Effects of polyaluminum chloride and lanthanum-modified bentonite on the growth rates of three Cylindrospermopsis raciborskii strains

Fabiana Araújo,José Luiz Attayde,Miquel Lürling,Vanessa Becker,Frank Van Oosterhout

doi:10.1371/journal.pone.0195359

Fabiana Araújo, José Luiz Attayde + Show 3 more

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https://doi.org/10.1371/journal.pone.0195359

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Abstract

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 all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, 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.

Highlights

The eutrophication of lakes and reservoirs often leads to blooms of cyanobacteria, which is considered the most important water quality problem worldwide [1,2]
The polyaluminum chloride (PAC) treatment caused a substantial increase in CHL-a of the top samples of the Brazilian and French strains (Fig 1a and 1b), while a minor increase was observed for the German strain (Fig 1c)
The combined addition of PAC and lanthanum-modified bentonite (LMB) resulted in a decreased turbidity in the top samples and an increase in turbidity in the bottom samples (Fig 1d–1f)

Summary

Introduction

The eutrophication of lakes and reservoirs often leads to blooms of cyanobacteria, which is considered the most important water quality problem worldwide [1,2]. Due to their toxicity, cyanobacteria blooms and their associated surface scums render water from freshwater. Effects of PAC and LMB on growth of C. raciborskii the flag of the CAPES (Brazil)/Wageningen University (The Netherlands): CAPES-WUR project 004/2008. Preparation of the manuscript was supported by the Conselho Nacional de Desenvolvimento Cientıfico e Tecnologico (CNPq) Process Number: Universal 407783/2016-4. The funders had no role in study design, data colletion and analysis, decision to publish, or preparation of the manuscript

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