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Ocean Acidification Program News

Acidification, eutrophication and HABs in estuarine waters: What do long-term data tell us?

Estuaries receive and process nutrient loads generated in coastal watersheds and often exhibit accelerated rates of primary production (eutrophication), phytoplankton blooms, hypoxia and associated water quality and habitat declines.  As such, they are highly dynamic with respect CO2 fixation and mineralization of autochthonous organic matter (OM), which modulate pH.  Watershed-derived (allochthonous) OM plays an additional role in mediating carbon fluxes and pH.  Increasing anthropogenic activities as well as climatic changes (more extreme episodic rainfall events and increasingly variable wet/dry cycles) impact nutrient and inorganic/organic carbon loading to estuaries.  Long-term monitoring of these parameters in North Carolina’s Neuse River Estuary and downstream Pamlico Sound, NC, as well as Chesapeake Bay’s main stem reveals dynamic responses in primary production, phytoplankton biomass (as chlorophyll a), organic and inorganic nutrients, dissolved inorganic carbon (DIC) and pH, reflecting the effects of variable nutrient-and OM-enriched freshwater discharge.  Data from >20 year monitoring of these estuaries show only marginal trends in pH. In both systems, pH has risen slightly at upstream, nutrient-enriched locations, while downstream there is either no change or slight negative trends. Acidification is controlled by multiple interacting factors, including rates of primary production (CO2 fixation), which in some estuaries have increased due to eutrophication, tending to drive pH up, and mineralization of autochthonous and allochthonous organic matter, driving pH down. Large storm events, including increasingly high rainfall tropical cyclones, cause episodic drops in pH through “freshening” accompanied by large OM loads. With regard to potential linkages of autochthonous (within system) OM production due to algal blooms and effects on pH, we note that the estuary cannot mineralize more organic matter (driving pH down) than what is produced by algae and higher plants (driving pH up), Therefore, unless every CO2 molecule that is fixed is remineralized, which is unlikely if we assume that some fixed C is buried or exported, one would expect no significant net acidification.  In conclusion, estuarine pH trends driven by atmospheric- and ultimately estuarine enrichment of CO2 are masked by the combined effects of allochthonous OM and nutrient loading, and resultant eutrophication.       
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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:


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


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


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


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

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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