The marine environment is the largest, most important, and yet most mysterious habitat on our planet. It contains more than 99% of the world's living space; produces half of its oxygen; plays a critical role in regulating its climate; and supports a remarkably diverse and exquisitely adapted array of life forms, from microscopic viruses, bacteria, and plankton to the largest existing animals. As the 21st century progresses human activities, such as overfishing, coastal development, plastic pollution, oil spills, nutrient pollution, the spread of exotic species, and the emission of climate changing greenhouse gases are posing a significant threat to the marine environment and to many of its life forms. In this unique Very Short Introduction, Philip Mladenov provides a comprehensive overview of marine biology, providing a tour of marine life and marine processes that ranges from the polar oceans to tropical coral reefs; and from the intertidal to the hydrothermal vents of the deep sea. ABOUT THE SERIES: The Very Short Introductions series from Oxford University Press contains hundreds of titles in almost every subject area. These pocket-sized books are the perfect way to get ahead in a new subject quickly. Our expert authors combine facts, analysis, perspective, new ideas, and enthusiasm to make interesting and challenging topics highly readable.