Presenter: John Amiel Flores (University of California, Los Angeles; The Diversity Project)

Description:
Many coral reefs have shifted to alternative stable states after a disturbance; in some cases, shifts are to foundational macroalgae that resist coral recovery, motivating research into the ecosystem services of these emergent alternative communities. Global climate change, predicted to amplify storm frequency and intensity in the South Pacific, may impact these emergent services. The macroalga Turbinaria ornata forms an alternative stable state that can dominate shallow hard-bottomed habitats in French Polynesia and provide trophic support to herbivorous fishes. To examine how storms (physical disturbance) of differing intensities (No disturbance, Storm, Large Storm, Typhoon) affect trophic support to herbivorous fishes, we experimentally removed different size classes of T. ornata (none, - thalli >10cm, - thalli > 5cm, -all algae + scouring). We recorded fish herbivory immediately (3 hours) and five days after disturbance, and used an NMDS to visualize use by the fish community, measured as the species-specific number of bites taken in each experimental unit. Without disturbance, the fish community did not differ between 3 hours and 5 days. In contrast, after a Storm, we found increased support of the most diverse fish community within 3 hours, which continued on day 5. In contrast, both the Large Storm and the Typhoon supported a narrower range of fishes than either no disturbance or Storm treatments immediately after the disturbance. However, community use of these treatments expanded after 5 days. These results imply the magnitude of disturbance to T. ornata communities influences community composition of fishes that target newly-available algal resources. However, this may represent an ephemeral food source to the herbivorous fish community, though longer term effects merit further exploration. Overall, this work provides insight into how emergent alternative stable state communities on coral reefs will function in an increasingly stormy Anthropocene.