Section 7-1
Aquatic Environments
Core Case Study:
Why Should We Care About Coral Reefs?
 Coral
reefs form in
clear, warm
coastal waters of
the tropics and
subtropics.


Formed by
massive colonies
of polyps.
Finding Nemo
Figure 6-1
Fig. 6-1a, p. 126
Fig. 6-1b, p. 126
Core Case Study:
Why Should We Care About 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
WATER’S IMPORTANCE,
AVAILABILITY, AND RENEWAL
 Comparison
of
population sizes
and shares of the
world’s freshwater
among the
continents.
Figure 14-2
Categorization of Aquatic Biomes
 Physical
characteristics
•
Salinity
•
Depth
•
Water flow
 Temperature
(not used for categorization)
Types of Biomes

•
•
•
•

Freshwater
Streams
Rivers
Lakes
Wetlands
Marine (saltwater)
• Estuaries
• Coral Reefs
• Open Ocean
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
– small drifting plants
 Niche – they are producers that support
most aquatic food chains
 Example – cyanobacteria & many types of
algae
 Description
Zooplankton
Description – herbivores that feed on
phytoplankton or other zooplankton
 Niche – food stock for larger consumers
 Example – krill; small crustaceans

Nekton
– larger, strongswimming consumers
 Niche – top consumers in the
aquatic ecosystem
 Example – fish, turtles, and whales
 Description
Benthos
 Description
– bottom-dwelling
creatures
 Niche – primary consumers,
decomposers
 Example – barnacles, oysters, and
lobsters
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.
The Ocean
Section 7-2
Saltwater Life Zones
SALTWATER LIFE ZONES

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
The Coastal Zone:
 The
•
•
coastal zone
The warm, nutrient-rich, shallow water
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
Contains 90% of all marine species.


Provides numerous ecological and economic
services.
Subject to human disturbance.
The Coastal Zone
Figure 6-5
Estuaries and Coastal Wetlands:

Estuaries include river
mouths, inlets, bays,
sounds, salt marshes in
temperate zones and
mangrove forests in
tropical zones.
Figure 6-7
Estuaries and Coastal Wetlands:
 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.
Rocky and Sandy Shores:
 Organisms
experiencing daily low and high
tides have 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
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
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.
Figure 6-13
Section 7-3
Freshwater Life Zones
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
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
Headwater Stream Characteristics
A
narrow zone of cold, clear water that
rushes over waterfalls and rapids. Large
amounts of oxygen are present. Fish
are also present. Ex. trout.
Downstream Characteristics
 Slower-moving
water, less oxygen,
warmer temperatures, and lots of
algae and cyanobacteria.
Energy Source
 Gravity
Standing Water
Ecosystems
Lakes, ponds, etc.
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.
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).
Littoral Zone
A
shallow area near the shore, to the
depth at which rooted plants stop
growing. Ex. frogs, snails, insects,
fish, cattails, and water lilies.
Limnetic Zone
 Open,
sunlit water that extends to the
depth penetrated by sunlight.
Profundal Zone
 Deep,
open water where it is
too dark for photosynthesis.
Lakes: Water-Filled Depressions
Figure 6-15
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.
 What
causes this overturning?
Thermal Stratification
 The
temperature difference in deep
lakes where there are warm
summers and cold winters.
Causes of Thermal Stratification
 During
the summer,
lakes become stratified
into different
temperature layers that
resist mixing because
summer sunlight warms
surface waters, making
them less dense.
Thermocline
 The
middle layer
that acts as a barrier
to the transfer of
nutrients and
dissolved oxygen.
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.
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.

Marshes
 An
area of temporarily flooded, often
silty land beside a river or lake.
Swamps
A
lowland region permanently
covered with water.
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 this for
wood.
Importance of freshwater wetlands
 They
filter & purify water.
 Habitat
plants.
for many animals and
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 flood-control costs.
Estuaries
Estuary Definition
A
partially enclosed area of coastal
water where sea water mixes with
freshwater.
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
 These
are along warm,
tropical coasts where there is
too much silt for coral reefs to
grow. It is dominated by salttolerant 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.
Overview Questions
 What
are the basic types of aquatic life zones
and what factors influence the kinds of life
they contain?
 What
are the major types of saltwater life
zones, and how do human activities affect
them?
 What
are the major types of freshwater life
zones, and how do human activities affect
them?