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Seasonal and spatial variability in surface pCO2 and air–water CO2 flux in the Chesapeake Bay

Citation: Chen, B., Cai, W.-J., Brodeur, J.R., Hussain, N., Testa, J.M., Ni, W. and Li, Q. (2020), Seasonal and spatial variability in surface pCO2 and air–water CO2 flux in the Chesapeake Bay. Limnol Oceanogr, 65: 3046-3065.

Interactions between riverine inputs, internal cycling, and oceanic exchange result in dynamic variations in the partial pressure of carbon dioxide (pCO2) in large estuaries. Here, we report the first bay-wide, annual-scale observations of surface pCO2 and air–water CO2 flux along the main stem of the Chesapeake Bay, revealing large annual variations in pCO2 (43–3408 μatm) and a spatial-dependence of pCO2 on internal and external drivers. The low salinity upper bay was a net source of CO2 to the atmosphere (31.2 mmol m−2 d−1) supported by inputs of CO2-rich Susquehanna River water and the respiration of allochthonous organic matter, but part of this region was also characterized by low pCO2 during spring and fall phytoplankton blooms. pCO2 decreased downstream due to CO2 ventilation supported by long water residence times, stratification, mixing with low pCO2 water masses, and carbon removal by biological uptake. The mesohaline middle bay was a net CO2 sink (−5.8 mmol m−2 d−1) and the polyhaline lower bay was nearly in equilibrium with the atmosphere (1.0 mmol m−2 d−1). Although the main stem of the bay was a weak CO2 source (3.7 ± 3.3 × 109 mol C) during the dry hydrologic (calendar) year 2016, our observations showed higher river discharge could decrease CO2 efflux. In contrast to many other estuaries worldwide that are strong sources of CO2 to the atmosphere, the Chesapeake Bay and potentially other large estuaries are very weak CO2 sources in dry years, and could even turn into a CO2 sink in wet years.

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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