One of the central questions in ecology is how the sum of repeated local interactions gives rise to ecological patterns at larger spatial scales (Jessup, 2004). Population-level rates of metabolism can be estimated quite accurately from abundance, body size, and temperature (Brown and Gillooly, 2003). In this study whole organism metabolic rates were predicted for individual fish and microbes on coral reefs across the Pacific. Individual metabolic rates were summed to estimate energy use at the community-level.  The reef locations represented systems experiencing relatively high (Main Hawaiian Islands) and low degrees of human impact (Wake Atoll and the Mariana Archipelago).  

Results/Conclusions

At all 35 sites, the amount of work done by the microbial community eclipsed the metabolic requirements predicted for the fish community.  In the MHI, average annual energy usage by the microbial community was 23 fold higher than that of the of the fish community.  Of the reefs visited on Wake and the Mariana Islands, the average energetic requirement of the microbial community was only 11 fold higher than that of the fish community.  Although both fish and microbial communities in MHI do more work overall, biomass-specific metabolic rates indicate that both fish and microbial communities in the MHI require less energy per gram. This finding indicates that the cost of existence is higher on “healthier” reefs for both fish and microbes.  This study sheds new light on energetic differences underlying system functionality of reefs experiencing high and low levels of anthropogenic impact. This study is also the first time metabolic scaling theory has been applied to coral reef bioenergetics.