Transcript Slide 1

Lecture Outlines
Chapter 16
Environment:
The Science behind the Stories
4th Edition
Withgott/Brennan
© 2011 Pearson Education, Inc.
This lecture will help you understand:
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The marine environment
Ocean-climate relationships
Marine ecosystems
Marine pollution
The state of ocean fisheries
Marine protected areas and
reserves
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Central Case: Collapse of the cod fisheries
• No fish has had more impact on
civilization than the Atlantic
cod
• Cod have been fished for
centuries
• Large ships and technology
have destroyed the cod fishery
• Even protected stocks are not
recovering
- Young cod are being preyed
on
• But other species are recovering
in protected areas
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Cod are groundfish
• Fish that live or feed along the
bottom
- Halibut, pollack, flounder
• Cod eat small fish and
invertebrates
• They inhabit cool waters on
both sides of the Atlantic
• The 24 stocks (populations) of
cod crashed
- Overfishing and destroyed
habitat
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The U.S. and Canada
have paid billions to
retrain fishermen who
lost their jobs
Oceans cover most of the Earth’s surface
• Oceans influence climate, team with biodiversity,
provide resources, and help transportation and
commerce
• Oceans cover 71% of Earth’s surface and contain 97.5%
of its water
• Oceans influence the
atmosphere, lithosphere,
and biosphere
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Seafloor topography can be rugged
• The seafloor consists of:
- Underwater volcanoes
- Steep canyons
- Mountain ranges
- Mounds of debris
- Trenches
- Some flat areas
• Some island chains are formed by reefs or volcanoes
- Topographically complex areas serve as habitat and
productive fishing grounds
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A stylized bathymetric profile of the ocean
A stylized map reflects the
ocean’s bathymetry
(depths) and topography
(landforms)
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Ocean water contains salt
• Ocean water is 96.5%
water
- Plus, ions of dissolved
salts
• Evaporation removes pure
water
- Leaving salt behind
• Low levels of nutrients
(nitrogen and phosphorus)
• Oxygen is added by plants,
bacteria, and atmospheric
diffusion
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Ocean water is vertically structured
• Temperature declines with depth
• Heavier (colder, saltier) water sinks
- Light (warmer, less salty) water stays near the surface
• Temperatures are more stable than land temperatures
- Water has high heat capacity (heat required to
increase temperature by a given amount)
- It takes more energy to warm water than air
• Oceans regulate Earth’s climate
- They absorb and release heat
- The ocean’s surface circulation moves heat around
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The ocean has several layers
• Surface zone
- Warmed by sunlight and stirred by wind
- Consistent water density
• Pycnocline = below the
surface zone
- Density increases with
depth
• Deep zone = below the
pycnocline
- Dense, sluggish water
- Unaffected by winds,
storms, sunlight, or temperature
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Ocean water flows horizontally in currents
• Currents = vast riverlike flows in the oceans
- Driven by density differences, heating and cooling,
gravity, and wind
- Influence global climate and El Niño and La Niña
- Transport heat, nutrients, pollution, the larvae of
many marine species, and people
• Some currents such as the Gulf Stream are rapid and
powerful
- The warm water moderates Europe’s climate
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Currents form patterns across the globe
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Vertical movement affects ecosystems
• Upwelling = the upward flow of cold, deep water
toward the surface
- High primary productivity and lucrative fisheries
- Also occurs where strong winds blow away from, or
parallel to, coastlines
• Downwellings = oxygen-rich water sinks where surface
currents come together
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Currents affect climate
• Horizontal and vertical movement of oceans affects
