Induced bleaching enhances cold tolerance in coral larvae: a potential strategy for cryopreservation optimization
摘要
Rising ocean temperatures represent a pressing threat to coral reef survival, leading to coral bleaching. While coral recovery remains uncertain, they might acquire thermal tolerance following bleaching events. Cryopreservation of coral larvae offers a promising ex situ conservation strategy to support long-term reef preservation. This study aimed to cryopreserve Pocillopora acuta larvae and assess whether bleaching enhances their cryotolerance during vitrification and laser warming. Bleaching was induced prior to assessing larval viability and settlement capacity following an 8 h incubation in low-temperature baths at 15 °C and 5 °C. The no-observed-effect concentration for five cryoprotectants was determined to identify the highest concentration that did not induce significant adverse effects on larval behavior or settlement. Two vitrification solutions (VSs) were tested for optimal vitrification success: VS1 (2 M ethylene glycol [EG], 1 M glycerol [GLY]) and VS2 (2 M GLY, 1 M EG). Vitrification was carried out using VS1, supplemented with 40% (w/v) Ficoll and 10% (v/v) gold nanoparticles, followed by nano-laser warming (300 V, 10 ms pulse width, 2 mm beam diameter). The results demonstrated that larvae treated with VS1 exhibited superior vitrifying property compared to those exposed to VS2. Bleached larvae showed enhanced cryotolerance, as evidenced by a significant increase in swimming activity following chilling and vitrification. P. acuta larvae were able to settle successfully after cryopreservation. These findings suggest bleaching may improve tolerance to chilling stress, providing a useful preconditioning step for optimizing coral larval cryopreservation workflows. This study advances the field of coral larval cryopreservation and highlights the importance of further investigating the long-term effects of bleaching on cryopreservation effectiveness.