Question

Why the algae change colour time by time?

Answer 1

Blue-green algae, also known as Cyanobacteria, are a group of photosynthetic bacteria" Blue-green algae are most often blue-green in color, but can also be blue, green, reddish-purple, or brown. Blue-green algae generally grow in lakes, ponds, and slow-moving streams when the water is warm and enriched with nutrients like phosphorus or nitrogen.

Answer 2

Phytochrome is a pigment present inside a plant that helps it to adapt to changing light conditions. Since algae lives inside water, the light intensity varies at different depths. Phytochromes inside Algae is different in that they are able to perceive light across the visible spectrum. Hence based on the light availability, they adapt and change their light harvesting chemistry. Therefore the colour changes from time to time.