Answers to STUDY BREAK Questions
Essentials 5th
Chapter 15
USES AND ABUSES OF THE OCEAN
1. Human population grew explosively in the last century. Is the number of humans
itself the main driver of resource demand?
The human population grew by 400% during the twentieth century. This growth,
coupled with a 4.5-fold increase in economic activity per person, resulted in accelerating
exploitation of Earth’s resources. By most calculations we have used more natural resources
since 1955 than in all of recorded human history up to that time.
2. Distinguish between physical and biological resources.
Physical resources result from the deposition, precipitation, or accumulation of useful
substances in the ocean or seabed. Most physical resources are mineral deposits, but
petroleum and natural gas, mostly remnants of once-living organisms, are included in this
category. Fresh water obtained from the ocean is also a physical resource. Biological
resources are living animals and plants collected for human use.
3. Distinguish between renewable and nonrenewable resources.
Renewable resources are naturally replaced on a seasonal basis by the growth of
marine organisms or by other natural processes. Non-renewable resources such as oil, gas,
and solid mineral deposits are present in the ocean in fixed amounts and cannot be
replenished over time spans as short as human lifetimes.
4. What are the three most valuable physical resources? How does the contribution of
each to the world economy compare to the contribution of that resource derived from
land?
The three most valuable physical resources are petroleum and natural gas, sand and
gravel, and fresh water.
About 34% of the crude oil and 30% of the natural gas produced in 2005 (the last
year for which I have reliable data) came from the seabed. More than 1.4 billion metric tons
(1.5 billion tons) of sand and gravel valued at about three-quarters of a billion dollars were
mined offshore in 2005. Only about 1.5% of the world's total sand and gravel production is
scraped and dredged from continental shelves each year, but the seafloor supplies about 20%
of the sand and gravel used in the island nations of Japan and the United Kingdom. Potable
water derived from the ocean makes an insignificant contribution to the total amount of fresh
water available to the world's human population. Still, desalination is becoming a big
business. More than 15,000 desalination plants are presently operating worldwide, producing
a total of about 32.4 million cubic meters (8.5 billion gallons) of fresh water per day.
Page 1 of 10
Answers to STUDY BREAK Questions
Essentials 5th
5. Is the discovery of new sources of oil keeping up with oil use? Is oil being made (by
natural processes) as fast as it is being extracted?
There is a growing deficit between consumption and the discovery of new reserves – in
2005, about 32 billion barrels of oil were consumed worldwide, while only eight billion
barrels of new oil reserves were discovered. Huge, easily exploitable oil fields are almost
certainly a thing of the past. It takes millions of years to turn organic material into oil and
natural gas – we’re depleting our supplies much more rapidly than they’re being synthesized.
6. What’s the largest known reservoir of hydrocarbons on Earth? Why is this resource
not being utilized?
The largest known reservoir of hydrocarbons on Earth is not coal or oil, but methanelaced ice crystals—methane hydrate—in the sediments of some continental slopes.
Though abundant, exploitation of this resource would be very costly and quite
dangerous. Even if engineers could bring the sediment to the surface before the methane
disappeared, extracting the methane from the sediment and liquefying it for efficient use
would be prohibitively expensive.
7. What are the sources of metals mined or extracted (or potentially mined or extracted)
from the sea?
Magnesium salts selectively evaporated from seawater are used as a source of
magnesium metal and magnesium compounds.
8. Is recovery of fresh water from seawater economically viable?
More than 15,000 desalination plants are currently operating in 125 countries, producing
a total of about 32.4 million cubic meters (8.5 billion gallons) of fresh water per day. The
largest desalination plant, in Ashkelon, Israel, produces about 165,000 cubic meters (44
million gallons) of pure water daily!
9. What renewable marine energy source is presently making a contribution to the
world economy?
Shown in Figure 10.22, the first successful commercial marine power plant began
operation in Northern Ireland’s Strangford Lough in August, 2007. Its 1.2 megawatt
generator provides clean electricity for about 1,000 homes. Also, France’s River Rance
estuary is spanned by the largest tidal power generator yet operating.
