Abstract
Yezin Dam is a man-made reservoir located close to Yezin village in Myanmar. Its water is used for irrigation, domestic purposes and as drinking water for many urban communities in the watershed area. In recent years, increased pollution due to the concurrent development around the dam has led to water quality deterioration. No detailed study on the distribution of cyanobacteria and toxin production has been conducted so far. In order to provide insight into the extent of cyanobacteria and cyanotoxins in the dam, water samples were collected once in January 2014 for the isolation of cyanobacterial strains and eight times between March 2017 and June 2018 for the investigation of physical, chemical and biological parameters. A total of 99 phytoplankton taxa belonging to 50 genera were recorded from Yezin Dam. Microscopic examination showed that a Dolichospermum sp. was the dominant cyanobacterium followed by small numbers of Microcystis, and Raphidiopsis raciborskii in all samples throughout the sampling period. 15 isolated cyanobacterial strains were classified morphologically and phylogenetically as Dolichospermum smithii, R. raciborskii and Microcystis and tested for microcystins (MCs), cylindrospermopsins (CYNs), saxitoxins (STXs) and anatoxins (ATXs) by liquid chromatography-tandem mass spectrometry (LC–MS/MS) and enzyme-linked immunosorbent assay (ELISA). The toxin analysis of all isolated Dolichospermum strains by ELISA and LC–MS did not indicate the presence of ATXs, STXs, CYNs nor MCs. Four of the five isolated Raphidiopsis strains produced CYN and deoxyCYN. One of the isolated Microcystis strains (AB2017/08) from Yezin Dam produced 22 MC congeners. Concentrations of 0.12 μg L−1 CYNs and 0.34 μg L−1 MCs were also found in an environmental sample from Yezin Dam by ELISA. The potential therefore exists for the use of untreated water from Yezin Dam to cause harmful effects on humans, domestic and wild animals.
Highlights
Like other countries in Asia, Myanmar’s economy is based on agri culture
Water samples were collected once in January 2014 for the isolation of cyanobacterial strains, 8 times between March 2017 and June 2018 for phytoplankton analyses and isolation of cyanobacterial strains and once in February 2020 to test for anatoxins, cylin drospermopsins, microcystins and saxitoxins using enzyme-linked immunosorbent assay (ELISA)
99 phytoplankton taxa belonging to 50 genera and 10 classes were identified in water samples from Yezin Dam
Summary
Myanmar has made vast investments in the construction of irrigation dams throughout the country to enhance the availability of water for irrigation during the dry season to increase agricultural pro duction and socioeconomic development (Oo et al, 2017). Sewage discharge and agricultural runoff are the main causes of eutrophication, and harmful algal and cyanobacterial blooms in these water bodies lead to deterioration in water quality and ecosystem health. One recent study has described in detail the presence of cyanobacteria and cyanobacterial toxins, in Meiktila Lake close to the city of Meiktila in Myanmar Application of RS/GIS for the assessment of Yezin Dam Watershed area. Forest Research Institute, Ministry of Forestry, Myanmar accessed on 16 September 2020. https://forestdepar tment.gov.mm/books/research/application-rsgis-assessment-yezin-dam-watersh ed-area
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