The global climate crisis has heightened the urgency for developing interventions to enhance resilience and recovery of coral reef ecosystems. However, research programs are often bottlenecked by availability of coral early life stage material due to the annual nature of coral mass spawning. We present a proof-of-concept of “out-of-season” spawning, utilising aquarium control technology to induce spawning in multiple Great Barrier Reef (GBR) corals held in long-term indoor aquaria. By applying a 6-month offset environmental profile encompassing seasonal temperature, photoperiod, and lunar cues, we induced synchronised coral spawning during austral autumn/winter between 2022-2023. We also “phase-shifted” the hour of sunset by four hours on spawning nights, creating a more favourable time window (i.e., minimising late nights) for gamete fertilisation. Spawning occurred on comparable nights after full moon (NAFM) and at similar times after sunset (TAS) to wild conspecifics, with 2023 cohorts showing the closest alignment. Gamete fertilisation was successful for six species: Acropora millepora, Acropora loripes, Acropora hyacinthus, Acropora elseyi, Acropora austera, and Montipora aequituberculata producing ~1.8 million larvae. We outline physiological insights into environmental regulation of coral spawning synchronicity and discuss the potential for out-of-season spawning to accelerate coral research and enhance reef restoration programs.

Little is known about the potential for acclimatization or adaptation of corals to ocean acidification and even less about the molecular mechanisms underpinning these processes. Here we examine global gene expression patterns in corals and their intracellular algal symbionts from two replicate population pairs in Papua New Guinea that have undergone long-term acclimatization to natural variation in pCO2. In the coral host, only 61 genes were differentially expressed in response to pCO2 environment, but the pattern of change was highly consistent between replicate populations, likely reflecting the core expression homeostasis response to ocean acidification. Functional annotations highlight lipid metabolism and a change in the stress response capacity of corals as key parts of this process. Specifically, constitutive downregulation of molecular chaperones was observed, which may impact response to combined climate-change related stressors. Elevated CO2 has been hypothesized to benefit photosynthetic organisms but expression changes of in hospite Symbiodinium in response to acidification were greater and less consistent among reef populations. This population-specific response suggests hosts may need to adapt not only to an acidified environment, but also to changes in their Symbiodinium populations that may not be consistent among environments, adding another challenging dimension to the physiological process of coping with climate change.