1. Ecosystems & Conservation
Chapter 55

2. Ecosystem
Ecosystem = all organisms in a community, as well as abiotic factors with which they interact
Chemoautotrophic bacteria, living below Antarctic glacier
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3. Ecosystems range from a microcosm, such as an aquarium, to a large area such as a lake or forest
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4. Ecosystem Dynamics
Regardless of ecosystem size, dynamics involve 2 main processes: energy flow & chemical cycling
Energy flows through ecosystems while matter cycles within them
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5. Physical laws govern energy flow and chemical cycling
Ecologists study transformations of energy and matter within ecosystems
Laws of physics and chemistry apply
1st law of thermodynamics (conservation of energy): energy cannot be created or destroyed, only transformed
Energy enters ecosystem as solar radiation, is conserved, and lost from as heat
2nd law of thermodynamics (entropy): every exchange of energy increases disorder of universe
Energy conversions not completely efficient; some energy always lost as heat
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6. Conservation of Mass
Law of conservation of mass: matter cannot be created or destroyed
Chemical elements are continually recycled within ecosystems
Forest ecosystem – most nutrients enter as dust or solutes in rain; and are carried away in water
Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products
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7. Energy, Mass, and Trophic Levels
Autotrophs build organic molecules using photosynthesis or chemosynthesis as energy source
Heterotrophs depend on biosynthetic output of other organisms
Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores)
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8. Decomposition connects trophic levels
Detritivores, or decomposers = consumers that derive energy from detritus, nonliving organic matter
Prokaryotes and fungi
Decomposition connects trophic levels
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9. Microorganisms and other detritivores Secondary and tertiary consumers
An overview of energy and nutrient dynamics in an ecosystem.
Sun
Key
Chemical cycling
Energy flow
Heat
Primary producers
Primary consumers
Detritus
Figure 55.4
Microorganisms and other detritivores
Secondary and tertiary consumers 9

11. Energy & other limiting factors control primary production
Primary production = amount of light energy converted to chemical energy by autotrophs during a given time period
In some ecosystems, chemoautotrophs are primary producers
Titanic Pictures
Extent of photosynthetic production sets spending limit for ecosystem’s energy budget
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12. Global Energy Budget
Amount of solar radiation reaching Earth’s surface limits photosynthetic output of ecosystems
Small fraction of solar energy actually strikes photosynthetic organisms; even less is of usable wavelength
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13. Gross and Net Production
Total primary production = gross primary production (GPP) - conversion of chemical energy from photosynthesis/unit time
Net primary production (NPP) = GPP - energy used by primary producers for respiration
NPP is expressed as
Energy per unit area per unit time (J/m2yr), or
Biomass added per unit area per unit time (g/m2yr)
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14. Net Primary Production
NPP is amount of new biomass added in given time period
Only NPP is available to consumers
Standing crop: total biomass of photosynthetic autotrophs at a given time
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15. Determining Primary Production using Satellites
TECHNIQUE
Determining Primary Production using Satellites 80 60 40 20
Snow
Clouds
Vegetation
Percent reflectance
Soil
Figure 55.5 Research Method:
Liquid water
400
600
800
1,000
1,200
Visible
Near-infrared
Wavelength (nm) 15

16. NPP Varies Greatly
Tropical rain forests, estuaries, and coral reefs are among most productive ecosystems per unit area
Marine ecosystems are relatively unproductive per unit area, but contribute much to global NPP because of volume
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17. Global Net primary production (kg carbon/m2yr)
Figure 55.6
Global Net primary production (kg carbon/m2yr) 3 2 1
Figure 55.6 Global net primary production. 17

18. Net Ecosystem Production
Net ecosystem production (NEP): measure of total biomass accumulation during given period
NEP = GPP - total respiration of all organisms (producers and consumers) in ecosystem
NEP estimated by comparing net flux of CO2 and O2 in ecosystem (why these 2 molecules?)
Release of O2 by system indicates storing CO2
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19. Impact: Ocean Production Revealed
Figure 55.7
Impact: Ocean Production Revealed
Float surfaces for 6–12 hours to transmit data to satellite.
Total cycle time: 10 days
Float descends to 1,000 m and “parks.”
O2 concentration is recorded as float ascends.
Figure 55.7
Drift time: 9 days 19

