Introduction
Ocean acidification is the ongoing decrease in the pH levels of the Earth’s oceans, caused by the uptake of carbon dioxide from the atmosphere that goes on for a long period of time. This happens as the ocean and atmosphere interact. They interact in many ways, in exchanges of heat, salt, water and momentum. When wind blows over the ocean, energy is transferred from wind which then drives ocean currents. However, not only natural things are happening to acidify the ocean, we play a part in it too. Fossil fuels and deforestation. Climate Interpreter’s website report how are humans causing ocean acidification? (Last updated December 18th 2013) states that “Fossil fuel emissions are the gases that are spewed out of most cars, airplanes, power plants, and factories that are burning fossil fuels (coal, oil or gas). Since the industrial revolution, fossil fuel consumption has risen exponentially to create many climate change-related issues, including ocean acidification. Deforestation is a two-fold issue. Burning down forests is similar to burning fossil fuels, it emits a lot of carbon dioxide into the atmosphere. Forests are important because large expanses of plant life (even in the ocean) are known to be carbon sinks, taking in carbon dioxide for photosynthesis. The CO2 being produced was in turn being absorbed. Deforestation not only creates more CO2, but it also destroys one of the very things that helps absorb it! Atmospheric CO2 is increasing so the ocean is taking up more of it- about 30% of atmospheric CO2 is absorbed by the ocean.”1 This then means oceanic CO2 is increasing causing changes to ocean chemistry. Ocean chemistry is changing- CO2 dissolves when it comes into contact with the sea water. The carbon dioxide reacts with water molecules to form carbonic acid. This compound then breaks down into a hydrogen ion and bicarbonate. The presence of all these hydrogen ions is what decreases the pH, or acidifies the ocean. The carbonic acid lowers the pH and bicarbonate. This changing chemistry is slowing the calcification rates of coral and other marine calcifiers. A marine calcifier is a sea animal that creates or makes a calcium carbonate shell or skeleton. Some examples are, Corals, Oysters, Mussels, Pteropods, Coccolithophores and Crustaceans. The increased amount of carbonic acid should also make it more difficult for many organisms to build their calcium carbonate shells or skeletons, which is affecting the ocean biology as well as the ocean chemistry. This is important as in the long run it could actually affect us. We eat some of these marine animals, therefore we are digesting all of it. Also, it is ruining our beautiful coral reefs- the Great Barrier Reef will most definitely not have as much tourism as it would have before. This would affect the economy of some countries which either rely on selling fish or tourism for their coral reefs. It is already predicted to cost the world’s economy £1 trillion by 2100. Ocean acidity is measured on the “pH” scale: liquids with a pH less than 7 are acidic and those with a pH above 7 are basic. So far, the ocean’s pH has dropped from about 8.2 to around 8.05. However, this seemingly small change is already affecting ocean organisms, and future CO2 emissions could lower ocean pH even further. The aim of this report is to explain how ocean acidification will or is affecting different marine species. Also to educate people on how ocean acidification affects us on a global scale. I am looking at the response of various species to ocean acidification to see how help can be given to them in order to help them calcify, and grow and to determine whether or not there is one species we should be more worried about.
