Plankton and planktonic bacteria share two features. First, they are both single-celled creatures. Second, they live as floating organisms in the respective environments.

Plankton and planktonic bacteria are actually quite different from one another. Plankton is comprised of two main types, neither of which is bacterial. One type of plankton, the one of most relevance to this volume, is phytoplankton. Phytoplankton are plants. The second type of plankton is zooplankton. These are microscopic animals. Phytoplankton form the basis of the food chain in the ocean.

Phytoplankton are fundamentally important to life on Earth for several reasons. In the oceans, they are the beginning of the food chain. Existing in the oceans in huge quantities, phytoplankton are eaten by small fish and animals that are in turn consumed by larger species. Their numbers can be so huge that they are detectable using specialized...