Decoding coral resilience: Transcriptomic and physio-biochemical responses of Duncanopsammia peltata to anthropogenic pressures, with a focus on nutrient overload

Coral reefs, vital marine ecosystems confronted with accelerated degradation under climate change and anthropogenic pressures, exhibit vulnerability to nutrient perturbations. While existing studies have documented the macro-level impacts of nutrient enrichment on corals, their molecular mechanisms remain unclear. Integrating transcriptomics (full-length and next-generation sequencing) with physio-biochemical analyses, this study compared adaptive responses in a stress-tolerant coral species (Duncanopsammia peltata) across three different environmental contexts including a protected area (PA) with minimal anthropogenic disturbance, a non-protected area (NPA) with high human activity impacts, as well as a controlled laboratory environment (LAB) simulating chronic hypernutrient conditions. Our results showed that, compared to PA samples, corals showed reduced photosynthetic efficiency and downregulated fatty acid metabolism-related pathways in both NPA and LAB. Furthermore, corals from the NPA exhibited decreased antioxidant enzyme activity and elevated malondialdehyde levels (an indicator of lipid peroxidation), demonstrating compromised antioxidant capacity and oxidative damage. While immunosuppression was observed in LAB corals (decreased flna/b/c and nfkb1 expression and alkaline phosphatase activity), nutrient stress adaptation was mediated through upregulation of detoxification genes (gstu20, mgst1, and mgst3), along with enhanced antioxidant levels and oxidative phosphorylation pathways. Additionally, a 96-h acute nutrient stress experiment under laboratory conditions further revealed rapid dynamic regulation of the antioxidant system and immune responses to nutrient overload, highlighting D. peltata's plasticity. These findings reveal a coordinated adaptive strategy in corals facing environmental stressors and provide molecular and physio-biochemical insights for coastal ecosystem conservation.