A calcification rate is how quick a marine species calcifies. Although photosynthesis rates are not shown above, it is shown in the figures below, it means how quick a species photosynthesizes. As shown in the graphs above, some marine calcifiers are affected more than others by this decrease in pH. Coccolithophores, Corallina and Oysters have a decrease in their calcification rates. Coccolithophores had a decrease of 0.4% when they went from 0.8% to 0.4%. Corallina had a decrease of 0.2% when they went from 0.6% to 0.4% and Oysters went from 0.3% to 0.15% with a decrease of 0.15% as the pH decreased per day. However Sea Urchins are quite the opposite of the others. As the pH decreases their calcification rate increases. It goes from about 0.2 to about 0.35% per day. Blue Mussel and Coral are a bit up and down here. At the pH values 8.02 and 7.86, corals calcification rate increases by about 0.1% per day but at 7.83 it decreases by 0.25% again. Blue Mussel increases its calcification rate at a pH of 8.02 by 0.07% per day but then decreases again at 7.77 by 0.08%. Another experiment was taken place by scientists and the analysis found that under the high emissions scenario, between 21-32% of calcifying species would be significantly affected, based on a threshold of 10% of a species population being affected. In the low emissions scenario, only 7-12% of species would be affected. According to The Guardian’s report, Ocean Acidification is a deadly threat to marine life, finds eight-year study (Monday 23 October 2017 16.02) “Marine life such as crustaceans and organisms that create calcified shelters for themselves in the oceans were thought to be most at risk, because acid seas would hinder those forming shells. However, the research shows that while these are in danger, perhaps surprisingly, some – such as barnacles are often unaffected, while the damage from acidification is also felt much higher up the food chain, into big food fish species.” 2 All of this is happening because ocean pH is decreasing.
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Figures
Discussion
The calcification rate of the marine calcifiers mainly decreases when the pH decreases. This is because their shells or skeletons are being eroded. Sea Urchins calcification rates is actually the opposite. This is because they are adapting to ocean acidification. Corals are being eroded as the hydrogen ions attack the calcium carbonate ions, this then means they also stop growing. As I said before by increasing the presence of hydrogen ions, the additional carbonic acid that forms in the oceans ultimately results in the conversion of carbonate ions into bicarbonate ions. This net decrease in the amount of carbonate ions available may make it more difficult for marine calcifying organisms, such as coral and some plankton, to form calcium carbonate shells, and such structures become vulnerable to dissolution. About 22% of marine life is homed in coral reefs. However while marine calcifiers aren’t doing that well, non-marine calcifiers are doing ok- for example seagrass. Studies show that in fact crustaceans like crabs, lobsters, and shrimps grow quicker in more acidic water. Even though all marine life is important, there are two creatures we should be most worried about in the future of ocean acidification. These are coccolithophores and coral. We should be most worried about these as an increase in CO2 means they are being dissolved. This is then affecting the food chain as coccolithophores are at the base of it. Which is then affecting ocean chemistry and ocean biology. Also it is affecting different marine life species as they will have less places to live- coral homes a lot of marine life-therefore it is indirectly affecting fish as they have less food and less habitats. I feel that between these two species, coral is the most important. I think this because many other species/ecosystems depend upon it to survive. Coral reefs also serve as protectors and wave breakers. A report from The Coral Guardian Why are coral reefs so important? states “By their massive formation between the surface and the first few tens of meters deep, coral reefs are a very effective for absorbing elements coming from the ocean. They absorb wave’s energy and contribute to environmental protection through the reduction of coastal erosion. They reduce the damage in case of storms, hurricanes, and in some way, the energy of tsunamis. In doing so, they protect both ecosystems located between the reefs and coasts, such as seagrass and lagoon for example, and human settlements located by the sea.”3 Also answers.com tells me that they are important to humans because animals in the corals reefs can be used to make medical drugs that help cure diseases, they can provide food for more that 1million people, and some lime stone reefs can be used for human bone grafts.4 There are many geoengineering approaches we could try. According to Oxford Geoengineering Program’s website What is geoengineering? It is the deliberate large-scale intervention in the Earth’s natural systems to counteract climate change. It can be split into two categories. Solar Radiation Management (SRM) or Solar Geoengineering SRM techniques aim to reflect a small proportion of the