Question

The following image shows the penetration capacity of different colours of visible light in open ocean and coastal waters.

Name the types of algae that would be found at each depth:

• A. 150-200m - Brown algae
  100-150m - Green algae
  0-50m - Red algae
• B. 150-200m - Red algae
  100-150m - Brown algae
  0-50m - Green algae
• C. 150-200m - Green algae
  100-150m - Red algae
  50-100m - Brown algae
• D. 150-200m - Brown algae
  100-150m - Red algae
  50-100m - Green algae

Answer 1

The correct option is B 150-200m - Red algae
100-150m - Brown algae
0-50m - Green algae

Green algae possess the pigment chlorophyll, which mainly absorbs blue and red light, and themselves, appear green. The red light has the lowest penetration capacity. So, green algae are found near the water surface (upto 50m).

Brown algae contain the pigment fucoxanthin, which absorbs green andviolet lights and appear brown. So, they are found in the region where the green and violet light can penetrate (100-150m).

Red algae contain phycobilins, which primarily absorb blue light and appear red. Blue light can penetrate deepest in the ocean. So, red algae are found deepest in the ocean (150-200m).

Thus, red algae are found deepest, green algae at the uppermost layers, and brown algae intermediate between these.