Elkhorn coral form thick branching calcium carbonate skeletons. Ocean acidification threatens the integrity of this structural reef builder which provides habitat for other reef dwellers. Ocean acidification also has the potential to compromise the successful fertilization, larval settlement and survivorship of Elkhorn coral. This along with other stressors such as disease, hurricanes, predation, bleaching, algae overgrowth, sedimentation, temperature and salinity variation, and low genetic diversity threaten the long term survival of this endangered species.

Ocean Acidification

The ocean absorbs carbon dioxide from the atmosphere which results in seawater becoming more acidic (lower pH). This increase in ocean acidity makes it difficult for some calcifying organisms (e.g. calcareous plankton, oysters, clams, corals, etc.) to make or maintain their shells or exoskelatons. Other important physiological processes of marine organisms can be disrupted by increased acidity as well. Many of the potentially impacted ocean plants and animals are important in marine food webs or are important commercial species.


Coccolithophores (L) and pteropods (R) are small organisms whose ability to form calcium carbonate shells is affected by ocean acidification.

What We Do

NOAA Fisheries supports the NOAA-wide Ocean Acidification Program, established by Congress in 2009, which will plan and oversee a long-term coastal and open ocean monitoring program, lead research on the impacts of ocean acidification on marine ecosystems and the socioeconomic implications of these impacts. ST continues to provide guidance on Ocean Acidification Program development and funding opportunities. For more information go to the Ocean Acidification Program website.



Interagency Working Group on Ocean Acidification