Question

Which of the following statement(s) is/are true regarding the biogeochemical cycle in the ocean?

• A. Shutdown of the biological pump in the ocean would have resulted in higher CO₂ concentration in the atmosphere compared to present-day.
• B. If atmospheric CO₂ concentration increases, the solubility pump would lead to a decrease in dissolved inorganic carbon in the ocean.
• C. All carbon sequestered by marine photosynthesis settles down on the ocean floor as organic matter.
• D. Calcification (the process of making shells and skeletons) by marine organisms in the surface ocean layer would lead to an increase in the surface ocean CO₂.

Hint:

The biological pump and calcification processes play crucial roles in regulating CO₂ concentrations in the atmosphere and the ocean. A shutdown of the biological pump would increase atmospheric CO₂, while calcification by marine organisms can lead to higher surface ocean CO₂.

Answer 1

The Correct Option is A, D

The ocean plays a crucial role in the global carbon cycle, primarily through processes such as the biological pump, the solubility pump, and the process of calcification. Let’s break down the options: - Option (A) Shutdown of the biological pump in the ocean would have resulted in higher CO₂ concentration in the atmosphere compared to present-day:
This is correct. The biological pump refers to the process by which carbon is transferred from the surface ocean to the deep ocean through the activity of marine organisms, such as phytoplankton. If this process were shut down, less carbon would be removed from the atmosphere and stored in the deep ocean, resulting in higher atmospheric CO₂ concentrations.
- Option (B) If atmospheric CO₂ concentration increases, the solubility pump would lead to a decrease in dissolved inorganic carbon in the ocean:
This is incorrect. The solubility pump is responsible for the uptake of CO₂ from the atmosphere into the ocean, primarily through the dissolution of CO₂ in cold, polar waters. If atmospheric CO₂ concentration increases, the solubility pump would lead to an increase in dissolved inorganic carbon in the ocean, not a decrease.
- Option (C) All carbon sequestered by marine photosynthesis settles down on the ocean floor as organic matter:
This is incorrect. While a significant portion of carbon sequestered by marine photosynthesis does settle to the ocean floor as organic matter, not all of it remains there. Some of the carbon is re-mineralized in the water column or consumed by marine organisms, and only a portion reaches the ocean floor.
- Option (D) Calcification (the process of making shells and skeletons) by marine organisms in the surface ocean layer would lead to an increase in the surface ocean CO₂:
This is correct. Calcification, the process by which marine organisms (such as corals and mollusks) produce calcium carbonate shells, consumes carbonate ions (CO₃²⁻) from the water. This process reduces the buffering capacity of the ocean and can result in an increase in CO₂ concentration in the surface ocean, as it disrupts the equilibrium between dissolved CO₂ and carbonate ions. Thus, (A) and (D) are the correct answers.