Burning fossil fuels releases vast amounts of nitrous oxides, ammonia and sulphur dioxide into the atmosphere as well as carbon dioxide. Coastal areas are particularly at risk due to the short lifespan of these chemicals (up to 7 days)- most are deposited on land. In the ocean, the sulphur and nitrogen takes the form of dissociated products of nitric and sulphuric acid. These acids are strong and so dissociate completely in the seawater, lowering its pH. However, the overall process of acidification is more complicated than this as there are many chemicals dissolved in the oceans, each of which effects its own change when these new chemicals are added in. Although the changes in the sea due to nitrogen and sulphur compounds are only a fraction of the amount caused by carbon dioxide, the effects are compounded in coastal areas with 10-50% of the change due to these chemicals.
Doney SC, Mahowald N, Lima I, Feely RA, Mackenzie FT, Lamarque J-F & Rasch PJ. Impact of anthropogenic atmospheric nitrogen and sulphur deposition on ocean acidifiaction and the inorganic carbon system. PNAS; 2011: 104(37): 14580-14585
The oceans are an integral part of our world, covering approximately 71 percent of the earth’s surface. Ocean acidification is occurring in oceans all over the world, but is perhaps most troublesome in the waters closest to you and I. Coastal waters are used by humans every day both out of necessity and to have a little fun. Because of their close proximity to people, coastal ecosystems are put under a lot of stress before ocean acidification is even taken into effect. The acidity of the ocean’s coastal waters is already slightly higher than most other places due to pollution and runoff. When you put ocean acidification into the mix, organisms in coastal ecosystems will have a great deal of adapting to do in order to survive.
Bivalves, an important species to the ecosystem as well as to humans, have already been shown to have a negative reaction to increased acidity. Because the calcium carbonate needed to make their hard shells isn’t as readily available, bivalves are having a harder time reproducing and developing to maturity. Some species of lobsters, shrimp, and sea urchins are experiencing the same problems. While ocean acidification is affecting these species individually, it could have an even greater effect by harming organisms that make coastal habitats. Coral reefs are an integral part of coastal ecosystems, providing habitat for thousands of organisms. However, increased acidity and ocean temperatures are known to be extremely harmful to coral species. Without coral reefs, coastal ecosystems would lose valuable habitat and diversity.
Although it may seem cut-and-dry that ocean acidification is harmful to coastal ecosystems, there are many species not affected or positively affected by increased acidity. Some species of oysters, lobster, and crabs were actually found to thrive in the lower pH. This makes it reasonable to believe that other organisms might be able to adapt to the changes in acidity. Another species found to thrive in acidified waters is sea grass. Sea grass is another major habitat provider in coastal ecosystems. Because it thrives in the lower pH, it could possibly make up for some of the habitat loss of coral reefs.
It is quite difficult to argue the fact that coastal waters are becoming more and more acidic. In fact, the EPA has directed states to list areas of water where the acidity is increased as impaired. Throughout the United States coastlines, there are over 41,000 areas listed as impaired due to ocean acidification. While the fact of increased acidity is hard to argue, the future effects of this increase are quite vague. Humans need to be cautious either way, because losing the resources provided by coastal ecosystems would do serious economical and environmental damage.
Coastal ecosystems play an important role in marine life. They are home to several shellfish hatcheries and finfish, and they are highly productive. Within recent years, the effects of ocean acidification on coastal ecosystems have been apparent, especially pertaining to the shellfish that represent a large part of coastal organisms. In particular, scientists recognized both positive and negative outcomes on oyster populations in relation to calcification, growth rates and reproduction, and death rates.
The increasing amount of CO2 entering the earth’s oceans slowly decreases the pH level and therefore, affects the amount of calcium carbonate available to oysters. This compound is vital for many species of oysters in order for them to produce their protective shells. Over the past decade, ocean acidification has decreased calcification rates for many oyster species such as the Sydney rock oyster (Saccostrea glomerata), and the Pacific oyster (Crassistrea gigas). However, the Suminoe oyster Crassostrea ariakensis did not exhibit the same consequences. This demonstrates that while ocean acidification may be detrimental to some species of oysters, there are other species that exhibit little difference and may even thrive in oceans with larger concentrations of CO2.
Other research has been fulfilled to explore the impacts of ocean acidification on growth rates and reproduction. A particularly interesting study on Sydney rock oysters (S. glomerata) showed that elevated pCO2 negatively affected their larvae, resulting in an overall reduction of their growth, rate of development, and survival. However, when adult S. glomerata were exposed to elevated pCO2, their offspring were actually influenced in a positive way; They were larger and developed faster than S. glomerata not in waters with higher concentrations of pCO2. The results of this study suggest that it could be possible for oysters to adapt or acclimate over time to an environment with more pCO2.
