CB - DBEZ - Artigos publicados em periódicos

URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/102

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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, Miquel
In 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 blooms
Shallow lake restoration and water quality management by the combined effects of polyaluminium chloride addition and benthivorous fish removal: a field mesocosm experiment
(Springer, 2015-12-10) Becker, Vanessa; Araújo, Fabiana
Polyaluminium chloride (PAC) has beenused in lake restoration and water quality management as a flocculent to remove algal biomass and organic matter from the water column and increase water transparency. However, benthivorous fish may suspend the sedimented flocs and reduce the efficiency of PAC in improving water quality. Therefore, we hypothesized that PAC is more efficient in reducing algal biomass, suspended solids and total phosphorus concentrations in the water, and increasing water transparency, when benthivorous fish is removed. To test this hypothesis, we performed a field experimentcombining the presence and absence of PAC (2 mg Al l-1) with the presence and absence of benthivorous fish (350 g m-2). Contrary to our hypothesis, no significant interactions were found between the effects of PAC addition and benthivorous fish removal on the measured variables. Both techniques significantly decreased chlorophyll a and phosphorus concentrations and increased water transparency, but their effects were independent of each other. The above results suggest that either of the treatments may improve water quality, but this goal would be better achieved by the combination of both techniques than by the application of one or other technique in isolation

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