global and regional climates
• Thermohaline circulation = a worldwide current system
- Warmer, fresher water moves along the surface
- Cooler, saltier, denser water moves beneath the surface
• North Atlantic Deep Water (NADW) = one part of the
thermohaline conveyor belt
- Water in the Gulf Stream flows to Europe
- Released heat keeps Europe warmer that it would be
- Sinking cooler water creates a region of downwelling
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The North Atlantic Deep Water
• Interrupting the thermohaline circulation could trigger
rapid climate change
- Melting ice from Greenland will run into the North
Atlantic
- Making surface waters even less dense
- Stopping NADW formation and shutting down the
northward flow of warm water
- Europe would rapidly cool
• This circulation is already slowing
- But Greenland may not have enough runoff to stop it
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El Niño–Southern Oscillation (ENSO)
• ENSO = a systematic shift in atmospheric pressure, sea
surface temperature, and ocean circulation
- In the tropical Pacific Ocean
• Normal winds blow east to west, from high to low
pressure
- This forms a large convective loop in the atmosphere
• Winds push water west, causing it to “pile up”
- Nutrient-rich, cold water along Peru and Ecuador rises
from the deep
• Decreased pressure in the eastern Pacific triggers El Niño
- Warm water flows eastward, suppressing upwellings
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Effects of El Niño and La Niña
• Coastal industries (e.g., Peru’s anchovy fisheries) are
devastated
- Worldwide, fishermen lost $8 billion in 1982–1983
• Global weather patterns change
- Rainstorms, floods, drought, fires
• La Niña = the opposite of El Niño
- Cold waters rise to the surface and extend westward
• ENSO cycles are periodic but irregular (every 2–8
years)
- Globally warming sea and air may be increasing the
strength and frequency of these cycles
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ENSO, El Niño, and La Niña
Normal conditions
El Niño conditions
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Climate change is altering the oceans
• Global climate change will affect ocean chemistry and
biology
• Burning fossil fuels and removing vegetation increase
CO2, which warms the planet
- Oceans absorb carbon dioxide (CO2) from the air
• But oceans may not be able to absorb much more CO2
• Increased CO2 in the ocean makes it more acidic
- Ocean acidification makes chemicals less available for
sea creatures (e.g., corals) to form shells
- Fewer coral reefs decrease biodiversity and ecosystem
services
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Marine and coastal ecosystems
• Regions of ocean water differ greatly
- Some zones support more life than others
• Photic zone = well-lighted top layer
- Absorbs 80% of solar energy
- Supports high primary productivity
• Pelagic = habitats and ecosystems between the ocean’s
surface and floor
• Benthic = habitats and ecosystems on the ocean floor
• Most ecosystems are powered by solar energy
- But even the darkest depths host life
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Open ocean systems vary in biodiversity
• Microscopic phytoplankton are the base of the marine
food chain
- Algae, protists, cyanobacteria
- They feed zooplankton
- Which then feed fish, jellyfish, whales, etc.
• Predators at higher trophic
levels
- Larger fish, sea turtles,
sharks, and fish-eating
birds
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Animals of the deep ocean
• Animals adapt to extreme water pressure and the dark
- Scavenge carcasses or organic detritus
- Predators
- Others have mutualistic relationships with bacteria
- Some carry bacteria that produce light chemically by
bioluminescence
• Hydrothermal vents support
tubeworms, shrimp, and other
chemosynthetic species
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Kelp forests harbor many organisms
• Kelp = large, dense, brown algae growing from the floor
of continental shelves
• Dense strands form kelp forests along temperate coasts
- They provide shelter and food for organisms
• They absorb wave energy and protect shorelines from
erosion
• People use it in food,
cosmetics, paints, paper,
soap, etc.
