Chapter 54
Ecosystems
I. Energy Flow and Chemical
Cycling
Energy transfer and thermodynamics
– Converting energy and energy loss
– Chemicals are recycled
Trophic relationships
– Primary producers
– Primary consumers
– Secondary consumers
– Detritivores/Decomposers
LE 54-2
Tertiary
consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
Sun
II. Limits to Primary Production
Gross Primary Productivity (GPP)
Net Primary Productivity
– NPP = GPP – R
– Measured as energy per unit area per unit
time or biomass (newly produced)
LE 54-4
Open ocean
Continental shelf
Estuary
Algal beds and reefs
Upwelling zones
Extreme desert, rock, sand, ice
Desert and semidesert scrub
Tropical rain forest
Savanna
Cultivated land
Boreal forest (taiga)
Temperate grassland
Woodland and shrubland
Tundra
Tropical seasonal forest
Temperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Lake and stream
5.2
0.3
0.1
0.1
4.7
3.5
3.3
2.9
2.7
2.4
1.8
1.7
1.6
1.5
1.3
1.0
0.4
0.4
0
Key
Marine
Terrestrial
125
360
65.0
10 20 30 40 50 60
Percentage of Earth’s
surface area
Freshwater (on continents)
24.4
5.6
1,500
2,500
1.2
0.9
0.1
0.04
0.9
500
3.0
90
22
2,200
7.9
9.1
9.6
5.4
3.5
900
600
800
600
700
140
0.6
7.1
4.9
3.8
2.3
0.3
1,600
1,200
1,300
2,000
250
0
500 1,000 1,500 2,000 2,500
Average net primary
production (g/m2/yr)
0
10 15 20 25
5
Percentage of Earth’s net
primary production
Limitations to NPP
In marine and freshwater
– Light limitations
– Nutrient limitations – limiting nutrients (Fig.
54.6, p. 1189)
Eutrophication
In terrestrial and wetlands
– Actual evapotranspiration
LE 54-6
30
5
4
15
11
21
Shinnecock
19
Bay
Moriches Bay
Atlantic Ocean
2
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
Phytoplankton
Inorganic
phosphorus
2
11 3015 19 21
Station number
Great
Moriches
South Bay
Bay
4
5
Inorganic phosphorus
(µm atoms/L)
Phytoplankton
(millions of cells/mL)
Coast of Long Island, New York
Shinnecock
Bay
Phytoplankton biomass and phosphorus concentration
Phytoplankton
(millions of cells per mL)
30
24
Ammonium enriched
Phosphate enriched
Unenriched control
18
12
6
0
Starting 2
algal
density
4
5 11 30
Station number
15
Phytoplankton response to nutrient enrichment
19
21
Live, above-ground biomass
(g dry wt/m2)
LE 54-9
300
N+P
250
200
150
N only
100
Control
P only
50
0
0
June
July
August 1980
Energy Transfer Efficiency
Secondary production
Production efficiency - % not used for
respiration
Trophic efficiencies and pyramids
– Pyramid of production (Energy)
– Pyramid of biomass
– Pyramid of numbers
LE 54-10
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
33 J
Growth (new biomass)
Cellular
respiration
LE 54-11
Tertiary
consumers
Secondary
consumers
Primary
consumers
Primary
producers
10 J
100 J
1,000 J
10,000 J
1,000,000 J of sunlight
LE 54-12a
Trophic level
Tertiary consumers
Dry weight
(g/m2)
1.5
Secondary consumers
11
Primary consumers
37
Primary producers
809
Most biomass pyramids show a sharp decrease in biomass at
successively higher trophic levels, as illustrated by data from a
bog at Silver Springs, Florida.
LE 54-12b
Trophic level
Dry weight
(g/m2)
Primary consumers (zooplankton)
21
Primary producers (phytoplankton)
4
In some aquatic ecosystems, such as the English Channel, a small
standing crop of primary producers (phytoplankton) supports a larger
standing crop of primary consumers (zooplankton).
LE 54-13
Trophic level
Tertiary consumers
Number of
individual organisms
3
Secondary consumers
354,904
Primary consumers
708,624
Primary producers
5,842,424
LE 54-14
Trophic level
Secondary
consumers
Primary
consumers
Primary
producers
IV. Biogeochemical Cycles
See figure 54.18, p.1198
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
LE 54-16
Reservoir a
Reservoir b
Organic
materials
available
as nutrients
Organic
materials
unavailable
as nutrients
Fossilization
Living
organisms,
detritus
Assimilation,
photosynthesis
Coal, oil,
peat
Respiration,
decomposition,
excretion
Burning
of fossil fuels
Reservoir c
Reservoir d
Inorganic
materials
available
as nutrients
Inorganic
materials
unavailable
as nutrients
Atmosphere,
soil, water
Weathering,
erosion
Formation of
sedimentary rock
Minerals
in rocks
LE 54-17a
Transport
over land
Solar energy
Net movement of
water vapor by wind
Precipitation
over ocean
Evaporation
from ocean
Precipitation
over land
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
LE 54-17b
CO2 in atmosphere
Photosynthesis
Cellular
respiration
Burning of
fossil fuels
and wood
Higher-level
Primary consumers
consumers
Carbon compounds
in water
Detritus
Decomposition
LE 54-17c
N2 in atmosphere
Assimilation
Nitrogen-fixing
bacteria in root
nodules of legumes Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
NO3–
Nitrifying
bacteria
Nitrification
NO2–
NH4+
Nitrifying
bacteria
Denitrifying
bacteria
LE 54-17d
Rain
Geologic
uplift
Weathering
of rocks
Plants
Runoff
Consumption
Sedimentation
Soil
Leaching
Plant uptake
of PO43–
Decomposition
LE 54-18
Consumers
Producers
Decomposers
Nutrients
available
to producers
Abiotic
reservoir
Geologic
processes
V. Human Disruption on Cycles
Nutrient enrichment
– Agriculture and nitrogen cycling
 criticial load in aquatic ecosystems  cultural
eutrophication
Acid precipitation
Toxins and biological magnification
Rising atmospheric CO2
Depletion of ozone
LE 54-21
4.6
4.3
4.6
4.3
4.6
4.1
4.3
4.6
Europe
North America
LE 54-23
Concentration of PCBs
Herring
gull eggs
124 ppm
Lake trout
4.83 ppm
Smelt
1.04 ppm
Zooplankton
0.123 ppm
Phytoplankton
0.025 ppm
LE 54-24
390
1.05
380
0.90
CO2 concentration (ppm)
Temperature
0.60
360
0.45
350
0.30
340
CO2
0.15
330
0
Temperature variation (°C)
0.75
370
320
–0.15
310
–0.30
300
–0.45
2005
1960
1965
1970
1975
1980 1985
Year
1990
1995
2000
LE 54-26
Ozone layer thickness (Dobson units)
350
300
250
200
150
100
50
0
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year (Average for the month of October)
LE 54-27
Chlorine atoms
Chlorine from CFCs interacts with ozone
(O3), forming chlorine monoxide (CIO) and
oxygen (O2).
O2
Chlorine
O3
CIO
O2
Sunlight causes
Cl2O2 to break
down into O2 and
free chlorine atoms.
The chlorine atoms
can begin the cycle
again.
CIO
Cl2O2
Sunlight
Two CIO molecules
react, forming chlorine
peroxide (Cl2O2).