Toxic cyanobacteria and microcystin dynamics in a tropical reservoir: assessing the influence of environmental variables
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GREEN TECHNOLOGIES FOR SUSTAINABLE WATER
Toxic cyanobacteria and microcystin dynamics in a tropical reservoir: assessing the influence of environmental variables Thanh-Luu Pham 1,2
&
Thi Hoang Yen Tran 2 & Kazuya Shimizu 3 & Qintong Li 4 & Motoo Utsumi 3
Received: 25 April 2020 / Accepted: 13 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Toxic cyanobacterial blooms (TCBs) have become a growing concern worldwide. The present study investigated the dynamic of toxic cyanobacteria and microcystin (MC) concentrations in the Tri An Reservoir (TAR), a tropical system in Vietnam, with quantitative real-time polymerase chain reaction (qPCR) and high-performance liquid chromatography (HPLC), respectively. The results of the qPCR quantification revealed that Microcystis was the dominant group and the primary MC producer in the TAR. Potentially toxigenic cyanobacteria varied from 1.2 × 104 to 1.58 × 107 cells/mL, and the mean proportion of toxic Microcystis to that of the total toxic cyanobacteria varied from 21 to 88%. Microcystin concentrations in raw water and sediment samples often peaked during June to October as blooms occurred and varied from 0.27 to 6.59 μg/L and from 1.79 to 544.9 ng/g in wet weight, respectively. The results of this study indicated that conditions favoring Microcystis proliferation lead to the selection of more toxic genotypes. Water temperature and light availability were not driving factor in the formation of TCBs in the TAR. However, the high loads of total nitrogen (TN), phosphate, and total phosphorus (TP) into the water via rainfall runoff in combination with a high total suspended solid (TSS) and decreased water level during the early months of the rainy seasons did lead to a shift in Microcystis blooms and higher proportions of toxic genotypes of Microcystis in the TAR. This research may provide more insight into the occurrence mechanism of TCBs in tropical waters. The strategy to control TCB problems in tropical regions should be focused on these limnological and hydrological parameters, in addition to a reduction in nitrogen and phosphorus loading. Keywords Harmful algae bloom . Cyanotoxins . Real-time PCR . Sediment
Introduction Toxic cyanobacterial blooms (TCBs) have become a worldwide problem, especially for countries that depend on surface
Responsible Editor: Vitor Manuel Oliveira Vasconcelos * Thanh-Luu Pham [email protected] 1
Ho Chi Minh City University of Technology (HUTECH), 475A Dien Bien Phu Street, Ward 25, Binh Thanh District, Ho Chi Minh City 700000, Vietnam
2
Institute of Tropical Biology, Vietnam Academy of Science and Technology (VAST), 85 Tran Quoc Toan Street, District 3, Ho Chi Minh City 700000, Vietnam
3
Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
4
Toyo University, 1-1-1 Izumino, Itakura-machi, Ora-gun, Gunma 374-0193, Japan
waters as drinking water resources (Gurbuz et al. 2016; Pham and Utsumi 2018; Te and Gin 2011), and the problem
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