Phytoplankton are microscopic plants that live in the ocean. Phytoplankton obtain energy through a process called photosynthesis and must therefore live in the well-lit surface layer of an ocean, sea, lake or other body of water. Through photosynthesis, phytoplankton are responsible for much of the oxygen present in the Earth's atmosphere – half of the total amount produced by all plant life. They are also the basis for the oceanic food chain. Since phytoplankton depend upon certain conditions for growth, they are a good indicator of change in their environment. For these reasons, and because they also exert a global-scale influence on climate, phytoplankton are of primary interest to oceanographers and Earth scientists around the world. This book provides current research on this very important marine plant species. The increasing numbers of entrepreneurs who are exploring and investing in marine phytoplankton as sources of food additives, pharmaceutics, therapeutics and bioenergy are discussed as well.