Impact of the Increase of Carbon Dioxide Emissions on Marine Life and the Use of Olivine

How has an increase in carbon dioxide emissions affected marine life in our oceans and how can olivine be used to limit this?  

SHE Strand: The use of scientific knowledge may have beneficial or unexpected consequences; this requires monitoring, assessment, and evaluation of risk, and provides opportunities for innovation.

Our oceans are warming and sea levels are beginning to rise due to increasing concentrations of greenhouse gases in the atmosphere. Oceans around the world are becoming more acidic as they absorb $C{O}_2$

, hence undergoing reactions which result in a decreased pH. Ocean acidification makes it difficult for marine animals to form their skeletons and shells, restricting their growth and development (Australian Institute of Marine Science , 2019). Therefore, society has been persistent in developing solutions to this problem, such as a grounded mineral, olivine being used soak up hydrogen ions and hence increasing the pH. This solution does have promise due to the benefits it offers but also many unexpected consequences which need to be monitored and further researched before being released into society.

The concentration of $C{O}_2$

in the atmosphere is rapidly increasing with oceans absorbing around 30 percent of this gas. Hence, as this concentration increases, so does the amount absorbed by the ocean. When $C{O}_2$

dissolves in water, the particles may react with water molecules to form a slightly acidic solution, carbonic acid:

  $C{O}_{2 \left(\mathit{aq}\right)}+H_2{O}_{\left(l\right)}\leftrightarrow H_{2}C{O}_{3 \left(\mathit{aq}\right)}$

However, this solution is a weak acid and hence only some dissociates, producing $H^{+}$

ions and hydrogen carbonate:

  ${H_{2}C{O}_{3\left(\mathit{aq}\right)}\to H}_{\left(\mathit{aq}\right)}^{+}+\mathit{HC}{O}_{3 \left(\mathit{aq}\right)}$

.

This hydrogen carbonate further ionises to form a greater quantity of $H^{+}$

and carbonate ions:

$\mathit{HC}{O}_{3 \left(\mathit{aq}\right)}\to H_{\left(\mathit{aq}\right)}^{+}+C{O}_{3 \left(\mathit{aq}\right)}^{2–}$

Le Chatelier’s Principle states that if a change occurs to the temperature, concentration or pressure within a system then the equilibrium will shift to counteract this change. Thus, this principle demonstrates that as the amount of carbon dioxide increases, the equilibrium will shift to the right and hence more hydrogen ions are formed. Hereafter, the pH will decrease due to the direct link between

concentration and pH, given by pH= -log[H+] (Moore, 2016) . Marine creatures, such as oysters, mussels, and crustaceans use both calcium and carbonate to assist them in building their shells and skeletons. The rate which calcium carbonate forms in the ocean is controlled by the amount of carbonate ions available. Therefore, as the pH decreases and the ocean becomes more acidic, the natural equilibrium in the sea is disturbed and hence this equilibrium shifts back to the left, decreasing the concentration of carbonate.

In lower pH conditions, more hydrogen ions will float around and therefore instead of producing carbonate, hydrogen carbonate is more likely to form, thus disrupting the process which strengthens marine shells. (Johnston & Matear, 2019). 

Figure 1: Showing the effect of a lack of carbonate ions onto the shells and skeletons of marine creatures- (Littschwager, 2019)

In seawater, a horizontal boundary known as the saturation horizon forms due to the temperature, pressure, and depth of the water. Calcium carbonate occurs in two common forms, aragonite and calcite. Aragonite is more soluble then calcite, thus the aragonite saturation horizon is closer to the surface. Hence, these organisms which produce aragonite may be more vulnerable to changes in ocean acidity due to weaker shells forming in these saturation horizons. As, calcification of marine organisms is decreased when the saturation state is lower, occurring near the surface. Thus, marine creatures who habitat in this area, commonly oysters, are more in danger due to the limited calcification and consequently weak structure of their shells (The Royal Society, 2018).

The concentration of carbon dioxide remains relatively balanced due to the natural equilibrium of this gas in the atmosphere. However, this equilibrium can be disrupted by anthropogenic activities, thus increasing $C{O}_2$

at an alarming rate. Anthropogenic activities have placed pressure on ocean ecosystems and consequently impacted marine life (Parliament of Australia , 2016). Ocean acidification is a concern within society, hence potential theories are being developed by society to reduce its impact. Ocean acidity has placed marine life at risk, jeopardizing one of the most valued seafood, oysters. Oysters use calcium carbonate to form and strengthen their shells. The acidic water causes this process to become problematic and subsequently a portion of these oysters will die before they can form their shells. The increasing levels of acidity in our oceans are becoming an enormous threat to any living creature with a shell.

