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Toxins 2013, 5(5), 939-957;

Sedimentation Patterns of Toxin-Producing Microcystis Morphospecies in Freshwater Reservoirs

Departamento de Biología, Universidad Autónoma de Madrid, C/Darwin, 2, Madrid 28049, Spain
Author to whom correspondence should be addressed.
Received: 21 February 2013 / Revised: 16 April 2013 / Accepted: 22 April 2013 / Published: 3 May 2013
(This article belongs to the Special Issue Cyanotoxins)
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Understanding the annual cycle of Microcystis is essential for managing the blooms of this toxic cyanobacterium. The current work investigated the sedimentation of microcystin-producing Microcystis spp. in three reservoirs from Central Spain during the summer and autumn of 2006 and 2007. We confirmed remarkable settling fluxes during and after blooms ranging 106–109 cells m−2 d−1, which might represent 0.1%–7.6% of the organic matter settled. A comprehensive analysis of the Valmayor reservoir showed average Microcystis settling rates (0.04 d−1) and velocities (0.7 m d−1) that resembled toxin settling in the same reservoir and were above most reported elsewhere. M. aeruginosa settling rate was significantly higher than that of M. novacekii and M. flos-aquae. Despite the fact that colony sizes did not differ significantly in their average settling rates, we observed extremely high and low rates in large colonies (>5000 cells) and a greater influence of a drop in temperature on small colonies (<1000 cells). We found a 4–14 fold decrease in microcystin cell quota in settling Microcystis of the Cogotas and Valmayor reservoirs compared with pelagic populations, and the hypothetical causes of this are discussed. Our study provides novel data on Microcystis settling patterns in Mediterranean Europe and highlights the need for including morphological, chemotypical and physiological criteria to address the sedimentation of complex Microcystis populations. View Full-Text
Keywords: Microcystis; microcystins; hepatotoxins; sedimentation; settling; water reservoirs; annual cycle Microcystis; microcystins; hepatotoxins; sedimentation; settling; water reservoirs; annual cycle

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Cirés, S.; Wörmer, L.; Carrasco, D.; Quesada, A. Sedimentation Patterns of Toxin-Producing Microcystis Morphospecies in Freshwater Reservoirs. Toxins 2013, 5, 939-957.

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