Question

Ocean acidification reduces carbon sequestration mainly by affecting

• A. Nitrogen fixation
• B. Phytoplankton respiration
• C. Calcifying organisms
• D. Dissolved oxygen

Hint:

Ocean acidification: \[ \boxed{ CO_2 + H_2O \rightarrow H_2CO_3 } \] reduces carbonate ions, affecting \[ \boxed{\text{Calcifying organisms}.} \]

Answer 1

The Correct Option is C

Step 1: Recall what ocean acidification changes.
As seawater absorbs more carbon dioxide, its pH falls and the concentration of carbonate ions available in the water drops.
Step 2: Think about who needs those carbonate ions.
Corals, molluscs and coccolithophores rely on carbonate ions to build their calcium carbonate shells and skeletons.
Step 3: Trace the effect on carbon storage.
With fewer carbonate ions available, these organisms calcify less, and since their shells are a major long term carbon sink, overall carbon sequestration falls.
\[ \boxed{\text{Calcifying organisms}} \]