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.

Reference:

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

BioScience (2010)

Cheryl A. Logan discusses the causes, effects, possible solution, and awareness of ocean acidification. Ocean acidification is caused by carbon dioxide dissolving into the Earth’s oceans, generating carbonic acid. Over the past 200 years the pH of the ocean has decreased by 0.1 units, a 30% drop. Ocean acidification affects the ability of several species to calcify, which could affect the food chain and indirectly damage the economy. Scientist have looked into geoengineering as a way to palliate the situation, but reducing carbon emissions is the largest way to help.

Logan also looked into the public and government awareness of ocean acidification. While it seems that the public knows little on the subject, no actual research has been done to prove this. However, the government seems to be much more informed and there are several organizations that are working to improve the situation. In general, Logan suggests using social-networking sites, films, the blogoshpere, and other media to increase awareness.

Under lead author Andrea J. Fassbender, researchers studied the transportation of subsurface waters containing high carbon dioxide levels in the California Current System to the surface of the ocean near shorelines.  Specifically, they studied an event of upwelling near coastal northern California.  As the water traveled toward shore, subsurface respiration added dissolved inorganic carbon along its path, making the water undersaturated in terms of Aragonite.  In the mixed layer, levels of pCO(2) decreased due to the addition of DIC, addition of alkalinity, and gas exchange.  The contribution of each process depended on the distance of the area from land.  According analysis of the results, when waters arrive at the surface of the ocean gas exchange and biological productivity reduce ocean acidification over time, but respiration processes along the path followed by the upwelling tend to increase the acidification of the upwelling waters.

Continental Shelf Research 31, 1180-1192 (2011)

This research article will be paramount in explaining why we are testing the hypothesis that we are testing. This article explains that other chemical compounds and ions can effect the acidity of the ocean more than carbon dioxide. The main arguement in this article is that other significant chemical compounds and ions have a great effect on eutrophication, which is turn has a greater influence on the acidity of the coastal oceans, that athropogenic carbon dioxide.

According to Borges and Gypens, marine organisms can respond to ocean acidification through nitrogen gas and nitrogen fixation.  An increase in nitrogen can increase eutrophication, because nitrogen is a nutrient for many photosynthetic organisms and other bacteria. Our group will research any trends in nitrogen ion composition in the coastal oceans of Georgia, to determine if ocean acidificiation is occuring.

In the results section of this primary research article, Borges and gypens concluded that from 1990 to 1998 a decrease in the phosphate ions in a river resulted in a significant decrease in primary productions. They conducted simulations in which they compared other chemical compounds such as nitrogen,  ammonium, phospate, and nitrate all show greater signifcant effects in the change in PH,  a greater change in the saturation state of calcite and a greater change in the saturation state of aragonite.

DOI: 10.4319/lo.2010.55.1.0346

Ishii et al. from Japan’s Environment and Marine Department has analyzed time series observations of many oceanic CO2 parameters measured just off the southern coast of Honshu, Japan. Their measurements, spanning a 14-year period from 1994-2008, consisted of partial pressures of CO2, pH levels, aragonite saturation rates, and calcite saturation rates. The results from Ishii’s analysis shows a moderate trend of increasing pCO2 levels, and decreasing pH levels, aragonite saturation rates, and calcite saturation rates over the 14-year period. The trends discovered in the study all show that ocean acidification is continuing to intensify and particularly threatening calcifying species with the declining aragonite and calcite saturation rates. However, the data show a very significant seasonal pattern where pH and carbonate saturation rates peak during the summer months and dip in the winter months. Ishii et al. attributed this to the lower water temperatures as well as upwelling of CO2 rich waters up to the surface during the winter months.

Journal of Geophysical Research 116, 649-659 (2010)

Midorikawa et al. (2010), from the Geochemical Research Department, evaluated long-term trends of ocean acidification across latitudes in the North Pacific Ocean. Focused on evaluating latitudinal variations, they took samples from the 3°N to the 33°N, all on the 137°E. At these points, they measured partial pressure of CO2 in the sea (pCO2 sea), sea surface salinity, sea surface temperature and amount of dissolved inorganic carbon (DIC). They found in the time series data that there were decreasing trends in pH in the Pacific Ocean. This pH decrease each year came with seasonal changes ranging from 0.0015 to 0.0021 in the winter and 0.0008 to 0.0019 in the summer. Variability in pH was greatly affected by seasonal and temperature change and latitudinal differences. In fact, rising sea surface temperature accounted for up to 44% of the pH decrease in the southern subtropical region while sea surface temperature actually slowed the pH decrease in the northern subtropical region.

