| A | B |
|---|
| Composition of seawater | Ocean water is 96.5% water. The rest consists of ions of dissolved salts |
| Vertical structure of oceans | Temperature declines with depth. Heavier (colder saltier) water sinks. Temperatures are more stable than land temperatures, and oceans regulate the earth’s climate |
| Surface zone | Warmed by sunlight, stirred by wind |
| Pynocline | Layer below the surface zone. Density increases rapidly with depth |
| Deep zone | Below the pycnocline. Dense, sluggish water. |
| Nutrient availability | Nutrients are far more available towards the surface |
| Photic zone | Most productive areas in the oceans |
| Currents and vertical water flow | Currents are vast flows of water that move horizontally and follow long-lasting patterns across the globe. They are driven by density differences, heating and cooling, gravity, and wind. They transport heat, nutrients, pollution, and the larvae of many marine species. Water also moves in horizontal currents, through upwelling and downwelling. |
| El Niño | When upwelling stops it’s called El Niño. These conditions are triggered when air pressure decreases in the eastern Pacific and increases in the western Pacific, weakening the equatorial winds and allowing the warm water to flow eastward. This suppresses upwelling along the Pacific coast, shutting down the delivery of nutrients. |
| La Niña | The opposite of El Niño. Cold waters rise to the surface and extend westward in the equatorial Pacific when winds blowing to the west strengthen. |
| Upwelling | The upward flow of cold, deep water toward the surface. Occurs where horizontal surface currents diverge or flow away from one another |
| Downwelling | Occurs in areas where surface currents converge and surface water sinks. This transports warm water rich in dissolved gasses, providing influx of oxygen to deep-water life. |
| Ocean conveyor belt | Water freezing and sinking causes downwelling, while upwelling brings that water to the surface. |
| Marine pollution | Threatens resources. Even into the mid-20th century, coastal U.S. cities dumped trash and untreated sewage along their shore. We pollute with oil, plastic, chemicals excess nutrients, raw sewage, and abandoned fishing gear |
| Marine ecosystems: Deep ocean | Animals adapt to extreme water pressure and the absence of light. Food is scarce, but hydrothermal vents support tubeworms, shrimp, and other chemosynthetic species. In order to adapt, some species carry bacteria that produce light chemically by bioluminescence. |
| Marine ecosystems: Coral Reefs | Masses of calcium carbonate composed of the skeletons of corals. Protect shorelines, high biodiversity. |
| Marine ecosystems: Intertidal zones | Where the ocean meets the land. High diversity. Rocky shorelines, tide pools. Temperature, salinity, and moisture change dramatically from high to low tide |
| Marine ecosystems: Salt marshes | Occur along coasts at temperate latitude. Tides wash over gently sloping, sandy, silt substrates. High primary productivity. Critical habitat for birds and commercial fish and shellfish species. Filter pollution, stabilize shorelines against storm surges. People have altered or destroyed many for development |
| Marine ecosystems: Mangroves | Trees with unique roots, they line coasts. Nurseries for commercial fish and shellfish and nesting areas for birds. Half of all mangrove forests have been destroyed. Even though they slow runoff, filter pollutants, retain soil and protect communities against storm surges. |
| Coral bleaching | Occurs when zooxanthellae leave the coral. Coral lose their color and die, leaving white patches. The result of climate change, pollution, or unknown natural causes. Nutrient pollution causes algal growth, which covers coral. Acidification of oceans deprives corals of necessary carbonate ions for their structural parts |
| By-catch | The accidental capture of non-target animals when fishing |
| Trawling | Entails dragging immense, cone-shaped nets through the water with weights at the bottom and floats on the top. Bottom trawling involves dragging weighted nets across the floor of the continental shelf to catch ground fish and can destroy entire ecosystems. |
| Long-line fishing | Involves setting out extremely long lines with up to several thousand baited hooks spaced along their lengths. Usually target swordfish or tuna. |
| Drift netting | Chains of transparent nylon mesh nets arrayed to drift with currents and catch passing fish |
| Catch-per-unit effort | Amount of fishing and gear needed to catch fish. Now fleets travel further to reach less-fished parts of the ocean. They also increase effort to catch the same amount of fish. |
| Fishing down the food chain | As fishing increases, the size and age of fish caught decline, and as species become too rare to fish, fleets target other species. Shifting from large, desirable species to smaller, less desirable ones. Entails catching species at lower trophic levels |
| Role technology plays in marine conservation | With DNA technology scientists are able to monitor markets to see if endangered species are being sold |
| Fisheries management | Fisheries managers conduct surveys, study fish population biology, and monitor catches. The goal is to allow for maximal harvests while keeping fish available for the future – the concept of maximum sustainable yield. |
| Marine Protected Areas (MPAs) | Established mostly along coastlines in developed countries. However, nearly all MPAs still allow fishing or other extractive activities. |
| Marine Reserves | Improve fisheries, because young fish will disperse into surrounding areas. Many commercial, recreation fishers, and businesses do not support reserves although they increase fish size, fish biomass and total catch. |
