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Understanding Anthropogenic Impacts on pH and Aragonite Saturation State in Chesapeake Bay: Insights From a 30-Year Model Study

Citation: Shen, C., Testa, J. M., Li, M., & Cai, W.-J. (2020). Understanding anthropogenic impacts on pH and aragonite saturation state in Chesapeake Bay: Insights from a 30-year model study. Journal of Geophysical Research: Biogeosciences, 125, e2019JG005620.

Ocean acidification (OA) is often defined as the gradual decline in pH and aragonite saturation state (ΩAr) for open ocean waters as a result of increasing atmospheric pCO2. Potential long-term trends in pH and ΩAr in estuarine environments are often obscured by a variety of other factors, including changes in watershed land use and associated riverine carbonate chemistry and estuarine ecosystem metabolism. In this work, we investigated the anthropogenic impacts on pH and ΩAr over three decades (1986–2015) in Chesapeake Bay using retrospective coupled hydrodynamic-biogeochemical model simulations. Simulation results demonstrated a clear estuarine acidification signal in the midbay region, with a long-term increase in the annual duration of acidified bottom waters (pH < 7.5, ~2 days/yr) as well as a shallowing of the saturation horizon (~0.1 m/yr). In contrast, scenario results revealed basification in the upper bay consistent with increased alkalinization of the Susquehanna River. Significant long-term pH and ΩAr declines in the lower bay were driven by nearly equal contributions from OA and lowered surface ecosystem production. The midbay pH variability was primarily influenced by OA and biological processes, while river basification along with OA played a key role in regulating the long-term ΩAr variability. This study quantifies the contributions from multiple anthropogenic drivers to changes in estuarine carbonate chemistry over three decades, highlighting the complex interactions in regulating the dynamics of pH and ΩAr and informing regional natural resource management and ecosystem restoration.

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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