A new report published in the American Geophysical Union’s (AGU) Biogeochemical Cycles highlights the work of University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science researchers findings that the limestone that forms the foundation of coral reefs along the Florida Reef Tract is dissolving rapidly during the fall and winter months” in the upper Florida Keys.
The AGU explains that previous laboratory projections have led scientists to predict that ocean “pH would not fall low enough to cause reefs to start dissolving until 2050-2060.” This new report illustrates that like other climate change impacts throughout the world, eco system destruction is occurring much faster than expected in the Florida Keys as well.
The results showed reef dissolution is a significant problem on reefs in the upper Keys with the loss of limestone exceeding the amount the corals are able to produce on an annual basis. As a result, these reefs are expected to begin wasting away, leaving less habitat for commercially- and recreationally-important fish species. Florida Keys’ reefs have an estimated asset value of $7.6 billion. The study was accepted for publication today in the journal Global Biogeochemical Cycles, a journal of the American Geophysical Union.
In the natural scheme of things in the spring and summer months, environmental conditions in the ocean such as water temperature, light and seagrass growth are favorable for the growth of coral limestone. During the fall and winter, low light and temperature conditions along with the annual decomposition of seagrass result in a slowing, or small-scale loss of reef growth.
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However, as atmospheric carbon dioxide is absorbed by seawater, ocean pH declines. The result is that the natural summer growth cycle of coral is no longer large enough to offset the effects of dissolution from ocean acidification.
“We don’t have as much time as we previously thought,” said Chris Langdon, professor of marine biology and ecology at the University of Miami Rosensteil School of Marine & Atmospheric Science and a senior author of the study. “The reefs are beginning to dissolve away.”
Carysfort 2016 - The extensive thickets of staghorn corals are gone today replaced by a structure-less bottom littered with the decaying skeletons of staghorn coral. Credit: Chris Langdon, Ph.DThe National Ocean Service defines ocean acidification by noting that the process causes a reduction in the pH of the ocean.
For more than 200 years, or since the industrial revolution, the concentration of carbon dioxide (CO2) in the atmosphere has increased due to the burning of fossil fuels and land use change. The ocean absorbs about 30 percent of the CO2 that is released in the atmosphere, and as levels of atmospheric CO2 increase, so do the levels in the ocean.
When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in the increased concentration of hydrogen ions. This increase causes the seawater to become more acidic and causes carbonate ions to be relatively less abundant.
Carbonate ions are an important building block of structures such as sea shells and coral skeletons. Decreases in carbonate ions can make building and maintaining shells and other calcium carbonate structures difficult for calcifying organisms such as oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton.
These changes in ocean chemistry can affect the behavior of non-calcifying organisms as well. Certain fish's ability to detect predators is decreased in more acidic waters. When these organisms are at risk, the entire food web may also be at risk.
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