The ocean plays as fundamental a role in the natural scheme of things as does the atmosphere, although its functions, being considerably more varied and diffuse, are probably neither as well appreciated nor as well understood. The sea profoundly affects the weather and climate and in turn is affected by the atmosphere, acting as both a heat reservoir for storing, distributing, and releasing solar energy and as the source for most atmospheric moisture. It interacts with the bounding land and air over times ranging from minutes to millennia. Geological activity on all time and space scales takes place in and under the seas, which serve as the repository for the detritus of man and nature and, just as important, as practicable sources of petroleum and a few useful minerals. Its currents and dilutant powers are called upon to disperse sewage, poisonous and nonpoisonous wastes, solid trash, and excess heat, while it maintains a role as the aqua viva for an extremely complicated and commercially important food chain and a role as a means of recreation and refreshment for people. In the estuaries and the coastal zones these conflicting demands are especially severe.