Page 2 of 10
Answers to STUDY BREAK Questions
Essentials 5th
10. About how much of humanity’s nutritional protein needs are supplied by the ocean?
Compared to the production from land-based agriculture, the contribution of marine
animals and plants to the human intake of all protein is small, probably around 4%.
11. What’s the most valuable biological resource?
Fish, crustaceans, and mollusks are the most valuable living marine resources.
12. Fishing effort has increased greatly over the last decade. Has the per capita harvest
also increased?
The cost to obtain each unit of seafood has risen dramatically in spite of all this hightech assistance. The increasing expense of fuel for the fishing fleets and processing plants,
the rising cost of wages for the crews, and the greater distances that boats must cover to catch
each ton of fish have all helped drive up the cost of seafood. In spite of greater efforts, the
total marine catch leveled off in about 1970 and remained surprisingly stable until 1980,
when greater demand and increasing prices began to drive the tonnage upward again.
Harvests are now declining in spite of increasingly desperate attempts to increase yields.
Since 1970 the world human population has grown; so the average per capita world fish
catch has fallen significantly.
13. What is meant by “overfishing?” Are most of the world’s marine fishes overfished?
Overfishing occurs when a species is taken more rapidly than the breeding stock of
that species can generate replacements. Even when faced with evidence that it is depleting a
stock and disrupting the equilibrium of a fragile ecosystem, the fishing industry's response is
usually to increase the number of boats and develop more efficient techniques for capturing
animals in order to maintain profits. The result is commercial extinction, depletion of a
resource species to a point where it is no longer profitable to harvest. Most of the world’s
marine fishes are overfished.
14. What is “bycatch?”
In some fisheries, bycatch—animals unintentionally killed while collecting desirable
organisms—sometimes greatly exceeds target catch.
15. Does anyone still kill whales? Why?
Under intense pressure from its major fishing industry, Norway resumed whaling in
Page 3 of 10
Answers to STUDY BREAK Questions
Essentials 5th
1993. Japan never stopped. Their prime target, the minke whale, is the smallest and most
numerous of the great whale species (see Figure 13.25). The meat and blubber of this whale
is prized in Japan as an expensive delicacy to be eaten on special occasions.
16. Can mariculture make a significant contribution to marine economics?
Worldwide mariculture production is thought to be about one-eighth that of
freshwater aquaculture. Several species of fish, including plaice and salmon, have been
grown commercially, and marine and brackish-water fish account for to thirds of the total
production. Shrimp mariculture is the fastest growing and most profitable segment, with an
annual global value exceeding US$15 billion in 2005.
17. Are any drugs derived from the ocean presently approved for use by humans?
Yes. A compound derived from cyanobacteria stimulated the immune system of test
animals by 225% and cells in culture by 2,000%; the drug may be useful in treating AIDS.
Vidabarine, another antiviral drug developed from sponges, may attack the AIDS virus
directly. Cone shell toxins show great promise for the relief of pain and treatment of
neurological disorders such as epilepsy and Alzheimer’s disease -- a new drug (Prialt)
derived from cone shells was approved for clinical use in 2007. Cystic fibrosis may soon be
treated with a mucus-clearing drug (Brevenal) derived from the toxic dinoflagellate Karenia.
18. What use of the ocean in place (a non-extractive resource) is most valuable?
Non-extractive resources are uses of the ocean in place -- transportation of people and
commodities by sea, recreation, and waste disposal are examples. Transportation and
recreation are the most valuble nonextractive resources the oceans provide.
19. How has the advent of containerized shipping changed world economics?
Modern harbors are essential to transportation. Cargoes are no longer loaded and offloaded piece by piece by teams of longshoremen. Today’s harbors bristle with automated
bulk terminals, high-volume tanker terminals (both offshore and dockside), containership
facilities (see Figures 15.25), roll-on–roll-off ports for automobiles and trucks, and passenger
facilities required by the growing popularity of cruising. Most of this specialized construction
has occurred since 1960. New Orleans is now the greatest North American port; nearly 204
million tons of cargo—most of it grain—passed through its docks in 2004. The world’s
busiest container terminal is in Hong Kong, China. In 1995, it was the first facility to move
more than 1 million containers in a single month; its present capacity is more than three times
that number!