Between 2005 and 2009, Pacific oyster hatcheries viewed drastic death rates. Whiskey Creek Shellfish Hatchery lost 75 percent of it’s oyster population in 2007, while Taylor Shellfish Farm’s hatchery was 60 percent below average in the year 2009. These large losses in oysters were primarily due to ocean acidification. However, natural processes also played a role in the outcome of oyster production per year. Taylor’s production in 2010 was it’s best ever because of winds that reduced the amount of upwelling and kept the surface waters away from waters rich in CO2.
Since Whiskey Creek and Taylor’s hatcheries were subject to major reductions in their oyster populations, the need for further studies became more apparent. The decrease in oyster productions had economic consequences because many people rely on oysters for their jobs. In 2010, the federal budget dedicated $500,000 towards monitoring CO2 levels in hatcheries. One popular monitoring device is the IOOS buoy, which allows people to truly look at the changes in water conditions. It was said that, “putting an IOOS buoy in the water is like putting headlights on a car.”
Although the affects of ocean acidification range depending on location, oyster species, and connection with natural occurring processes, it is clear that ocean acidification changes the conditions of oysters and other coastal organisms.
Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean. Washington, D.C.: National Acadamies , 2010. 68-72. Print.
Coastal ecosystems such as kelp forests, sea grass beds, barrier reefs, and many others play home to many different marine organisms and species crucial to human fish trading and recreation. Additionally coastal ecosystems protect the inhabited coasts from dangerous storm surges by absorbing much of the initial force long before it reaches land.
Coastal ecosystems, like most other ocean ecosystems, are feeling the effects of such anthropogenic problems such as ocean acidification, climate change, and eutrophication due to excessive human runoff. Unlike the other ecosystems, the coastal ecosystems are especially at risk, and could even be said to be the sentinel ecosystem for the others, due to the close proximity with the mainland and human population. This leads to those ecosystems (sometimes including tropical reefs) taking the first and often strongest hit from pollutants and, in theory, retaining significant amounts of dissolved CO2.
One of the most prevalent malicious effects of ocean acidification that has been observed is the disruption of the formation of CaCO3 (Calcium Carbonate), which is needed for the creation of many marine organisms skeletal systems. This also holds true in the coastal ecosystems. There are many such organisms in these environments such as common bivalves like mussels and oysters. These organisms rely on CaCO3 for the formation of their productive exoskeleton. Likewise many other organisms rely on these bivalves for services such as providing habitat and protection. There have recent studies that show that benthic (bottom dwelling) invertebrates such as mollusks and the aforementioned bivalves are sensitive to seawater carbonate chemistry changes, which are a proven effect of ocean acidification. Thus the effects of ocean acidification, and other forces such as climate change, will not only affect those organisms dependent on CaCO3 for skeletal construction, but it will also severely affect all those smaller organisms that depend on those larger ones for protection and habitat as well as those organisms (including humans) that rely on them as sources of food and, in the specific case of humans, commerce.
The flip side of the coin appears when inspecting one of the coastal ecosystems more closely; the sea grass beds. Seagrass beds are very highly productive ecosystems and are areas with high, or dense populations of seagrasses that support and large amount and variety of marine species and are found in shallow ocean areas and lagoons. Among the better known species that seagrasses support are sea turtles and manatees that rely on the grasses as a food source. There has been research showing that increased dissolved CO2, a cause of ocean acidification, could increase the area and primary production of the seagrasses, which in turn could lead to higher productivity within the seagrass ecosystem populations. However, most ecosystems would not experience this beneficial boost, and it is uncertain whether the other effects of ocean acidification (the actual pH drop) would have a more adverse effect on the seagrass community.
Due to the lack of specifics on ocean acidification it is still unknown exactly how and to what extent it will alter the marine ecosystems of the world, but due to its alteration of the chemistry, especially that of the carbonate chemistry, in the ocean it would be a safe assumption that, if not slowed or halted, ocean acidification will wreak havoc on marine species and ecosystems.
Fabry, V. J., Seibel, B. A., Feely, R. A., and Orr, J. C. 2008. Impacts of ocean acidification on marine fauna and ecosystem processes. – ICES Journal of Marine Science, 65: 414–432.
Florida Medical Entomology Laboratory. “Seagrass Beds.” Florida Medical Entomology Laboratory. University of Florida, 2008. Web. 04 Sept. 2011. <http://fmel.ifas.ufl.edu/habitat/seagrass_beds.shtml>.
Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean. Washington, D.C.: National Academies, 2010. Print.