Plankton are the numerous, primarily microscopic inhabitants of the pelagic environment (see Figure 3). They are critical components of food chains in all marine environments (see Figure 1 in the article on community ecology) because they provide nutrition for the nekton (e.g., crustaceans, fish, and squid) and benthos (e.g., sea squirts and sponges). They also exert a global effect on the biosphere because the balance of components of the Earth’s atmosphere depends to a great extent on the photosynthetic activities of some plankton. The term plankton is derived from the Greek planktos, meaning wandering or drifting, an apt description of ...(100 of 6754 words)