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Pretty in Pink

How Coral Reefs Track with Ocean Chemistry

Background: Rose Atoll Coralline Algae

Rolling off the boat at Rose Atoll, Dr. Hannah Barkley plunges beneath the water’s surface to find a diverse coral reef covered in a vibrant pink. Corals make and grow their skeletons out of calcium carbonate, the same family of minerals as limestone or chalk. The pink Dr. Barkley sees in this reef comes from another important calcifier – crustose coralline algae – which uses these same mineral building blocks for its structure. So, why are the coral reefs here doing so well compared to other places in the Pacific Islands? Dr. Barkley and colleagues set out to find out what ocean conditions drive coral reef accretion and the best ways to measure the effects of our changing ocean.

"Reefs in Rose Atoll have the highest carbonate saturation we measure in the U.S. Pacific Islands. This creates a favorable chemical environment for coral reefs and other calcifiers."

Dr. Hannah Barkley

Fun Fact: While not named for the pink color, Rose Atoll is one island in American Samoa and the most southern point in the United States. More fun facts about Rose Atoll.

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."

It takes a village

Hundreds of people contributed to these extensive expeditions and maintain monitoring in the Pacific Islands. Research and monitoring occurred in American Samoa, the Mariana Archipelago, the main and Northwestern Hawaiian Islands, and the U.S. Pacific Remote Island Areas to evaluate coral reef community structure and reef processes.

Did you know that the United States has a National Coral Reef Monitoring Program (NCRMP)? These efforts to better understand drivers of reef health were largely conducted through and supported by NCRMP. The Program is a strategic framework for conducting sustained observations of biological, climatic, and socioeconomic indicators in U.S. states and territories.

"This unique long-term monitoring is important because it helps us understand how to best track and respond to the impacts of ocean acidification on coral reefs."

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

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

Credits

Cover: Wendy Cover/NOAA; Diver and Sensors from vessel images: Pacific Islands Fisheries Science Center/NOAA; Pink corals & NOAA dive team images: NOAA Fisheries; Statistics graphic: NOAA Ocean Acidification Program

Effects of ocean acidification and temperature on Alaskan crabs

Red King Crab
Image credit: David Csepp, NMFS AKFSC ABL

Long-term declines of red king crab in Bristol Bay, Alaska may be partially attributed to ocean acidification conditions. These impacts may be partially responsible for the fishery closures during the 2021–2022 and 2022–2023 seasons. Researchers found that ocean acidification negatively impacts Alaskan crabs generally by changing physiological processes, decreasing growth, increasing death rates and reducing shell thickness. Funded by the Ocean Acidification Program, scientists at the Alaska Fisheries Science Center continue to investigate the responses of early life history stages and study the potential of various Alaska crabs to acclimate to changing conditions. Results will inform models that will use the parameters studied to predict the effects of future ocean acidification on the populations of red king crab in Bristol Bay as well as on the fisheries that depend on them. Fishery managers will better be able to anticipate and manage stocks if changing ocean chemistry affects stock productivity and thus the maximum sustainable yield.

More about this work

Forecasts for Alaska Fisheries

Crab pots and fishing nets in Alaska's Dutch Harbor
Image credit: Michael Theberge

Understanding seasonal changes in ocean acidification in Alaskan waters and the potential impacts to the multi-billion-dollar fishery sector is a main priority. Through work funded by NOAA’s Ocean Acidification Program, the Pacific Marine Environmental Laboratory developed a model capable of depicting past ocean chemistry conditions for the Bering Sea and is now testing the ability of this model to forecast future conditions. This model is being used to develop an ocean acidification indicator provided to fisheries managers in the annual NOAA Eastern Bering Sea Ecosystem Status Report.

ADAPTING TO OCEAN ACIDIFICATION

The NOAA Ocean Acidification Program (OAP) works to prepare society to adapt to the consequences of ocean acidification and conserve marine ecosystems as acidification occurs. Learn more about the human connections and adaptation strategies from these efforts.

Adaptation approaches fostered by the OAP include:

FORECASTING

Using models and research to understand the sensitivity of organisms and ecosystems to ocean acidification to make predictions about the future, allowing communities and industries to prepare

Closeup of oysters cupped in someone's hands

MANAGEMENT

Using these models and predictions as tools to facilitate management strategies that will protect marine resources and communities from future changes

TECHNOLOGY DEVELOPMENT

Developing innovative tools to help monitor ocean acidification and mitigate changing ocean chemistry locally

REDUCING OUR CARBON FOOTPRINT

50 more ways to reduce your carbon footprint >

On the Road

Drive fuel-efficient vehicles or choose public transportation. Choose your bike or walk! Don't sit idle for more than 30 seconds. Keep your tires properly inflated.

With your Food Choices

Eat local- this helps cut down on production and transport! Reduce your meat and dairy. Compost to avoid food waste ending up in the landfill

With your Food Choices

Make energy-efficient choices for your appliances and lighting. Heat and cool efficiently! Change your air filters and program your thermostat, seal and insulate your home, and support clean energy sources

By Reducing Coastal Acidification

Reduce your use of fertilizers, Improve sewage treatment and run off, and Protect and restore coastal habitats

TAKE ACTION WITH YOUR COMMUNITY

You've taken the first step to learn more about ocean acidification - why not spread this knowledge to your community?

Every community has their unique culture, economy and ecology and what’s at stake from ocean acidification may be different depending on where you live.  As a community member, you can take a larger role in educating the public about ocean acidification. Creating awareness is the first step to taking action.  As communities gain traction, neighboring regions that share marine resources can build larger coalitions to address ocean acidification.  Here are some ideas to get started:

  1. Work with informal educators, such as aquarium outreach programs and local non-profits, to teach the public about ocean acidification. Visit our Education & Outreach page to find the newest tools!
  2. Participate in habitat restoration efforts to restore habitats that help mitigate the effects of coastal acidification
  3. Facilitate conversations with local businesses that might be affected by ocean acidification, building a plan for the future.
  4. Partner with local community efforts to mitigate the driver behind ocean acidification  – excess CO2 – such as community supported agriculture, bike & car shares and other public transportation options.
  5. Contact your regional Coastal Acidification Network (CAN) to learn how OA is affecting your region and more ideas about how you can get involved in your community
       More for Taking Community Action