POSTER Session 2

ECOLOGICAL EVALUATION OF THE FRACTION OF ABSORBED PHOTOSYNTHETICALLY ACTIVE RADIATION FOR CORAL REEF COMMUNITIES

The fraction of absorbed photosynthetically active radiation (fAPAR) quantifies the capacity of an organism or community to capture light for photosynthesis, and thus sets a limit on primary production. In terrestrial systems, fAPAR has been designated as an essential climate variable, used to evaluate global productivity. fAPAR may be applied similarly to analogous marine ecosystems, such as coral reefs, which are driven primarily by photosynthesis. A novel approach has been recently developed to estimate coral reef fAPAR from underwater orthomosaics at the community scale (~10 m × 10 m). In this study, we apply the new method to 282 sites visited during the validation campaigns for the NASA COral Reef Airborne Laboratory (CORAL) mission, including locales in the Great Barrier Reef, Palau, Guam, and Hawai‘i. Sites span virtually all reef geomorphologic zones, and benthic community structure varies widely between algae-, coral-, and sand-dominated. Broadly, fAPAR is near 0.6 for sandy areas and mostly greater than 0.9 for coral/algae areas. Disregarding sand-dominated sites, there is a slight trend of increasing fAPAR with depth, albeit with wide variability. There is a more clear trend of increasing fAPAR with increasing coral relative to algae cover, again with considerable variability. There are no apparent differences in fAPAR trends between regions. Taken together, these results help explain why coral-rich areas generally exhibit higher primary productivity, as well as why production rates are consistent across and between reef biogeographic regions.

*Ceridwyn Hunter, Arizona State University Bermuda Institute of Ocean Sciences (ASU BIOS), Bermuda https://orcid.org/0000-0001-6267-6135

Eric Hochberg, Arizona State University Bermuda Institute of Ocean Sciences (ASU BIOS), Bermuda, https://orcid.org/0000-0001-5400-9252

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