AME 48:1-12 (2007)  -  doi:10.3354/ame048001

Microcystis genotype succession in relation to microcystin concentrations in freshwater lakes

W. Edwin A. Kardinaal1,3,*, Ingmar Janse2,4,*, Miranda Kamst-van Agterveld2, Marion Meima2, Josje Snoek1, Luuc R. Mur1, Jef Huisman1, Gabriel Zwart1,2,5, Petra M. Visser1,**

1Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS, Amsterdam, The Netherlands
2Department of Microbial Wetland Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Centre for Limnology, Rijksstraatweg 6, 3631 AC Nieuwersluis, The Netherlands
3Present address: DHV consultancy, PO Box 1132, 3800 BC Amersfoort, The Netherlands
4Present address: National Institute for Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands
5Present address: Waterboard Peel en Maasvallei, PO Box 3390, 5902 RJ Venlo, The Netherlands
*Both authors contributed equally to this work
**Corresponding author. Email:

ABSTRACT: Potentially toxic Cyanobacteria, like Microcystis, form a serious threat in recreational waters and drinking-water reservoirs. We monitored the population dynamics of toxic and non-toxic Microcystis strains using rRNA of the internal transcribed spacer region in combination with DGGE to determine whether there is a seasonal succession of toxic and non-toxic Microcystis genotypes in freshwater lakes and, if so, whether this succession can explain seasonal dynamics of the toxin microcystin. We studied 3 lakes in The Netherlands, all dominated by Microcystis during summer. Coexistence of several genotypes was observed in all lakes. The seasonal succession in a deep, stratified lake started with a population consisting of several toxic genotypes at the onset of the bloom, which changed into a population dominated by non-toxic genotypes at the end of the bloom. In this lake, the genotype succession clearly accounted for the observed microcystin dynamics. In 2 unstratified lakes, we also observed a seasonal replacement of Microcystis genotypes; however, the relation between genotype succession and microcystin dynamics was less conspicuous, since toxic strains dominated throughout the bloom period. A seasonal succession of different Microcystis genotypes might often be a key mechanism determining microcystin concentrations in Microcystisdominated lakes. Therefore, factors driving the succession of toxic and non-toxic genotypes deserve further study.

KEY WORDS: Harmful cyanobacteria · Microcystis · Microcystins · Genotypes · Succession · ITS · DGGE

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