Page 4 of 10
Answers to STUDY BREAK Questions
Essentials 5th
20. Which is the largest U.S. Port. What is its main export?
New Orleans is now the greatest North American port; nearly 204 million tons of cargo—
most of it grain—passed through its docks in 2004. The world’s busiest container terminal is
in Hong Kong, China. In 1995, it was the first facility to move more than 1 million containers
in a single month; its present capacity is more than three times that number!
21. What is the world’s largest industry? Is it ocean-related?
Tourism is now the world’s largest industry. In the last decade, the cruise industry has
experienced spectacular growth. Passengers on luxurious ocean liners and cruise ships can
enjoy a few relaxing days on the ocean crossing the North Atlantic, visiting tropical islands,
or touring places accessible to the public only by ship.
22. What is pollution? What factors determine how dangerous a pollutant is?
We define marine pollution as the introduction into the ocean by humans of
substances or energy that change the quality of the water or affect the physical and biological
environment.
A pollutant causes damage by interfering directly or indirectly with the biochemical
processes of an organism. In most cases, an organism's response to a particular pollutant will
depend on its sensitivity to the combination of quantity and toxicity of that pollutant. Some
pollutants are toxic to organisms in tiny concentrations. For example, the photosynthetic
ability of some species of diatoms is diminished when chlorinated hydrocarbon compounds
are present in parts-per-trillion quantities. Other pollutants seem harmless, as when
fertilizers flowing from agricultural land stimulate plant growth in estuaries. Still other
pollutants may be hazardous to some organisms but not to others. For example, crude oil
interferes with the delicate feeding structures of zooplankton and coats the feathers of birds
but simultaneously serves as a feast for certain bacteria.
Pollutants also vary in their persistence; some reside in the environment for thousands
of years while others last only a few minutes. Some pollutants break down into harmless
substances spontaneously or through physical processes (like the shattering of large
molecules by sunlight). Sometimes pollutants are removed from the environment through
biological activity. For example, some marine organisms escape permanent damage by
metabolizing hazardous substances to harmless ones. Indeed, many pollutants are ultimately
biodegradable, that is, able to be broken down by natural processes into simpler compounds.
Most pollutants resist attack by water, air, sunlight, or living organisms, however, because
the synthetic compounds of which they are composed resemble nothing in nature.
23. How does oil enter the marine environment? Which source accounts for the greatest
amount of introduced oil?
Page 5 of 10
Answers to STUDY BREAK Questions
Essentials 5th
Oil is a natural part of the marine environment. Oil seeps have been leaking large
quantities of oil into the sea for millions of years. The amount of oil entering the ocean has
increased in recent years, however, because of our growing dependence on marine
transportation for petroleum products, offshore drilling, nearshore refining, and street runoff
carrying waste oil from automobiles (Table 15.2).
24. What is biomagnification? Why is it dangerous?
The level of synthetic organic chemicals in seawater is usually very low, but some
organisms at higher levels in the food chain can concentrate these toxic substances in their
flesh. This biomagnification is especially hazardous to top carnivores in a food web.
25. How do heavy metals enter the food chain? What can be the results?
Among the most dangerous heavy metals being introduced into the ocean are mercury
and lead. Human activity releases about five times as much mercury and 17 times as much
lead as is derived from natural sources, and incidents of mercury and lead poisoning, major
causes of brain damage and behavioral disturbances in children, have increased dramatically
over the last two decades.
Lead particles from industrial wastes, landfills, and gasoline residue reach the ocean
through runoff from land during rains, and the lead concentration in some shallow water
bottom feeding species is increasing at an alarming rate. Consumers should be wary of
seafood taken near shore in industrialized regions.
26. What is eutrophication? How can “good eating” be hazardous to marine life?
Eutrophication is a set of physical, chemical, and biological changes that take place when
excessive nutrients are released into the water. Too much fertility can be as destructive as too
little. Eutrophication stimulates the growth of some species to the detriment of others,
destroying the natural biological balance of an ocean area. The extra nutrients come from
wastewater treatment plants, factory effluent, accelerated soil erosion, or fertilizers spread on
land. They usually enter the ocean from river runoff and are particularly prevalent in
estuaries. Eutrophication is occurring at the mouths of almost all the world’s rivers.
