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Water is Essential to Life
Importance
 Leonardo
da Vinci said
that “Water is the driver of
nature.” Without water,
the other nutrient cycles
would not exist in their
present forms, and
current forms of life on
earth could not exist.
Water’s Unique Properties
 There
are strong forces of attraction between
molecules of water.
 Water exists as a liquid over a wide
temperature range.
 Liquid water changes temperature slowly.
 It takes a large amount of energy for water to
evaporate.
 Liquid water can dissolve a variety of
compounds.
 Water expands when it freezes.
Attraction Between Molecules
 The
strong forces of attraction
between molecules of water.
 Hydrogen bonds
 Result in many
distinctive properties
Liquid state
Exists in liquid state over wide range of
temperatures:
32° F to 212° F
Without water’s high boiling point,
oceans would have evaporated
long ago
Heat Capacity
 Water
changes temp very slowly because
it can store heat. This protects living
organisms from the shock of abrupt
temperature changes.
Heat Capacity
 Also moderates earth’s climate
 Water warms & cools slower than
surrounding land
Universal Solvent:
 Water
can dissolve a
many substances.
• Carry nutrients
•
•
•
flush wastes
distribute particles
facilitate other cycles
Universal Solvent
 Water
can dissolve
a wide variety of
compounds. This
means it can easily
become polluted by
water-soluble
wastes.
Water Cycle
Water moves through
ecosystems
transporting trash
and other pollutants
Expansion When Frozen
 Ice
has a lower density than liquid
water. Thus, ice floats on water.
Capillary action
Long narrow
columns of
water rise
through
roots to
leaves
Surface tension
 Surface
behaves
like an elastic
membrane
Chapter 6
Aquatic Biodiversity
Coral Reefs
Among the oldest, most diverse, most productive ecosystems
Marine equivalent to tropical rain forests
 Coral
reefs form in
clear, warm
coastal waters of
the tropics and
subtropics.

Formed by
massive colonies
of polyps and
algae
Figure 6-1
Coral Reefs
 Help
moderate atmospheric temperature by
removing CO2 from the atmosphere.
 Act
as natural barriers that help protect 14%
of the world’s coastlines from erosion by
battering waves and storms.
 Provide
habitats for a variety of marine
organisms.
AQUATIC ENVIRONMENTS
 Saltwater
and freshwater aquatic life zones
cover almost three-fourths of the earth’s
surface
Figure 6-2
AQUATIC ENVIRONMENTS
Figure 6-3
Factors Affecting Aquatic Ecosystems
‣
Abiotic (physical) factors are
the influences of the nonliving parts of the ecosystem.
Examples include pH,
salinity, temperature,
turbidity, nutrients, wind
speed and direction,
humidity, precipitation, water
pressure, and light intensity
and water quality.
‣
Biotic factors are the
influences of the living parts
of the ecosystem. Producers
and consumers interact as
competitors, parasites,
pathogens, symbionts, and
predators.
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).
Phytoplankton & Zooplankton

Phytoplankton are an
autotrophic group of weakly
swimming, free-floating biota
that are producers that support
most aquatic food chains.
These organisms provide much
of the oxygen in the Earth’s
atmosphere and include:
Phytoplankton (plant-like
organisms and cyanobacteria
Different types of phytoplankton
‣ Zooplankton are
herbivores that feed
on plankton and are,
in turn, the food stock
for larger consumers
like whales. These
organisms include:
Krill are one of the most important organisms in aquatic
food chains especially for whales.
Krill and small
crustaceans
Nekton and Benthos

Nekton are larger, actively
swimming consumers
usually the top consumers
in the aquatic ecosystems
and include:
Fish, whales and turtles

Benthos are bottomdwelling creatures that
may be primary
consumers or
decomposers. These
highly diverse organisms
may live in tide pools,
shelves or the abyss and
include:
Barnacles, oysters,
lobsters and sea
anemones
Sharks and Turtles are nektonic species
Benthos or “depths of the sea” are
organisms that live on the ocean floor
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 (upper layer in deep water
habitats): sunlight can penetrate –
photosynthesis.
Ocean Zones
Benthic Zone
(Ocean Floor):
Bacteria are common &
can survive down to
500 meters below
ocean floor.
Abyssal
Zone

Coastal and Euphotic
Zone: Lots of light. From
0 - 200 meters.
Photosynthesis takes
place here

Bathyal Zone: The dimly
lit part of ocean. From
200 - 1500 meters.

