LAUSR

Ocean warming is altering life on Earth from individuals to ecosystems. The impacts on standing biomass and food webs functioning are less evident due to the paucity of data and difficulty to generate reliable models. We modeled the food web of a tropical near-pristine reef ecosystem and analyzed changes on living biomass across trophic levels as a response to ocean warming over the twenty-first century. By the end of the century, total standing biomass will decrease by 1%, 8% and 44% under different ocean warming scenarios (from reduced RCP 2.6 emission scenario to business-as-usual RCP 8.5 scenario). As total biomass decreases, the ecosystem structure shifts favoring invertivorous fishes, suspension feeding zooplankton, and algal turfs while corals collapse. The mean trophic transfer efficiency is expected to decrease by ~ 2% between 2012 and 2100 under the RCP 8.5, while biomass residence time (mean time that a unit of biomass remains in the ecosystem) will decrease by ~ 10%. Such food web degradation can alter the dominant biomass flow jeopardizing biomass replenishment, resulting in a less productive ecosystem with increasing dependency on pelagic energy subsidies, reducing the resilience of tropical reef ecosystems.