Question

The most significant factor limiting the primary production at a depth of 20 meters in sea is the:

• A. Availability of $C{O}_2$
• B. Availability of nutrients
• C. Quality of light
• D. Temperature

Answer 1

The correct option is C Quality of light

The amount of biomass or organic matter produced per unit area over a time period by plants is termed primary productivity. It depends upon a variety of environmental factors like carbon dioxide availability, light quality, availability of nutrients and photosynthetic capacity of plants.
Quality of light is the most significant factor limiting primary production at a depth of 20 meters in sea. With depth, the intensity of sunlight decreases rapidly. The colors as well as the amount of light is affected with the depth of the water. Light with longer wavelengths is absorbed more quickly than that with shorter wavelengths thereby varying the quality of light with increasing depth. Because of this, the higher energy light with short wavelengths is able to penetrate more deeply. Maximum photosynthesis occurs in a plant in red and blue regions but with increasing depth quality of light will reduce thereby affecting productivity.