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Sustaining Aquatic Biodiversity
Chapters 6 & 12
Key Concepts
• Important aquatic resources:
economic and ecological importance
• Effects of human activities and the power of
choice
• Solutions to protecting and sustaining aquatic
diversity: for example, wetland restoration in
estuarine habitats
AQUATIC ENVIRONMENTS
• Saltwater and freshwater aquatic life zones
cover almost three-fourths of the earth’s
surface
AQUATIC ENVIRONMENTS
What Kinds of Organisms Live in
Aquatic Life Zones?
• Aquatic systems contain floating, drifting,
swimming, bottom-dwelling, and decomposer
organisms.
– Plankton: important group of weakly swimming,
free-floating biota.
• Phytoplankton (plant), Zooplankton (animal),
Ultraplankton (photosynthetic bacteria)
– Necton: fish, turtles, whales.
– Benthos: bottom dwellers (barnacles, oysters).
– Decomposers: breakdown organic compounds
(mostly bacteria).
Life in Layers
• Life in most aquatic systems is found in surface,
middle, and bottom layers.
• Temperature, access to sunlight for
photosynthesis, dissolved oxygen content,
nutrient availability changes with depth.
– Euphotic zone: brightly lit surface layer, low nutrients,
high DO, area of photosynthetic activity
– Bathyl zone: dimly lit middle layer, no PA, organisms
migrate to EZ to feed at night
– Abyssal zone: dark bottom layer, very cold, little DO
Marine Ecosystems
 Scientists
estimate
that marine systems
provide $21 trillion in
goods and services
per year – 70% more
than terrestrial
ecosystems.
The Coastal Zone:
Where Most of the Action Is
• The coastal zone: the warm, nutrient-rich,
shallow water that extends from the high-tide
mark on land to the gently sloping, shallow
edge of the continental shelf.
• The coastal zone makes up less than 10% of
the world’s ocean area but contains 90% of all
marine species.
– Provides numerous ecological and economic
services.
– Subject to human disturbance.
The Coastal Zone
Centers of Aquatic Biodiversity
• ~ 25 000 spp of fish – 63%
marine + 37% freshwater
• Centers of aquatic
diversity:
- coral reefs
- deep sea
- coastal & estuaries
• Food and chemicals
Human Impacts on
Aquatic Biodiversity
• Greatest threats:
- habitat loss &
degradation
- overfishing
- non-native spp
- pollution
- global warming
• Habitat loss:
- 50% of wetlands lost in
US and globally
- > 25% of coral reefs
damaged
- > 33% of mangroves lost
- Ocean bottom degraded
by trawling
HUMAN IMPACTS ON AQUATIC
BIODIVERSITY
 Area
of ocean before and after a
trawler net, acting like a giant plow,
scraped it.
Fish farming
in cage
Trawler fishing
Spotter airplane
Sonar
Trawl flap
Purse-seine
fishing
Trawl lines
Trawl bag
Fish school
Drift-net fishing
Float
Buoy
Long line fishing
Lines with hooks
Deep sea aquaculture cage
Fish caught by gills
Commercial Whaling
After many of the world’s whale
species were overharvested,
commercial whaling was banned
in 1960, but the ban may be
overturned
Despite ban, Japan, Norway, and
Iceland kill about 1,300 whales
of certain species for scientific
purposes.
Although meat is still sold
commercially.
FRESHWATER LIFE ZONES
• Freshwater life zones
include:
– Standing (lentic)
water such as lakes,
ponds, and inland
wetlands.
– Flowing (lotic)
systems such as
streams and rivers
Lakes: Water-Filled Depressions
Freshwater Streams and Rivers:
From the Mountains to the Oceans
Water flowing from mountains to the sea creates
different aquatic conditions and habitats.
Human Impacts on
Aquatic Biodiversity
• Invasive species threaten marine and freshwater
biodiversity.
– Bioinvaders are blamed for about 2/3 of
fish extinctions in the U.S. between
1900- 2000.
• ~50% world world’s people live on or near a
coastal zone
• 80% of ocean water pollution comes
from land land-based human activities.
Ocean Pollution
Ocean Pollution
Freshwater Pollution
Freshwater Pollution
Eutrophication
• Plant nutrients from a lake’s environment affect
the types and numbers of organisms it can
support.
– Oligotrophic (poorly nourished) lake: Usually newly
formed lake with small supply of plant nutrient input.
– Eutrophic (well nourished) lake: Over time, sediment,
organic material, and inorganic nutrients wash into
lakes causing excessive plant growth.
• Cultural eutrophication:
– Human inputs of nutrients from the atmosphere and
urban and agricultural areas can accelerate the
eutrophication process.
Too Much of a Good Thing
Plant nutrients from a lake’s environment affect the types
and numbers of organisms it can support.
Why is it difficult to protect
aquatic biodiversity?
•
•
•
•
•
Rapidly increasing human impacts
Invisibility of problems
People are just unaware
Lack of legal jurisdiction hinders protection
Many people incorrectly view the oceans as
an inexhaustible resource
Commercial Extinction and
Tragedy of the Commons
• Overfishing leads to commercial
extinction
• Estimated sustainable yield catch rate at which spp renews
itself
• Tragedy of the Commons as one
cause
• Large open ocean fish and
bottom dwellers have declined
90% since the early 1950s
Protecting and Restoring Rivers to
help salmon and other riverine spp.
• Pollution
• Disruption of water
flow
• Loss of biodiversity
• Invasive species
PROTECTING, SUSTAINING, AND
RESTORING LAKES AND RIVERS
• Dams can provide many human benefits but
also disrupt ecological services rivers provide.
• 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.
Protecting and Sustaining
Marine Biodiversity
• Legally protect rare species
• Sustainable management of
marine fisheries
• Establish protected areas (marine
reserves make up <0.3% of world
ocean area)
• Integrated coastal management
• Regulate and prevent ocean
pollution
Managing and Sustaining the World’s
Marine FisheriesManaging Fisheries
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•
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Economic approaches
By-catch reduction
Control nonnative species
Consumer information
PROTECTING, SUSTAINING, AND
RESTORING WETLANDS
• 50% lost in US US--90% in CA!
• Permits for filling or destroying U.S. wetlands
has slowed their loss (Clean Water Act)
• Attempts to weaken this protection continue
Restoration is underway!
• Returning the natural, indigenous ecosystem
• Includes species and natural processes
• Wetland restoration projects across the
country ….
Florida Everglades
South Bay San Fran
Silver Sands Milford
Restoring the
Florida
Everglades
The project has been
attempting to restore
the Everglades and
Florida water supplies.
90% of park90% park’s wading birds
have vanished.
Other vertebrates down 75--95%.
Large volumes of water diverted for
crops and cities.
Runoff has caused noxious algal
blooms.
The Everglades needs its water regime
and quality
South Bay Salt Pond Restoration:
Wildlife Island in an Urban Sea
• Why restore estuarine habitats like the San
Francisco Bay?
•Immense natural capital and
value to society
•Flood protection
•Fisheries support: no
wetlands, no fish!
•Water quality protection
•Incredible productivity and
biodiversity
•Carbon sequestration
Moving Forward with Restoration
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Use the best existing data
Collect more data during planning
Implement the most scientifically -sound plan
Use adaptive management to learn &
improve
How might these projects
effect you?
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Flood protection is a central goal
More recreation
More plants and animals
Healthier coastal ecosystems
Improved water quality
Opportunities for volunteering & research