20. Primary Production in Aquatic Ecosystems
In marine and freshwater ecosystems, both light and nutrients control primary production
Depth of light penetration affects primary production in photic zone of ocean or lake
More than light, nutrients limit primary production in regions of ocean and lakes
Limiting nutrient = element that must be added for production to increase
Nitrogen and phosphorous are typically nutrients that most often limit marine production
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21. Phytoplankton density (millions of cells per mL)
Figure 55.8
Which element is the limiting nutrient along the Long Island coast?
RESULTS 30 24 18 12 6
Ammonium enriched
Phosphate enriched
Unenriched control
Phytoplankton density (millions of cells per mL)
Figure 55.8 Inquiry: Which nutrient limits phytoplankton production along the coast of Long Island? A B C D E F G
Collection site 21

22. Which element is the limiting nutrient in the Sargasso Sea?
Table 55.1
Which element is the limiting nutrient in the Sargasso Sea?
Table 55.1 Nutrient Enrichment Experiment for Sargasso Sea Samples 22

23. Production in Aquatic Ecosystems
Upwelling of nutrient-rich waters in parts of oceans contributes to regions of high primary production
Addition of large amounts of nutrients to lakes has wide range of ecological impacts
Sewage runoff has caused eutrophication of lakes, which can lead to loss of most fish species
In lakes, phosphorus limits cyanobacterial growth more often than nitrogen; phosphate-free detergents
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24. Production in Terrestrial Ecosystems
Terrestrial ecosystems – temperature and moisture affect primary production
Primary production increases with moisture
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25. Net annual primary production (above ground, dry g/m2 yr)
Global relationship between NPP and mean annual precipitation for terrestrial ecosystems
1,400
1,200
1,000
800
600
400
200
Net annual primary production (above ground, dry g/m2 yr)
Figure 55.9 A global relationship between net primary production and mean annual precipitation for terrestrial ecosystems. 20 40 60 80
100
120
140
160
180
200
Mean annual precepitation (cm) 25

26. Evapotranspiration
Water transpired by plants and evaporated from a landscape
Affected by precipitation, temperature, solar energy
Related to net primary production
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27. Nutrient Limitations and Adaptations
On local scale, soil nutrient is often limiting factor in primary production
In terrestrial ecosystems, nitrogen is most common limiting nutrient
Phosphorus can also be limiting nutrient, especially in older soils
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28. Adaptations help plants access limiting nutrients
Mutualisms with nitrogen-fixing bacteria
Mutualisms with mycorrhizal fungi, which supply plants with phosphorus and other limiting elements
Root hairs to increase surface area
Release of enzymes that increase availability of limiting nutrients
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29. Energy transfer ~10% efficient
Secondary production is amount of chemical energy in food converted to new biomass during given period of time
When caterpillar eats leaves, only about 1/6 of leaf’s energy is used for secondary production
Organism’s production efficiency = fraction of energy stored in food not used for respiration
Production
efficiency 
Net secondary production  100%
Assimilation of primary production
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30. Energy partitioning within a link of the food chain.
Figure 55.10
Energy partitioning within a link of the food chain.
Plant material eaten by caterpillar
200 J
67 J
Figure 55.10
Cellular respiration
100 J
Feces
33 J
Not assimilated
Growth (new biomass; secondary production)
Assimilated 30

31. Birds and mammals have efficiencies of 13% because of high cost of endothermy
Fishes – around 10%
Insects and microorganisms – 40% or more
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32. Trophic Efficiency and Ecological Pyramids
Trophic efficiency: % of production transferred from one trophic level to next
Usually about 10% (range of 5% to 20%)
Trophic efficiency multiplied over length of food chain
~0.1% of chemical energy fixed by photosynthesis reaches tertiary consumer
Pyramid of net production represents loss of energy with each transfer
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33. An idealized pyramid of net production
Figure 55.11
An idealized pyramid of net production
Tertiary consumers
10 J
Secondary consumers
100 J
Primary consumers
1,000 J
Primary producers
Figure
10,000 J
1,000,000 J of sunlight 33

34. Turnover time: ratio of standing crop biomass to production
Biomass pyramid – each tier represents dry weight of organisms in trophic level
Most biomass pyramids show sharp decrease at successively higher trophic levels
Certain aquatic ecosystems have inverted pyramids: producers (phytoplankton) consumed so quickly they are outweighed by primary consumers
Turnover time: ratio of standing crop biomass to production
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35. Pyramids of biomass (standing crop). Trophic level Dry mass (g/m2)
Figure 55.12
Trophic level
Pyramids of biomass
(standing crop).
Dry mass (g/m2)
Tertiary consumers
Secondary consumers
Primary consumers
Primary producers
1.5 11 37
809
(a) Most ecosystems (data from a Florida bog)
Figure 55.12
Trophic level
Dry mass (g/m2)
Primary consumers (zooplankton)
Primary producers (phytoplankton) 21 4
(b) Some aquatic ecosystems (data from the English Channel) 35