Sun’s energy back into space, counteracting the temperature rise caused by increased levels of greenhouse gases in the atmosphere which absorb energy and raise temperatures and Carbon Dioxide Removal (CDR) or Carbon Geoengineering. This is when CDR techniques aim to remove carbon dioxide from the atmosphere, directly countering the increased greenhouse effect and ocean acidification. These techniques would have to be implemented on a global scale to have a significant impact on carbon dioxide levels in the atmosphere.5 One technique that has been proposed is direct air capture (DAC). According to David Keith’s website on the Harvard Site’s Keith Group titled Direct Air Capture DAC refers to a set of technologies that can capture industrial-scale quantities of CO2 from atmospheric air, as opposed to point-source CCS which captures only from flue stacks where CO2 is much more concentrated. 6 The center for carbon removal (September 24 2015) tells us some pros are, because DAC systems do not need to be sited directly at power plants, they can be sited close to sequestration/manufacturing sites, eliminating the sometimes costly CO2 transportation step associated. In addition, DAC systems take up a relatively small land footprint. A study by the American Physical Society showed that a square kilometer of DAC machines could generate around 1 million tons of CO2/year (meaning that 3 sq.-km of DAC projects could offset the same amount of coal power that the Topaz Solar Field does using over 25 sq.-km of land). However a con to Direct Air Capture is that high costs compared to other greenhouse gas abatement approaches. 7 It would cost £25m to build and $600 per tonne of carbon dioxide captured. Even though this could be effective, there are people out there we need to appeal to such as environmentalists who would disagree with this and would want to do it naturally. This could be done by marine cloud brightening. The marine cloud brightening project says it is when clouds reflect solar radiation (sunlight) back to space, producing cooling effects locally, and on the planet. The reflectivity of clouds increases as the number of water droplets inside the cloud increases and their size decreases, making the clouds brighter and longer lasting, reflecting sunlight and increasing cooling.8 As I said there are many steps we could take but would these help our coccolithophores and coral?
Conclusion
Finally, the calcification rates of most marine calcifiers are decreasing as more carbon dioxide enters the ocean. I think we should be worried about ocean acidification in the future as although the pH has only a seemingly small increase, it is actually huge. I do think there is one species we should be worried about. Every marine calcifier will be under threat however there will be more of an effect on coral or coccolithophores. This is because they are linked to other things as well as being eroded themselves. We need to focus more on coral or coccolithophores as we progress as these are the species that in the long run will affect us. We eat these fish, and if there are no coccolithophores then as they are the base of the food chain, the fish will not have as much food to eat. Also if there is no coral left it would mean less habitats for the fish. I have achieved my aim of determining which species we should be most worried about and discovering why the calcification rates either increased or decreased. Future research should focus on trying to help or prevent ocean acidification or at least slow it down. There have been many proposals or plans and now one of them needs to be put into action.
Abstract
Ocean pH is increasing. There is more carbon dioxide in the atmosphere and the ocean is absorbing it. This is affecting marine calcifiers and other marine species. I am trying to determine which species will be most affected in the future of ocean acidification and figure out a way to help them. Also to work out how we can stop or at least slow down the process. Is there one species that will be affected the most? Or will all marine life equally be a risk? That is the aim of this report. The calcification rates of most marine species are decreasing however there are one or two species that are doing ok. This is mainly because of shells being eroded or the marine life not being able to build their calcium carbonate shells. There needs to be future research done and steps taken to prevent these species being affected. But mainly focusing on the marine creatures that are going to be most affected by ocean acidification, not just now but it the long run too.
1. https://climateinterpreter.org/content/how-are-humans-causing-ocean-acidification
2. https://www.theguardian.com/environment/2017/oct/23/ocean-acidification-deadly-threat-to-marine-life-finds-eight-year-study Monday 23 October 2017 16.02
3. https://www.coralguardian.org/en/coral-reef-important/
4. http://www.answers.com/Q/Why_is_coral_important_to_the_coral_reef#slide=1
5. http://www.geoengineering.ox.ac.uk/what-is-geoengineering/what-is-geoengineering/
6. https://keith.seas.harvard.edu/direct-air-capture
7. http://www.centerforcarbonremoval.org/blog-posts/2015/9/20/direct-air-capture-explained-in-10-questions September 24 2015
8. http://mcbproject.org/
