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The importance of small colonies in sustaining M icrocystis population exposed to mixing conditions: an exploration through colony size, genotypic composition and toxic potential
Author(s) -
Sabart Marion,
Misson Benjamin,
Descroix Aurélie,
Duffaud Emilie,
Combourieu Bruno,
Salençon MarieJosé,
Latour Delphine
Publication year - 2013
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12077
Subject(s) - biology , bloom , population , ecosystem , population size , ecology , genotype , competition (biology) , algal bloom , ribosomal rna , gene , genetics , phytoplankton , demography , sociology , nutrient
Summary M icrocystis is a toxic colony‐forming cyanobacterium, which can bloom in a wide range of freshwater ecosystems. Despite the ecological advantage of the colonial form, few studies have paid attention to the size of M icrocystis colonies in the field. With the aim of evaluating the impact of a fluctuating physical environment on the colony size, the genotypic composition and the toxic potential of a M icrocystis population, we investigated five different colony size classes of a M icrocystis bloom in the G rangent reservoir ( F rance). By sequencing the internal transcribed spacer of the ribosomal operon, we evidenced changes in the genetic structure among size classes in response to environmental change. While similar genotypes were seen in every size class in stable conditions, new dominant genotypes appeared in the smallest colonies (< 160 μm) concomitantly with mixing conditions, strongly suggesting the importance of these colonies in response to disturbances. Moreover, these small colonies played a major role in microcystin production during this bloom, since very high microcystin contents (> 1 pg.cell. −1 ) were found in their cells. These findings indicate that the colony size distribution of a M icrocystis population in response to disturbance could be an adaptive strategy that may explain its ecological success in freshwater ecosystems.