How The pH Affects The Ecosystem in The Ocean

Ocean acidification can best be described as a decrease in pH levels in the Earth’s oceans. As the pH decreases, the ocean's’ acidity increases. One main reason this occurs is due to the carbon dioxide that is released into the atmosphere. The oceans absorbs carbon dioxide from the atmosphere, and the when the carbon dioxide dissolves with salt water, carbon molecules bond with oxygen molecules to form a compound known as carbonic acid (CO2 + H2O→H2CO3).

When carbonic acid is produced, the acid breaks apart in the water and releases harmful components such as hydrogen ions. An excessive amount of hydrogen ions is harmful to marine life. Plants such as photosynthetic algae require CO2 so they may benefit from the excessive amounts of CO2. However, shelled organisms are at a risk, and this affects not only them, but the entire food web.

In the two experiments conducted, we tested how the pH level of the ocean could be affected by different factors and the effects on the ecosystem. To be specific, we will test how carbon dioxide affects pH levels in the first experiments, and in the second experiments, we will test how pH levels of the water itself affects shells.

In the “Bubbles Protocol” Lab, we will be blowing into the water, so that we can add carbon dioxide in the water. When we blow it, the carbon dioxide gas reacts with the water and makes the water more acidic. Using a universal indicator, we are measuring any changes in the water every 30 seconds. Measuring the pH levels of the water indicates the acidity. The carbon dioxide reacting with the water will produce an acidic pH of water. My group’s hypothesis was that if carbon dioxide is blown into the water, then the acidity of the water will increase.

The independent variable is the type of water. In the controlled experiment, the water will be salt water. In the experimental experiment, the water will be tap water. The dependent variable is the pH level of the water, which will change based on the water type. The constants will be the amount of waters. They will both be 100 mL. Also, both of the beakers of water will be covered in plastic wrap, and a straw will be inserted into both of them.

When the blower of our group blew through the straw, carbon dioxide was added into the water. Although this significantly affected the pH level during the first 30 seconds of the experiment, the pH level remained constant after. The pH decreased, so the acidity increased. The salt in the salt water in the control group probably contributed to the acidity being higher than in the tap water.

Our initial hypothesis of carbon dioxide makes the water more acidic was correct. The water did become acidic as the pH levels of both waters dropped. This was due to the hydrogen ions from the carbonic acid. I learned that ocean acidification is a serious concept that affects several different species, and it’s caused mainly by humans releasing carbon dioxide gas into the atmosphere, which ends up turning into hydrogen ions in the ocean.

Organisms make their shells by using calcium carbonate. I expect a solution like vinegar which is very acidic to dissolve the shells. Carbon dioxide reaches oceans by the ocean absorbing it from the environment. Humans are another source of carbon dioxide as we released carbon dioxide through the process of respiration.

My group’s hypothesis was that if the shells were to be placed in an acidic solution, then they will begin to dissolve. My group predicted that vinegar would dissolve the shells more than the seawater would.

In the “Shells Protocol” Lab, we will test the effects of a solution’s pH level on shells. We started the experiment by weighing 4 shells and calculating their initial mass. 2 shells were placed in a controlled group and another 2 were placed in an experimental group. The independent variable was the type of solution. Seawater was the control group and vinegar was the experimental group. The dependent variable was the mass of the shells after 30 minutes. The constant variables were the amount of the solutions, which was 150 mL and the length of time the shells were in the solutions, which was 30 minutes.

When the strength of the shells was tested, those that were dropped in seawater didn’t have much of an effect but those that were in the vinegar solution dropped and cracked. Our initial hypothesis that the shells that were placed in vinegar would dissolve quickly was correct. The vinegar solution dissolved more shells than the seawater did due to the higher acidity. During this lab, I learned that carbon dioxide not only affects the atmosphere, but also affects shelled organisms in marine ecosystems.