Global climate change poses a severe threat to tropical coral reefs, prompting the poleward range expansion of reef-building corals into higher-latitude habitats. Driven by warming and ocean currents, these corals are increasingly replacing temperate kelp forests in regions such as Shikoku Island, Japan. While these emergent temperate reefs may serve as crucial thermal refugia, they present novel environmental challenges, notably colder winter temperatures and higher seasonal variability. Although the physiological adaptations of migrating corals and reef fishes have been largely documented, the thermal tolerances and metabolic adjustments of the migrating coral-associated macroinvertebrates remain overlooked, representing a critical knowledge gap. This study aims to assess the impact of these marginal thermal conditions on the metabolic performance of coral-associated macroinvertebrates and to identify potential physiological mismatches between their thermal tolerances and those of their host corals. The research focuses on a temperate emergent community model comprising the coral host Pocillopora sp. alongside three vital invertebrates from interacting functional groups: Drupella sp. (an obligate corallivorous snail), Diadema setosum (an opportunistically corallivorous sea urchin), and Trapezia sp. (a coral-dwelling guard crab). This design elucidates how thermal challenges impacts the complex ecological interactions and functioning within the coral community. Using a comparative experimental design, the study evaluates an established subtropical community in Hong Kong and a pioneer temperate community in Ōtsuki, Japan. Following acclimatization, live specimens (n=64) undergo a thermal ramping cycle of ±1°C/day to reach target temperatures ranging from 13°C to 35°C. Closed-chamber respirometry is then utilized to measure species-specific metabolic rates via proxy of respiration. The empirical data will be used to generate Thermal Performance Curves (TPCs) for each species. Ultimately, these TPCs will be integrated with global SSP climate change scenarios to construct predictive Habitat Suitability Models (HSMs). These time-scaled models will forecast the future distribution and viability of coral-associated macroinvertebrates in high-latitude habitats, providing critical insights into how physiological mismatches could impact community dynamics at poleward range edges.
 

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