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NCCOS Project

Vulnerability of Deep-Sea Coral Ecosystems to Ocean Acidification

This project began in March 2014 and was completed in March 2019.

The high acidity and high dissolved inorganic carbon of the California Current ecosystem make it a natural laboratory to study the effects of ocean acidification and ocean warming on deep-sea organisms. Using a remotely operated vehicle (ROV), we are studying the health and condition of deep-sea Lophelia pertusa and gorgonian corals in the mesophotic depth zone. Researchers are monitoring water chemistry and water temperature in and around these deep reefs to assess the vulnerability of this ecosystem to ocean acidification and ocean warming.

Why We Care

Anthropogenic input of carbon dioxide has resulted in warming oceans and rapid development of acidified waters and shoaling (shallowing) of the aragonite saturation horizon (ASH). The location and viability of calcifying species, like corals, are believed to be controlled by the saturation states of calcium carbonate minerals, among other things. If the depth of the ASH becomes less than the depth of cold-water coral reefs, a decrease in net calcification is expected with potential for dissolution of existing coral structures. As temperatures rise, cold-adapted species may suffer, but the effects will vary with depth and duration of anomalies.

It is projected that there will be more frequent warming events in the future, and by 2050, all known aggregations of stony corals in the Channel Islands National Marine Sanctuary will be in corrosive conditions that favor coral dissolution. Progression of acidification is expected to occur most rapidly at depths near 100 meters (328 feet), where large aggregations of stony corals have recently been discovered. These reefs support extensive fish and invertebrate ecosystems, including commercially fished species.

What We Are Doing
Our work will help establish a baseline to assess the effects of climate change in the deep sea. We will conduct water sampling and benthic surveys near aggregations of deep-sea coral between 80–350 meters deep (262–1,148 feet) in the Channel Islands National Marine Sanctuary (CINMS). Our goals are:

  1. to use this region as a natural laboratory to understand the effects of ocean acidification on the stony coral, Lophelia pertusa;
  2. to contribute to a climate vulnerability assessment of sanctuary resources in support of the CINMS Condition Report; and
  3. to educate the local community about ocean acidification.

We will use ship time aboard NOAA ship Bell M Shimada in March 2015 to build on work initiated in 2014 by CINMS and the NCCOS Center for Coastal Environmental Health and Biomolecular Research. Preliminary results of NCCOS benthic surveys in 2014 indicate that deep-water corals in in the sanctuary are already experiencing the effects of acidification.

Using ROV surveys in 2015, we will characterize unexplored habitat, assess abundance and condition of corals, and test existing habitat suitability models. We will process video and still images to NOAA Deep Sea Coral Research and Technology Program national database standards and distribute our results online in a “site characterization report” in early 2016.

CINMS and the NCCOS Center for Coastal Monitoring and Assessment are partners in this work. The project is supported by NOAA's National Centers for Coastal Ocean Science, NOAA’s Deep Sea Coral Research and Technology Program, and NOAA’s Office of Ocean Exploration and Research, among others. The Schmidt Ocean Institute and NOAA’s National Sea Grant Office provided start-up funds and initial support for the acidification study.

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