The Diversity of the Sea

by Robert Langreth

The oceans harbor at least as great a variety of life as do the lands. An estimated five million species, most of which have not yet been classified, reside beneath the waves. The web of marine life starts with the tiny phytoplankton-unicellular plants that are eaten by the slightly larger zoo-plankton, young shrimp, and other small animals.

Moving up the food chain we find sponges, corals, mollusks, and other sedentary animals; then mobile creatures, including hard-shelled crustaceans; soft-bodied squids and jellyfish; eels and snakes; and small fish. At the top, of course, lurk large predators like killer whales, swordfish, and sharks.

The densest life exists in the first 200 meters of water. Below this, little light penetrates and the population density declines sharply. However, the diversity of life remains great even on the ocean floor, where explorers have discovered everything from giant clams to hoselike red tube worms.

Ocean Planet Exhibition Floorplan

gene carl feldman ( (301) 286-9428
Judith Gradwohl, Smithsonian Institution (Curator/Ocean Planet)