Increasing Prevalence of Coral Health Issues in Narara Reef, Gulf of Kachchh

Coral health issues have increased significantly in recent decades due to climate change, rising sea temperatures, ocean acidification, and anthropogenic stressors, posing a major threat to reef ecosystems. The Gulf of Kachchh (GoK), known for its high turbidity caused by tidal currents, sediment influx, and coastal development, harbours marginal reefs that are increasingly vulnerable to thermal stress, disease outbreaks, and habitat degradation. To understand the stress levels on corals in these reefs, we recorded coral health issues over four years (2021 to 2024) by quantifying the prevalence of disease and health issues. Five sites in Narara Reef in the Gulf of Kachchh MNP were sampled periodically during the study duration. At each site, six replicate belt transects were established along the subtidal edge, aligned parallel to the shoreline. Four coral diseases namely yellow band disease, white syndrome, focal bleaching, and trematodiasis, and seven non-disease conditions, including fish predation, algal overgrowth, sponge overgrowth, CCA overgrowth, ascidian overgrowth, zooanthids overgrowth and worm infestation were identified. Of the 15 coral genera recorded, Porites was the most affected by health issues, which was also the second dominant genus next to Goniastrea. The prevalence of disease and coral health issues increased significantly, from 2.1% in 2021 to 5.6% in 2024 in the case of the former and from 7% to 23.1% in the latter, with non-disease health issues more widespread. Focal bleaching was the most common disease and was observed to be non-fatal to coral colonies, whereas sponge invasion was the most severe non-disease condition, with infected colonies experiencing complete mortality. These findings highlight the urgent need for targeted conservation efforts to keep disease and coral health issues in check.