Constructed wetland mesocosms improve the biodegradation of microcystin-LR and cylindrospermopsin by indigenous bacterial consortia

Lasse Ahrenkiel Thyssen; Alba Martinez I Quer; Carlos Alberto Arias; Lea Ellegaard-Jensen; Pedro N Carvalho; Anders Johansen

doi:10.1016/j.hal.2023.102549

Constructed wetland mesocosms improve the biodegradation of microcystin-LR and cylindrospermopsin by indigenous bacterial consortia

Harmful Algae. 2024 Jan:131:102549. doi: 10.1016/j.hal.2023.102549. Epub 2023 Nov 27.

Authors

Lasse Ahrenkiel Thyssen¹, Alba Martinez I Quer¹, Carlos Alberto Arias², Lea Ellegaard-Jensen³, Pedro N Carvalho⁴, Anders Johansen³

Affiliations

¹ Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
² Department of Biology, Aarhus University, Ole Worms Allé 1, 8000 Aarhus C, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
³ Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
⁴ Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark. Electronic address: pedro.carvalho@envs.au.dk.

PMID: 38212082
DOI: 10.1016/j.hal.2023.102549

Abstract

Cyanobacterial blooms releasing harmful cyanotoxins, such as microcystin (MC) and cylindrospermopsin (CYN), are prominent threats to human and animal health. Constructed wetlands (CW) may be a nature-based solution for bioremediation of lake surface water containing cyanotoxins, due to its low-cost requirement of infrastructure and environmentally friendly operation. There is recent evidence that microcystin-LR (MC-LR) can efficiently be removed in CW microcosms where CYN degradation in CW is unknown. Likewise, the mechanistic background regarding cyanotoxins transformation in CW is not yet elucidated. In the present study, the objective was to compare MC-LR and CYN degradation efficiencies by two similar microbial communities obtained from CW mesocosms, by two different experiments setup: 1) in vitro batch experiment in serum bottles with an introduced CW community, and 2) degradation in CW mesocosms. In experiment 1) MC-LR and CYN were spiked at 100 µg L^-1 and in experiment 2) 200 µg L^-1 were spiked. Results showed that MC-LR was degraded to ≤1 µg L^-1 within seven days in both experiments. However, with a markedly higher degradation rate constant in the CW mesocosms (0.18 day^-1 and 0.75 day^-1, respectively). No CYN removal was detected in the in vitro incubations, whereas around 50 % of the spiked CYN was removed in the CW mesocosms. The microbial community responded markedly to the cyanotoxin treatment, with the most prominent increase of bacteria affiliated with Methylophilaceae (order: Methylophilales, phylum: Proteobacteria). The results strongly indicate that CWs can develop an active microbial community capable of efficient removal of MC-LR and CYN. However, the CW operational conditions need to be optimized to achieve a full CYN degradation. To the best of our knowledge, this study is the first to report the ability of CW mesocosms to degrade CYN.

Keywords: Bacterial degradation; Bioremediation; Cyanotoxins; Microbial community; Treatment wetlands.

MeSH terms

Alkaloids*
Animals
Bacterial Toxins* / metabolism
Biodegradation, Environmental
Cyanobacteria Toxins
Cyanobacteria* / metabolism
Humans
Marine Toxins*
Microcystins / analysis
Wetlands

Substances

cylindrospermopsin
cyanoginosin LR
Microcystins
Bacterial Toxins
Cyanobacteria Toxins
Alkaloids
Marine Toxins