Resilience-Based Assessment of Shallow Water Patchy Reefs in Palk Bay of South East Coast of India

The health of coral reefs in Palk Bay has been influenced by several natural and anthropogenic stressors over the last four decades. This study assessed the resilience potential of Scleractinian corals and their associated biota in Palk Bay to understand the corals' capacity for resistance and provide a detailed account of positive and negative factors that drive reef health to deliver suggestions for management action. In the present study, the survey on underwater marine fauna was conducted using line intercept transect and quadrat sampling methods at four locations in Palk Bay from February 2022 to February 2023. During the current course of investigation, a total of 26 coral species belonging to 8 families and 14 genera were documented. The overall percentage of live coral cover in Palk Bay was recorded as 30.83 ± 2.40, and massive coral forms were found to be the most dominant in all the study sites. Matrix plot on the distribution of juvenile corals in different study sites revealed a higher density of juvenile corals (> 1 indv/m²) in the Vedhalai and Vadakkad sites along Palk Bay. The overall resilience score (0.62) for the Palk Bay reefs was in the medium range (0.60–0.79), indicating that the reef's ecological integrity is currently compromised by several ongoing threats. Macroalgal proliferation (20.00 ± 2.40) is the most serious threat to all of Palk Bay's reefs, although animal invasion (9.25 ± 1.98), sedimentation (7.40 ± 1.30), coral disease (9.45 ± 0.93), and ghost nets (5.35 ± 0.87) are also exerting a detrimental effect on the reef system. In addition, the present study concludes that despite the presence of active threats in Palk Bay, the evidence of resistant coral species, a moderate percentage of live benthic cover, connectivity to the fish assemblage, and survival of young or juvenile coral species will contribute to the recovery potential of Palk Bay reefs and strengthen reef resilience.