A Comparative Survey of the Phytoplanktonic Flora in Three Lagoons in Southern Sri Lanka with Special Reference to their Usage as Biomonitors

Abstract

Sri Lanka is located in the Indian Ocean between the latitudes 5° 51′ and 9° 51′N and longitudes 79°41′ and 81°51′E. Themain island which is roughly pear shaped extends maximally 445 km North-South and 225 km East-West with a land area of 65,610 sq km. The island has a coastal plain which extends on all sides and a south-central mountainous region ranging from 900 m to a maximum of 2,524 m. Climate conditions in the island are affected by its proximity to the equator, elevation above sea level and the monsoons. Mean temperature below 150 m elevation ranges between 26°C and 28°C while in the upper montane zone above 1,500 m elevation, it ranges between 14°C and 19°C. The rainfall occurs during the two monsoons, namely the South-West monsoon between May to July and the North-East monsoon between December to February. Inter monsoonal rains are either convectional or depressional. The coastline of Sri Lanka is dotted with a large number of lagoons (Figure 23.1). Lagoons which are among the most productive ecosystems in the world, are not only biologically but also socio-economically important areas. As a result of the intensification of developmental activities in the coastal areas of Sri Lanka during the last few decades, a number of environmental and social problems, that threaten the lagoon environs have been envisaged.