Quantitative observations of Cyanobacteria and Dinoflagellata in reservoirs of Sri Lanka

Abstract

Abstract:. Cyanobacterial and dinoflagellate blooms have a range of social, environmental and economic impacts due to their potential of toxin production under extreme environmental conditions. Therefore, the present study aimed to understand the species abundance, distribution and the relationship between species distribution and measured environmental variables within the 45 reservoirs studied, covering three major climatic regions of Sri Lanka (Wet, Intermediate and Dry). Plankton samples were obtained using a 34µm plankton net. Both field and laboratory analyses were conducted to obtain limnological data of each reservoir. Multivariate statistical techniques were used to understand the species distribution along measured environmental gradients. Thirteen species of Cyanobacteria were identified and seven of them were toxigenic. The Dry Zone showed the highest diversity of Cyanobacteria including toxigenic species and the Wet Zone showed the lowest. While Cylindrospermopsis raciborskii was the dominant species recorded in 22% of the sampled reservoirs, Pseudoanabaena limnetica was the least dominant. Only one species of Dinoflagellate, Peridinium aciculiferum was identified from all the climatic regions. Multivariate statistical analysis revealed that temperature is the most important environmental variable that determines the species variation and abundance among the sites.

Influence of hydrology on water quality and trophic state of irrigation reservoirs in Sri Lanka

“…Thus, it is imperative that a trade‐off is achieved in reservoir management to maintain water quality suitable for human consumption, while also supporting food fish production. This is particularly important because there are concerns about increasing trends of eutrophication in Sri Lankan reservoirs, resulting in a proliferation of toxigenic cyanobacteria such as Microcystis (Jayatissa et al, ; Senanayake & Yatigammana, ; Sethunge & Manage, ). In reservoirs in the Mekong River basin, for example, increased densities of bloom‐forming cyanobacteria ( Dolichospermum spp.)…”

“…Nutrient enrichment in reservoirs can cause noticeable changes in reservoir trophic status and may increase harmful algal blooms. Yatigammana and Cumming (2016) noted that Sri Lankan reservoirs could be categorized as phosphate-limited systems, although Jayatissa, Silva, McElhiney, and Lawton (2006) and Senanayake and Yatigammana (2017) argued that there would be a potential risk of increasing toxigenic algae such as Microcystis in irrigation reservoirs of Sri Lanka. This situation is even serious from a human health perspective because a proliferation of toxigenic algae in some Sri Lankan reservoirs that supply drinking water has been reported by Sethunge and Manage (2010).…”

Patterns, Trends and Drivers of Water Transparency in Sri Lanka Using Landsat 8 Observations and Google Earth Engine

“…The water quality variation in Sri Lanka was driven by several natural (geographical and climatic) and anthropogenic factors [14,17,19,20,38]. We categorized them two-fold: precipitation, temperature, wind speed, average water depth, elevation as natural drivers, and population density and Normalized Difference Vegetation Index (NDVI) as anthropogenic factors.…”

“…Here, we also showed that temperature was negatively associated with Z SD in intermediate zone reservoirs. This was probably due to the availability of favorable temperature conditions for the growth of phytoplankton in these reservoirs [17,58].…”

“…Z SD is still widely in use locally [8][9][10] and globally [11,12]. In Sri Lanka, there have been a limited number of in-situ Z SD based studies reported at reservoirs or river basin scale [13][14][15][16][17]. However, so far, an island wide comprehensive investigation of water transparency distribution and its dynamics has not been executed and remains unknown.…”