ENV100Y5 Chapter Notes - Chapter 13: Pearson Education, Marine Protected Area, Overfishing
66 views2 pages
Withgott, Brennan, Murck
Environment: The Science Behind the Stories, Second Canadian Edition
Chapter 13 – Answers to End-of-Chapter Questions
Testing Your Comprehension
1. Approximately 71% of Earth’s surface is covered by ocean waters containing, on average, about
3.5% salt. Water temperature declines with depth, and density increases slightly at lower
temperatures and higher salinities. Therefore, deep water tends to be colder, saltier, and denser than
the surface water.
2. Ocean currents are driven by the prevailing wind currents at the surface at the surface, by gradients
in water temperature, by gravity, and by the Coriolis effect. Surface currents move horizontally in
large circulation patterns. Vertical currents (upwellings and downwellings) slowly mix the deep
waters with the surface waters, affecting the distribution of nutrients and primary productivity.
3. Biologically productive areas are concentrated in areas of upwelling, in the shallower waters along
continental margins, and at hydrothermal vents of the deep mid-ocean ridges.
4. Along the coasts there are kelp forests that shelter invertebrates, smaller fishes, seals, and top
carnivores such as great white sharks. Coral reef communities, which include zooxanthellae,
anemones, sponges, hydroids, tubeworms, molluscs, flatworms, starfish, urchins, and thousands of
fish species, are among the most diverse and productive ecosystems on Earth. Intertidal ecosystems
include rocky and sandy beaches, salt marshes, estuaries, and mangrove forests, which serve to
buffer the land from the effects of storm surges and act as nursery areas for many marine organisms
of economic importance, such as shrimp.
5. Coral reefs absorb wave energy and protect shorelines from damage, as well as providing essential
habitat for many species. Increased water temperatures from global climate change, turbidity,
nutrient influx (as from agricultural fertilizers in runoff), and toxic pollutants can all damage coral
reef communities. Salt marshes and mangrove forests are often drained and converted to residential,
commercial, recreational, or agricultural uses.
6. Salt marshes and mangrove trees line the edge of the water on land that humans desire to inhabit. As
a result, both these ecosystems are removed. The removal of these results in erosion of the land by
the sea and the subsequent degrading of any offshore coral reefs.
7. The three ways ocean pollution can be combated are as follows: (1) Prevent raw sewage from being
discharged into the ocean from either cities or towns along the shore or ocean-going vessels. (2)
Prevent the dumping of plastics and other solid waste garbage from entering the sea. (3) Stop the
dumping of toxic industrial waste from being deposited in the ocean.
8. Overfishing can remove the larger and fully mature fish faster than they are replaced by the
population, thereby resulting in a decline in catch size and quality, and a decrease in the fish
population because the death and export of individuals exceeds birth and import. Some fishing
techniques (bottom trawling, for instance) physically damage or destroy certain marine ecosystems.
The collapse of North Atlantic cod fisheries is a prime example of overexploitation through trawling
damage and direct fishing pressure.
9. Commercial driftnetting catches and kills (by drowning) marine mammals and turtles, as well as
many nontarget fish species that die from exposure to air on ships’ decks. Similar by-catch problems
exist with longline fishing, which hooks unwanted species as well as those desired, and even catches
and kills marine birds. Bottom-trawling disturbs the seafloor and reefs, destroying habitat inhabited
by many species.
10. Nearly all marine protected areas allow fishing or other extractive activities, whereas marine
reserves do not permit such activities. Such marine reserves can serve as production areas for fish
larvae that then disperse outside the reserve and stock other parts of the ocean.
Copyright © 2013 Pearson Canada Inc.