Coral reefs are among the most diverse ecosystems on Earth, providing habitats for 30% of marine species. Reef-building corals form symbiotic relationships with microbes, including bacteria, fungi, viruses and algae1. Environmental stressors, such as ocean warming, acidification and pollution, can disrupt coral microbiome composition and symbiosis, increasing coral susceptibility to diseases and bleaching1. Understanding microbiome–coral interactions can help to determine how to improve coral health and resilience in a changing environment1.

A recent study in Animal Microbiome by Epstein and colleagues explores how coral-associated microbes mediate a fundamental trade-off between growth rate and disease susceptibility. Life-history trade-offs refer to how organisms handle allocating limited resources for various functions, for example, growth versus repair or immune defence. The study investigated the potential trade-offs between coral microbiome composition, growth rates and disease in 1,283 stony coral samples obtained from 42 reefs across eastern and western Australia, the Red Sea, the Indian Ocean, the Coral Triangle, the Caribbean, and the eastern Pacific, covering 132 species and 64 genera. They also included 157 outgroup samples from species that are closely related to corals (the ingroup) but not part of it, such as sea anemones, soft corals and jellyfish. Outgroups are used to root evolutionary trees and identify ancestral traits compared with more recently evolved ones. Trait data were obtained from the Coral Trait Database2, a global community effort that provides centralized and systematic storage of information on coral characteristics, for example, growth, size, reproduction and symbiont type. Disease traits were obtained through long-term (5 to 16 years) field survey records from Florida, Hawaiʻi and Australia documenting 6 common Indo-Pacific coral diseases (black band, white syndrome, skeletal eroding band, brown band, growth anomalies and atramentous necrosis)3.