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| Because of the darkness, cold, and extreme pressure, scientists have had to develop new technology to enable them to study the ... | deep ocean floor |
| Sonar | A system that determines the distance of an object under water by recording echoes of sound waves; gets its name from sound navigation and ranging. |
| continental shelf | A gently sloping, shallow area of the ocean floor that extends outward from the edge of a continent. |
| continental slope | An incline leading down from the edge of the continental shelf. |
| seamounts | A mountain on the ocean floor that is completely underwater. |
| abyssal plain | A smooth, nearly flat region of the deep ocean floor. |
| mid-ocean ridge | The undersea mountain chain where new ocean floor is produced; a divergent plate boundary. |
| trench | A deep canyon in the ocean floor. |
| Some physical factors that determine where marine organisms can live include | salinity, water temperature, light, dissolved gases, nutrients, and wave action. |
| plankton | Tiny algae and animals that float in water and are carried by waves and currents. |
| nekton | Free-swimming animals that can move throughout the water column. |
| benthos | Organisms that live on the bottom of the ocean or another body of water. |
| food web | The pattern of overlapping food chains in a habitat or ecosystem. |
| intertidal zone | The area that stretches from the highest high-tide line on land out to the point on the continental shelf exposed by the lowest low tide. |
| Organisms that live in the rocky intertidal zone must be able to tolerate the pounding of the waves and changes in salinity and temperature. They must also withstand periods of being | underwater and periods of being exposed to the air. |
| estuary | A coastal inlet or bay where fresh water mixes with salty ocean water. |
| Along the United States coasts, most coastal wetlands are either | salt marshes or mangrove forests. |
| neritic zone | The region of shallow water in the ocean that extends from the low-tide line out to the edge of the continental shelf. |
| open-ocean zone | The area of the ocean beyond the edge of the continental shelf. |
| The shallow water over the continental shelf receives sunlight and a steady supply of | nutrients washed from the land into the ocean. |
| holdfast | A bundle of rootlike strands that attaches algae to the rocks. |
| atoll | A ring-shaped coral island found far from land. |
| The surface zone is the only part of the open ocean that receives enough sunlight to | support the growth of algae. |
| bioluminescence | The production of light by living things. |
| hydrothermal vent | An area where ocean water sinks through cracks in the ocean floor, is heated by the underlying magma, and rises again through the cracks. |
| The chemical nutrients in the heated water support the unique group of organisms that are found around | hydrothermal vents. |
| New fish are born, replacing those that are caught, but only as long as the fishery is not overfished. Overfishing causes | the supply of fish to decrease. |
| aquaculture | The farming of saltwater and freshwater organisms. |
| nodule | A black, potato-shaped lump formed when metals build up around pieces of shell on the ocean floor. |
| Because the world ocean is a continuous body of water that has no boundaries, it is difficult to determine | who, if anyone, should control portions of it. |
| Nations must cooperate to manage | and protect the oceans. |
