| A | B |
|---|
| abyssal zone | a subdivision of the benthic zone characterized by extremely high pressures, low temperatures, low oxygen, few nutrients, and no sunlight |
| benthic zone | the marine-life zone that includes any sea-bottom surface regardless of its distance from shore |
| benthos | the forms of marine life that live on or in the ocean bottom; includes marine algae, sea stars, and crabs |
| chemosynthesis | the process by which certain microorganisms use chemical energy to produce food |
| density | mass per unit volume of a substance, usually expressed as grams per cubic centimeter |
| food chain | a succession of organisms through which food energy is transferred, starting with primary producers |
| food web | a group of interrelated food chains |
| intertidal zone | the area where land and sea meet and overlap; the zone between high and low tides |
| mixed zone | an area of the ocean surface with uniform temperatures created by the mixing of water by waves, currents, and tides |
| nekton | organisms that can move independently of ocean currents by swimming or other means of propulsion; includes most adult fish and squid, marine mammals, and marine reptiles |
| neritic zone | the marine-life zone that extends from the low-tide line out to the shelf break |
| oceanic zone | the marine-life zone beyond the continental shelf |
| pelagic zone | open ocean of any depth; Animals in this zone swim or float freely. |
| photic zone | the upper part of the ocean into which sunlight penetrates |
| photosynthesis | the process by which plants, algae, and certain prokaryotes use light energy to convert water and carbon dioxide into energy-rich glucose molecules |
| phytoplankton | algal plankton, which are the most important community of primary producers in the ocean |
| plankton | passively drifting or weakly swimming organisms that cannot move independently of ocean currents; includes microscopic algae, protozoa, jellyfish, and larval forms of many animals |
| primary productivity | the production of organic matter from inorganic substances through photosynthesis or chemosynthesis |
| pycnocline | a layer of water in which there is a rapid change of density with depth |
| salinity | the proportion of dissolved salts to pure water, usually expressed in parts per thousand (‰) |
| thermocline | a layer of water in which there is a rapid change in temperature with depth |
| trophic level | a nourishment level in a food chain; Plant and algae producers constitute the lowest level, followed by herbivores and a series of carnivores at progressively higher levels. |
| zooplankton | animal plankton |
