How do inert dyes like erioglaucine and tartazine effectively control algae?

Inert dyes like erioglaucine and tartazine effectively control algae by reducing light availability in the water. These dyes function by absorbing specific wavelengths of light, which prevents sufficient sunlight from penetrating the water column. Since algae and other aquatic plants rely on light for photosynthesis, a significant reduction in light availability inhibits their growth and reproduction. By creating a shade effect in the water, these dyes can disrupt the photosynthetic process essential for algae survival, thus helping to manage algal blooms and maintain healthier water bodies.

In contrast, promoting algae growth or enhancing photosynthesis in higher plants would lead to increased algal proliferation, which is undesirable in the context of controlling algae. Increasing available nutrients in the water would further exacerbate the problem, as it would provide the necessary components that fuel the growth of algae. Therefore, reducing light availability serves as a more effective strategy for controlling harmful algal populations.