CHAPTER 10 Focus Points

• Five oceans: The Pacific Ocean is the largest and oldest of the five ocean basins.

• Layers: The oceans can be divided into five vertical layers. Sunlight enters only the uppermost layer.

• Surface ocean currents: Surface ocean currents are driven by wind. Coriolis force deflects the moving water, creating large circular ocean currents called gyres.

• Seafloor features: Seafloor topography includes continental shelves, continental slopes, abyssal plains, major mountain ranges, and deep-sea trenches.

• Ecosystem types: Marine ecosystems along continental margins range from tropical coral reefs to kelp forests, rocky shorelines, and beaches.

• Human footprint: All coastal marine ecosystems are influenced by human activity, particularly pollution, overfishing, habitat loss, and non-native species.

• Fish nurseries: Mangroves, seagrass meadows, and estuaries provide important shelter for young fish.

• Conservation: Coastal ecosystems provide long-term, sustainable benefits for people when they are preserved rather than converted to other uses.

• Human footprint: Polar marine ecosystems are relatively little affected by people.

• Food webs: Phytoplankton form the base of the food web in marine ecosystems.

• Seasonal productivity: Polar waters are highly productive during spring and summer.

• Migration: Many marine organisms migrate vertically between ocean surface waters and deeper layers. Others migrate horizontally across ocean basins.

• Bioluminescence: Many deep-water organisms produce light to find mates, capture prey, and avoid predators.

• Biodiversity: Seamounts and hydrothermal vents support species-rich ecosystems on the deep seafloor.

• Fishing: Industrial fishing employs drift nets, trawling, longlines, and seining to catch seafood.

• Path to the oceans: Plastic enters the oceans mostly by stream runoff from towns and cities and from beaches.

• Gyres and beaches: Marine plastic is concentrated in the centers of ocean gyres and deposited on beaches.

• Problems: Marine plastic carries high concentrations of industrial pollutants absorbed from seawater. Wildlife may eat toxic plastic or become entangled in plastic.

• Fixing the problem: Solving this problem requires changing the way we use and make plastic.