Chapter 54Chapter 54

EcosystemsEcosystems

I. Energy Flow and Chemical I. Energy Flow and Chemical CyclingCycling

Energy transfer and thermodynamicsEnergy transfer and thermodynamics– Converting energy and energy lossConverting energy and energy loss– Chemicals are recycledChemicals are recycled

Trophic relationshipsTrophic relationships– Primary producersPrimary producers– Primary consumersPrimary consumers– Secondary consumersSecondary consumers– Detritivores/DecomposersDetritivores/Decomposers

LE 54-2

Microorganismsand other

detritivores

Tertiaryconsumers

Secondaryconsumers

Detritus Primary consumers

Sun

Primary producers

Heat

Key

Chemical cycling

Energy flow

II. Limits to Primary ProductionII. Limits to Primary Production

Gross Primary Productivity (GPP)Gross Primary Productivity (GPP)

Net Primary ProductivityNet Primary Productivity– NPP = GPP – RNPP = GPP – R– Measured as energy per unit area per unit Measured as energy per unit area per unit

time or biomass (newly produced)time or biomass (newly produced)

LE 54-4

Open oceanContinental shelf

Upwelling zonesExtreme desert, rock, sand, ice

Swamp and marshLake and stream

Desert and semidesert scrubTropical rain forest

Temperate deciduous forestTemperate evergreen forest

Tropical seasonal forest

SavannaCultivated land

EstuaryAlgal beds and reefs

Boreal forest (taiga)Temperate grassland

Woodland and shrublandTundra

0.40.4

1.01.31.51.61.71.82.42.72.93.33.54.7

0.30.10.1

5.265.0

Freshwater (on continents)

Terrestrial

Marine

Key Percentage of Earth’ssurface area

Average net primaryproduction (g/m2/yr)

6050403020100 2,5002,0001,5001,0005000

Percentage of Earth’s netprimary production

2520151050

125

2,500

3601,500

5003.090

900600

800

2,200

600

250

1,6001,2001,300

2,000

700140

0.3

7.99.19.6

5.43.5

0.67.1

4.93.8

2.3

24.45.6

1.20.9

0.10.040.9

22

Limitations to NPPLimitations to NPP

In marine and freshwaterIn marine and freshwater– Light limitationsLight limitations– Nutrient limitations – limiting nutrients (Fig. Nutrient limitations – limiting nutrients (Fig.

54.6, p. 1189)54.6, p. 1189)EutrophicationEutrophication

In terrestrial and wetlandsIn terrestrial and wetlands– Actual evapotranspirationActual evapotranspiration

LE 54-6

Atlantic Ocean

ShinnecockBay

Moriches Bay

Long Island

2

45

30

1115

19

21

Coast of Long Island, New York

Great South Bay

Phytoplankton

Inorganicphosphorus

GreatSouth Bay

MorichesBay

ShinnecockBay

Station number2119153011542

8

5

4

3

21

0

6

78

5

4

3

21

0

6

7

Phytoplankton biomass and phosphorus concentration

Ph

yto

pla

nk

ton

(mil

lio

ns

of

cel

ls/m

L)

Ino

rga

nic

ph

os

ph

oru

s(µ

m a

tom

s/L

)

Ammonium enriched

Station number2119153011542

30

Ph

yto

pla

nk

ton

(mil

lio

ns

of

cel

ls p

er m

L)

Startingalgal

density

Phytoplankton response to nutrient enrichment

24

18

12

6

0

Phosphate enrichedUnenriched control

LE 54-9

Control

August 1980JulyJune00

100

200

300L

ive,

ab

ove

-gro

un

d b

iom

ass

(g d

ry w

t/m

2 )

50

150

250N + P

N only

P only

Energy Transfer EfficiencyEnergy Transfer Efficiency

Secondary productionSecondary production

Production efficiency - % not used for Production efficiency - % not used for respirationrespiration

Trophic efficiencies and pyramidsTrophic efficiencies and pyramids– Pyramid of production (Energy)Pyramid of production (Energy)– Pyramid of biomassPyramid of biomass– Pyramid of numbersPyramid of numbers

LE 54-10

Growth (new biomass)

