The given graphs shows the productivity of an aquatic ecosystem measured in terms of dissolved oxygen produced and consumed by green plants and photosynthetic algae where PS=photosynthesis and R=respiration. What will happen during algal bloom?

1. PS will be increase, R will be decreased
2. PS will be decreased, R will be increased.
3. PS and R will not change.
4. PS+R will increase.

Options

A. PS will be increase, R will be decreased
B. PS will be decreased, R will be increased.
C. PS and R will not change.
D. PS+R will increase.

Answer

D

Explanation

During photosynthesis, green plants produce oxygen which leads to increase in dissolved oxygen in an aquatic ecosystem. Respiration uses oxygen and hence causes decrease in dissolved oxygen. The excess growth of planktonic algae that causes colouration of water is called algal bloom. The increased growth in photosynthetic algae will lead to more photosynthesis which will increase PS+ R ultimately.