Abyssal Zone:
Completely dark.
Extends to a depth of
4000 to 6000 meters
(2.5 to 3.7 miles). Water
here is very cold & has
little dissolved oxygen.
Sun
Euphotic Zone
Photosynthesis
Estuarine
Zone
Continental
shelf
Open
Sea
Sea level
Bathyal Zone
Abyssal
Zone
Darkness
High tide Coastal
Zone
Low tide
Fig. 6-5, p. 130
Marine Ecosystems

The oceans that occupy
most of the earth’s
surface provide many
ecological and economic
services.
 Scientists estimate that
marine systems provide
$21 trillion in goods and
services per year – 70%
more than terrestrial
ecosystems.
Figure 6-4
Natural Capital
Marine Ecosystems
Economic
Services
Ecological
Services
Climate moderation
Food
CO2 absorption
Animal and pet
feed
Nutrient cycling
Waste treatment
Reduced storm
impact (mangroves,
barrier islands,
coastal wetlands)
Habitats and
nursery areas
Pharmaceuticals
Harbors and
transportation routes
Coastal habitats for
humans
Recreation
Employment
Genetic
resources and
biodiversity
Oil and natural gas
Scientific
information
Building materials
Minerals
Fig. 6-4, p. 129
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.
Reefs

Reefs:
Reefs are Marine Protected Areas like
national parks and wildlife refuges and have
significant economic value because of
tourism. Calcium carbonate living systems in
warm shallow water where light penetrates,
reefs are the habitat for many species.
Loss of reefs removes habitats. Reefs are
the food source for marine life, breeding
grounds for fish and bird species, and shelter
and hiding place for many species.
The loss of biodiversity or richness could
cause the extinction or decrease in
populations of marine organisms.
Reefs serve as a buffer and protection for
coastal areas from waves and storms, which
could lead to destruction of coastal habitats
or the erosion of shoreline habitats.
Reefs are a major carbon sink in the ocean
and this carbon storage would be lost.
Sea Grass and Kelp

Kelp (Seaweed):
Brown algae groups that provide habitats and
food for many organisms. Overfishing leads to
the degradation of kelp forests as the
herbivores are released from the potential
predators. (Sea otter and the urchin.)
Kelp is being considered as a renewable
resource because it is fast growing and yields
large amounts of methane. The fast growing
algae has been the topic of renewable energy
talks because of the lack of an irrigation
requirement.
 Seagrass:
Seagrass is highly adaptable and serves as a
producer for many marine ecosystems.
Seagrass can reduce erosion and increase
sedimentation through roots that stabilize the
seabed.
These coastal seagrass zones provide shelter
for organisms, wave protections, oxygen
production and carbon storage.
Estuaries
Estuaries: Definition
A
partially enclosed area of coastal
water where sea water mixes with
freshwater.
Estuaries and Coastal Wetlands:
Centers of Productivity
 Estuaries
include river
mouths, inlets, bays,
sounds, salt marshes
in temperate zones
and mangrove forests
in tropical zones.
Figure 6-7
Estuaries

Estuaries are a partially enclosed
area of coastal water where sea
water mixes with freshwater and
are constantly changing.

Salinity, temperature, suspended
solids, storms (precipitation), and
tidal cycles fluctuate with the time
of year.
The organisms that live in this
unique habitat must be able to
tolerate these conditions.

Nutrients that are transported
from rivers brings a high amount
of nutrients.
This allows a place of breeding
for many ocean species and
thus makes estuaries highly
productive and fertile
supporting complex food
webs.
Estuary Ecosystem Services

Estuaries serve as a carbon sink by absorbing large amounts of
CO2 (sink) and they also serve as filters for pollutants by trapping
sediments and pollutants.
 They act as sponges as they absorb water recharging
groundwater stores and controlling flooding by slowing flow of
water.
 Economically wetlands are important as well:
Provide employment and recreational income through fishing,
recreation, and photography.
Allow for protected waterway passage between rivers and
oceans.
Protect property by buffering shores form flow of water and
erosion.
Treat sewage and storm water that would otherwise be paid for
by the local community.

