Diversity of Sponges in Marine Protected Areas of North Andaman, India

The continental shelf of the Andaman and Nicobar Islands harbours rich sponge diversity. Despite being one of the most important components of the reef ecosystem, comprehensive inventories of marine sponges of the protected areas of these Islands are still lacking. The present study was devoted to provide an outline of the sponge species composition of the island sanctuaries and adjoining areas of North Andaman and to compare the species assemblage from east and west coasts. The intertidal and subtidal sponges were surveyed from 41 sites covered under 23 locations (17 island sanctuaries and 6 undesignated locations) during March 2016 - September 2017. A total of 43 sponges distributed among 16 orders, 25 families and 35 genera were identified and recorded. The number of sponges per location was ranging from 6 to 20 in the east coast with a mean (mean +/- SE) of 14 +/- 2.07 and 3 to 21 in the west coast with a mean of 9.13 +/- 1.44, indicating a significant difference on a spatial scale, notwithstanding the geographical proximity of the survey locations. Haplosclerida was the most represented order (9 species), contributing approximately 21% to the total sponge biodiversity, followed by Axinellida and Dictyoceratida (6 species). Two species namely, Carteriospongia foliascens (18 locations) followed by Neopetrosia exigua (16 locations) were dominant from the survey locations, indicating their ubiquitous occurrences throughout the survey locations. Sixteen growth forms were observed of which, cushions were the most dominant growth form (18.6%) followed by thin sheets (16.28%) and massive-globose (11.63%), suggestive of their survival ability in the coral-reef environments. Nevertheless, the significant differences in the species composition and growth forms among the survey locations are likely to be attributed to numerous ecological and environmental factors. Further research on sponges should be devoted in understanding their interaction with other fauna.