Abstract
Mitigation of harmful cyanobacterial blooms that constitute a serious threat to water quality, particularly in eutrophic water, such as in aquaculture, is essential. Thus, in this study, we tested the efficacy of selected cyanocides towards bloom control in laboratory and outdoor mesocosm experiments. Specifically, we focused on the applicability of a group of cationic disinfectants, alkyltrimethyl ammonium (ATMA) compounds and H2O2. The biocidal effect of four ATMA cations with different alkyl chain lengths was evaluated ex situ using Microcystis colonies collected from a fish pond. The most effective compound, octadecyl trimethyl ammonium (ODTMA), was further evaluated for its selectivity towards 24 cyanobacteria and eukaryotic algae species, including Cyanobacteria, Chlorophyta, Bacillariophyta, Euglenozoa and Cryptophyta. The results indicated selective inhibition of cyanobacteria by ODTMA-Br (C18) on both Chroccocales and Nostocales, but a minor effect on Chlorophytes and Bacillariophytes. The efficacy of ODTMA-Br (C18) (6.4 μM) in mitigating the Microcystis population was compared with that of a single low dose of H2O2 treatments (117.6 μM). ODTMA-Br (C18) suppressed the regrowth of Microcystis for a longer duration than did H2O2. The results suggested that ODTMA-Br (C18) may be used as an effective cyanocide and that it is worth further evaluating this group of cationic compounds as a treatment to mitigate cyanobacterial blooms in aquaculture.
Highlights
IntroductionPhosphorus and other nutrients make cyanobacteria proliferate exceptionally
It was reported that alkyltrimethyl ammonium (ATMA) cations with longer alkyl chain exhibit stronger cyanocidal effect on unicellular Microcystis cultures [21]
Microcystis colonies, the effectiveness of ATMA with alkyl chain length (C12 to C18) was examined using colonies collected in fish ponds
Summary
Phosphorus and other nutrients make cyanobacteria proliferate exceptionally. The massive accumulation of cyanobacterial biomass can damage water quality [1]. Some cyanobacteria are known to produce toxic secondary metabolites, such as microcystins, which can be harmful to zooplankton, fish and even humans [2,3]. Extensive feeding protocols lead to water hyper-eutrophication that facilitates frequent and persistent occurrence of cyanobacterial harmful algal blooms (cyanoHABs). Continuous pond aeration is usually required to eliminate hypoxia or anoxic conditions resulting from large amounts of photosynthetic and respiratory activities (respectively) caused by large water blooms, as well as the associated additional costs in Microorganisms 2021, 9, 2258.
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