The seas of the world are inhabited by innumerable billions of tiny, drifting organisms called plankton. Some of this is animal life, but the vegetable plankton, largely one-celled diatoms or algae, is the basic food of the ocean; for all marine animals either eat the vegetable plankton or devour other animals which in turn are directly or indirectly dependent on it.
Vegetable plankton use sunlight and carbonic acid dissolved in the sea to produce carbohydrates. By measuring the amount of carbonic acid which thus disappears from a unit volume of water, marine biologists...