An Assessment of Cyanobacterial Biodiversity in a Freshwater River System Associated with Thermal Discharge from a Power Station

Abstract

Free floating, unattached photosynthetic micro-organisms in water are together known as phytoplanktons. In an aquatic ecosystem phytoplanktons are the primary producers, the estimate of which can be used as water quality indicator (Gupta, 2007). Any change in water or environmental conditions can be detected by response of algae as they occur at first trophic level of food chain. Phytoplanktons possess short life cycle so they respond fast towards temperature changes (Trivedy, 1989). Being easily available, cheap in use, more convincing and informative, algae are used as bioindicators (Lata Dora et al., 2010). Changes in water quality of aquatic system can be studied through bioassessment (Smith, 1992). newline newline In phytoplankton community algae and blue-green algae form the important component. Blue-green algae have bluish green colour imparted by dominant phycocyanin pigment (Smith, 1994). But due to their close affinity to prokaryotic bacteria than to eukaryotic algae they are popularly known as cyanobacteria. The cells of cyanobacteria do not possess a well defined nucleus. newline newline Cyanobacteria are the most primitive, cosmopolitan, thallophytic, photosynthetic prokaryotic algae which came into existence almost 3.5 billion years ago. The evidence of their origin can be traced through carbon isotopic data and study of microfossils which states their dominance during Precambrian period (Lee, 2008; Whitton, 2012). newline newline They thrive well in variety of habitats from freshwater to marine, acidic to alkaline, hot water to soil, desert to snow so are cosmopolitan in nature (Smith, 1994). They grow best at temperature of 30°C to 40°C (Lata Dora et al., 2010). They are even able to tolerate temperatures more than 50 °C. Cyanobacteria like Synechococcus are even able to grow at temperature up to 73°C-74°C and are most thermophilic (Langford, 2001; Lee, 2008). These are the most successful organisms that are still in existence and are exploiting every possible extreme of habitats for billions of years since their existence (Dodds and Wh