Genetic diversity of Microcystis blooms (Cyanobacteria) in recently constructed reservoirs in Tigray (Northern Ethiopia) assessed by rDNA ITS
van Gremberghe, Ineke × Van der Gucht, Katleen Vanormelingen, Pieter Asmelash, Tsehaye Dejenie, Tadesse D'hondt, Sofie Declerck, Steven De Meester, Luc Vyverman, Wim #
Kluwer Academic Publishers
Aquatic Ecology vol:45 issue:2 pages:289-306
The cyanobacterium Microcystis is notorious for forming extensive and potentially toxic blooms in nutrient-rich freshwater bodies worldwide. However, little is known about the factors underlying the genetic diversity and structure of natural Microcystis populations, despite the fact that this knowledge is essential to understand the build-up of blooms. Microcystis blooms are common and occur year-round in Africa, but are underinvestigated in this continent. We studied the genetic diversity and structure of Microcystis populations in 30 man-made reservoirs in Tigray (Northern Ethiopia) using Denaturing Gradient Gel Electrophoresis of the 16S-23S rDNA internal transcribed spacer (ITS) region and assessed the importance of local environmental conditions and geographic position of the reservoirs for the observed patterns. The analyses showed that both regional and local Microcystis ITS diversity in these recently constructed reservoirs was relatively low, with several dense blooms containing only a single ITS type. Especially one non-toxic ITS type dominated a considerable fraction of Microcystis blooms, but appeared restricted in its geographic distribution. The relationship between Microcystis ITS population structure and abiotic variables (water clarity, pH) and with zooplankton (Daphnia biomass) indicates a (limited) influence of environmental conditions on Microcystis population structure in the reservoirs of Tigray.