Title : Ecological responses of coral reefs to marine heatwaves and cold spells in the tropical Indo-Pacific: A case from Lombok, Indonesia
Abstract:
Coral reefs are among the most biologically diverse and economically valuable marine ecosystems but increasingly threatened by climate change-related thermal stress events. This study examines the impacts of marine heatwaves (MHWs) and marine cold spells (MCSs) on coral reef assemblages of the Lombok Strait of Indonesia and the degree to which they induce coral bleaching and loss. Using 1998-2022 day-to-day sea surface temperature (SST) records, we identified and characterized MHW and MCS events by frequency, amplitude, and persistence. Fluctuations in coral cover were remotely estimated from Landsat imagery (Landsat 5, 6, and 7) and measured in situ through surveys conducted in 2016. We revealed that both MCSs and MHWs are primary drivers of coral bleaching, especially during years with extreme temperature anomalies. Notably, intense MCS events in 2000 and MHWs in 1998, 2016, and 2022 were simultaneous with widespread coral loss, with reef cover reducing by approximately 30%. Large-scale climate patterns, namely El Niño–Southern Oscillation (ENSO) phases, were also found to enhance thermal stress in key years, boosting bleaching and reef harm. Spatial analysis further indicated that vulnerability varied across reef zones, depending on regional oceanographic circulation. These findings highlight increasing intensity and frequency of thermal extremes in the area and their marked ecological effects. Apart from thermal stress, local anthropogenic stresses such as pollution and overfishing also increase coral reef loss. Our work highlights the urgent need for adaptive coral reef management and mitigation actions to counter global climate change as well as local stressors. Future research should aim to enhance monitoring efforts, explore synergistic environmental stressors, and develop predictive models to assess long-term ecosystem resilience in a warming ocean.
