Chapter 11
Mola
Mola!
Sustaining Aquatic
Biodiversity
Chapter Overview Questions

What do we know about aquatic biodiversity, and
what is its economic and ecological importance?

How are human activities affecting aquatic
biodiversity?

How can we protect and sustain marine
biodiversity?

How can we manage and sustain the world’s
marine fisheries?
Chapter Overview Questions (cont’d)
 How
can we protect, sustain, and restore
wetlands?
 How
can we protect, sustain, and restore
lakes, rivers, and freshwater fisheries?
Core Case Study: A Biological Roller
Coaster Ride in Lake Victoria
 Lake
Victoria has lost many of its endemic
fish species to large introduced predatory
fish, the Nile perch.
Figure 12-1
Lake Victoria Cichlids
About 200 of 400 Lake Victoria endemic cichlid species
have become extinct since the introduction of the Nile
perch.
Pundamilia nyererei
Astatotilapia latifasciata
Haplochromis sp. 44 "Red Tail"
Figure 12-1
Core Case Study: A Biological Roller
Coaster Ride in Lake Victoria
 Reasons
for Lake Victoria’s loss of
biodiversity:




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 (!)
AQUATIC BIODIVERSITY
 We
know fairly little about the biodiversity of
the world’s marine and freshwater systems.
 We know more about deep space than the
abyssal zones of the ocean (why?).


The greatest marine biodiversity occurs in coral
reefs, estuaries and the deep ocean floor.
Biodiversity is higher near the coast and surface
because of habitat and food source variety.
 The
world’s marine and freshwater systems
provide important ecological and economic
services.
AQUATIC BIODIVERSITY

About 50% of the
world’s people depend
on the sea as their
primary source of food.
Indonesian fishing prau
Lake Victoria fishers
Georgia shrimper
AQUATIC BIODIVERSITY

About 90% of fish spawn in the world’s coral reefs,
mangrove swamps, coastal wetlands, or rivers.
Coastal Wetlands: Salt marsh or Mangroves
Coastal Wetlands: Salt marsh or Mangroves
Coastal Wetlands: Salt marsh or Mangroves
Snook!
Kayaking Mangroves
Kayaking Mangroves
Kayaking Mangroves
HUMAN IMPACTS ON AQUATIC
BIODIVERSITY
 Human
activities have destroyed, disrupted
or degraded a large proportion of the world’s
coastal, marine and freshwater ecosystems.




Approximately 20% of the world's coral reefs
have been destroyed.
During the past 100 years, sea levels have risen
1.0-2.5 centimeters.
We have destroyed more than 1/3 of the world’s
mangrove forests, mostly for shipping lanes.
Shrimp farming is a big, new threat to mangroves
HUMAN IMPACTS ON AQUATIC
BIODIVERSITY
Area of ocean before and after a trawler net passed by.
Note: East coast shrimp trawlers work in relatively open areas
and do not do this much damage
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.
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.
 Almost
Population Growth and Pollution

Each year plastic items
dumped from ships and
washing in to the ocean
from land threaten
marine life.

“Red tide” is a toxic
algae bloom that is
exacerbated by excess
nutrients entering the
water from terrestrial
sources
Figure 12-3
Population Growth and Pollution:
Excess Nutrients

Since 1860, humans
have doubled the flow
of nitrogen, mostly as
nitrate fertilizers, into
the ocean.
N P K
Potassium
Nitrogen
Phosphorous
“potash”
Figure 12-3
Overfishing and Extinction:
Gone Fishing, Fish Gone
75% of the world’s commercially
valuable marine fish species are over fished
or fished near their sustainable limits.
 About




Big fish are becoming scarce.
Smaller fish are next.
We throw away 30% of the fish we catch
(bycatch)
We needlessly kill sea mammals and birds.
Overfishing and Extinction:
Gone Fishing, Fish Gone
 Commercial
depletion occurs when a species
has been over fished to the point where it is
no longer profitable as a fishery.
Overfishing and Extinction:
Gone Fishing, Fish Gone
 Review!
When too many people using the
same resource in a way that makes sense for
them as individuals results in the collapse of
the resource, it is called…
The Tragedy of the Commons
Fish farming
in cage
Trawler
fishing
Spotter airplane
Sonar
Trawl flap
Trawl
lines
Fish
school
Purse-seine fishing
Trawl bag
Drift-net fishing a.k.a. gill netting
Long line
fishing
Float Buoy
Lines with
hooks
Deep sea
aquaculture cage
Fish caught
by gills
Fig. 12-A, p. 255
Why is it Difficult to Protect Aquatic Biodiversity?
 Human
ecological footprint is increasing
so rapidly
 Much damage done to oceans is
“invisible” to most people
 Most citizens are unaware of the scope
and severity of the problems
 Lack of legal jurisdiction
 Many people incorrectly view the oceans
as an inexhaustible resource.
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 (TEDs)

Sea turtle tourism brings in almost three times as
much money as the sale of turtle products.
Turtle Excluder Devices (TEDs)
Turtle Excluder Devices (TEDs)
Turtle Excluder Devices (TEDs)
Bycatch Reduction Devices (BRDs)
Bycatch Reduction Devices (BRDs)
PROTECTING AND SUSTAINING
MARINE BIODIVERSITY

Six of the world’s seven
major turtle species are
threatened or
endangered because of
human activities.
*beach development
*harvesting eggs
*turtle shell jewelry
*leather made of flippers
Figure 12-4
Case Study: The Florida Manatee
and Water Hyacinths
 Manatee
can eat
unwanted Water
Hyacinths.
 Endangered due to:





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
Japan has a significant
whaling industry and
whale meat market
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
Toothed whales
*Sperm
whale
with
squid
Killer whale
Narwhal
Bottlenose dolphin
Baleen whales
Blue whale
Fin whale
Bowhead
whale
Right
whale
Sei whale
Humpback
whale
Gray whale
*Minke whale
Fig. 12-5, p. 258
PROTECTING AND SUSTAINING
MARINE BIODIVERSITY

Fully protected marine reserves make up less than
0.3% of the world’s ocean area.
 Marine Reserves Work:

Studies show that in protected areas:
• fish populations double
• fish size grows by almost a third
• reproduction triples
• species diversity increases by almost one fourth.

