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Chapter 6
Major Ecosystems of the World
Overview of Chapter 6
PART 1
 Earth’s Major Biomes
PART 2
 Aquatic Ecosystems
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Freshwater ecosystems
Estuaries
Marine Ecosystems
Interaction of Life Zones and Humans
Part 2: Aquatic Ecosystems
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Fundamental Division:
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Saltwater (Marine)
Freshwater
Aquatic ecosystems also
affected by
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Dissolved oxygen
Light penetration
Water chemistry (pH,
salinity, etc.)
Water currents
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Aquatic Ecosystems
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Three main categories of aquatic organisms
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Plankton - free floating
Nekton - strong swimming
Benthos - bottom dwelling
Plankton
Nekton
Benthos
Freshwater Ecosystems
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Include:
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Rivers and streams
Lakes and ponds
Marshes and swamps
Represent 2% of
earth’s surface
Assist in recycling
water back to the
oceans
Rivers and Streams
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Lakes and Ponds
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Body of freshwater that
does not flow
Three zones
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Littoral
Limnetic
Profundal
Experience thermal
stratification (depending
on depth)
Lakes and Ponds
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Littoral Zone - shallow water area along the shore
Limnetic Zone - open water beyond the littoral zone
Profundal Zone - beneath the limnetic zone of deep
lakes
Lakes and Ponds
Limnetic Zone
Littoral Zone
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Thermal Stratification
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Temperature
changes sharply with
depth
Thermocline
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Temperature
transition between
warmer surface
water and colder
water at depth
Only present in
warm months
Fall Turnover
Fall Turnover
Echo Lake, California
Summer
Winter
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Marshes and Swamps
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Lands covered by shallow,
fresh water for at least part
of the year
Historically filled in for
development
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Process called “Reclamation”
Current law recognizes their
ecosystem services and
ecological value
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Flood protection, water
purification, nesting habitat, etc.
Marshes and Swamps
Napa-Sonoma Marsh
Marshes and Swamps
Napa-Sonoma Marsh (Restoration)
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Marshes and Swamps
Napa-Sonoma Marsh (After Restoration)
Estuaries
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Where freshwater and saltwater mix
Highly variable environment
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Highly productive
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Temperature, salinity, depth of light penetration
Nutrients transported
from land
High level of light
penetrates shallow water
Plants provide
photosynthetic carpet
Estuaries
San Francisco Bay
(Estuary)
 Largest estuary
on west coast
of United States
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Marine Ecosystems
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Subdivided into life zones
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Intertidal zone – land/sea interface
Benthic zone – sea bottom
Pelagic environment – open ocean
Tide pools
Open ocean
Benthic Zone
Ocean floor, extending from tidal zone to
deep sea trenches
Sediment is mostly mud
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Burrowing worms and clams
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Deep benthos
Shallow benthos
Productive Benthic Communities
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Seagrass Beds
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Kelp Forest
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Present to depth of 10 m
Provide food and habitat to ecosystem
60 m long brown algae found off rocky shores
Large Biodiversity
Coral Reefs
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Built from accumulated layers of CaCO3
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Found in shallow warm water
Most diverse of all marine environments
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Colonies of millions of tiny coral animals
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Productive Benthic Communities
Seagrass
Bed
Coral
Reef
Kelp Forest
Human Impacts on the Ocean
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