Abstract:
There are seven species of marine turtles living in the world and five of them are
occurring in Sri Lanka. All those five species: Green Turtle (Chelonia mydas), Olive
Ridley (Lepidochelys olivacea), Hawksbill (Eretmochelys imbricata), Loggerhead
(Caretta caretta) and Leatherback (Dermochelys coriacea) are nesting on Southern
coastal belt of Sri Lanka and it comprises with largest marine turtle rookeries. Although,
many characteristics of beaches are affecting turtle nesting; sand composition, sand
porosity, vegetation cover, debris composition, soil temperature and soil pH level are
considered as majors. Here eight most prominent turtle nesting beaches on the Southern
coast: Yala, Bundala, Rekawa, Kalamatiya, Ussangoda, Habaraduwa, Mirissa, and
Kosgoda were selected to study the sand characteristics since there is a lack of studies
regarding this. The studied characteristics are sand porosity, sorting coefficient (Sφ) and
mean diameter (Mn φ) and sorting level of beaches by collecting sand samples using
piston core sampler up to 50cm depth level. Average sand porosities of different sites
were as 28.67, 43.86, 40.77, 50.56, 30.32, 42.51, 55.23 and 21.43% while average sorting
coefficient were as 0.56mm, 0.45mm, 0.60mm, 0.60mm, 0.77mm, 0.33mm, 0.95mm and
0.32mm respectively. Average mean diameters of sands of different sites were as
0.45mm, 0.34mm, 0.48mm, 0.50mm, 0.70mm, 0.24mm, 0.97mm and 0.23mm while
average sorting levels were as 1.09, 0.85, 0.91, 1.02, 0.97, 0.71, 0.87 and 0.69
respectively. Among these sites, Mirissa has the highest porosity, sorting coefficient and
mean diameter of sands. Yala and Kalamatiya have poorly sorted soil and other sites have
moderately sorted soil. According to the literature, Kosgoda and Rekawa have the highest
turtle nesting frequency. However, other characteristics of beaches and different turtle
populations have to be incorporated by conducting more researches to afford strong
inference on turtle nesting.
Keywords: Species, Coastal characteristics, Sand, Rekawa, Turtle population of Sri Lanka
