Publication Abstract

Rising atmospheric CO₂ levels have significantly increased ocean acidification, endangering coral reefs. This study was carried out to assess the prevailing Ocean Acidification (OA) level around the Sri Lankan coral reef areas using Aragonite Saturation Level (Ω_Ar) as an indicator and also analyzed the Nitrate (NO₃^-) and Phosphate (PO₄^3-) concentration over the coral reef sites. This study was conducted on coral reefs on the eastern coast (EC), southern coast (SC), northern coast (NC), and west coast (WC) of Sri Lanka during the April to June period in 2024. The Ω_Ar were supersaturated (Ω_Ar > 1), and which range from 2.98±0.04 to 4.92±0.12. The NC of Sri Lanka associated with significantly lower Ω_Ar (3.2±0.64), which was below the ecological threshold (3.5-3.6) may be due to the ocean currents. During the study period country's study sites Ω_Ar did not hit 2.92±0.16, meaning the country’s coral ecosystem was not susceptible to degradation. The NO₃^- concentrations of 2-5 μmol L^-1 were generated from human activities, which may intensify coral bleaching during heat stress. The study result showed that SC (2.19±1.28 µmol L^-1) and WC (3.52±1.48) had NO₃^- above range may be due to waste discharge, anthropogenic activities, and high runoff. The data confirmed significantly higher PO₄^3- concentrations in EC (0.35±0.07 µmol L^-1). The OA risk assessment confirmed that anthropogenically driven climate change are high risk to the coral reef ecosystems that impact on key species, coral habitats, and society in Sri Lanka. Lowering the coral calcification rate and reproduction, and damaging the breeding ground of the coral-associated species are the most prioritized OA risks.

R.S.P.K. Abhishek^{1 2}, E.P.D.N. Thilakarathne², R.S.M. Samarasekara³, Piyali Chowdhury⁴, K. Reinursha¹, Meththika Vithanage^1*