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Show simple item record Zohary, T Pais-Madeira, AM Robarts, RD Hambright, KD 2007-06-29T06:13:50Z 2007-06-29T06:13:50Z 1995
dc.identifier.citation Zohary, T, et al. 1995. Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake. Water Science and Technology, vol. 32(4), pp 103-104 en
dc.identifier.issn 0273-1223
dc.description Copyright: 1995 Pergamon-Elsevier Science Ltd en
dc.description.abstract 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. en
dc.language.iso en en
dc.publisher Pergamon-Elsevier Science Ltd en
dc.subject Haartebeesport dam en
dc.subject Species composition en
dc.subject Microcystis aeruginosa en
dc.subject Oocystis lacustris en
dc.subject Competitive exclusion en
dc.title Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake en
dc.type Article en

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