Cellularrespiration

Feces100 J

33 J

67 J

200 J

Plant materialeaten by caterpillar

LE 54-11

1,000,000 J of sunlight

10,000 J

1,000 J

100 J

10 JTertiaryconsumers

Secondaryconsumers

Primaryconsumers

Primaryproducers

LE 54-12a

Trophic level Dry weight(g/m2)

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

1.5

11

37

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)

Primary producers (phytoplankton)

21

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 Number ofindividual organisms

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

3

354,904

708,624

5,842,424

LE 54-14

Trophic level

Secondary consumers

Primary consumers

Primary producers

IV. Biogeochemical CyclesIV. Biogeochemical Cycles

See figure 54.18, p.1198See figure 54.18, p.1198

Water cycleWater cycle

Carbon cycleCarbon cycle

Nitrogen cycleNitrogen cycle

Phosphorus cyclePhosphorus cycle

LE 54-16

Fossilization

Reservoir a Reservoir b

Reservoir c Reservoir d

Organicmaterialsavailable

as nutrients

Organicmaterialsunavailableas nutrients

Inorganicmaterialsavailable

as nutrients

Inorganicmaterialsunavailableas nutrients

Livingorganisms,detritus

Coal, oil,peat

Atmosphere,soil, water

Mineralsin rocks

Assimilation,photosynthesis Burning

of fossil fuels

Weathering,erosion

Formation ofsedimentary rock

Respiration,decomposition,excretion

LE 54-17a

Transportover land

Precipitationover landEvaporation

from oceanPrecipitationover ocean

Net movement ofwater vapor by wind

Solar energy

Evapotranspirationfrom land

Runoff andgroundwater

Percolationthroughsoil

LE 54-17b

Cellularrespiration

Burning offossil fuelsand wood

Carbon compoundsin water

Photosynthesis

Primaryconsumers

Higher-levelconsumers

Detritus

Decomposition

CO2 in atmosphere

LE 54-17c

Assimilation

N2 in atmosphere

DecomposersNitrifyingbacteria

Nitrifyingbacteria

Nitrogen-fixingsoil bacteria

Denitrifyingbacteria

NitrificationAmmonification

Nitrogen-fixingbacteria in rootnodules of legumes

NO3–

NO2–NH4

+NH3

LE 54-17d

Sedimentation

Plants

Rain

Runoff

Weatheringof rocks

Geologicuplift

SoilLeaching

Decomposition

Plant uptakeof PO4

3–

Consumption

LE 54-18

Nutrientsavailable

to producers

Decomposers

Geologicprocesses

Abioticreservoir

Consumers

Producers

V. Human Disruption on CyclesV. Human Disruption on Cycles

Nutrient enrichmentNutrient enrichment– Agriculture and nitrogen cyclingAgriculture and nitrogen cycling

criticial load in aquatic ecosystems criticial load in aquatic ecosystems cultural cultural eutrophicationeutrophication

Acid precipitationAcid precipitation

Toxins and biological magnificationToxins and biological magnification

Rising atmospheric CORising atmospheric CO22

Depletion of ozoneDepletion of ozone

LE 54-21

North America

Europe

4.3 4.6

4.14.3

4.6

4.34.6

4.6

LE 54-23

Zooplankton0.123 ppm

Phytoplankton0.025 ppm

Lake trout4.83 ppm

Smelt1.04 ppm

Herringgull eggs124 ppm

Co

nc

en

tra

tio

n o

f P

CB

s

LE 54-24

Temperature

CO

2 c

on

ce

ntr

ati

on

(p

pm

)

CO2

1.05

Te

mp

era

ture

va

ria

tio

n (

°C)

0.90

0.75

0.60

0.45

0.30

0.15

0

–0.15

–0.30

–0.45

390

380

370

360

350

340

330

320

310

3001960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Year

LE 54-26

Ozo

ne

la

ye

r th

ick

ne

ss

(D

ob

so

n u

nit

s)

350

300

250

200

150

100

50

01960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Year (Average for the month of October)

1955

LE 54-27

Chlorine atoms

O3Chlorine

Cl2O2

CIO

O2

O2

CIO

Chlorine from CFCs interacts with ozone (O3), forming chlorine monoxide (CIO) and oxygen (O2).

Sunlight causes Cl2O2 to break down into O2 and free chlorine atoms. The chlorine atoms can begin the cycle again.

Two CIO molecules react, forming chlorine peroxide (Cl2O2).

Sunlight