Coastal ecosystems can easily be affected by rising sea levels,
storms, temperature change, and rate of water cycling.
Estuaries and Coastal Wetlands:
Centers of Productivity
 Estuaries
and coastal marshes provide
ecological and economic services.



Filter toxic pollutants, excess plant nutrients,
sediments, and other pollutants.
Reduce storm damage by absorbing waves
and storing excess water produced by storms
and tsunamis.
Provide food, habitats and nursery sites for
many aquatic species.
Salt Marshes
 The
ground here is saturated with water and
there is little oxygen, so decay takes place
slowly. It has a surface inlet and outlet, and
contains many invertebrates. It is also the
breeding ground for many ocean animals. Ex.
crabs and shellfish.
Mangrove Forests
 Are
found along
about 70% of
gently sloping
sandy and silty
coastlines in
tropical and
subtropical
regions.
Figure 6-8
Mangrove Forests

These are along warm, tropical
coasts where there is too much silt
for coral reefs to grow. It is
dominated by salt-tolerant trees
called mangroves (55 different
species exist). It also helps to
protect the coastline from erosion
and provides a breeding nursery
for some 2000 species of fish,
invertebrates, and plants.
Importance of Estuaries
 Just
one acre of estuary provides $75,000
worth of free waste treatment, and has a value
of about $83,000 when recreation and fish for
food are included.
 Prime Kansas farmland has a top value of
$1,200 and an annual production value of
$600.
Mouth of river carrying erosion
Ocean Margin Plants
‣ Ocean margin plants, e.g. intertidal
seaweeds and mangroves, must cope
with high salt content in the water and
changing tidal conditions.
‣ Sea level rise may change these
areas, leading to a loss in species.
‣ Construction, building, roads and other
residential, commercial, and industrial
projects may have a negative impact.
Mangrove pneumatophores
Seaweeds
growing in the
intertidal zone
tolerate
exposure to
the drying air
every 12 h.
Some mangrove
species take in
brackish water and
excrete the salt
through glands in the
leaves.
Rocky and Sandy Shores:
Living with the Tides
 Organisms
experiencing daily low and high
tides have evolved a number of ways to
survive under harsh and changing conditions.


Gravitational pull by moon and sun causes tides.
Intertidal Zone: area of shoreline between low
and high tides.
Rocky and Sandy Shores:
Living with the Tides
 Organisms
in
intertidal zone
develop specialized
niches to deal with
daily changes in:



Temperature
Salinity
Wave action
Figure 6-9
Rocky Shore Beach
Hermit crab
Sea star
Shore crab
High tide
Periwinkle
Sea urchin
Anemone
Mussel
Low tide
Sculpin
Barnacles
Kelp
Sea lettuce
Monterey flatworm
Nudibranch
Fig. 6-9, p. 132
Barrier Beach
Beach flea
Peanut worm
Blue crab
Tiger
Beetle
Clam
Dwarf
Olive
High tide
Sandpiper
Low tide
Silversides
Mole
Shrimp
White sand
macoma
Sand dollar
Ghost
Shrimp
Moon
snail
Fig. 6-9, p. 132
Barrier Islands
 Low,
narrow, sandy islands that form offshore
from a coastline.
 Primary and secondary dunes on gently
sloping sandy barrier beaches protect land
from erosion by the sea.
Figure 6-10
Effects of Human Activities on Marine
Systems: Red Alert

Human
activities are
destroying or
degrading many
ecological and
economic
services
provided by the
world’s coastal
areas.
Threats to
Coral Reefs:
Increasing
Stresses
 Biologically
diverse and
productive coral
reefs are being
stressed by
human activities.
Figure 6-11
Natural Capital Degradation
Coral Reefs
Ocean warming
Soil erosion
Algae growth from fertilizer runoff
Mangrove destruction
Bleaching
Rising sea levels
Increased UV exposure
Damage from anchors
Damage from fishing and diving
Fig. 6-12, p. 135
Bleached Coral
Bleached coral reef that has lost most of its algae because of
changes in the environment (such as cloudy water, too warm
temperatures, acidification). With the algae gone, the white
limestone of the coral skeleton becomes visible. If the
environmental stress is not removed and no other algae
species fill the abandoned niche, the corals die.
Ocean Acidity

The ocean acts as a CO2 sink, absorbing much of the CO2
produced by the burning of fossil fuels.