27. Why is plastic so dangerous to marine organisms?
The attributes that make plastic items useful to consumers, their durability and
stability, also makes them a problem in marine environments. Scientists estimate that some
kinds of synthetic materials—plastic six-pack holders, for example—will not decompose for
about 400 years! While oil spills get more attention as a potential environmental threat,
plastic is a far more serious danger. Oil is harmful but, unlike plastic, it eventually
biodegrades.
Page 6 of 10
Answers to STUDY BREAK Questions
Essentials 5th
28. Which areas are most at risk for disruption by introduced species?
Exotic species can sometimes overwhelm a climax ecosystem. If no predators exist
for an introduced species, it could reproduce explosively and destabilize environmental
balances. Estuaries and harbors are especially vulnerable to attack.
29. What benefits to estuaries provide? What are some threats to marine estuaries?
The hardest hit habitats are estuaries, the hugely productive coastal areas at the
mouths of rivers where fresh water and seawater meet. Pollutants washing down rivers enter
the ocean at estuaries, and estuaries often contain harbors, with their potentials for oil spills.
As little as 1 part of oil for every 10 million parts of water is enough to seriously affect the
reproduction and growth of the most sensitive bay and estuarine species. Some of the
estuaries along Alaska’s Prince William Sound, site of the 1989 Exxon Valdez accident, were
covered with oil to a depth of 1 meter (3.3 feet) in places. The spill’s effects on the $150million-a-year salmon, herring, and shrimp fishery will be felt for years to come.
30. What dangers threaten coral reef communities?
Some coral reefs are in jeopardy from intentional chemical pollution. Especially
damaging to tropical reefs has been the practice of using cyanide to collect tropical fish.
Fishermen squirt a solution of sodium cyanide over the reef to stun valuable species. Many
fish die; those that survive are sent to collectors all over the world. At the same time the
invertebrate populations of the sensitive coral reef communities are decimated.
31. Have areas set aside for marine conservation areas and sanctuaries grown in overall
size or become smaller in the last decade?
Beginning in 1972, the U.S. federal government has established a dozen national
marine sanctuaries. These areas are intended as safe havens for marine life. They vary in
size, but now cover about 410,000 square kilometers (158,000 square miles) of coral reefs,
whale migration corridors, undersea archaeological sites, deep canyons, and zones of
extraordinary beauty and biodiversity (Figure 15.37).
32. Where are the world’s largest marine sanctuaries?
On 15 June 2006 President George W. Bush created the world’s largest marine
conservation area. Situated off the coast of the northern Hawaiian Islands, the preserve will
encompass nearly 364,000 square kilometers (140,000 square miles) of U.S. waters,
including 11,700 square kilometers (4,500 square miles) of relatively undisturbed coral reef
Page 7 of 10
Answers to STUDY BREAK Questions
Essentials 5th
habitat that is home to more than 7,000 species. The monument will be managed by the
Department of the Interior’s U.S. Fish and Wildlife Service and the Commerce Department’s
National Oceanic and Atmospheric Administration in close coordination with the State of
Hawaii.1
33. What is ozone? How can its absence in the upper atmosphere affect conditions at
Earth’s surface?
Ozone is a molecule formed of three atoms of oxygen. Ozone occurs naturally in the
atmosphere. A diffuse layer of ozone mixed with other gases—the stratospheric ozone
layer—surrounds the world at a height of about 20 to 40 kilometers (12 to 25 miles).
Stratospheric ozone intercepts some of the high-energy ultraviolet radiation coming from the
sun. Ultraviolet radiation injures living things by breaking strands of DNA and unfolding
protein molecules. Species normally exposed to sunlight have evolved defenses against
average amounts of ultraviolet radiation, but increased amounts could overwhelm those
defenses.
34. What is “greenhouse effect?” What gases are most responsible for it?
The surface temperature of Earth varies slowly over time. The global temperature
trend has been generally upward in the 18,000 years since the last ice age, but the rate of
increase has recently accelerated. This rapid warming is probably the result of an enhanced
greenhouse effect, the trapping of heat by the atmosphere.
