Pretty in Pink How Coral reefs track with ocean chemistry

Most of the Pacific Islands have a strong, stable gradient in carbonate chemistry across reefs. Some areas like Rose Atoll have high saturation of calcium carbonate minerals while others areas experience less saturated waters. The ocean is a great sponge for absorbing carbon dioxide from the atmosphere. This causes ocean acidification, a change in ocean chemistry that both increases the seawater’s acidity and can impact the saturation of calcium carbonate minerals. Barkley found that the traditional measures of coral reefs like percent coral cover or diversity didn’t reveal the effects of ocean acidification. Rather, metrics of coral reef net carbonate accretion (how much the entire reef grew) provide a critical tool for monitoring the long-term impacts of ocean acidification.

Coral reefs like Rose Atoll are currently the least impacted by ocean acidification and show how fast reef accretion occurs in highly saturated waters. However, across other reefs in the Pacific, reef growth slows as carbonate saturation decreases.

"In the future, we should use reef accretion metrics that most strongly correlate to ocean chemistry to monitor the long-term impacts of ocean acidification on coral reefs."

Fun Fact: The ocean absorbs about 25% of the carbon dioxide in the atmosphere. (Global Carbon Budget, 2022)

The ability to decipher temporal and spatial patterns in coral reefs along gradients of ocean chemistry would not be possible without a sustained, integrated ecosystem approach. For 10 years, ocean carbonate chemistry, benthic coral reef surveys, and reef accretion monitoring occurred in the same locations.

"This co-location of environmental and ecological data allows us to assess changes in and drivers of coral reef health."

This story featured the great efforts of the Pacific Islands Fisheries Science Center, National Coral Reef Monitoring Program, and was partially supported by the NOAA Ocean Acidification Program.

Publication: Coral reef carbonate accretion rates track stable gradients in seawater carbonate chemistry across the U.S. Pacific Islands. (Nov 2022). Barkley H.C., Oliver T.A., Halperin A.A., Pomeroy N.V., Smith J.N., Weible R.M., Young C.W., Couch C.S., Brainard R.E. and Samson J.C. Front. Mar. Sci. 9:991685. doi: 10.3389/fmars.2022.991685

Image Credits

Cover: NOAA/Wendy Cover; Diver and Sensors from vessel images: NOAA/Pacific Islands Fisheries Science Center; Pink corals & NOAA dive team images: NOAA Fisheries; Statistics graphic: NOAA Ocean Acidification Program and NOAA images; Diver with pink coral at Rose Atoll: NOAA/Courtney Couch

NOAA Ocean Acidification Program, 2023