Some communities work together to develop
integrated plans for managing their coastal areas.
Revamping Ocean Policy
 Two
recent studies called for an overhaul of
U.S. ocean policy and management.






Create a National Oceans Agency within the
Executive Office of the President
Develop unified national policy.
Double federal budget for ocean research.
Set up network of marine reserves.
Reorient fisheries management towards
ecosystem function.
Increase public awareness.
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.

Modern fisheries have weakened the ability of
many coastal communities to regulate their own
fisheries.
Solutions
Managing Fisheries
FISHERY REGULATIONS
Set catch limits well below the
maximum sustainable yield
Improve monitoring and enforcement
of regulations
ECONOMIC APPROACHES
Sharply reduce or eliminate fishing
subsidies
BYCATCH
Use wide-meshed nets to allow
escape of smaller fish
Use net escape devices for sea
birds, sea turtles, and bycatch fish
Ban throwing edible and
marketable fish back into the sea
AQUACULTURE
Charge fees for harvesting fish and shellfish
from publicly owned offshore waters
Restrict coastal locations for fish
farms
Certify sustainable fisheries
Control pollution more strictly
PROTECTED AREAS
Depend more on herbivorous fish
species
Establish no-fishing areas
Establish more marine protected areas
Rely more on integrated coastal
management
CONSUMER INFORMATION
Label sustainably harvested fish
Publicize overfished and threatened species
NON-NATIVE INVASIONS
Kill organisms in ship ballast water
Filter organisms from ship ballast
water
Dump ballast water far at sea and
replace with deep-sea water
Fig. 12-7, p. 261
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
PROTECTING, SUSTAINING, AND
RESTORING WETLANDS
The US has lost more than 50% of our original wetlands
Figure 12-8
PROTECTING, SUSTAINING, AND
RESTORING WETLANDS

Mitigation banking allows wetlands to be developed
as long as an equal area of wetland is created or
restored


At least 50% of wetland mitigation projects fail
Mitigation has worked in Coastal Georgia salt marshes
Figure 12-8
Solutions
Protecting Wetlands
Legally protect existing wetlands
Steer development away from existing wetlands
Use mitigation banking only as a last resort
Require creation and evaluation of a new wetland before
destroying an existing wetland
Restore degraded wetlands
Try to prevent and control invasions by nonnative species
Fig. 12-9, p. 264
Case Study:
Restoring the Florida Everglades
Case Study:
Restoring the Florida Everglades
world’s largest ecological restoration
project involves trying to undo some of the
damage inflicted on the Everglades by
human activities.
 The




Large volumes of water that once flowed through
the park have been diverted for crops and cities.
90% of park’s wading birds have vanished.
Other vertebrate populations down 75-95%.
Runoff has caused noxious algal blooms in
nearby coastal waters.
Restoring the
Florida
Everglades
 The
the US Army
Corps of Engineers
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.

Sea lamprey, zebra mussel, quagga mussel,
Asian carp.
Columbia
River:
Former
(Future?)
Salmon
Habitat
PROTECTING, SUSTAINING, AND
RESTORING LAKES AND RIVERS
Migrate
to “natal
stream”
Spawn
SeptNov
Sept-Dec
In stream
gravel JanApril
Mature in
ocean
2-5 yrs
Emerge
May-June
Migrate to
ocean in
April- Aug
A few
months to
2 years
PROTECTING, SUSTAINING, AND
RESTORING LAKES AND RIVERS
Natural Capital
Ecological Services of Rivers
• Deliver nutrients to sea to help sustain
coastal fisheries
• Deposit silt that maintains deltas
• Purify water
• Renew and renourish wetlands
• Provide habitats for wildlife
Fig. 12-11, p. 267
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.



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 (economic implications?)
PROTECTING, SUSTAINING, AND
RESTORING LAKES AND RIVERS
 We
can help sustain freshwater fisheries by
building and protecting populations of
desirable species, preventing over-fishing,
and decreasing populations of less desirable
species.
 A federal law helps protect a tiny fraction of
U.S. wild and scenic rivers from dams and
other forms of development.

National Wild and Scenic Rivers Act (1968).
National Wild and Scenic Rivers Act

2% of US rivers remain
free flowing
 0.2% of US rivers are
protected by the Wild
and Scenic Rivers Act
Vermillion River, IL
Smith River, CA
National Wild and Scenic Rivers Act
Skagit River, North Cascade Mountains, WA
National Wild and Scenic Rivers Act
 Wild
Rivers- untamed and inaccessible except
by trail; no widening, straightening, dredging,
filling, or damming; no motor boats allowed
 Scenic
Rivers- of great scenic value and
accessible by a few roads; free of dams, mostly
undeveloped; no motor boats allowed
 Recreational
Rivers- easily accessible; may
have some dams or shore development; motor
boats allowed.