Conservation 47: 1–12.Google Scholar
- Hoagland, D. R. & D. I. Arnon, 1938. Growing Plants Without Soil by the Water Culture Method. California Agricultural Experimental Station, University of California, College of Agriculture, Berkeley: 29–32.Google Scholar
- Jewell, W. J., 1971. Aquatic weed decay: dissolved oxygen utilization and nitrogen and phosphorus regeneration. Water Pollution Control Federation 43: 1457–1467.Google Scholar
- Jha, H. K., B. S. Singh & A. K. Varshney, 2015. Local survey of Hydrilla verticillata (L.F.) Royle: an invasive and valuable aquatic weed. The Journal of the Indian Botanical Society 94: 149–152.Google Scholar
- Matthews, J., K. R. Koopman, R. Beringen, B. Ode, R. Pot, G. Velde, J. L. C. H. Van Valkenburg & R. S. E. W. Leuven, 2014. Knowledge Document for Risk Analysis of the Non-native Brazilian Waterweed (Egeria densa) in the Netherlands. Department of Environmental Science, Radboud University, Nijmegen.Google Scholar
- Morris, K., K. A. Harrison, P. C. E. Bailey & P. I. Boon, 2004. Domain shifts in the aquatic vegetation of shallow urban lakes: the relative roles of low light and anoxia in the catastrophic loss of the submerged angiosperm Vallisneria americana. Marine & Freshwater Research 55: 749–758.CrossRefGoogle Scholar
- Netten, J. J. C., G. H. P. Arts, R. Gylstra, E. H. Van Nes, M. Scheffer & R. M. M. Roijackers, 2010. Effect of temperature and nutrients on the competition between free-floating Salvinia natans and submerged Elodea nuttallii in mesocosms. Fundamental and Applied Limnology 177: 125–132.CrossRefGoogle Scholar
- Oberholster, P. J. & P. J. Ashton, 2008. State of the Nation Report: An Overview of the Current Status of Water Quality and Eutrophication in South African Rivers and Reservoirs. Parliamentary Grant Deliverable, Council for Scientific and Industrial Research (CSIR), Pretoria.Google Scholar
- Pistori, R. E. T., A. F. M. Camargo & G. G. Henry-Silva, 2004. Relative growth rate and doubling time of the submerged aquatic macrophyte Egeria densa Planch. Acta Limnologica Brasiliensia 16: 77–84.Google Scholar
- R Development Core Team, 2014. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/.
- Scheffer, M., 2009. Alternative stable states and regime shifts in ecosystems. In Levin, S. A., R. S. Carpenter, H. C. J. Godfray, A. P. Kinzig, M. Loreau, J. B. Losos, B. Walker & B. S. Wilcove (eds), The Princeton Guide to Ecology. Princeton University Press, Princeton: 359–406.Google Scholar
- Smart, R. M., J. W. Barko, & D. W. McFarland, 1994. Competition between Hydrilla. verticillata and Vallisneria americana under different environment conditions. Technical Report A-94-1. NTIS No. AD A279 172. US Army Engineer Waterways Experiment Station, Vicksburg.Google Scholar
- Stewart, R. I., M. Dossena, D. A. Bohan, E. Jeppesen, R. L. Kordas, M. E. Ledger, M. Meerhoff, B. Moss, C. Mulder, J. B. Shurin & B. Suttle, 2013. Mesocosm experiments as a tool for ecological climate-change research. In Woodward, G. & E. J. O’Gorman (eds), Global Change in Multispecies Systems: Advances in Ecological Research. Elsevier, London: 71–182.CrossRefGoogle Scholar
- Van Ginkel, C. E., 2011. Eutrophication: present reality and future challenges for South Africa. Water SA 37: 693–701.Google Scholar
- Viaroli, P., M. Bartoli, G. Giordani, M. Naldi, S. Orfanidis & J. M. Zaldivar, 2008. Community shifts, alternative stable states, biogeochemical controls and feedbacks in eutrophic coastal lagoons: a brief overview. Aquatic Conservation: Marine and Freshwater Ecosystems 18: 105–117.CrossRefGoogle Scholar