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Coral reefs are treasure troves of
biodiversity
• Coral reef = a mass of calcium carbonate composed of
the skeletons of tiny marine animals (corals)
- They may be an extension of a shoreline
- Or exist along a barrier island, parallel to the shore
- Or as an atoll (a ring around a submerged island)
• Corals = tiny colonial invertebrate animals
- Related to sea anemones and jellyfish
- Attach to a rock or reef and capture passing food with
stinging tentacles
- Get food from symbiotic algae (zooxanthallae)
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Most corals are colonial
• Reefs consist of millions of densely packed animals
• Reefs are located in shallow subtropical and tropical
waters
- Protect shorelines by absorbing waves
- Innumerable invertebrates and fish species find food
and shelter in reef nooks and crannies
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Coral reefs are in worldwide decline
• “Coral bleaching” = occurs when zooxanthellae leave
the coral or die
- Corals lose their color and die, leaving white patches
- From climate change, pollution, or unknown natural
causes
• Nutrient pollution causes algal growth
- Which smothers coral
• Divers damage reefs by using cyanide to capture fish
• Acidification of oceans deprives corals of carbonate
ions for their structural parts
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Deepwater coral reefs exist
• They thrive in waters outside the tropics
- On ocean floor at depths of 200–500 m (650–1,650 ft)
• Occur in cold-water areas off the coasts of Spain, the
British Isles, and elsewhere
- Little is known about these reefs
• Already, many have been badly damaged by trawling
- Some reefs are now being protected
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Intertidal zones undergo constant change
• Intertidal (littoral) ecosystems = where the ocean
meets the land
- Between the uppermost reach of the high tide and the
lowest limit of the low tide
• Tides = periodic rising and falling of the ocean’s height
due to the gravitational pull of the sun and moon
• Intertidal organisms spend part of their time submerged
in water and part of their time exposed to sun and wind
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A typical intertidal zone
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Intertidal zones are a tough place to live
• But they have amazing diversity
- Rocky shorelines, crevices,
pools of water (tide pools)
- Anemones, mussels,
barnacles, urchins, sea slugs
- Starfish and crabs
• Temperature, salinity, and
moisture change dramatically
from high to low tide
• Sandy intertidal zones have
slightly less biodiversity
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Salt marshes line temperate shorelines
• Salt marshes = occur along coasts at temperate latitudes
- Tides wash over gently sloping sandy, silty substrates
• Tidal creeks = channels that rising and falling tides flow
into and out of
• Salt marshes have very high primary productivity
- Critical habitat for birds, commercial fish, and
shellfish
- They filter pollution
- They stabilize shorelines against storm surges
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People change and destroy salt marshes
• People want to live or do business along coasts
- We lose key ecosystem services
- Flooding (e.g., from Hurricane Katrina) worsens
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Mangrove forests line coasts
• In tropical and subtropical latitudes
- They replace salt marshes along sandy coasts
• Mangroves = salt-tolerant trees
- Their unique roots curve up for oxygen and down for
support
• Nesting areas for birds
• Nurseries for fish and shellfish
Mangroves provide food,
medicine, tools, and
construction materials
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Mangrove forests have been destroyed
• Half the world’s mangrove forests are gone
- Developed for residential, commercial, and
recreational uses
- Shrimp farming
• Once destroyed, coastal areas no longer:
- Slow runoff
- Filter pollutants
- Retain soil
- Protect communities against storm surges
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Fresh and salt water meet in estuaries
• Estuaries = water bodies where rivers flow into the
ocean, mixing fresh and salt water
• They are biologically productive
- Have fluctuations in salinity
• Critical habitat for shorebirds and shellfish
• Transitional zone for fish that spawn in streams and
mature in salt water
• They have been affected by development, pollution,
habitat alteration, and overfishing
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Marine pollution
• People use oceans as a sink for waste and pollutants
• Even into the mid-20th century, coastal U.S. cities
dumped trash and untreated sewage along their shores
• Nonpoint source pollution comes from all over
- Oil, plastic, chemicals, excess nutrients
In 2008, 391,000 Ocean Conservancy volunteers from
104 nations picked up 3.1 million kg (6.8 million lb) of
trash from 27,000 km (17,000 miles) of shoreline
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Nets and plastic debris endanger life
• Plastic items dumped into the
sea harm or kill wildlife
- Wildlife mistake it for food
- 98% of dead northern
fulmars had plastic in their
stomachs