Glass in a greenhouse is transparent to light but not to heat. The light is absorbed by
objects inside the greenhouse, and its energy is converted into heat. The temperature inside a
greenhouse rises because the heat is unable to escape. On Earth greenhouse gases—carbon
dioxide, water vapor, methane, CFCs, and others—take the place of glass. Heat that would
otherwise radiate away from the planet is absorbed and trapped by these gases, causing a
surface temperature to rise. Figure 15.40 shows this mechanism.
35. Is greenhouse effect always bad?
The greenhouse effect is necessary for life; without it, Earth’s average atmospheric
temperature would be about -18°C (0°F). Earth has been kept warm by natural greenhouse
gases. The sources of these gases are volcanic and geothermal processes, the decay and
burning of organic matter, and respiration and other biological sources. The removal of these
gases by photosynthesis and absorption by seawater appears to prevent the planet from
overheating.
1
This is not the world’s largest marine sanctuary. In 1994 the International Whaling Commission voted
overwhelmingly to ban whaling in about 21 million square kilometers (8 million square miles) around
Antarctica, thus protecting most of the remaining large whales, which feed in those waters. The killing ban is
not enforced.
Page 8 of 10
Answers to STUDY BREAK Questions
Essentials 5th
36. What causes global warming?
Earth is now absorbing about 0.85 watts per square meter more energy from the Sun
than it is emitting into space. There has been a 5°C (9°F) rise in global temperature from the
end of the last ice age until today. Carbon dioxide and other human-generated greenhouse
gases produced since 1880 are thought to be responsible for some of that increase.
37. What effects might be caused by global warming?
Among the more serious are:

Warming may shift the strength and position of ocean surface currents. What would
happen to the agricultural economy of Europe if the warming Gulf Stream were to
alter course?

The ocean is becoming more acidic. As you may recall from Chapter 6, seawater
becomes slightly more acidic when CO2 dissolves in it to form carbonic acid.
Average oceanic pH has fallen by 0.025 units since the early 1990s and is expected to
drop to pH 7.7 by 2100, lower (that is, more acidic) than any time in the last 420,000
years. Because an acidic environment tends to dissolve calcium carbonate, shell- and
bone-forming species are being affected, with coral reefs at greatest risk.

Phytoplankton productivity in the last 20 years has dropped by about 9% in the North
Pacific and nearly 7% in the North Atlantic. This may be due in part to warmer ocean
water and diminished winds to provide the light dusting of terrestrial iron needed for
their metabolism. Deeper penetration of ultraviolet radiation may also play a role.
Less phytoplankton means less carbon dioxide uptake and significant changes in
oceanic ecosystems.

Diseases may spread more rapidly. Mosquito-borne infections may become more
troublesome because a warmer climate prolongs their breeding and feeding seasons.

Ecosystems and crop production could be damaged beyond repair. For example,
North American farmers have already noticed a northward “migration” of fields
suitable for winter wheat.

Financial effects could be severe. Though a link between an increased rate of
warming and the severity of tropical cyclones has not been demonstrated, the
economic losses from severe storms in 2005 were the worst on record. Will rising sea
level require us to relocate the world’s vast port infrastructure? How many billions of
dollars of real estate will be devastated by erosion?
Page 9 of 10
Answers to STUDY BREAK Questions
Essentials 5th
38. What alternatives exist for burning hydrocarbon fuels for energy?
The leading alternatives are wind and solar power, energy from tidal flow and currents,
and nuclear energy.
39. What was the “tragedy” implicit in Hardin’s “The Tragedy of the Commons?”
Garrett Hardin suggests that absolute freedom in a commons brings ruin to all. If each of
us continues to keep the benefit of environmental use for ourselves, but shares his and her
discards with all the world, balance unsustainable. No economy can be based on perpetual
growth.
40. Is there is a solution to the difficult environmental solutions in which we presently
find ourselves? What form might that solution take? What are the alternatives?
Each of us can make a difference. A moment's careful reflection on the
environmental consequences of what to purchase, how to traveling to work or class, to what
degree to use air conditioning and heating, and how to recycle materials can make a large
difference if enough of us are willing to make changes. But we have entered a time of
inadvertent global experimentation, and the trials ahead will be interesting, indeed.
As I wrote in the book's Afterword: There is much good in the world. Go and add to
it.
Page 10 of 10