Two-thirds of our planet's surface is covered in water, yet the global importance of the oceans is only just becoming apparent. Marine microbes, for example, are responsible for half of the Earth's primary productivity and play a fundamental role in regulating world climate. In this Insight, Naturepresents articles on marine microorganisms, ecosystems and global nutrient cycles that have furthered our understanding of biological processes in the oceans and may be critical to comprehending global nutrient cycles in a time of rapid environmental change.
