The eye's coral reef: toward a planetary-health agenda for ocular-microbiome stewardship.

Coral reefs and the human ocular surface represent ecologically distinct yet structurally comparable microbial ecosystems in which resilience depends on finely regulated host-microbe interactions. In coral reef science, microbial shifts precede visible bleaching and ecosystem collapse, enabling the development of predictive stress indices such as Degree Heating Weeks (DHW). Comparable principles are emerging in host-associated, low-biomass microbiomes, where subtle perturbations may trigger disproportionate functional consequences. Here, we propose a systems-level conceptual framework linking coral reef holobionts and the ocular surface as sentinel ecosystems governed by cumulative stress, threshold dynamics, and microbial instability. We introduce two heuristic constructs-the Cumulative Desiccating Load (CDL) and the Ocular Dysbiosis Sentinel Index (ODSI)-to frame dysbiosis as a trajectory of resilience loss driven by cumulative perturbations. Aging-related conditions such as age-related macular degeneration are discussed as examples of microbial and metabolic senescence within the human holobiont, conceptually paralleling coral reef decline under chronic sublethal stress. By integrating environmental and host-associated microbiome research within a planetary-health perspective, this article advances a resilience-oriented systems framework applicable across biological scales.