Distribution pattern and community structure of zoanthids (Zoantharia) along the coast of Saurashtra, Gujarat, India

Coral reef environments support a great diversity of benthic organisms, of which zoanthids form an integral part. Studies have been carried out regarding the degradation of coral reefs and changes in community structure under the present dynamics of climatic change. Zoanthids are dominant among the observed fauna in these degrading reef ecosystems. Zoanthids are observed at mid and lower intertidal zones beyond 20 m from highest high tide level. In the present study, distribution patterns of zoanthid species along three coastal villages of Saurashtra coast, Gujarat were studied. Line intercept transect method was performed to assess the zoanthid coverage. A total of seven species of zoanthids were recorded during the survey. Palythoa mutuki formed the abundant species in the area with 45.99% coverage, followed by Zoanthus sansibaricus with 33.67% and Zoanthus cf. sansibaricus with 12.26% coverage. Abiotic parameters (sea surface temperature, salinity, dissolved oxygen, pH) and nutrient data (ammonia, phosphate, total suspended solids and nitrate) were also recorded during sampling to determine their influence on zoanthid colonies. Higher levels of DO were found to favour the growth of Palythoa mutuki and Isaurus tuberculatus, whereas increased SST was tolerated by Palythoa tuberculosa only. Ammonia and phosphate were negatively impacting the growth of Palythoa mutuki and Zoanthus spp. The study provides new information on quantitative zoanthid distribution and the dynamic changes exhibited by zoanthids in relation to various environmental parameters. Zoanthids could be looked upon as an adaptive species which may support reef resurgence in degraded reefs under stress from climate change effects.