Midorikawai T, Masao I, Saitoi S, Sasanoi D, Kosugii N, Motoi T, Kamiya H, Nakadate A, Nemoto K, and Inoue HY. Decreasing pH trend estimated from 25-year time series of carbonate parameters in the western North Pacific. Tellus. 10 June 2010. [cited 2011 Nov 14]; 62B: 649-659.

Proceedings of the National Academy of Sciences of the United States of America, Vol. 106, Issue 30, pp. 12235-12240 (2009)

Research by John E. Dore, Roger Lukas, Daniel W. Sadler, Matthew J. Church, and David M. Karl sheds light on short and long-term modulations of ocean acidification in the central North Pacific. The team of researchers analyzed nearly twenty years worth of time series data (seawater pH and related statistics) at Station ALOHA near Hawaii and came to many important conclusions. In terms of short-term trends, they were able to establish a clear seasonal pattern in the pH of surface waters; the pH hits a peak during the winter (January to April) and hits a minimum during the summer (July to October). They also noted that the swings in pH were mirror images of the swings in water temperature (carbon dioxide is most soluble in water at low temperatures). In terms of long-term trends, they observed a rate of pH decline of about .0019 per year. These findings are quality additions to our knowledge of how ocean acidification functions.

Journal of Geophysical Research. Vol. 110. (2005).

Ken Caldeira, working at the Carnegie Institution, performed a study on ocean acidification that predicts the pH and aragonite saturation of the ocean in 2100 based on several different atmospheric carbon dioxide prediction models. He predicts aragonite will be undersaturated in the Southern Ocean by 2100. The model that predicts this happens to be one of the most conservative projections also. This leaves many to question whether ocean organisms will be able to sustain shell calcification past this date. This models predicting future pH measurements of the ocean are useful for other researchers. It gives them a good pH range to expose organisms to. The way they respond in the these environments will enable scientists to better understand organism specific responses to ocean acidification. The study also argues against the use of deep-sea carbon dioxide injection. Caldeira states that this will solve approximately ten percent of the problem but does not offer a better solution.

Is the response of coral calcification to seawater acidification related to nutrient loading?

Coral Reefs 30 (2011) 911–923

Ocean acidification, or the increasing concentration of CO₂ in ocean water, has been shown to have a negative effect on coral calcification. Increasing CO₂ lowers aragonite saturation state (Ω).  Generally, Ω decreases linearly with calcification; however, in some cases, it has little or no effect on calcification. Can higher nutrient content be mitigating the negative effects of low Ω?

A study by Chauvin, Denis, and Cuet shows that nutrients do, in fact, play a role in promoting coral calcification in low Ω environments. Their experiment found that a modest nitrate addition increased calcification. Nitrates play a role in photosynthesis, and consequently promoted photosynthesis could be the factor directly stimulating calcification. These nutrient-enriched coral showed no relationship between calcification and Ω, suggesting that an excess nutrient environment compensates for low values of Ω. This evidence can be used to explain why some coral reef environments thrive even under low Ω conditions.

In a study by Mathew Nisbet and Teresa Myers published by the Oxford University Press on behalf of the American Association for Public Opinion Research, the two sought to compile a confirmed and definitive summary of public opinion on global warming.  In order to accomplish this task, the two sifted trough hundreds of polling questions chosen from over 70 news organization, academic and nonpartisan public opinion surveys that have been distributed over the past 20 years. The study found that as a result of a very little amount of media and news attention, when surveyed in 1986, a mere 39% of the public responded that they “heard or read anything about the greenhouse effect.” However, after a summer with record breaking heat strokes and thus increasing amounts of media attention in the 1990s, the percentage of the public who had heard or read anything about global warming was approximately 80% and passed 90% in 2006. The results of this survey convey a high correlation between public awareness and media coverage. When the public is more directly concerned with and experiencing the detrimental ramifications of a phenomenon, they are more likely to understand and become aware of it. Unfortunately, Ocean Acidification, although posing dire threats to our marine and coastal ecosystems, barely receives media attention. The science behind climate change alone is very complex and therefore the public generally finds it difficult to comprehend and to relate to.  However, ocean acidification, just one subtopic of global warming, is an even more arduous concept to grasp, especially without a background in science. As a result, public awareness regarding the understanding and consequences of ocean acidification remains at a very low level. However, if paid more attention to and given more media coverage, the study suggests that public awareness on ocean acidification will drastically increase. If more people are concerned with and aware of the consequences of ocean acidification, it is much more likely that they will join movements towards mitigating its harmful and potentially catastrophic effects.

Nisbet, M. C. and T. Myers. 2007. Twenty years of public opinion about global warming. Public Opinion Quarterly. 71: 444-470.