, Volume 502, Issue 1–3, pp 133–143 | Cite as

Steady-state assemblages in a Mediterranean hypertrophic reservoir. The role of Microcystis ecomorphological variability in maintaining an apparent equilibrium

  • Luigi Naselli-Flores
  • Rossella Barone


Lake Arancio is a hypertrophic Mediterranean man-made lake, located on the southern coast of Sicily. Its artificial origin and the climate make it a very dynamic environment, strongly characterised by very wide water-level fluctuations. These vertical water movements interfere with the thermal stability of the water body often causing the breaking of the thermocline in mid-summer. In addition, the summer level-decrease influences the nutrient dynamics and modifies the zmix/zeu ratio. All these modifications were observed to support a high environmental variability, which was reflected by the richness of its phytoplankton composition and by its dynamics. Nevertheless, an investigation carried out from March 2001 to March 2002 showed that the assemblage was strongly dominated by a few species, one by one. In particular, two different Microcystis morphotypes dominated the assemblage from mid-April till the beginning of October. The prolonged dominance of these `species' should suggest that a steady state condition took place in Lake Arancio during spring and summer 2001. This is in contrast with previous investigations, which showed high diversity values especially occurring in the period of strong environmental instability when the continuous dewatering caused the breaking of the thermocline in the middle of summer. Nevertheless, this dominant species showed a very wide morphological variability and alternated among `more S', `S', and `R' (sensu Reynolds) ecotypes. The ever-changing morphological features suggest a different ecological behaviour of the species involved. They seem to confirm that the environmental variability of Mediterranean reservoirs sustains high diversity values, even though this diversity has to be sought in the amplitude of morphological plasticity of one or a few species, rather than in the coexistence of a variety of species.