• Plastic is nonbiodegradable
- Drifts for decades
- Breaks into tiny pieces
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Trillions of tiny
plastic pellets float in
the oceans and are
eaten
Plastic trash is accumulating in the oceans
• Circulating currents bring and trap plastic trash to areas
- The northern Pacific Gyre stretches from California to
Hawaii to Japan
- This “Great Pacific Garbage Patch” is the size of
Texas and has 3.3 plastic bits/m2
• The 2006 Marine Debris Research, Prevention, and
Reduction Act is not enough
• We must reduce, reuse, and recycle more plastic
- Participate in efforts such as the International Coastal
Cleanup
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Oil pollution comes from spills of all sizes
• 30% of oil and 50% of natural gas come from
seafloor deposits
- North Sea, Gulf of Mexico
• Drilling in other places is banned
- Spills could harm valuable
fisheries
• The Deepwater Horizon
exploded off Louisiana’s coast
in April 2010
- Spilling 140 gallons/min
- Hitting coasts of four states
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Oil spills have severe consequences
Major oil spills cause severe environmental and economic
problems
• Major spills make headlines
- Foul beaches
- Coat and kill animals
- Devastate fisheries
• Countless non-point sources
produce most oil pollution
- Small boat leaks, runoff
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Oil spills have decreased
• Due to emphasis on spill
prevention and response
- Stricter regulations are
resisted by the oil industry
• The U.S. Oil Pollution Act
(1990)
- Created a $1 billion
prevention and cleanup fund
- Requires that all ships have
double hulls by 2015
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Recently, oil spills have
decreased
Toxic pollutants contaminate seafood
• Toxic pollutants can make food unsafe to eat
• Mercury contamination from coal combustion and other
sources bioaccumulates and biomagnifies
- Dangerous to children and pregnant or nursing women
• Avoid eating swordfish, shark, and albacore tuna
- Eat seafood low in mercury (catfish, salmon, canned
light tuna)
• Avoid seafood from areas where health advisories have
been issued
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Excess nutrients cause algal blooms
• Harmful algal blooms =
nutrients increase algae that
produce powerful toxins
• Red tide = algae that produce
red pigments that discolor water
- Illness and death to wildlife
and humans
- Economic loss to fishing
industries and beach tourism
• Reduce runoff
• Do not eat affected organisms
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Emptying the oceans
• Overharvesting is the worst marine problem
• We are putting unprecedented pressure on marine
resources
- Half the world’s marine fish populations are fully
exploited and can’t be fished more intensively
- 28% of fish population are overexploited and
heading to extinction
• Total fisheries catch leveled off after 1988
- Despite increased fishing effort
• The maximum wild fisheries potential has been
reached
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The global fisheries catch has increased
It is predicted that populations of all ocean species we
fish for today will collapse by 2048
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We have long overfished
• People began depleting sea life centuries ago
• Species have been hunted to extinction: Caribbean monk
seal, Steller’s sea cow, Atlantic gray whale
• Overharvesting Chesapeake Bay oyster beds led to its
collapse, eutrophication, and hypoxia
• Decreased sea turtle populations cause overgrowth of sea
grass and can cause sea grass wasting disease
• Overharvesting nearly exterminated many whale species
• People never thought groundfish could be depleted
- New approaches or technologies increased catch rates
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Fishing has industrialized
• Factory fishing = huge vessels
use powerful technologies to
capture fish in huge volumes
- Even processing and
freezing their catches at sea
• Driftnets for schools of
herring, sardines, mackerel,
sharks, shrimp
• Longline fishing for tuna and
swordfish
• Trawling for pelagic fish and
groundfish
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Fishing practices kill nontarget animals
• Bycatch = the accidental capture of animals
• Drift netting drowns dolphins, turtles, and seals
- Fish die on deck
- Banned in international waters
- But it is still used in national waters
• Longline fishing kills turtles, sharks, and over 300,000
seabirds/year
- Methods (e.g., flags) are being developed to limit
bycatch
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Dolphins and tuna
• Dolphins are trapped in purse seine nets used to catch
tuna
- Hundreds of thousands of dolphins were killed
• The 1972 Marine Mammal Protection Act forced fleets to
try to free dolphins
- Bycatch dropped dramatically
• Other nations fished for tuna, and bycatch increased
• The U.S. government required that nations exporting tuna
to the U.S. minimize dolphin bycatch
- Dolphin-safe tuna uses methods to avoid bycatch
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Dolphin deaths have declined, but …
• Rules and technology
have decreased dolphin
deaths
• Other animals (e.g.,
sharks) are still caught
• Dolphins have not
