Oceanic Productivity and High-Frequency Temperature Variability—Not Human Habitation—Supports Calcifier Abundance on Central Pacific Coral Reefs

Past research has demonstrated how local-scale human impacts—including reduced water quality, overfishing, and eutrophication—adversely affect coral reefs. More recently, global-scale shifts in ocean conditions arising from climate change have been shown to impact coral reefs.

Here, we surveyed benthic reef communities at 34 U.S.-affiliated Pacific islands spanning a gradient of oceanic productivity, temperature, and human habitation. We re-evaluated patterns reported for these islands from the early 2000s in which uninhabited reefs were dominated by calcifiers (coral and crustose coralline algae) and thought to be more resilient to global change. Using contemporary data collected nearly two decades later, our analyses indicate this projection was not realized. Calcifiers are no longer the dominant benthic group at uninhabited islands.

We then asked whether oceanic productivity, past sea surface temperatures (SST), or acute heat stress supersede the impacts of human habitation on benthic cover. Indeed, we found variation in benthic cover was best explained not by human population densities, but by remotely sensed metrics of chlorophyll-a, SST, and island-scale estimates of herbivorous fish biomass.

Our results reveal that human habitation is no longer a primary correlate of calcifier cover on central Pacific island reefs, and highlight the addition of oceanic productivity and high-frequency SST variability to the list of factors supporting reef builder abundance.

Huntington B, Vargas-Angel B, Couch CS, Barkley HC, Abecassis M. 2022. Oceanic productivity and high-frequency temperature variability-not human habitation-supports calcifier abundance on central Pacific coral reefs. Frontiers in Marine Science. 9:1075972.  https://doi.org/10.3389/fmars.2022.1075972.