36. Dynamics of energy flow in ecosystems have important implications for humans
Eating meat: relatively inefficient way of tapping photosynthetic production
Worldwide agriculture could feed many more people if humans ate only plant material
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37. Biological and geochemical processes cycle nutrients and water
Life depends on recycling elements
Nutrient circuits in ecosystems involve biotic and abiotic components – called biogeochemical cycles
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38. Biogeochemical Cycles
Gaseous carbon, oxygen, sulfur, nitrogen occur in atmosphere and cycle globally
Less mobile elements include phosphorus, potassium, and calcium
Elements cycle locally in terrestrial systems, but more broadly in aquatic systems
Model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirs
Elements cycle between organic & inorganic reservoirs
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39. Burning of fossil fuels Formation of sedimentary rock
Figure 55.13
Reservoir A
Organic materials available as nutrients
Reservoir B Organic materials unavailable as nutrients
A general model of nutrient cycling.
Fossilization
Living organisms, detritus
Peat
Coal
Oil
Respiration, decomposition, excretion
Burning of fossil fuels
Assimilation, photosynthesis
Reservoir D Inorganic materials unavailable as nutrients
Reservoir C Inorganic materials available as nutrients
Figure 55.13
Weathering, erosion
Atmosphere
Minerals in rocks
Water
Formation of sedimentary rock
Soil 39

40. In studying cycling, ecologists focus on 4 factors:
Chemical’s biological importance
Forms in which each chemical is available or used by organisms
Major reservoirs for each chemical
Key processes driving movement of each chemical through its cycle
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41. Water Cycle Essential to all organisms
Liquid water - 1° physical phase which is used
Oceans contain 97% of water; 2% in glaciers and polar ice caps; 1% in lakes, rivers, groundwater
Water moves by evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater
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42. Movement over land by wind
Figure 55.14a
Movement over land by wind
Evaporation from ocean
Precipitation over land
Precipitation over ocean
Evapotranspira- tion from land
Figure Exploring: Water and Nutrient Cycling
Percolation through soil
Runoff and groundwater 42

44. Carbon Cycle Organic molecules – essential to organisms
Photosynthetic organisms convert CO2 to organic molecules that are used by heterotrophs
Reservoirs: fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, atmosphere, and sedimentary rocks
CO2 taken up and released (photosynthesis & respiration); volcanoes & burning of fossil fuels contribute CO2 to atmosphere
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45. Burning of fossil fuels and wood
Figure 55.14b
CO2 in atmosphere
Photosynthesis
Photo- synthesis
Cellular respiration
Burning of fossil fuels and wood
Phyto- plankton
Consumers
Figure Exploring: Water and Nutrient Cycling
Consumers
Decomposition 45

47. Nitrogen Cycle Component of amino acids, proteins, nucleic acids
Main reservoir is atmosphere (N2); this must be converted to NH4+ or NO3– for uptake by plants (nitrogen fixation by bacteria)
Organic nitrogen decomposed to NH4+ by ammonification; NH4+ is decomposed to NO3– by nitrification
Denitrification converts NO3– back to N2
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48. Decomposition and sedimentation
Figure 55.14c
N2 in atmosphere
Reactive N gases
Industrial fixation
Denitrification
N fertilizers
Fixation
Runoff
Dissolved organic N
NO3–
Terrestrial cycling N2
NH4+
NO3–
Aquatic cycling
Denitri- fication
Figure Exploring: Water and Nutrient Cycling
Decomposition and sedimentation
Assimilation
Decom- position
NO3–
Fixation in root nodules
Uptake of amino acids
Ammonification
Nitrification
NH3
NH4+
NO2– 48

50. Phosphorus Cycle
Major constituent of nucleic acids, phospholipids, and ATP
Phosphate (PO43–) is most important inorganic form of phosphorus
Largest reservoirs – sedimentary rocks of marine origin, oceans, and organisms
PO43– binds with soil particles; movement often localized
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51. Wind-blown dust Geologic uplift Weathering of rocks Runoff Consumption
Figure 55.14d
Wind-blown dust
Geologic uplift
Weathering of rocks
Runoff
Consumption
Decomposition
Plant uptake of PO43–
Plankton
Dissolved PO43–
Uptake
Leaching
Figure Exploring: Water and Nutrient Cycling
Sedimentation
Decomposition 51

