Recruitment pattern of Scleractinian coral spats on neighbouring artificial substrates at Kurusadai Reef Complex, Gulf of Mannar, India

Abstract

This study was conducted to assess the recruitment rate of coral spats and other invertebrates near to the coral reef ecosystem of Gulf of Mannar. The reef region examined was at Kurusadai Reef Complex (Gulf of Mannar) for this assessment. There were two sets of invertebrate settlement tripods deployed and exposed at a depth of 2m. Seventy two settlement tiles measuring 20x20 cm in two different angles were fixed in these tripods in the benthic reef ecosystem. In order to assess the impact of Sea surface temperature on the invertebrate settlement, Onset Hobo Pendant® Temperature logger was also attached with the tripods. The sediment traps in duplicate were also erected in the study site to assess the sedimentation rate of the reef ecosystem. About 80% of recruited coral spats were observed on the tiles which were exposed at 60° angle. Principal component analysis also supported that the most influencing species were coral spats followed by barnacles and bivalves in the 60° angle exposed settlement tiles. It was also observed that the most influencing place of coral spats’ recruitment was on the inner tiles. The mean sedimentation rate observed was 14.6 ± 4.8 mg.cm−2.d−1. The lower density of coral spats observed on 90° and 60° angle exposed outer tiles might be due to the observed sedimentation rate and it is believed that coral spats preferred the shaded environment initially for further perpetuation in the environment. Moreover, Bray-Curtis cluster analysis supported that the coral spats found on the inner tiles having 80% similarity in this assessment. The coral spats found in this assessment were species from Pocilloporidae and Poritidae.