thermal stability mixing regime phytoplankton morphology C-S-R-strategy 


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  1. Allen, T. F. H. & T. B. Starr, 1982. Hierarchy: perspectives for ecological complexity. University of Chicago Press, Chicago.Google Scholar
  2. Barone, R. & L. Naselli-Flores, 1994. Phytoplankton dynamics in a shallow, hypertrophic reservoir (Lake Arancio, Sicily). Hydrobiologia 289: 199–214.Google Scholar
  3. Grime, J. P., J. G. Hodgson & R. Hunt, 1996. Comparative plant ecology. A functional approach to common British species. Chapman & Hall, New YorkGoogle Scholar
  4. Harris, G. P., 1986. Phytoplankton Ecology. Strucure, function and fluctuation. Chapman and Hall, London.Google Scholar
  5. Hillebrand, H., C.-D. Dûrselen, D. Kirschtel, U. Pollingher & T. Zohary, 1999. Biovolume calculation for pelagic and benthic microalgae. J. Phycol. 35: 403–424.Google Scholar
  6. Kennedy, R. H., T. Cole, W. Boyd & K. Barko, 2002. Operational influences on the limnological characteristics of reservoirs: a model study. Extended Abstracts of the 4th International Conference on Reservoir Limnology and Water Quality, Èeské Budìjovice, Czech Republic, August 12-16, 2002. pp. 168–170.Google Scholar
  7. Komárek, J. & P. Marvan, 1992. Morphological differences in natural populations of the genus Botryococcus (Chlorophyceae). Archiv für Protistenkunde 141: 65–100.Google Scholar
  8. Komárek, J., J. Komárkova-Legnerová, C. Sant'Anna, M.T. de Paiva Azevedo & P.A.C. Senna, 2002. Two common Microcystis species from tropical America. Cryptogamie/Algologie 23: 159–177.Google Scholar
  9. Margalef, R., 1978. Life forms of phytoplankton as survival alternatives in an unstable environment. Oceanologica Acta 1: 493–509.Google Scholar
  10. Margalef, R., 2000. Exosomatic structures and captive energies relevant in succession and evolution. In Jørgensen S. E. (ed.), Thermodynamics and ecological modelling. Lewis Publishers, Boca Raton: 3-15.Google Scholar
  11. Naselli-Flores, L. 2003. Man-made lakes in Mediterranean semiarid climate: The strange case of Dr Deep Lake and Mr Shallow Lake. Hydrobiologia (in press).Google Scholar
  12. Naselli-Flores, L. & R. Barone, 1998. Phytoplankton dynamics in two reservoirs with different trophic state (Lake Rosamarina and Lake Arancio, Sicily, Italy). Hydrobiologia 369/370: 163–178.Google Scholar
  13. Naselli-Flores, L. & R. Barone, 2000. Phytoplankton dynamics and structure: a comparative analysis in natural and man-made water bodies of different trophic state. Hydrobiologia 438: 65-74.Google Scholar
  14. Naselli-Flores, L., J. Padisák, M. T. Dokulil & I. Chorus, 2003. Equilibrium/steady-state concept in phytoplankton ecology. Hydrobiologia 502 (Dev. Hydrobiol. 172): 395–403.Google Scholar
  15. Naselli-Flores, L., R. Barone & R. Mosello, 2003b. Eutrophication control by lime addition: a preliminary approach in Sicilian reservoirs. Hydrobiologia (in press).Google Scholar
  16. Padisák, J., 1992. Seasonal succession of phytoplankton in a large, shallow lake (Balaton, Hungary) - a dynamic approach to ecological memory, its possible role and mechanisms. J. Ecol. 80: 217–230.Google Scholar
  17. Padisák, J., C. S. Reynolds & U. Sommer (eds), 1993. Intermediate Disturbance Hypothesis in Phytoplankton Ecology. Developments in Hydrobiology 81. Kluwer Academic Publishers, Dordrecht, The Netherlands.Google Scholar
  18. Padisák, J., F. Barbosa, R. Koschel & L. Krienitz, 2003. Deep layer cyanoprokaryota maxima in temperate and tropical lakes. In Koschel R. & D. Adams (eds), Lake Stechlin. An Approach to Understanding an Oligotrophic Lowland Lake. Archiv für Hydrobiologie/Advances in Limnology (in press).Google Scholar
  19. Reynolds, C. S., 1997. Vegetation processes in the pelagic: A model for ecosystem theory, Ecology Institute, D-21385 Oldendorf, Germany.Google Scholar
  20. Reynolds, C. S. & E. G. Bellinger, 1992. Patterns of abundance and dominance of the phytoplankton of Rostherne Mere, England: evidence from an 18-year data set. Aquat. Sci. 54: 10-36.Google Scholar
  21. Reynolds, C. S., G. H. M. Jaworski, H. A. Cmiech & G. F. Leedale, 1981. On the annual cycle of the blue-green alga, Microcystis aeruginosa Kütz. emend. Elenkin. Phil. Trans. r. Soc. Lond. Ser B 293: 419–477.Google Scholar
  22. Reynolds, C. S., V. L. Huszar, C. Kruk, L. Naselli-Flores & S. Melo, 2002. Towards a functional classification of the freshwater phytoplankton. J. Plankton Res. 24: 417–428.Google Scholar
  23. Robarts, R. D. & T. Zohary, 1984. Microcystis aeruginosa and underwater light attenuation in a hypertrophic lake (Hartbeespoort Dam, South Africa). J. Ecol. 72: 1001-1017.Google Scholar
  24. Scheffer, M., S. Reinaldi, J. Huisman & F. J. Weissing, 2003. Why plankton communities have no equilibrium: solutions to the paradox. Hydrobiologia 491: 9-18.Google Scholar
  25. Senese, F. A., 2003. http://antoine.frostburg.edu/chem/sene se/javascript/water-density.html.Google Scholar
  26. Sommer, U., J. Padisák, C. S. Reynolds & P. Juhász-Nagy, 1993. Hutchinson's heritage: the diversity-disturbance relationship in phytoplankton. Hydrobiologia 249: 1-7.Google Scholar
  27. Straškraba, M., I. Dostálková, J. Hejzlar & V. Vyhnálek, 1995. The effect of reservoirs on phosphorus concentration. Int. Rev. ges. Hydrobiol. 80: 403–413.Google Scholar
  28. Van Rijn, J. & M. Shilo, 1985. Carbohydrate fluctuations, gas vacuolation, and vertical migration of scum-forming cyanobacteria in fishponds. Limnol. Oceanogr. 30: 1219-1228.Google Scholar
  29. Wallace, B. B. & D. P. Hamilton, 1999. The effect of variations in irradiance on buoyancy regulation in Microcystis aeruginosa. Limnol. Oceanogr. 44: 1127-1138.Google Scholar
  30. Wallace, B. B. & D. P. Hamilton, 2000. Simulation of waterbloom formation in the cyanobacterium Microcystis aeruginosa. J. Plankton Res. 22: 1127-1138.Google Scholar
  31. Wallace, B. B., M. C. Bailey & D. P. Hamilton, 2000. Simulation of vertical position of buoyancy regulating Microcystis aeruginosa in a shallow eutrophic lake. Aquat. Sci. 62: 320–333.Google Scholar
  32. Whittaker, R. H., 1975. Communities and Ecosystems. Macmillan, New York.Google Scholar
  33. Whittaker, R. H. & S. A. Levin, 1977. The role of mosaic phenomena in natural communities. Theor.Pop. Biol. 12: 117–139.Google Scholar

Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • Luigi Naselli-Flores
    • 1
  • Rossella Barone
    • 1
  1. 1.Dipartimento di Scienze BotanicheUniversità di PalermoPalermoItaly

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