How does the decomposition of sea shells (measured in terms of mass loss over a time period of 10 days) depend on the acidity of the medium (measured in terms of pH) it is immersed in and the type of sea shell?

Investigation of the effect of Ocean Acidification and type of sea shells on the decomposition of sea shells.

Increased Carbon Dioxide due to human activity in the atmosphere is absorbed by the ocean; carbon dioxide molecules react with water molecules to form carbonic acid. The pH level in the ocean drops thus increasing the acidity. Carbonic Acid is a weak acid, however when it is produced in huge quantities it makes the ocean highly acidic in nature. This process is known as Ocean Acidification. It poses a threat to the marine animals and sea shells present in the ocean.  The skeletons of the seashells are made up of calcium carbonate. If the ocean or seawater is acidified, less carbonic acid is available for marine animals to create sea shells. If the ocean is extremely acidified, sea shells begin to decompose which makes organisms such as Oysters, Mussels, Mollusks, and more are vulnerable to being eaten.

The impact of Ocean Acidification remains significant specifically in India, Bay of Bengal. 30 sea surface samples, 4 marine sediments, and 28 sea shells, oyster, and coral reef samples were collected.

The investigation focuses on the north - eastern part of the bay. The study recorded the average pH level of 7.75 and the lowest value was recorded at 7.47. The average amount of bicarbonate recorded was 138.940. Indicating a strong positive correlation between the pH level and bicarbonate given a value of 0.930. Indicating that the bay was highly acidic. The chemical composition of oysters and mollusks was compared to their standard composition. The study investigated that about 17% of the chemical composure of the shells were reduced in comparison to their standard composition. It also showed that the shell membrane of the mollusks were directly impacted, making the shells weaker in nature. The chemical bonding of CaCO₃ was broken down as well as the amount of CaCO₃ in the shell membrane was reduced.

Another survey that was conducted along the continental shelf from Northern Washington to Southern California, depicted high levels of ocean acidity impacting pteropods.

Pteropods are marine snails that swim near the ocean's surface and are a source of food for many other organisms such as salmon, mackerel, and herring. They are vulnerable to acidity because they build shells from aragonite, which is a soluble form of CaCO₃, that is highly sensitive to acidity. The research was conducted during the upwelling season in California, where Co₂ levels are high. The picture on the left indicates a healthy seashell and the picture on the right indicates the after effects of the shell dissolving in corrosive waters. Almost 53% of shells in the region had dissolved sea shells.

From the results that the researchers collected they found out that the percentage of Pteropods in this region with dissolving sea shells have doubled, and they predicted that it may triple by 2050.

This topic is also significant in the ESS syllabus in chapter 7, where we learn about climate change and how human activity such as the excessive use of fossil fuels leads to ocean acidification.

The environmental issue that will be investigated is Ocean Acidification and how it will affect the decomposition of seashells. It is related to the research question because the independent variable in my investigation is acidity. The parameter that I will be using to describe the growth of the sea shells is the mass of the sea shell which I will be measuring. Also, I will be studying how the effect of ocean acidification varies depending upon the type of sea shells.

• Type A sea shell was chosen.
• 25 plastic cups were placed on a flat surface and all of them were numbered.
• A digital mass balance was switched on, the sea shell was placed on the balance, and its initial mass was recorded.
• The mass of the petri dish was kept to 0.00 before placing the seashell on the balance.
• After recording the initial mass of the sea shells, it was placed inside each of the plastic cups.
• For the first 5 cups (1 - 5), 10cc of vinegar was transferred using a graduated measuring cylinder.
• Next, 90cc of water was added to all the 5 cups.
• This process was repeated with different variations of vinegar for the remaining 20 cups.
  • 20cc vinegar, 80cc water (6 - 10)
  • 30cc vinegar, 70cc water (11 - 15)
  • 40cc vinegar, 60cc water (16 - 20)
  • 50cc vinegar, 50cc water (21 - 25)
• The cups were kept for a time period of 10 days and then the new mass of the sea shells were recorded.
• The same procedure was repeated for type B and C sea shells.

• Plastic cups - 100 cups
• Sea shells - 3 types
  • Moonshell
  • Turitella
  • Lucine
• Vinegar - 5 L
• Digital mass balance
• Graduated measuring cylinder
• Tap water

All Seashells were purchased from the market and the equipment was provided from the school laboratory.

