Sedimentation Patterns of Toxin-Producing Microcystis Morphospecies in Freshwater Reservoirs

Abstract

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.

First Evidence of Potential Toxic Cyanobacteria in the Water-Sediment Interface of a Tropical Drinking Water Reservoir

“…This behavior has been associated with the presence of mucilage in their colonies (Bauza and Giannuzzi 2011). Microcystis is one of the best-studied genera: in temperate zones it has a benthic phase during its life cycle and has the ability to form blooms and to produce microcystins in freshwater ecosystems, affecting the water quality management (Cirés et al 2013); it is also one of the most reported in tropical environments, America not being the exception (Mowe et al 2014, Aguilera et al 2018. The study in the Riogrande II reservoir confirmed that cyanobacteria can survive in a 23-m depth.…”

“…Cyanobacteria of the Chroococcales order, such as the genera Microcystis, dominate the taxocenosis of the phytoplankton in several eutrophic aquatic ecosystems Blomqvist 2002, Misson andLatour 2012). Although they do not form resistance structures as Nostocales, they can survive as inactive colonies in surface sediments as part of their cycle life (Head et al 1999, Ståhl-Delbanco et al 2003, Cirés et al 2013, keeping some cellular activity, the colonial and cellular structure and its microcystin content (Tsujimura et al 2000, Misson andLatour 2012).…”

Monitoring and removal of cyanobacterial toxins from drinking water by algal-activated carbon

“…These problems include taste and odor production, clogging of filters, interference with coagulation and flocculation processes, and passage into distribution systems (Dugan and Williams, 2006). It is becoming increasingly clear that almost every part of the world depending on surface waters have or will encounter problems with toxic cyanobacteria in its drinking water system (Cirés et al, 2013; Hoeger et al, 2005). They are well known to produce a set of potent toxins including microcystins (MCs), nodularins, and cylindrospermopsin (Agha et al, 2013; Codd et al, 2005; Taylor et al, 2014).…”

Características ambientales, composición del fitoplancton y variación temporal de microcistina-LR disuelta en el embalse de As Forcadas (Galicia, NW España)

“…La presencia de M. aeruginosa es común en los embalses de la Península Ibérica (Vasconcelos et al 1995(Vasconcelos et al , 1996Vasconcelos 2001;De Hoyos et al, 2004;Carrasco et al, 2006;Cobo et al, 2012;Cirés et al, 2013aCirés et al, , 2013bAgha Frías, 2013) y bajo ciertas condiciones (temperatura, luz, estratificación del agua, etc. ), puede dar lugar a afloramientos excepcionales, sobre todo en los meses de septiembre a octubre, acompañadas frecuentemente de casos de toxicidad (Cobo et al, 2012).…”