Distribution and diversity of reef associated organisms in the Andaman Islands

Abstract

The sensitivity of coral reef ecosystems to natural and anthropogenic stresses makes them vulnerable to changes such as global warming. As a result, coral reef ecosystems need to be prioritized for conservation action. Thus, monitoring their health is essential to understand the impact of human activities on the ocean. However, documenting marine biodiversity is logistically challenging, and in addition, many taxa may be difficult to identify in the field. To overcome these challenges, novel methodologies like ARMS (Autonomous Reef Monitoring Structures) provide a standardized protocol to monitor reef ecosystems worldwide. This study aimed to explore the cryptic biodiversity of the Andaman Islands using the ARMS methodology, the first such initiative in the Indian subcontinent. This project aimed to study the differences in the colonization of sessile assemblages at two sites with different anthropogenic pressures and sedimentation rates. In addition, we aimed to examine the differences in colonization patterns within the units, where each category of plates provides a different habitat for the sessile assemblages. In total, ten ARMS units were recovered and analyzed using photographic analysis. I used photographic analysis to document the occurrence of different species on the plates and units; the percentage cover for the six most commonly observed taxa was determined using Coral Point Count Excel extension software (CPCe). The results showed that the inter-site differences in sedimentation and anthropogenic stresses did not induce a change in the colonization patterns of the observed taxa. On the other hand, the plate orientation (PO) and the spacer type (ST) resulted in distinct colonization patterns. Sessile suspension feeders dominated most of the bottom-facing plates, whereas polychaete tubes and algae dominated most of the top-facing plates. Although the contrast in the colonization was apparent for the top and bottom surfaces, there was large variation in cover across all plates. In conclusion, different ARMS ‘microhabitats’ revealed colonization preferences of the observed taxa for surface orientation, irrespective of the site locations.