Chitosan as coagulant on cyanobacteria in lake restoration management may cause rapid cell lysis. (1st July 2017)

• Record Type: Journal Article
• Authors: Mucci, Maíra; Noyma, Natalia Pessoa; de Magalhães, Leonardo; Miranda, Marcela; van Oosterhout, Frank; Guedes, Iamê Alves; Huszar, Vera L.M.; Marinho, Marcelo Manzi; Lürling, Miquel
• Is Part Of: Water research. Volume 118(2017)
• Page Start: 121
• Page End: 130
• Publication Date: 2017-07-01
• Subjects: Cell lysis -- Cell viability -- Cyanobacterial blooms -- Eutrophication -- Lake restoration -- Photosystem II efficiency; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2017.04.020
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Combining coagulant and ballast to remove cyanobacteria from the water column is a promising restoration technique to mitigate cyanobacterial nuisance in surface waters. The organic, biodegradable polymer chitosan has been promoted as a coagulant and is viewed as non-toxic. In this study, we show that chitosan may rapidly compromise membrane integrity and kill certain cyanobacteria leading to release of cell contents in the water. A strain of Cylindrospermopsis raciborskii and one strain of Planktothrix agardhii were most sensitive. A 1.3 h exposure to a low dose of 0.5 mg l −1 chitosan already almost completely killed these cultures resulting in release of cell contents. After 24 h, reductions in PSII efficiencies of all cyanobacteria tested were observed. EC50 values varied from around 0.5 mg l −1 chitosan for the two sensitive strains, via about 5 mg l −1 chitosan for an Aphanizomenon flos-aquae strain, a toxic P. agardhii strain and two Anabaena cylindrica cultures, to more than 8 mg l −1 chitosan for a Microcystis aeruginosa strain and another A. flos-aquae strain. Differences in sensitivity to chitosan might be related to polymeric substances that surround cyanobacteria. Rapid lysis of toxic strains is likely and when chitosan flocking and sinking of cyanobacteria is considered in lake restoration, flocculation efficacy studies should be complemented with investigation on the effects of chitosan on the cyanobacteria assemblage being targeted. Graphical abstract: Highlights: Controlling cyanobacteria with chitosan has been proposed in lake restoration. Chitosan damages membranes of certain cyanobacterial strains rapidly. Cell contents like pigments are released from the damaged and dying cells. Effects of chitosan should be tested prior to each lake restoration application.