In Figure 25, Turitella and Lucine, change in the mass of both these sea shells is increasing as the percentage concentration is increasing. If there is more vinegar, or if the medium becomes more acidic, there is a higher loss of mass in the seashell. Hence, both Turitella and Lucine have been proven that an acidic environment is not favourable. Comparing the trend of Turitella and Lucine, Lucine has a steeper trend than Turitella. This means that the decrease in mass because of increasing the acidity of the medium is more impactful with Lucine in comparison to Turitella. Acidity is a harmful factor for seashells, more specifically Lucine, than Turitella. The findings for Moonshell are different. The trend line for Moonshell indicates that the change in mass is decreasing as the percentage concentration is increasing. There may be a few reasons why this could occur. It could be that the data collected was inaccurate or there was a random error in the experiment, or the seashell has certain biological features that allows it to produce more calcium carbonate as the acidity of the medium increases.

When the percentage concentration of vinegar is increased, from 10.00 to 20.00%, the change in mass is decreasing from 0.60g to 0.22g. From 30.00 to 40.00%, it is decreasing again, from 0.72g to 0.62g. Lastly from 40.00 to 50.00%, the concentration is increasing from 0.62g to 0.75g. Overall, there is no trend or correlation witnessed from the data obtained. However, the hypothesis states that higher the concentration of vinegar, there will be a higher loss of mass. The pattern obtained for Turitella and Lucine from Figure 25 is different from the pattern obtained from Moonshell. When a cumulative representation of all values is taken and if the data collected for Moonshell is inaccurate, it will affect the overall result of the data. Hence, this could be the reason why there is no proper correlation obtained for Figure 25.

The research question stated that How does the decomposition of sea shells (measured in terms of mass loss over a time period of 10 days) depend on the acidity of the medium (measured in terms of pH) it is immersed in and the type of sea shell? The experiment conducted partly answered the research question. The hypothesis stated that if the percentage concentration of vinegar increases, the overall mass of the Seashell will decrease. The trend for Turitella and Lucine proved the hypothesis to be right. The values obtained for the trend showed an increase in average change of mass (0.49, 0.57, 0.62) as the concentration was increased. However, the data collected for Moonshell had a different approach. The trend line showed a decrease in the mass of the sea shell (0.20, 0.85, 0.52) when the vinegar concentration was increased. Hence, the overall trend was inaccurate. Possibly, the inaccuracy of the results obtained could be due to a random error in the experiment, or Moonshell may have certain biological features that produces more calcium carbonate as the acidity of the medium increases.

Strengths:

• The data was varied consistently in a definite interval (10%, 20%, 30%, 40%, 50%) which means there was a good range of data collected for the independent variable.
• There were 5 trials conducted for each seashell thereby reducing random errors.

Weaknesses:

• The data collected was not precise enough, therefore giving inaccurate trends shown in Figure 26 For instance, the data collected for Type C 40% vinegar concentration, the value obtained from the first paper cup is 1.11g and the 5th cup has a value of 0.00g, demonstrating that there is not enough precision within the data.
• The readings recorded were only for 3 types of Seashells, including a variety of seashells would have provided more accurate results.
• During the experiment, the cups were not covered. Water may have evaporated from the cup and this could have changed the concentration of the solution again leading to inaccurate results.
• The effect of salinity could also have been investigated where NaCl could have been used instead of Vinegar. The entire process could have been repeated with different percentages of NaCl.

Livestock farming is a major source of contributing towards greenhouse gas emissions. Reducing or legislating the demand for meat, may reduce carbon emissions. Grain production requires immense fertilizers, pesticides and fuel to feed livestock that release Nitrogen oxide in the environment, contributing to the greenhouse effect. However, livestock farming is a significant practice because it yields large amounts of crop production. In addition, it’s difficult to limit meat consumption due to the growing demand for meat all over the world. Energy derived from the burning of fossil fuels is the reason why carbon emissions are extremely high. Alternative renewable energy sources such as solar, wind, and geothermal can reduce carbon emissions, reduce the reliance on fossil fuels and work towards sustainability. Although, these energy sources can be costly whereas fossil fuels such as coal, oil are cheaper to purchase.

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