I’m McKensie Daugherty, your host for On the Ocean. One of the world’s most diverse, and potentially most fragile ecosystems is directly impacted by ocean acidification. Coral reefs are often referred to as the “rainforests of the ocean”, but some coral reefs hold even more diversity of life than rainforests. Coral reefs are made up of incredible animals, all built on an animal backbone. That’s right, corals are actually animals. What you see on coral reefs are calcium carbonate skeletons built by coral polyps. Each polyp is its own animal, which looks like a tiny sea anemone. Colonies of millions of polyps form massive skeletons that make up the three dimensional reef structure that provides habitat for a myriad of marine organisms. The process of creating calcium carbonate skeletons is called calcification. But the reef structure is harder to build and can be dissolved if there is too much acid in the water. This corrosion of the coral skeleton makes coral reefs more susceptible to erosion from waves and storms, and also bioerosion from clams and tube worms that break down the reef. The calcification of coral reefs has been in decline over at least the past 40 years, caused by global warming, overfishing, pollution, and ocean acidification. This decline in reef health threatens incredibly important ecosystems and economies. Coral reefs serve as storm barriers for coastal communities, and support tourism and fishing trades that are the lifeblood of many island nations. Coral reef research is also leading to the development of new pharmaceuticals for revolutionary solutions to many medical problems. Coral reefs are under direct threat from ocean acidification, and scientists are working toward understanding when and how these reefs will react to the increase in ocean acidity. This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.
These image show a baby coral, approximately 3 weeks old, with a single polyp with short tentacles on the right and its calcium carbonate skeleton on the left. This single polyp would eventually make copies of itself in a process called “budding” and grow into a large coral colony. From Drenkard et al. 2013.
These images show the calcium carbonate skeletons of baby corals grown at different CO2 levels for three weeks. The top image shows a healthy coral skeleton grown at today’s CO2 levels and the bottom image shows a smaller, less developed coral skeleton grown at CO2 levels expected for the end of this century. From Drenkard et al. 2013.
I’m McKensie Daugherty, your host for On the Ocean. This month we are talking about ocean acidification and its impacts on coral reefs. All across the world, the ocean and atmosphere exchange gasses and even microscopic particles. Atmospheric oxygen, hydrogen, dust, carbon dioxide, and more are constantly interacting with the earth’s oceans. This means that when humans burn fossil fuels for energy, the excess carbon dioxide introduced into the atmosphere gets directly and indirectly absorbed into the ocean. When carbon dioxide interacts with ocean water, it reacts to form carbonic acid. So each carbon dioxide molecule introduced into the ocean forms an acidic molecule in the water column. This is the phenomenon known as ocean acidification. Since the industrial revolution, ocean acidification has been happening on such a massive scale, that the ocean’s overall pH levels are actually decreasing in response, becoming more acidic over time. Even though ocean waters are still slightly basic, the acidity of the earth’s oceans has increased by 30 percent since the industrial revolution. This is the largest and fastest change in ocean chemistry that has occurred in millions of years. This change in oceanic pH has many negative impacts on ocean life, especially on ecosystems that are already vulnerable to changes, like coral reefs. Researchers at Texas A&M University and across the globe are studying ocean acidification in an effort to better understand the impacts this change will have on coral reefs and other marine ecosystems. This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.
This graph shows that the growth (i.e. calcification rate) of coral communities in laboratory experiments (open symbols) and of real coral reef ecosystems (solid symbols) slows as CO2 increases and aragonite saturation state (Omega ar) decreases. Omega ar is a measure of the stability of aragonite (what coral skeletons are made of) in seawater. From Shamberger et al. 2011.
This graph shows the correlation between rising levels of carbon dioxide (CO2) in the atmosphere at Mauna Loa in Hawaii with rising CO2 levels in the nearby ocean at Station Aloha in the north Pacific. As CO2 accumulates in the ocean, the pH of the ocean decreases. Modified after R. A. Feely, Bulletin of the American Meteorological Society, July 2008. Image created by, and posted with permission from, NOAA PMEL Carbon Group (http://www.pmel.noaa.gov/co2/).
I’m McKensie Daugherty, your host for on the ocean. Imagine a cold, dark planet with virtually nothing to eat, even for microorganisms. Now imagine that the only places to live on this planet are in the tiny water-logged fissures and cracks in the rocks that make up the planet’s crust, miles below the crushing weight of an ocean. Does this sound like the beginning of a science fiction novel? It turns out that this describes our very own Earth quite well because Earth’s largest habitat is inside the ocean crust, making Earth on average, a cold, dark, planet inhospitable to human or animal life. Ours is a microbial planet, and researchers at Texas A&M University are working to understand who the microbes are that live in this vast habitat of crust below the ocean and what they are doing to survive. While in any one crack or fissure there are very few microbes, maybe a few hundred to a few thousand, in all cracks in all of the crust under all of the oceans, they add up, making it important to know how they process the Earth’s elements with their metabolisms. Because the ocean circulates through the underlying crust the same way ground water circulates on land, the microbes living in the ocean crust likely affect the chemical nature of global seawater. Moreover, what these microbes are doing below the bottom of the sea may affect life on land over vast geological timescales, as they modify the rocks they live in, which are eventually recycled through the ocean ridge system and brought to land through volcanic activity. These microbes may be tiny, but they are many and they have potential to modify our world in ways that we are just beginning to understand. This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.
I’m McKensie Daugherty, your host for on the ocean. Global climate change is the result of more than just carbon dioxide in the atmosphere. Carbon Tetrachloride, also known as carbon tet, is a man-made compound, made up of one carbon and four chlorine atoms, and is known to play a part in climate change, by destroying the ozone layer. It is also a significantly more potent green-house gas then carbon dioxide. After it is released into the atmosphere, it can go to the stratosphere where the ozone layer is, soils, or the oceans where the large scale destruction occurs. In science, there is a mathematical way to quantify this process using a value that is unique for every compound and each specific path to destruction, called a rate loss constant. Back in the 90’s the countries from around the world collaborated to prevent future damage from Ozone depleting substances by enacting the international treaty called the Montreal Protocol. This effectively banned Carbon Tet and required its usage and emissions to be reported. So by using the reported emissions and the known rate loss constants for each place of destruction, scientists have predicted there to be about a 4% per year decrease in atmospheric Carbon Tet concentrations. However, it was observed that it is decreasing at a rate of only about 1% per year. Scientists at Texas A&M University are trying to obtain a more accurate value for the rate loss constant for the ocean, since many components of this value are still unknown. Hopefully, this research will lead to closing the gap between the expected decline, and observed decline of this dangerous compound from the atmosphere. This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.