52. Decomposition & Nutrient Cycling Rates
Decomposers (detritivores) play key role in pattern of chemical cycling
Rates at which nutrients cycle in different ecosystems vary greatly (differing rates of decomposition)
Rate of decomposition controlled by temperature, moisture, nutrient availability
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53. How does temperature affect litter decomposition in an ecosystem?
Figure 55.15
EXPERIMENT
Ecosystem type
Arctic
Subarctic
Boreal
Temperate
Grassland
Mountain A G M
B,C D P T
H,I S
E,F N L O U J K Q R
How does temperature affect litter decomposition in an ecosystem?
RESULTS 80 70 60 50 40 30 20 10
Figure Inquiry: How does temperature affect litter decomposition in an ecosystem? R U K O Q
Percent of mass lost T J P D S N F C I M L A H B E G
–15
–10 –5 5 10 15
Mean annual temperature (C) 53

54. Rapid decomposition results in relatively low levels of nutrients in soil
Tropical rain forest – material decomposes rapidly; most nutrients tied up in trees
Cold, wet ecosystems store large amounts of undecomposed organic matter
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55. Case Study: Nutrient Cycling
Hubbard Brook Experimental Forest – used to study nutrient cycling in forest since 1963
Research team constructed dam to monitor loss of water and minerals
60% of precipitation exits through streams and 40% lost by evapotranspiration
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56. Nitrate concentration in runoff (mg/L) Completion of tree cutting
Figure 55.16
Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research.
(a) Concrete dam and weir
(b) Clear-cut watershed 80 60 40 20
Deforested
Figure Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research.
Nitrate concentration in runoff (mg/L)
Completion of tree cutting 4 3 2 1
Control
1965
1966
1967
1968
(c) Nitrate in runoff from watersheds 56

57. Hubbard Experimental Forest
In one experiment, the trees in one valley were cut down, and the valley was sprayed with herbicides
Net losses of water were 3040% greater in the deforested site than the undisturbed (control) site
Nutrient loss was also much greater in the deforested site compared with the undisturbed site
For example, nitrate levels increased 60 times in the outflow of the deforested site
These results showed how human activity can affect ecosystems
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58. Restoration ecologists help return degraded ecosystems to a more natural state
Given enough time, biological communities can recover from many types of disturbances
Restoration ecology seeks to initiate or speed up the recovery of degraded ecosystems
Two key strategies are bioremediation and augmentation of ecosystem processes
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59. A gravel and clay mine site in New Jersey,
Figure 55.17
A gravel and clay mine site in New Jersey,
before and after restoration.
Figure 55.17
(a) In 1991, before restoration
(b) In 2000, near the completion of restoration 59

60. Bioremediation Use of living organisms to detoxify ecosystems
Organisms most often used are prokaryotes, fungi, or plants
Organisms can take up, & sometimes metabolize, toxic molecules
Bacterium Shewanella oneidensis can metabolize uranium and other elements to insoluble forms; less likely to leach into streams and groundwater
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61. Concentration of soluble uranium (M)
Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee. 6 5 4 3 2 1
Concentration of soluble uranium (M)
Figure Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee. 50
100
150
200
250
300
350
400
Days after adding ethanol 61

62. Biological Augmentation
Uses organisms to add essential materials to a degraded ecosystem
For example, nitrogen-fixing plants can increase the available nitrogen in soil
For example, adding mycorrhizal fungi can help plants to access nutrients from soil
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63. Restoration Projects Worldwide
The newness and complexity of restoration ecology require that ecologists consider alternative solutions and adjust approaches based on experience
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64. Exploring: Restoration Ecology Worldwide
Figure 55.19a
Exploring: Restoration Ecology Worldwide
Equator
Figure 55.19 64

65. Kissimmee River, Florida
Figure 55.19b
Figure Exploring: Restoration Ecology Worldwide
Kissimmee River, Florida 65

66. Figure 55.19c
Figure Exploring: Restoration Ecology Worldwide
Truckee River, Nevada 66

67. Tropical dry forest, Costa Rica
Figure 55.19d
Figure Exploring: Restoration Ecology Worldwide
Tropical dry forest, Costa Rica 67

68. Figure 55.19e
Figure Exploring: Restoration Ecology Worldwide
Rhine River, Europe 68

69. Succulent Karoo, South Africa
Figure 55.19f
Figure Exploring: Restoration Ecology Worldwide
Succulent Karoo, South Africa 69

70. Coastal Japan Figure 55.19 Exploring: Restoration Ecology Worldwide 70
Figure 55.19g
Figure Exploring: Restoration Ecology Worldwide
Coastal Japan 70

71. Maungatautari, New Zealand
Figure 55.19h
Figure Exploring: Restoration Ecology Worldwide
Maungatautari, New Zealand 71