Here's a problem to solve: Fertilizer from an agricultural area runs off into a river. The river carries the nutrients from this fertilizer and deposits them into an ocean bay. After the nutrients enter the bay, scientists monitoring the water would most likely see a decrease in which of these dissolved gases?

Among the 4 following options, which is the correct answer?

- A: oxygen
 
- B: nitrogen
 
- C: carbon dioxide
 
- D: carbon monoxide
 