Title
Marine Botany

Diatoms: Critical Depth for Photosynthesis

The intensity of light in the ocean changes with the depth below the surface. When sunlight hits the surface of the water, the intensity is at a maximum. The light is absorbed as it percolates down into the water column. Thus, the farther below the surface of the water an alga lives, the less intense light it sees.

With increasing depth, light may become the limiting factor affecting the rate of photosynthesis. At a particular depth, it becomes too dark for an alga to do enough photosynthesis to meet its energy needs. This is the critical depth, below which an alga cannot grow and reproduce.

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copyright John Becker 1996.

Last updated: Feb. 25, 2005