Even if these oysters do survive and grow in waters with high levels of acidity, they develop much smaller with brittle shells which tend to break easily (Hill, 2019). Many oceans around the world have had a decline in their pH, dropping from 8.2 to 8.1, with predictions that this could further drop by 0.4 by the end of the century. Thus, a contingency plan is essential to limit the future effects this could have on our oceans. Marine ecosystems provide immense amounts of resources which benefit society and hence a significant proportion of the world’s population depend on oceans for survival and well-being. Healthy marine life is vital for society as they provide food security, raw materials for medicine, building materials, and most importantly natural protection against hazards such as coastal erosion (Blue Planet, Oceans and Society, 2019). Therefore, society have been strongly influencing the rate at which a scientific solution is established to protect these oceans.

For the past several years, reports have shown that many oyster companies are struggling as ocean acidification has prompted a significant decrease in marine creatures, oysters being just one of many species rapidly declining. A new study by researchers at Oregon State University have recognized why these oysters appear sensitive in acidic waters and found that, despite the dissolving of their shells, the high carbon dioxide alters shell formation, energy usage, and the growth and survival of young oysters (Waldbusser, 2013). Hence, society have been thoroughly considering many solutions by evaluation to see how each would serve to benefit our ocean ecosystems, with consideration of the unexpected consequences. The use of olivine is one solution which has been proposed by numerous scientists and after many tests is envisioned to act as a future resolution to ocean acidification. Olivine is a magnesium silicate, found in the Earth’s surface, and can soak up hydrogen ions. When placed in seawater, it gradually swaps magnesium ions for hydrogen ions, therefore reducing acidity.

Figure 2: showing the process of $H^{+}$

ions being soaked up by Olivine, hence increasing the pH (Climitigation , 2019).

A professor at the University of Utrecht predicts that if olivine is scattered around an area of low saturation, after a year the ${\mathit{CO}}_2$

will decrease by approximately 20 percent. Stating that, “if this process is repeated every year with 7 cubic kilometres of olivine, it may compensate for the entire human proportion of ${\mathit{CO}}_2$

” (Schuiling, 2017).

However, despite the innovative promise this offers for future reductions of ocean acidity, mention has been made regarding many concerns which are being closely monitored. Testing was done on this mineral and for this solution to work on a global level, the quantity needed is too excessive. Though, the amount required to reduce acidity in local oceans is more sustainable. However, ethical concerns have arisen which need to be considered as, when valid testing was conducted the data showed conflicting results.

When 1.5cm layer of this mineral was trialed, the pH of the water increased slightly and showed no other effects. However, when 3cm was used, many marine organisms died as the pH change was too drastic. Thus, this needs to be evaluated before being released to the public to trial a new quantity which researchers deem to be effective in reaching their goal, but also safe for marine life (Klein, 2016).

Furthermore, researchers are currently discussing the safety of applying a thin layer of grounded olivine in oceans. A main issue being whether the potential effects of olivine can be reversed if harm was to be inflicted, or would it involve permanent damage (Klein, 2016). Despite these potential side effects, olivine has become a stepping stone and hence with further testing and research more innovation can arise. Society has and will continue to be drastically impacted by the revolution of this science as society are devastated by the decline in seafood- around 102 million tons of it being consumed last year (Fears, 2016). A study undertaken over four years on 7,800 marine species has concluded that the long-term trend of these species can be predicted. By 2048, the expected decline will be more than 90 per cent. Dr. Boris Worm states that, “this is not an ideal situation, however if no counter actions are taken, this predicted trend will continue to decline. Marine animals are not merely embellishments to be looked at, they are essential to the health of our oceans and well-being of society” (Clover, 2016). Therefore, people are demanding a resolution before this problem causes drastic changes to the population of marine species.

Figure 3: trend representing the decline in marine life in our oceans- (Clover, 2016).

Henceforth, this proposed solution to this global problem would vastly impact society and inflict major benefits to the decreasing population of marine life.                  

Hence, ocean acidification is becoming a severe problem globally due to its irreversible effect on the shells and skeletons of marine species and hereafter, could result in many creatures dying due to this changing pH. Society relies on these marine creatures and hence are influencing science due to their push to find a resolution to reduce ocean acidity. Many theories and tools have been developed, each being thoroughly evaluated. Olivine, a mineral, may be used due to its method of eliminating hydrogen ion concentration by producing magnesium ions instead, consequently increasing the pH. Though, there have been unexpected limitations which have arisen regarding an overuse of this causing marine life to placed in more harm. Thus, more testing and research is vital to conduct a solution which has overcome these consequences, hence providing innovation to reduce ocean acidity and increase the quality of life of marine creatures.  

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