CO2 reacting with water forms carbonic acid through the
chemical reaction:
CO2 + H2O
H2CO3

An increase in carbonic acid levels is causing the pH of the
oceans to fall. This has major implications for marine life.
8.4
pH of ocean surface
8.3
8.2
8.1
8.0
8.3
7.9
8.2
7.8
8.1
7.7
7.6
25
Possible
pH range
8.0
20
15
10
5
Time (millions of years before present)
0 7.9
5
7.8
1850
1900 1950
2000
2050
2100
Atmospheric
carbon dioxide
CO2
Dissolved
carbon
dioxide
CO
+ 2
Water
H2O
Effect of Ocean
Acidification
Hydrogen ions+ Carbonate ions
from the sea
H+
CO32Carbonic acid
H2CO3
‣
Because the oceans are naturally alkaline,
acidification will not produce acid waters.
‣
Shells will not dissolve but organisms
will find it more difficult to gain the CO32- ions
needed to make shells.
‣
Shell making organisms are able to use
CO32- but cannot use HCO3-.
‣
Acidification lowers the amount of CO32- available.
Bicarbonate
ions
HCO3-
Deformed shells
Ocean pH

pH is a logarithmic scale, so even a small pH change
represents a large change in H+. Thus a pH of 5 is 100x
more acidic than a pH of 7.

Some areas are affected by pH change more than
others. Changes may be due to:
higher human activity, e.g. sea traffic in the North Sea
natural processes that affect CO2 uptake, e.g. underwater
eruptions
Change of -0.07
pH units
Image: Plumbago using GLODAP data
Amount of
change in
ocean surface
pH since 1900
-0.12
- 0.1
- 0.08
- 0.06
- 0.04
- 0.02
0 (or no data)
Effects



Oceans and seas are
now being affected by
an increase in global
mean atmospheric
temperature which can
cause a rise in sea level.
Melting glaciers,
continental ice caps, and
melting ice sheets
(Greenland and
Antactica) causes the
amount of water in the
ocean to increase.
Thermal expansion of
the ocean causes the
warm water molecules to
move farther apart,
increasing the volume of
the ocean.
Nutrients, Oxygen & Upwelling


CANADA
Newfoundland

Grand Banks
Ocean currents are the result
of upwelling and water density.
The Grand Banks of the North
American continental shelf.
The shape of the deep seafloor causes nutrient rich water
to well up to the surface and
the relatively shallow plateau
allow a huge range of fishes to
proliferate.
The Grand Banks have been
fished since the fifteenth
century but continual over
fishing has devastated many
fish stocks.
Freshwater Ecosystems
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.
Figure 6-14
Natural Capital
Freshwater Systems
Ecological
Services
Economic
Services
Climate moderation
Food
Nutrient cycling
Drinking water
Waste treatment
Irrigation water
Flood control
Hydroelectricity
Groundwater
recharge
Transportation
corridors
Habitats for many
species
Recreation
Genetic resources
and biodiversity
Employment
Scientific
information
Fig. 6-14, p. 136
Thermal Stratification
Lakes: Water-Filled Depressions
 During
summer and winter in deep temperate
zone lakes the become stratified into
temperature layers and will overturn.


