Effects Of Acidification On The Marine Ecosystem

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The Effects of Ocean Acidification on the Southern Ocean Marine Organisms and the Ecosystem

The Southern Ocean has changed slightly over the last thirty years (Constable, A.J, Melbourne-Thomas J, Corney S.P, et al. 2014). Modern society burn fossil fuels which cause a steady increase in carbon dioxide in the atmosphere. The carbon dioxide combines with seawater producing carbonic acid and causes seawater to become more acidic, a process known as ocean acidification (Cooley S, Mathis J, Yates K. 2013). Antarctic krill is one of many marine organisms affected by the ocean acidity changing. Pteropods, commonly known as sea butterflies, are a small shelled marine organism about the size of a pea, like krill they are a major food source for larger
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2012). These marine organisms decrease in numbers or even extinction would have a huge negative impact on the Antarctic marine ecosystem. If carbon dioxide in the atmosphere continues to increase, the Antarctic ecosystem will become unbalanced, with the possibility of endangering other larger marine organisms that rely on these smaller ones.

Modern humans have caused a rapid 40% increase in carbon dioxide in the atmosphere from 280ppm (parts per million) to 397ppm. One third of all atmospheric carbon dioxide ends up in the ocean (Saba G.K, Schofield O, Trres J.J, et al. 2012). Today the increasing oceanic carbon dioxide is causing a small decrease in pH leading to a slightly more acidic ocean, which is slowly affecting the more polar marine organisms. Antarctic krill, (Euphausia superba) is one of the key organisms required to keep a balanced, stable ecosystem. They are resilient creatures and survive in a range of depths in Antarctic oceans. A study observed the effect of different carbon dioxide levels on fertilised Antarctic krill eggs. At the lower levels of carbon dioxide, such as 380µatm and
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They use this to produce aragonite for their shells (Tenniswood C.M.H et al. 2013). Unfortunately for the Southern Ocean, saturation is lower in colder, high altitude regions such as Antarctica. This results from calcium carbonate dissolving in water (Doney S.C. Fabry V.J. Feely R.A. Kleypas J.A. 2009). In an experiment pteropods were taken from the upper levels of the Southern Ocean (where aragonite is formed). They were exposed to differing amounts of carbon dioxide, and incubated. The experiment was performed to observe the dissolution process. As a result they found pCO2 of 675 μatm was enough to cause substantial dissolution of the shell matrix (Bednarsek N. Tarling G.A, Bakker D.C.E, Fielding S, et al. 2012). Besides the experiment, computer simulations of the scenario were done and consequently showed the entire water column of the Southern Ocean will become under-saturated with aragonite by the end of this century (Blank N. 2007), thus posing a huge threat to the pteropods, because their shells show signs of extensive erosion in under-saturated conditions. Unfortunately it is not yet known if their shells can maintain their calcification (Blank N. 2007). Pteropods not being able to calcify their shells could cause a fatal end for the population. This would especially affect

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