OCEAN & COASTAL ACIDIFICATION
The burning of fossil fuels has resulted in an increase of carbon dioxide (CO2) in the atmosphere. The oceans absorb about one-third of this carbon dioxide, resulting in changes to ocean chemistry. Additionally, increases in freshwater and nutrient runoff can also cause changes in the carbonate chemistry of coastal waters. These local and regional processes play a particularly important role in acidification of the Southeast region. Explore monitoring locations and ecosystem chemistry below.
Coral reefs represent an economically valuable resource in Florida and are particularly vulnerable to changing ocean chemistry. The carbonate chemistry around coral reefs is a function of multiple processes that change with both diel (day and night) and tidal cycles. The changes that occur between day and night are a function of photosynthesis, respiration, and calcification. Photosynthesis during the day draws down carbon dioxide, increasing pH, while respiration at night does the opposite. Determining the balance between all of these reef ecosystem processes helps scientists quantify overall reef growth. There is evidence that reefs at the northern edge of the Florida Reef Tract experience seasonal dissolution (Muehllehner et al. 2016).
The Gray’s Reef National Marine Sanctuary is an extensive area of live-bottom reef off the coast of Georgia. The rocky region of the seafloor hosts a diversity of marine life. The Gray’s Reef ocean acidification mooring is located 40 nautical miles southeast of Savannah, Georgia. The mooring provides valuable information about the carbonate chemistry of the region, detecting changes to chemistry from both land-based inputs and atmospheric carbon dioxide.
Recent research from data collected at the mooring helps discern whether the region is primarily a source or sink for atmospheric carbon dioxide. Learn more about ocean acidification research at Gray’s Reef National Marine Sanctuary.
Acidification in the U.S. Southeast
SOCAN members recently published an article, Acidification in the U.S. Southeast: Causes, Potential Consequences and the Role of the Southeast Ocean and Coastal Acidification Network, in Frontiers in Marine Science.
Estuaries are dynamic coastal ecosystems that experience rapid swings in chemistry. The carbonate chemistry of Southeast estuaries is influenced by respiration of organisms (breathing out carbon dioxide, just like us), the decay of organic material and freshwater outflow from rivers. Increases in any of these processes would increase carbon dioxide content in coastal waters in addition to ongoing acidification from increasing atmospheric carbon dioxide.
The Southeast is one of the most rapidly developing regions of the U.S. Increases in development leads to an increase in impervious surfaces (surfaces that don’t allow rainwater to infiltrate). This means that there is more freshwater and pollution runoff into coastal ecosystems. Increases in freshwater reduce the ability of coastal ecosystems to buffer against changes in carbon dioxide, reducing the pH, and making the seawater more acidic. Runoff can also cause increases in nutrients (e.g. from fertilizers) in local waterways leading to algal blooms. Through a mechanism called eutrophication, this also has the potential to alter carbonate chemistry in coastal ecosystems.
Though these are very different mechanisms by which carbon dioxide can increase in the ocean and coastal waters, the impacts to coastal organisms may be similar. Understanding the source of changing chemistry is important for mitigation efforts and SOCAN seeks to increase monitoring that will help interpret the source of these changes.