Abstract Summary
Ecological restoration of forests, meadows, reefs or other foundational ecosystems in the face of climate change depends on the discovery and use of individuals able to withstand future conditions. For coral reef restoration, finding climate tolerant colonies does not guarantee clonal progeny will remain tolerant in different environments because of widespread environmental adjustment of coral physiology and contributions from internal symbionts. Here, we test if simple proxies of heat tolerance for parent corals are predictive of nursery growth and bleaching tolerance. Before the 2015 natural bleaching event in American Samoa, we set out 800 coral fragments from 80 colonies of four species that had been selected by prior tests to have a range of intraspecific natural heat tolerance. After the event, clones from heat tolerant parents resisted bleaching 20-85% better across species than clones from less tolerant parents and retained higher clonal diversity through the bleaching event than did less heat tolerant corals. The three simplest proxies for thermal tolerance (response to experimental heat stress, location on the reef, and thermal microclimate) predicted the response of nursery clones of all four species to the bleaching event. Molecular biomarkers were also predictive but were highly species specific. Colony genotype explained the most variance in bleaching response (38%), playing a stronger role than the symbiont and demonstrating a key role for individual variation in the restoration process. Combined, our results show that selecting for host resilience produced a multi-species coral nursery that withstood multiple bleaching events and that proxies for thermal tolerance in restoration efforts can be species independent and inexpensive.
