Question 1

Question

Identify the role of carbon in the health of coral around the world. What happens to Earth’s coral reefs when excess CO2 is absorbed in the ocean? In your answer, explain how carbon dioxide gets into the ocean water in the first place.

Answer 1

Carbon plays a crucial role in the health of coral reefs, primarily through its involvement in the process of photosynthesis and its impact on ocean chemistry. Here’s a detailed explanation of these roles and the consequences of excess carbon dioxide (CO2) in ocean waters.

Role of Carbon in Coral Health

1. Photosynthesis: Coral reefs are home to symbiotic algae known as zooxanthellae, which live within the coral's tissues. These algae use sunlight to photosynthesize, converting carbon dioxide and water into glucose and oxygen. The glucose produced is utilized by both the algae and the coral for energy, growth, and building their calcium carbonate structures.

2. Calcium Carbonate Formation: Coral polyps secrete calcium carbonate (CaCO3) to create their skeletons, which are essential for building and maintaining coral reef structures. The process of calcification requires the presence of carbonate ions (CO3^2−) in the water, which in turn is influenced by the availability of dissolved carbon dioxide.

What Happens When Excess CO2 is Absorbed in the Ocean?

When excess CO2 from the atmosphere is absorbed by the ocean, several critical changes occur:

1. Ocean Acidification: The absorbed CO2 reacts with water to form carbonic acid (H2CO3), which dissociates into bicarbonate (HCO3^−) and hydrogen ions (H+). The increase in hydrogen ions lowers the pH of the ocean, leading to a more acidic environment. This phenomenon is known as ocean acidification.

2. Decreased Availability of Carbonate Ions: As the concentration of hydrogen ions increases, it reduces the availability of carbonate ions, which are necessary for corals to build their calcium carbonate skeletons. Lower carbonate ion concentration makes it more difficult for corals to calcify, leading to slower growth rates and weakened structures.

3. Impact on Coral Health and Ecosystems: The combination of increased acidity and reduced calcification negatively impacts coral health, making them more susceptible to disease, bleaching events, and other stressors. Bleaching occurs when corals expel the zooxanthellae due to stress, leading to a loss of color and a detrimental impact on their energy sources.

How CO2 Gets into Ocean Water

Carbon dioxide enters the ocean through several mechanisms:

1. Atmospheric Exchange: The ocean is in continuous contact with the atmosphere, and CO2 can diffuse from the air into the surface waters. This process is influenced by factors such as temperature, wind, and ocean currents.

2. Biological Processes: Marine organisms, including phytoplankton, consume CO2 during photosynthesis, and any imbalance between photosynthesis and respiration can lead to fluctuations in the levels of dissolved CO2.

3. Anthropogenic Emissions: Human activities, particularly the burning of fossil fuels and deforestation, have dramatically increased atmospheric CO2 concentrations. A significant portion of this excess CO2 is absorbed by the oceans, contributing to both ocean acidification and the challenges faced by marine ecosystems, particularly coral reefs.

In conclusion, carbon plays a vital role in the health of coral reefs through photosynthesis and calcification. However, excessive CO2 absorption leads to ocean acidification, which threatens coral growth and overall reef ecosystems, highlighting the urgent need for measures to reduce carbon emissions and protect marine biodiversity.