Red algae can grow at deeper depths when compared to other algal groups because they are adapted to absorb blue light, which is required for photosynthesis.
Explanation:
Red algae, also known as rhodophyta, usually occur in the depths of seas. This is because of a unique adaptation in their structures, due to the presence of phycoerythrin - a pigment that reflects light that is red, while equipping the algae to absorb blue light. Hence, the algae appears red in colour.
All plants (including algae) require sunlight to be able to synthesize their own food through the process of photosynthesis. For plants that live in the oceans, the sunlight penetrating the waters is the only source of radiation in this regard.
The blue light in the radiation spectrum has the characteristic features of having the highest energy, as well as the shortest wavelength. This makes it the most energetic section of light, enabling it to penetrate to the ocean depths.
The phyrcoerythrin in the red algae absorbs this blue light for photosynthesis. This process occurs even at depths upto 500 feet, hence becoming an adaptive advantage for red algae to be able to survive at greater depths.
