Functional Role of Uncharted CoralReefs in the Anthropocene

Tropical reef-building corals are vulnerable to breakage as a result of physical impact from wave energy and associated projectiles. Some corals also asexually reproduce via fragmentation, although many suffer mortality (Highsmith 1982, MEPS). Early descriptions of coral reefs noted the ability of these coral fragments to form expansive rubble beds (Odum & Odum 1955, Ecol Monogr), but their functional role as a habitat within the broader reef-scape has largely been ignored. We know very little about the spatial prevalence of rubble beds around tropical islands, their dynamics, and their role as a habitat for reef-associated organisms. As tropical coral reefs continue to change in appearance and function as a result of local and global human pressures, aconsistent transition is the mass mortality of reef-building corals and their conversion to dead coral rubble (Williams & Graham 2019, Funct Ecol). As such, the prevalence of rubble beds as a reef habitat is increasing and supporting novel species assemblages (Graham et al. 2020, Nature Communications), but whether newly emerging rubble beds resulting from reef degradation serve the same functional role as their more natural historical counterparts remains unclear. Using data collected from Palmyra Atoll, an uninhabited reef system in the central Pacific and reefs supporting large human populations in Hawaii, this project will answer a fundamental question within coral reef science: What are the functional roles of rubble beds on tropical coral reefs and are these changing?