Trace metals are key regulators of coral reef functioning, acting as essential micronutrients or toxic stressors depending on concentration, speciation, and biological regulation. Corals and their associated holobionts require metals such as iron, zinc, copper, manganese, cobalt, molybdenum, and vanadium for photosynthesis, antioxidant defense, calcification, and nutrient cycling, while elevated levels of these elements, and non-essential metals including cadmium, lead, mercury, and nickel can induce oxidative stress, disrupt metabolism, disrupt coral-algal symbiosis, and contribute to bleaching and mortality. This review synthesizes current knowledge on trace metals in corals using evidence from laboratory experiments, field studies, skeletal geochemistry, and omics-based investigations. The biological roles and regulation of trace metals within the coral holobiont, their physiological and molecular impacts across life stages, and the influence of biogeochemical cycling and environmental drivers on metal availability and exposure in reef systems are examined. Analytical and omics-based approaches for investigating coral and metal interactions are also evaluated. Altogether, current evidence indicates that coral responses to trace metals depend on external metal concentrations, physiological regulation and environmental context. As climate change and anthropogenic activities continue to modify ocean chemistry, redox conditions, and metal bioavailability, understanding these interactions will become increasingly important for anticipating coral responses to future environmental change. Substantial knowledge gaps remain regarding thresholds between essentiality and toxicity, interactions with climate stressors, and holobiont-level metal cycling. Addressing these gaps is essential for improving interpretation of coral metal records, predicting reef vulnerability, and informing effective conservation and management strategies in an increasingly anthropogenically altered ocean.
Versola J. J. N. & Rodriguez I. B, 2026. Trace metals in the coral holobiont: roles and regulation in a changing ocean. Coral Reefs: 1-18. Article.
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