Zohary, TPais-Madeira, AMRobarts, RDHambright, KD2007-06-292007-06-291995Zohary, T, et al. 1995. Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake. Water Science and Technology, vol. 32(4), pp 103-1040273-1223http://hdl.handle.net/10204/725Copyright: 1995 Pergamon-Elsevier Science LtdPhytoplankton species composition and abundance were recorded weekly or biweekly for nearly 7 years in a hypertrophic lake ( Hartbeespoort Dam, South Africa), together with a range of physical and chemical parameters. A total of 73 species were recorded, of which only 20 were occasionally abundant, and only 5 became dominant (>50% of total biomass) at least once (Microcystis aeruginosa, Oocystis lacustris, Aulacoseira (= Melosira) granulata, Cyclotella meneghiniana, Carteria cordiformis). The earlier years of the study (1982-1986) were drought years characterized by low water levels (10-15 m below the level at full supply), excess supply of nutrients at all times of the year, and overwhelming dominance of Microcystis aeruginosa. This K-selected species proved to be well adapted to withstand the range of environmental conditions throughout summer, fall and winter but it declined in spring each year when a fast successional episode followed. Several small-celled chlorophytes, diatoms and cryptophytes appeared and disappeared until Oocystis lacrustris became dominant for a few weeks, to be replaced by M. aeruginosa early in the summer. During the following rainy years (late 1986 to 1988), the lake re-filled. Major washout losses, concomitant with a considerable decline in surface water phosphorus concentrations and elevated TN/TP ratios, apparently led to the reduction in the abundance of M. aeruginosa. Its bloom extended over a smaller portion of the year in 1986 and 1987, and disappeared in May 1988, permitting the development of a more diverse phytoplankton community subject to control by 2ooplankton grazing. This long-term phytoplankton record from Hartbeespoort Dam demonstrates the key role of a dominant species in controlling community composition and diversity in hypertrophic lakes. Stable environments lead to low-diversity and high-biomass phytoplankton assemblages dominated by K-strategists, while disruptions of suitable strength and frequency allow for the development and maintenance of higher species diversity.enHaartebeesport damSpecies compositionMicrocystis aeruginosaOocystis lacustrisCompetitive exclusionArticleZohary, T., Pais-Madeira, A., Robarts, R., & Hambright, K. (1995). Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake. http://hdl.handle.net/10204/725Zohary, T, AM Pais-Madeira, RD Robarts, and KD Hambright "Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake." (1995) http://hdl.handle.net/10204/725Zohary T, Pais-Madeira A, Robarts R, Hambright K. Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake. 1995; http://hdl.handle.net/10204/725.TY - Article AU - Zohary, T AU - Pais-Madeira, AM AU - Robarts, RD AU - Hambright, KD AB - Phytoplankton species composition and abundance were recorded weekly or biweekly for nearly 7 years in a hypertrophic lake ( Hartbeespoort Dam, South Africa), together with a range of physical and chemical parameters. A total of 73 species were recorded, of which only 20 were occasionally abundant, and only 5 became dominant (>50% of total biomass) at least once (Microcystis aeruginosa, Oocystis lacustris, Aulacoseira (= Melosira) granulata, Cyclotella meneghiniana, Carteria cordiformis). The earlier years of the study (1982-1986) were drought years characterized by low water levels (10-15 m below the level at full supply), excess supply of nutrients at all times of the year, and overwhelming dominance of Microcystis aeruginosa. This K-selected species proved to be well adapted to withstand the range of environmental conditions throughout summer, fall and winter but it declined in spring each year when a fast successional episode followed. Several small-celled chlorophytes, diatoms and cryptophytes appeared and disappeared until Oocystis lacrustris became dominant for a few weeks, to be replaced by M. aeruginosa early in the summer. During the following rainy years (late 1986 to 1988), the lake re-filled. Major washout losses, concomitant with a considerable decline in surface water phosphorus concentrations and elevated TN/TP ratios, apparently led to the reduction in the abundance of M. aeruginosa. Its bloom extended over a smaller portion of the year in 1986 and 1987, and disappeared in May 1988, permitting the development of a more diverse phytoplankton community subject to control by 2ooplankton grazing. This long-term phytoplankton record from Hartbeespoort Dam demonstrates the key role of a dominant species in controlling community composition and diversity in hypertrophic lakes. Stable environments lead to low-diversity and high-biomass phytoplankton assemblages dominated by K-strategists, while disruptions of suitable strength and frequency allow for the development and maintenance of higher species diversity. DA - 1995 DB - ResearchSpace DP - CSIR KW - Haartebeesport dam KW - Species composition KW - Microcystis aeruginosa KW - Oocystis lacustris KW - Competitive exclusion LK - https://researchspace.csir.co.za PY - 1995 SM - 0273-1223 T1 - Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake TI - Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake UR - http://hdl.handle.net/10204/725 ER -