This equalizes the temperature at all depths.
Oxygen is brought from the surface to the lake
bottom and nutrients from the bottom are brought
to the top.
Definition
 The
temperature difference in deep
lakes where there are warm
summers and cold winters.
Lakes: Water-Filled Depressions
 During
summer and winter in deep temperate
zone lakes the become stratified into
temperature layers and do not mix
Thermocline
 The
middle layer
that acts as a barrier
to the transfer of
nutrients and
dissolved oxygen.
Overturn
 Happens
in fall and spring
 Waters at all level mix


This equalizes the temperature at all depths.
Oxygen is brought from the surface to the lake
bottom and nutrients from the bottom are brought
to the top.
Causes
 During
the summer,
lakes become stratified
into different temperature
layers that resist mixing
because summer
sunlight warms surface
waters, making them less
dense.
Fall Turnover
 As
the temperatures begin to drop, the
surface layer becomes more dense, and
it sinks to the bottom. This mixing
brings nutrients from the bottom up to
the surface and sends oxygen to the
bottom.
Spring Turnover
 As
top water warms and ice melts,
it sinks through and below the
cooler, less dense water, sending
oxygen down and nutrients up.

Upwelling: Spring and Fall
During summer and winter in deep
temperate zone lakes and oceans
become stratified into temperature
layers. The thermocline allows
exchanges nutrients and
temperatures and this exchange is
called upwelling or turnover and
occurs because of the different
densities of water.
The equalizing temperature occurs
at all depths so that there is a
distribution of heat
During the nutrient exchange,
oxygen is brought from the surface
of the lake or ocean to the bottom
and cold nutrient-rich water from
the bottom will rise to the surface.
Spring and Fall Turnover
Lakes: Water-Filled Depressions
 Lakes
are large natural bodies of standing
freshwater formed from precipitation, runoff,
and groundwater seepage consisting of:




Littoral zone (near shore, shallow, with rooted
plants).
Limnetic zone (open, offshore area, sunlit).
Profundal zone (deep, open water, too dark for
photosynthesis).
Benthic zone (bottom of lake, nourished by dead
matter).
Lakes: Water-Filled Depressions
Figure 6-15
Sunlight
Green
frog
Painted
turtle
Blue-winged
teal
Muskrat
Pond
snail
Littoral zone
Limnetic zone
Diving
beetle
Plankton
Profundal zone
Benthic zone
Yellow
perch
Bloodworms
Northern
pike
Fig. 6-15, p. 137
Effects of Plant Nutrients on Lakes:
 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.
Oligotrophic Lake
 Newly






formed lake
Nutrient poor
Deep, steep banks
Glacier & mountain stream fed
Crystal clear water
Low productivity
Small pop of fish & and
other life
Eutrophic Lake






Over time sediments, organic matter, & inorganic
nutrients wash into the lake
Nutrient rich
Murky water, poor visibility
Shallow
High productivity
Lots of plant/fish life
Effects of Plant Nutrients on Lakes:
Too Much of a Good Thing
 Cultural


eutrophication:
Human inputs of nutrients from the
atmosphere and urban and agricultural
areas can accelerate the eutrophication
process.
This can cause algae blooms, decreased
productivity, decreased dissolved oxygen,
and fish kills when the algae die and
decompose
Flowing Water Ecosystems
Because of different
environmental conditions in
each zone, a river is a system
of different ecosystems.
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
Freshwater Streams and Rivers:
From the Mountains to the Oceans
 Water
flowing from mountains to the sea
creates different aquatic conditions and
habitats.
Figure 6-17
Rain and
snow
Lake Glacier
Rapids
Waterfall
Tributary
Flood plain Oxbow
lake
Salt marsh
Delta Deposited
sediment
Ocean
Source Zone
Transition Zone
Water
Sediment
Floodplain Zone
Fig. 6-17, p. 139
Freshwater Streams and Rivers
 Watershed




Area that supplies runoff
Small streams join to form rivers
Begin in higher elevation – mountains
Rain or melting snow
 Three



or drainage basin
Zones
Source
Transition
Floodplain
Source Zone: Headwater

A narrow zone of cold, shallow, clear, swiftly flowing water
with waterfalls and rapids.
 Turbulent, large amounts of dissolved oxygen
 Cold water fish are also present. Ex. trout.
 Low nutrient, phytoplankton, & productivity
 Fish & animals flat, muscular, live under rocks, fight current
 Plants & algae attach to rocks
Transition Zone
 Streams
merge to form wider, deeper
 Gentle slopes with fewer obstacles
 lower dissolved oxygen
 Supports more producers (phytoplankton)
 Cloudy
 Slower flow
 Warmer
Floodplain: Downstream










Wide, deep rivers flow across broad, flat valleys.
Rich farm land
Higher temp
Provide habitat
Less dissolved O2
Slow moving water
Absorb flood water
Large pop of plants & algae
Erosion & runoff cause murky water with high levels of
suspended particulates (silt)
Mouth of river divides into many channels – Delta –
built up as silt is deposited
Case Study:
Dams, Wetlands, Hurricanes,
and New Orleans
 Dams
and levees have been built to control
water flows in New Orleans.
 Reduction in natural flow has destroyed
natural wetlands.


