Optimising uptake of wild-type and heat-evolved symbiodiniaceae in coral larvae and recruits for coral reef restoration

Reef-building corals depend on a mutualistic relationship with micro-algal symbionts from the dinoflagellate family Symbiodiniaceae. However, due to anthropogenic climate change, coral reefs are experiencing mass mortality from coral bleaching, a breakdown of the symbiotic relationship that leads to the loss of symbionts. Given the slow rate of coral adaptation, assisted evolution strategies can benefit from the shorter generation times of Symbiodiniaceae to rapidly enhance holobiont performance. This study will utilise symbionts from the genera Durusdinium and Cladocopium that have been heat-selected in culture, and test whether they can establish successful symbioses with coral larvae and juveniles, with the potential to enhance holobiont fitness. The symbiont acquisition, survival and growth of larvae and juveniles will be assessed in four coral species infected by either wild-type (WT) or heat-selected (HS) symbionts at four exposure densities (0.01k cells/mL, 0.1k cells/mL, 1k cells/mL, 10k cells/mL). Once juveniles are 6 months old, they will undergo a heat-stress experiment to assess the heat tolerance of the holobionts. The results of this project will contribute to active restoration strategies and policies, and to understanding the potential adaptive gains of pairing corals at different life stages with heat-resistant symbionts.