Diversity of mollusca in disturbed and undisturbed mangrove ecosystems of Tumpat, Kelantan.

Mangrove forest is one of the most important ecosystems in the world because of its significant role in the environment and fisheries. Molluscs of commercial importance comprise the biodiversity and secondary productivity of mangrove forest. Molluscs were studied in disturbed and undisturbed mangrove ecosystems of Tumpat Delta Kelantan and the study were conducted from October to November 2016. The diversity of mollusca was determined in disturbed and undisturbed area of Tumpat Delta. Molluscs in both sites were collected using dredging method when at high tide and gleaning method when at low tide. The biodiversity indices used in this research are Shannon- Wiener Index (H’), Pielou’s Evenness Index (J’) and Margalef’s Diversity Index (Dmg) to identify the diversity. Total species collected at disturbed and undisturbed areas were 14 species which is 6 species found in disturbed and 13 species found in undisturbed. Among 14 species of molluscs obtained, 5 species were from class Bivalvia and 9 species from class Gastropoda. The highest value for (H’) was represented in undisturbed area which was 1.99. The evenness value (J’) was higher in disturbed area
that represent 0.26 while undisturbed area was 0.15 but in generally for both area was not well distributed because their value was nearly to the lowest range. Dmg value was higher in undisturbed area of mangrove ecosystems with 1.94 while in disturbed area it was recorded 0.82. In term of size, the biggest species for both areas is Telescopium telescopium which is 7.62cm that represented in undisturbed area and 6.85cm in disturbed area while the smallest species is Cerithedia cingulata which is 1.56cm for disturbed area and 1.6cm for undisturbed area. The difference in growth of molluscs species in ecosystems depends on the quality and quantity of available food resources. It appears that the higher population density has effect on mollusca species growth. Undisturbed area have higher ecosystems diversity compared to the disturbed areas in mangrove ecosystems in Tumpat Delta Kelantan. This study also can be improved by adding more data analysis calculations to get specific information in details and varying the research in effective ways.