Changes to Ocean Chemistry

Al Gore famously said, “carbon dioxide is the exhaling breath of our civilization.[1]” Since the foundation of agriculture ten thousand years ago and the industrial revolution, humans have based their existence on the use, production, and consumption of components that contain or release carbon dioxide. The use of such products has caused an immense spike in carbon dioxide levels in the atmosphere which has disrupted Earth’s natural processes. These increased levels of greenhouse gases have a devastating effect on the ocean; the ocean is experiencing the creation of carbonic acid formed by the combination of carbon dioxide and water (H2O)[2]. It is vital to know the chemical properties of the ocean to understand the process and provide solutions to the effects of climate change; the ocean’s large abundance of life is in danger due to  an increase in greenhouse gases, rising sea levels, loss of coral reefs, loss of phytoplankton, acidification, and more. With that said, ocean chemistry is not an easy topic but we must look into it to understand the ocean’s role in climate change and what we can do to save it.

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We must first understand the water molecule in a smaller scale to understand the change the ocean is experiencing. The water molecule is made up of a weak hydrogen bond in which one oxygen atom is attached to two hydrogen atoms[3]. Hydrogen atoms are positively charged, but oxygen atoms are negatively charged; these opposite charges is what attracts one to the other, forming the bond[4]. All molecules are present in three different states: gas, solid, liquid. The determining factor for the three states is temperature; higher temperatures energize the molecules so that they move faster until the bond breaks and it converts to gas. Lower temperatures slow down the molecules enough to allow them to bond again and become liquid. When zero degrees Celsius is reached, water crystallizes forming ice – a solid. This ability to change states also give water other properties such as its ability to dissolve other substances.
This is part of the process of maintaining the ocean’s acidity balanced so that the carbon cycle is working properly without stress. However, climate change has affected the ocean’s pH levels by increasing the absorption of anthropogenic carbon dioxide due to high concentration in the atmosphere. Carbon dioxide has reached a concentration of approximately 385 parts per million in the atmosphere with projections it will continue to increase throughout the 21st century[5]. Ocean waters exchange approximately 25% to 30% of carbon dioxide in the atmosphere [6]. Yet, the excess carbon dioxide in the atmosphere has interrupted the process of balancing the acidity; this is also why they consider the ocean a ‘carbon sink’[7].
Seawater’s composition is measured in units of pH, which measure the consistency of aqueous solutions [8]; the unit tends to range from zero (acidic) to seven (neutral), and 14 (basic)[9]. Historically, the ocean’s pH levels have been measured as 8.2, but has recently fallen by .01 units[10]. The ocean remains basic but acidification refers to the addition of hydrogen ions (H^+)[11].  As mentioned the mixture of carbon dioxide and hydrogen ions creates carbonic acid which can form ions of hydrogen and carbonate. This is represented by the following reaction: CO2 + H2O H2CO3 [ [2H] ^++ CO3^ (-2)[12]. Thus, the ocean’s acidity is increasing steadily due to the excess carbon increasing the concentration of hydrogen ions which directly increase the acidity levels.
Now, all oceans are experiencing acidification but not at the same rate. Overall, cold waters tend to absorb carbon dioxide more readily making them more susceptible to the effects of acidification[13]. The Arctic Ocean, being the coldest, is the most vulnerable; ice-melt maintains temperatures colder, but it has less surface area to absorb carbon dioxide. At the same time, global warming is melting the ice resulting in the increase of surface area and escape of carbon dioxide from ice core bubbles[14]. The Arctic ocean has not only become more acidic but the acidity levels have deepened;  acidity levels expanded from 324 feet below the surface in the nineties to more than 800 feet by 2019[15]. Meanwhile, the Pacific Ocean also has colder waters due to the Arctic Ocean’s ice melt currents mixing and strong winds from coastal areas. The area is already lower in pH levels due to anthropogenic carbon dioxide, with the decrease measured as a loss of .11 units[16]. The Pacific’s pH unit is expected to rapidly decrease from .02 to nearly.3 units per decade[17]. Lastly, the Atlantic Ocean takes in seawater from both the Pacific and Arctic, which are highly acidic as it is; it is facing the same issues as well.
The direct effects of excessive carbon dioxide and acidification are presented in calcifier marine life that have shells and skeletons such as phytoplankton, zooplankton, and other invertebrates [18]. These shells are made up of calcium carbonate, CaCO3, which declines as acidity increases. As a result, these organism’s shells are deteriorating and become weaker, leading to potential death and extinction. At the same time, this causes a reduction in growth throughout development and inability to reproduce[19]. However, an organism’s reaction to the increased acidity depends on their habitat, adaptability, and sensitivity. Marine life that can withstand high acidity levels is thriving during the process; these creatures have a stronger composition without calcium carbonate.
Many organisms act as carbon storehouses, but when impaired by lower pH levels, are not able to store carbon dioxide effectively. For example, phytoplankton is an important organism in the marine environment; the abundance of phytoplankton is often in balance with the amount of carbon dioxide in the ocean[20]. Like plants, it uses photosynthesis to remove carbon dioxide and release oxygen. Thus, phytoplankton is significant to the process of dissolving carbon dioxide but acidification is rendering this process of carbon dioxide removal obsolete. Fish are impacted by the decrease of oxygen levels between water and their gills. Corals are also affected by this ongoing phenomenon, in which the deterioration of calcium carbonate weakens the bone structure and bleaches them. Thus, ocean acidification has a huge role in which it accelerates the deteriorating effects of climate change on other forms of life. Contrarily, algae are thriving in more acidic conditions where higher levels of carbon dioxide and sunlight provide more energy (through photosynthesis).
Ocean acidification also has implications on our economy and lifestyles. The fishing industry will take a huge hit due to the steady decrease of fish populations; not only will there be less fish, but it will be harder to find healthy fish for consumption. Yet, acidification is an important issue, but not for the sake of saving a few fish; the general public is not yet aware of the detrimental effects that are already occurring. The copious amount of trash in the ocean is also a huge problem that must be addressed, but the popularity of the issue is due to the increased sharing of pictures online of animals stuck in trash. Meanwhile, ocean acidification is connected to numerous problems that show the severity of climate change: loss of coral reefs, loss of marine life, increase of carbon dioxide levels, and more[21].
The ocean presents a large and staggering appearance that often leaves many with the impression that it’s a resilient environment. However, in reality the ocean is dynamic and sensitive with numerous problems due to pollution and climate change that will inevitably change our way of life. Even slight changes of less than one pH unit has had catastrophic impacts such as the decrease of ten percent of the Great Barrier Reef’s coral life[22] . Many organisms act as carbon storehouses, but when impaired by lower pH levels, are not able to store carbon dioxide effectively.
References
[1] (Mansoori 2015)
[2] (U.S. National Library of Medicine 2019)
[3] (Waldron 2014)
[4] (Waldron 2014)
[5] (NOAA 2013)
[6] (Allen 2017)
[7] (NOAA 2019)
[8] (Waldron 2014)
[9] (Waldron 2014)
[10] (Sverdrup, Johnson and Fleming 1942)
[11] (NOAA 2013)
[12] (Sverdrup, Johnson and Fleming 1942)
[13] (Lister and Fleming 2019)
[14] (Scholander 2017)
[15] (Allen 2017)
[16] (NOAA 2013)
[17] (Lister and Fleming 2019)
[18] (U.S. National Library of Medicine 2019)
[19] (U.S. National Library of Medicine 2019)
[20] (Sverdrup, Johnson and Fleming 1942)
[21] (NOAA 2013)
[22] (Sverdrup, Johnson and Fleming 1942)