Navegando por Autor "Lurling, Miquel"
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Artigo Effects of polyaluminum chloride and lanthanum-modified bentonite on the growth rates of three Cylindrospermopsis raciborskii strains(Public Library od Science, 2018-04-03) Becker, Vanessa; Araújo, Fabiana; Van Oosterhout, Frank; Attayde, José Luiz; Lurling, MiquelIn tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C.raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C.raciborskii in a test tube experiment and (2)impair C.raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of al lC.raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of al lstrains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C.raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C.raciborskii bloomsArtigo Is the future blue-green or brown? The effects of extreme events on phytoplankton dynamics in a semi-arid man-made lake(Springer, 2015-06-03) Becker, Vanessa; Medeiros, Luciana de Castro; Mattos, Arthur; Lurling, MiquelIn arid and semi-arid regions, a hydrological regime characterized by an annual cycle of drought and rainy seasons changes the volume and retention time of reservoirs. Such changes affect the limnological characteristics and lead to changes on phytoplankton community. Phytoplankton seasonal succession was studied in a Brazilian eutrophic semiarid water supply reservoir (Cruzeta). In this study, the changes in the biomass and species composition of phytoplankton during two annual hydrological cycles were analyzed, and the driving factors were evaluated.The composition of phytoplankton alternated between filamentous cyanobacteria, such as Cylindrospermopsis raciborskii, under conditions of mixing, and colonial species, such as Microcystis panniformis and Sphaerocavum brasiliensis, under conditions of high water column stability. The lower water level during a severe drought favored adaptive phytoplankton species with low requirement for resources, such as diatoms and cryptomonads. Extreme events, i.e., torrential rains and severe droughts, governed by the hydrological regime of the semi-arid region led to strong altered availability of resources in the watershed, directing the spatial and temporal dynamics of the phytoplankton in the Cruzeta man-made lake. The results showed an unusual behavior of the phytoplankton community contradicting the expectations about the climatic change scenario. Instead of an expected increase in cyanobacteria, the severe drought led to low biomass and resources, favoring diatoms and cryptomonads