Figure 1. Schematic representation of the ocean floor where scales are greatly exaggerated and not drawn to proportion (particularly the horizontal). See text for explanation of terms.

Figure 2. Some of the organisms commonly found in marine systems. A and B are planktonic whereas C–F are benthic. A is a copepod, a type of crustacean that is often very abundant in surface waters; B is a small jellyfish, which can also be very numerous in surface waters; C is a cumacean; D is a polychaete; E is a sipunculid; and F is a nematode. All of these benthic taxa live in bottom sediments. For scale most of these organisms are several millimetres in length. Photographs by Patricia Ramey.

Figure 3. Global distribution of corals, mangroves and salt marshes superimposed over map of seafloor bathymetry. Red areas are continental shelf, above which are found neritic communities, whereas blue areas are open ocean where oceanic communities occur. Green areas show plate spreading regions, along which vents and seeps occur. Bathymetry image from Walter Smith at National Oceanic and Atmospheric Administration, Boulder, Colorado.