recovered
- Too few fish to eat
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Bottom-trawling destroys ecosystems
• Heavy nets crush organisms and damage sea bottoms
- It is especially destructive to complex areas (e.g., reefs)
• It equals clear-cutting and strip mining
- Georges Bank has been trawled three times
- Destroying young cod as bycatch
- The reason the cod stock is not recovering
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Modern fleets deplete marine life rapidly
• Grand Banks cod have been fished for centuries
- Catches more than doubled with industrial trawlers
- Record-high catches lasted only 10 years
• George Bank cod fishery also collapsed
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Industrialized fishing is destroying fisheries
Oceans today contain only one-tenth of the large-bodied
animals they once did
• Worldwide, industrialized fishing is depleting marine
populations with astonishing speed
- 90% of large-bodied fish and sharks are eliminated
within 10 years after fishing begins
- Populations stabilize at 10% of their former levels
• Communities were very different before modern fishing
- Removing animals at higher trophic levels allows
prey to proliferate and change communities
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Several factors mask declines
• Industrialized fishing has depleted stocks
- But global catch has remained stable for the past 20
years
• How can stability mask population declines?
- Fishing fleets travel farther to reach less-fished areas
- Fleets fish in deeper waters (now at 250 m)
- Fleets spend more time fishing and set more nets
- Improved technologies: faster ships, sonar mapping,
satellite navigation, thermal sensing, aerial spotting
• Fleets expend more effort to catch the same number of
fish
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We are “fishing down the food chain”
• Figures on total global catch do tell the whole story
• As fishing increases, the size and age of fish caught
decline
- 10-year-old cod, once common, are now rare
• As species become too rare to fish, fleets target more
abundant species
- Shifting from large, desirable species to smaller, less
desirable ones
- This entails catching species at lower trophic levels
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Purchasing choices influence fishing
practices
• Buy ecolabeled seafood
- Dolphin-safe tuna
• Consumers don’t know how
their seafood was caught
- Nonprofit organizations
have devised guides for
consumers
- Avoid: Atlantic cod, wildcaught caviar, sharks,
farmed salmon
Best choices: farmed
catfish, mussels,
oysters, tilapia
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Diversity loss erodes ecosystem services
• Factors that deplete biodiversity threaten ecosystem
services of the oceans
• Systems with reduced species or genetic diversity show
less primary and secondary production
- They are less able to withstand disturbance
• Biodiversity loss reduces habitat for nurseries for fish and
shellfish
• Less diversity leads to reduced filtering and
detoxification
- Resulting in algal blooms, dead zones, fish kills, beach
closures
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Fisheries management
• Based on maximum sustained yield to maximize harvest
- While keeping fish available for the future
- Managers may limit the harvest or restrict gear used
• Despite management, stocks have plummeted
- It is time to rethink fisheries management
• Ecosystem-based management shifts away from species
and toward the larger ecosystem
- Considers the impacts of fishing on habitat quality,
species interactions, and long-term effects
- Sets aside areas of oceans free from human
interference
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We can protect areas in the ocean
• Marine protected areas (MPAs) = most are along the
coastlines of developed countries
- They still allow fishing or other extractive activities
• Marine reserves = areas where fishing is prohibited
- Leave ecosystems intact, without human interference
- Improve fisheries, because young fish will disperse
into surrounding areas
• Many commercial, recreation fishers, and businesses do
not support reserves
- Be sensitive to concerns of local residents
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Reserves work for both fish and fisheries
• Marine reserves:
- Increased densities of organisms by 91%
- Increased biomass by 192%
- Increased organism size by 31%
- Increased species diversity by 23%
• Benefits inside reserve boundaries include:
- Rapid and long-term increases in abundance,
diversity, and productivity of marine organisms
- Decreased mortality and habitat destruction
- Decreased likelihood of extirpation of species
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Areas outside reserves also benefit
• A “spillover effect” occurs when individuals of protected
species spread outside reserves
- Larvae of species protected within reserves “seed the
seas” outside reserves
- Improved fishing and ecotourism
• Local residents who were opposed support reserves once
they see their benefits
• Once commercial trawling was stopped on Georges Bank:
- Populations of organisms began to recover
- Fishing in adjacent waters increased
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How should reserves be designed?
