Intertidal Molluscan Diversity of Thirumullavaram, Kerala, India

Abstract

Intertidal molluscs are benthic macroinvertebrates that are integral to most intertidal ecosystems. Molluscan diversity along the coast of Thirumullavaram was surveyed for a period of one year (January to December 2021). Specimens were collected during the low tide for each month at four sampling stations through the quadrat method and random handpicking. The samples were photo-documented and preserved in 5% formalin. The collected specimens were identified and classified taxonomically using standard keys and references. A total of 27 species of molluscans were identified during the study period. 17 species were identified from Class Gastropoda, which comprised three orders and 12 families. Littoraria scabra was the most numerous gastropod found in all stations. Class Bivalvia was represented by eight species belonging to six families and five orders. Only two species were identified from Class Polyplacophora. 23 species were recorded from Station 1, an undisturbed area, followed by Station 2 with 20 species and station 3 with 13 species. The least was observed in Station 4 (11 species), where heavy human activities were noted. Various diversity indices were estimated for each sampling station. The Shannon-Weiner Diversity index (H') ranged from 1.14 to 1.55 among the sampling stations. Margalef diversity index was in the higher side for Station 1 and 3 (2.97 and 2.77 respectively) when compared to Stations 3 and 4 (1.82 and 1.57 respectively). The comparative assessment of the relative abundance of the molluscan assemblage revealed that, it did not vary significantly (P>0.05) among the four sampling stations. Littoraria scabra, L. undulata and Patella notata were obtained throughout the study period. Intertidal molluscans play important roles in ecosystem functioning by serving as food resources, promoting intertidal seaweed-litter decomposition, and nutrient cycling. Furthermore, they are acting as ecological indicators of microhabitats, hence continuous monitoring is highly recommended for enabling the conservation of their habitat.