Abstract
Coral reefs are known to have extremely high rates of primary production. However, common geochemical methods for determining bulk rates of reef metabolism cannot distinguish which organisms are responsible for primary production. Here we used a “bottom‐up” approach to estimate the contribution of diverse primary producers including hard corals, octocorals, and algae to gross primary production on coral reefs by scaling up taxon‐specific rates by the abundance of those taxa in the environment. Chamber‐based production rates of the dominant primary producers were obtained as a function of irradiance, the primary short‐term driver of photosynthesis. These rates were then combined with annotated three‐dimensional (3D) reconstructions of reef sections and a simple light field model to estimate reef‐scale gross and net primary production rates over time. At a degraded reef in the Florida Keys octocorals and algae were the main producers, but at a more intact site a scleractinian coral ( Acropora palmata ) was the most important producer. As a validation of the approach, rates of primary production estimated using the “bottom‐up” approach were compared with in situ eddy covariance fluxes. The daily integrated rates agreed within 16%, though maximal production was ~ 35% lower in the “bottom‐up” approach likely due to under‐representation of octocorals and macroalgae in the 3D reconstructions. The “bottom up” approach yielded results that were largely consistent with the in situ measurements of primary production and irradiance with the significant benefit of providing taxon‐specific and spatially‐explicit primary production rates.