Physiological responses of Microcystis aeruginosa NIES-843 (cyanobacterium) under the stress of chitosan modified kaolinite (CMK) loading.

Flocculation with clays is a promising and environmentally friendly way to remove algal blooms. Physiological responses of Microcystis aeruginosa NIES-843 under the stress of chitosan modified kaolinite (CMK) loading were first reported in this paper. Compared with the control, the contents of chlorophyll a (Chl a) and carotenoids showed no significant difference at a CMK loading of 40 mg/l, but the phycocyanin content was significant lower than the control at this loading level. The contents of Chl a, carotenoids, phycocyanin and allophycocyanin were all significantly lower than the control at 80 and 160 mg/l CMK, and the leakage of phycobilins occurred at these two loading levels suggesting that flocculation with CMK could cause the damage of cellular membranes. The activities of extracellular alkaline phosphatase activity (E-APA), superoxide dismutase (SOD) and catalase (CAT) were all dramatically boosted under the stress of CMK loading. The changes of cellular dehydrogenase activity exhibited the same trends as of Chl a and carotenoids, and it decreased to the levels of lower than detectable limits on 12 and 8th day at a CMK loading of 80 and 160 mg/l, respectively. These results indicated that flocculation with CMK could cause cell mortality of M. aeruginosa.