IDENTIFICATION AND CHARACTERIZATION OF BLOOM FORMING ALGAL SPECIES AND DEVELOPMENT OF REMOTE SENSING –  BASED PREDICTION MODELS FOR SRI LANKAN RESERVOIRS

Freshwaters are one of the most important natural resources on Earth. Globally, increased 
emergence of algal blooms in freshwaters has become one of the major reasons for water 
quality deterioration and thus, the importance of routing monitoring of waterbodies has 
been identified.   
However, the widely used, conventional monitoring strategies do not 
provide comprehensive overview on temporal and spatial variations in waterbodies. As a 
result, remote sensing is becoming an efficient, reliable and cost-effective method for 
bloom monitoring. The spectral signatures given by photosynthetic pigments such as 
chlorophyll-a of algae can be used to estimate pigment concentration in the bloom and to 
quantify algae cell density with the aid of remote sensing techniques. To our knowledge, 
any such attempt has not been taken in Sri Lanka to quantify algal blooms. Although, there 
are some successful stories reported from other countries, direct adoption of such models 
into Sri Lankan context would not provide an accurate prediction due to geographic 
limitations, detection range, atmospheric effects etc. Therefore, this study aimed to develop 
remote sensing-based prediction models with the aid of Landsat-8 and Sentinel-2 satellite 
imagery for detection and quantification of algal blooms in freshwater reservoirs in Sri 
Lanka through identification and characterization of bloom-forming algae. Bloom-forming 
algae were identified from 17 selected freshwater reservoirs across the country. 
Cyanobacteria were the most prominent bloom-forming algae while there was only one 
incident of Azadinium dinoflagellate bloom. Blooms of Azadinium has not been reported 
previously from Sri Lanka. None of the green algal blooms were found during the study. 
Among the cyanobacteria, Microcystis was the most frequent bloom-forming 
cyanobacterial genus. Microcystis blooms were always associated high concentrations of 
microcystin (MC) toxin, above the safe level (