• 20–50% of the ocean should be protected in no-take
reserves
- How large?
- How many?
- Where?
• Involving fishers is crucial in coming up with answers
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Conclusion
• Oceans cover most of our planet and contain diverse
topography and ecosystems
• As we learn about oceans and coastal environments,
we are intensifying our use of their resources and
causing severe impacts
• We need to address acidification, loss of coral reefs,
pollution, and fisheries depletion
• Setting aside protected areas can maintain and restore
natural systems and enhance fisheries
• Consumer choices can help us move toward
sustainable fishing
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QUESTION: Review
A “downwelling” is defined as:
a) The vertical flow of cold, deep water towards the
surface
b) The vertical flow of warm, deep water towards the
surface
c) Oxygen-rich water sinks
d) Oxygen-poor water sinks
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QUESTION: Review
The area of an ocean that contains habitats on the ocean
floor is called the _______ zone.
a)
b)
c)
d)
Littoral
Photic
Pelagic
Benthic
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QUESTION: Review
_____ is defined as “a mass of calcium carbonate
composed of the skeletons of tiny animals”.
a)
b)
c)
d)
A Coral reef
Red tide
Bottomfish
Kelp
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QUESTION: Review
Which statement about coral bleaching is correct?
a) Corals reproduce most efficiently in colder waters.
b) Fish move into coral reefs and kill them.
c) Zooxanthellae leave the coral due to climate change
or pollution.
d) Coral reefs expand their range after they have been
bleached.
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QUESTION: Review
An area that occurs along coasts at temperate latitudes is
called a(n):
a)
b)
c)
d)
Estuary
Mangrove swamp
Salt marsh
Coral reef
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QUESTION: Review
Which of the following does NOT mask the decline of
fisheries?
a) Fishing fleets travel longer distances to reach lessfished areas.
b) Fishing fleets spend more time fishing.
c) Fishing fleets use sophisticated methods of fishing.
d) Fleets fish in shallower waters nearer coasts.
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QUESTION: Review
Marine reserves have all the following benefits
EXCEPT:
a)
b)
c)
d)
Fishing increases in areas surrounding the reserve.
The size of fish decreases
Larvae can “seed” areas outside the reserve.
Decreased mortality and habitat destruction occur.
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QUESTION: Viewpoints
What would you think about letting another country
fish 10 miles off the U.S. coast?
a) That’s fine, as long as the fleet paid the United
States.
b) Let them fish, but make them follow the same
rules as U.S. fishermen.
c) Let only U.S. fishermen fish in these waters.
d) Prevent most fishing – we need to protect the last
fish stocks.
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QUESTION: Interpreting Graphs and Data
What does this graph show about the future of global
fisheries catch?
a) China will apply major
fishing pressure.
b) China’s role in fishing
pressure will decline.
c) The world will
decrease its fishing
pressure.
d) The United States is not
included in this graph.
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QUESTION: Interpreting Graphs and Data
Which conclusion can you draw from this graph about
commercial catches of Atlantic cod?
a) Intensified fishing
increased and the fishery
crashed.
b) It is easier to find fish
today.
c) There is little correlation
between fishing and fish
stocks.
d) Moratoria will bring the
stocks back.
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