Page 464 - Environment: The Science Behind the Stories

made to work and to be accepted, then they may well seed the to intensify our use of their resources and to exert more
seas and help lead us toward solutions to one of our most press- severe impacts. Ocean acidification, loss of coral reefs, sev-
ing environmental problems. eral types of pollution, and the ongoing depletion of many
of the world’s marine fish stocks are all major challenges
that we will need to address. Yet scientists are demonstrat-
Conclusion ing that setting aside protected areas of the ocean can serve
to maintain and restore natural systems and also to enhance
Oceans cover most of our planet, and we are still explor- fisheries. In the meantime, we can all contribute through
ing their diverse topography and ecosystems. As we learn consumer choices that can help move us toward sustainable
more about marine and coastal environments, we continue fishing practices.

Reviewing Objectives

you should now be able to: kelp forests, coral reefs, and pelagic and deep-water open
ocean systems. (pp. 444–445, 448–450)
Identify physical, geographical, chemical, and • Many of these systems are highly productive and rich in
biological aspects of the marine environment biodiversity. Many also suffer heavy impacts from human
influence. (pp. 444–445, 448–450)
• Oceans cover 71% of Earth’s surface and contain over 97%
of its water. (p. 439)
Assess impacts from marine pollution
• Seafloor topography can be complex. (pp. 439–440)
• Plastic trash harms marine life and accumulates in ocean
• Ocean water contains 96.5% H O by mass and various dis- regions, where it is trapped by currents. (pp. 450–454)
2
solved salts. (pp. 440–441)
• Marine oil pollution results from non-point sources on land
• Colder, saltier water is denser and sinks. Water tempera- as well as from spills at sea from tankers and drilling plat-
tures vary with latitude, and temperature variation is greater forms. (pp. 454–455)
in surface layers. (p. 441)
• Heavy-metal contaminants in seafood affect human health.
• Surface currents move horizontally through the oceans, (p. 455)
driven by wind and other factors. (pp. 441–442)
• Nutrient pollution can lead to dead zones and harmful algal
• Vertical water movement includes upwelling and down- blooms. (p. 455)
welling, which affect the distribution of nutrients and life.
(pp. 442–443)
Review the state of ocean fisheries and reasons for
their decline
Explain how the oceans influence and are influenced • Over half the world’s marine fish populations are fully
by climate
exploited, 28% are overexploited, and only 20% can yield
• The thermohaline circulation shapes regional climate, more without declining. (pp. 453–456)
for instance, keeping Europe warm. Global warming • Global fish catches have stopped growing since the late
could potentially shut down existing circulation patterns. 1980s despite increased fishing effort and improved tech-
(p. 443) CHAPTER 16 • M AR in E A nd Co A s TA l s ys TEM s A nd R E sou R CE s
nologies. (p. 456)
• El Niño and La Niña events alter climate and affect fisher- • People began depleting marine resources long ago, but
ies. (pp. 443–444)
impacts have intensified in recent decades. (p. 438)
• The oceans sequester atmospheric carbon and have slowed • Commercial fishing practices include driftnetting, longline
global climate change, but they could soon become satu- fishing, and trawling, all of which capture nontarget organ-
rated. (p. 444) isms, called bycatch. (pp. 456–457)
• Absorption of excess carbon dioxide leads to ocean acidi- • Non-target species are killed when they are captured as
fication, which hinders corals in forming reefs. (pp. 444, bycatch while fishing for commercially-valuable species.
446–447) (pp. 457–458)
• Today’s oceans hold just one-tenth as many large animals as
describe major types of marine ecosystems they did before industrialized commercial fishing. (p. 459)

• Major types of marine and coastal ecosystems include • As fishing intensity increases, fish become smaller and fish-
intertidal zones, salt marshes, mangrove forests, estuaries, ermen switch to less-desirable species. (p. 460) 463

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