A correlation study of algal diversity with reef characteristics of Akurala reef in the Southwest coast of Sri Lanka

Abstract

Akurala (N 06°. l l l-E 80°. 04l) reef is located approximately 90.5 km south o f Colombo. The reef forms part o f a fringe o f sandstone. It is about 35 m wide and does not slope gently from land to sea. The seaward face o f this platform is practically vertical. Even little wave action can cover the entire reef. However, waves break with fa irregularity on the seaward edge and then the water washes over most o f the platform. The reef can be recognized into 3 distinct zones described as Zone 1 - which is a Patchy Seaweed Zone in the inner part o f the reef flat, which is dug into a shallow basin and covered by a thin sheet o f water at low tide, Zone 2 ,which is the Corallinaceae Zone consisting o f calcareous elements with a fla t leveled top and Zone 3 ,where the Reef Glacis is slightly inclined seawards and exposed at low water o f springtide. A quantitative and a qualitative survey o f marine algae present on the reef was carried out at monthly intervals. A total o f 44 macroalgal taxa belonging to 25 genera and 19 families were recorded. O f them, 18 taxa belonged to the Chlorophyta,, 5 to the Phaeophyta a n d 21 to the Rhodophyta..Ulva Fasciata, Cheilosporum cultratum and Gracilaria hikkaduwa sis were the most abundant species. An observed feature was the seasonal variation o f the number o f species on the 3 biotopes