Causes city to lie below sea-level (up to 3
meters).
Global sea levels have risen almost 0.3 meters
since 1900.
Freshwater Wetlands
Freshwater Inland Wetlands:
Vital Sponges
 Inland
wetlands
act like natural
sponges that
absorb and store
excess water
from storms and
provide a variety
of wildlife
habitats.
Figure 6-18
Freshwater Inland Wetlands:
Vital Sponges
 Filter
and degrade pollutants.
 Reduce flooding and erosion by absorbing
slowly releasing overflows.
 Help replenish stream flows during dry
periods.
 Help recharge ground aquifers.
 Provide economic resources and recreation.
Inland Wetlands
Wetlands provide many ecosystem services

Inland wetlands are defined by their water quality, soil
type, and species composition.

Wetlands act like natural sponges that absorb and store
excess water from storms and provide a variety of
wildlife habitats. They also filter and degrade pollutants.

Wetlands replenish stream flows during dry periods and
recharge ground aquifers. If ground water is being
depleted then saltwater intrusion may occur.
Freshwater Wetland
Marshes
 An
area of temporarily flooded, often
silty land beside a river or lake.
Swamps
A
lowland region permanently
covered with water.
Hardwood Bottomland Forest
 An
area down by a river or stream
where lots of hardwoods, like oaks,
grow.
Prairie Potholes
 These
are depressions that hold water out
on the prairie, especially up north in
Canada. It is a very good duck habitat.
Peat Moss Bog
A
wet area that over time fills in (the last
stage of succession is peat moss). It can
be very deep. In Ireland, they burn peat
moss for wood.
Importance of freshwater wetlands
 They filter & purify water.
 Habitat for many animals and
plants.
 Since 1600s, over half of US
wetlands have been drained &
converted to farmland
Historical Aspects
 Developers
and farmers want Congress to
revise the definition of wetlands. This
would make 60-75% of all wetlands
unavailable for protection. The Audubon
Society estimates that wetlands provide
water quality protection worth $1.6 billion
per year, and they say if that wetlands are
destroyed, the U.S. would spend $7.7 billion
to $31 billion per year in additional floodcontrol costs.
Impacts of Human Activities on
Freshwater Systems

Dams, cities, farmlands, and filled-in wetlands alter
and degrade freshwater habitats.




Dams, diversions and canals have fragmented about 40%
of the world’s 237 large rivers.
Flood control levees and dikes alter and destroy aquatic
habitats.
Cities and farmlands add pollutants and excess plant
nutrients to streams and rivers.
Many inland wetlands have been drained or filled for
agriculture or (sub)urban development.
Human Effects on Aquatic
Systems

Most water used by humans comes
from rivers, lakes, & aquifers.
 Damming rivers for electricity
affects water flow downstream as
seen in the James Bay project in
Quebec with over 600 dams
blocking 19 rivers.

Irrigation and diversions for
drinking water displace vast
amounts of the water for these
resource stores.

Pollution from fertilizers, waste, an
sewage can have paralyzing
effects on rivers, lakes, and
oceans.

These actions can have dramatic
effects on the habitats and can
cause loss of biodiversity.
Irrigation can move move millions of liters of water from
rivers and aquifers, affecting land down stream.
Damming and diverting rivers lowers the availability
of water downstream and stops annual floods that
replace soil nutrients.
Dams, locks and other obstacles make it very difficult for
migratory fish to find their way to breeding grounds.
Impacts of Human Activities on
Freshwater Systems
 These
wetlands
have been ditched
and drained for
cropland
conversion.
Figure 6-19