Transcript Chapter 6

Chapter 11
Sustaining Aquatic
Biodiversity
Core Case Study: A Biological Roller
Coaster Ride in Lake Victoria
 Lake
Victoria has lost their endemic fish
species to large introduced predatory fish.
Figure 12-1
Core Case Study: A Biological Roller
Coaster Ride in Lake Victoria
 Reasons
for Lake Victoria’s loss of
biodiversity:
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Introduction of Nile perch.
Lake experienced algal blooms from nutrient
runoff.
Invasion of water hyacinth has blocked sunlight
and deprived oxygen.
Nile perch is in decline because it has eaten its
own food supply.
HUMAN IMPACTS ON AQUATIC
BIODIVERSITY
 Human
activities have destroyed, disrupted
or degraded a large proportion of the world’s
coastal, marine and freshwater ecosystems.
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Approximately 20% of the world's coral reefs
have been destroyed.
During the past 100 years, sea levels have risen
10-25 centimeters.
We have destroyed more than 1/3 of the world’s
mangrove forests for shipping lanes.
HUMAN IMPACTS ON AQUATIC
BIODIVERSITY
 Area
of ocean before and after a trawler net,
acting like a giant plow, scraped it.
Figure 12-2
HUMAN IMPACTS ON AQUATIC
BIODIVERSITY
 Harmful
invasive species are an increasing
threat to marine and freshwater biodiversity.

Bioinvaders are blamed for about 2/3 of fish
extinctions in the U.S. between 1900-2000.
 Almost
half of the world’s people live on or
near a coastal zone and 80% of ocean water
pollution comes from land-based human
activities.
Population Growth and Pollution
 Each
year plastic
items dumped from
ships and left as
litter on beaches
threaten marine
life.
Figure 12-3
Overfishing and Extinction:
Gone Fishing, Fish Gone
 About
75% of the world’s commercially
valuable marine fish species are over fished
or fished near their sustainable limits.
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Big fish are becoming scarce.
Smaller fish are next.
We throw away 30% of the fish we catch.
We needlessly kill sea mammals and birds.
Fish farming
in cage
Trawl flap
Trawler
fishing
Spotter airplane
Sonar
Purse-seine fishing
Trawl
lines
Trawl bag
Long line
fishing
Fish
school
Drift-net fishing
Float Buoy
Lines with
hooks
Deep sea
aquaculture cage
Fish caught
by gills
Fig. 12-A, p. 255
PROTECTING AND SUSTAINING
MARINE BIODIVERSITY
 Laws,
international treaties, and education
can help reduce the premature extinction of
marine species.
 Since 1989 the U.S. government has
required offshore shrimp trawlers to use turtle
exclusion devices.

Sea turtle tourism brings in almost three times as
much money as the sale of turtle products.
PROTECTING AND SUSTAINING
MARINE BIODIVERSITY
 Six
of the world’s
seven major turtle
species are
threatened or
endangered
because o human
activities.
Figure 12-4
Case Study: The Florida Manatee
and Water Hyacinths
 Manatee
can eat
unwanted Water
Hyacinths.
 Endangered due to:
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Habitat loss.
Entanglement from fishing
lines and nets.
Hit by speed boats.
Stress from cold.
Low reproductive rate
Figure 12-B
Case Study: Commercial Whaling
 After
many of the
world’s whale
species were
overharvested,
commercial
whaling was
banned in 1960,
but the ban may
be overturned.
Figure 12-6
Case Study:
Commercial Whaling
 Despite
ban, Japan,
Norway, and Iceland kill
about 1,300 whales of
certain species for scientific
purposes.

Although meat is still sold
commercially.
Figure 12-5
PROTECTING AND SUSTAINING
MARINE BIODIVERSITY
 Fully
protected marine reserves make up less
than 0.3% of the world’s ocean area.
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Studies show that fish populations double, size
grows by almost a third, reproduction triples and
species diversity increases by almost one fourth.
 Some
communities work together to develop
integrated plans for managing their coastal
areas.
MANAGING AND SUSTAINING
MARINE FISHERIES
 There
are a number of ways to manage
marine fisheries more sustainably and protect
marine biodiversity.
 Some fishing communities regulate fish
harvests on their own and others work with
the government to regulate them.
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Modern fisheries have weakened the ability of
many coastal communities to regulate their own
fisheries.
PROTECTING, SUSTAINING, AND
RESTORING WETLANDS
 Requiring
government permits for filling or
destroying U.S. wetlands has slowed their
loss, but attempts to weaken this protection
continue.
Figure 12-8
Case Study:
Restoring the Florida Everglades
 The
world’s largest ecological restoration
project involves trying to undo some of the
damage inflicted on the Everglades by
human activities.
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90% of park’s wading birds have vanished.
Other vertebrate populations down 75-95%.
Large volumes of water that once flowed through
the park have been diverted for crops and cities.
Runoff has caused noxious algal blooms.
Restoring the
Florida
Everglades
 The
project has
been attempting
to restore the
Everglades and
Florida water
supplies.
Figure 12-10
PROTECTING, SUSTAINING, AND
RESTORING LAKES AND RIVERS
 Lakes
are difficult to manage and are
vulnerable to planned or unplanned
introductions of nonnative species.
 For decades, invasions by nonnative species
have caused major ecological and economic
damage to North America’s Great lakes.
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Sea lamprey, zebra mussel, quagga mussel,
Asian carp.
PROTECTING, SUSTAINING, AND
RESTORING LAKES AND RIVERS
 Dams
can provide many human benefits but
can also disrupt some of the ecological
services that rivers provide.
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119 dams on Columbia River have sharply
reduced (94% drop) populations of wild salmon.
U.S. government has spent $3 billion in
unsuccessful efforts to save the salmon.
Removing hydroelectric dams will restore native
spawning grounds.