Nutrient Cycles in Nutrient Cycles in EcosystemsEcosystems

Biogeochemical CycleBiogeochemical Cycle

The flow of a nutrient from the The flow of a nutrient from the

environment to living organisms environment to living organisms

and back to the environmentand back to the environment

Main reservoir for the nutrient Main reservoir for the nutrient

is in the environmentis in the environment

geochemical cycleMain nutrient reservoirs in the

environment

fraction of nutrient

available to ecosystem

primary producers

herbivores, carnivores, parasites

detritivores, decomposers

Fig. 47-14, p.852

Three CategoriesThree Categories

Hydrologic cycleHydrologic cycle WaterWater

Atmospheric cycles Atmospheric cycles Nitrogen and carbonNitrogen and carbon

Sedimentary cycles Sedimentary cycles Phosphorus and sulfurPhosphorus and sulfur

Hydrologic CycleHydrologic CycleAtmosphere

Ocean Land

evaporation from ocean

425,000

precipitation into ocean 385,000

evaporation from land plants (evapotranspiration)

71,000

precipitation onto land 111,000

wind-driven water vapor40,000

surface and groundwater flow 40,000

Figure 47-15Page 853

EVAPORATION PRECIPITATION TRANSPIRATION

dripping, tricklingdown along stems

falling throughto ground

interception by plants

surface pooling, etc.

infiltration of soil

moisture in soil

seepage, percolation

groundwater storage

DEEP OUTFLOW

overland flow

lateral flow

base flow

STREAM OUTFLOW

Fig. 47-16, p.853

Water Use and ScarcityWater Use and Scarcity

Most of Earth’s water is too Most of Earth’s water is too

salty for human consumptionsalty for human consumption

Desalinization is expensive Desalinization is expensive

and requires large energy and requires large energy

inputsinputs

Irrigation of crops is the main use of Irrigation of crops is the main use of

freshwaterfreshwater

Fig. 47-18, p.855

Negative Effects of IrrigationNegative Effects of Irrigation

Salinization, mineral buildup in soilSalinization, mineral buildup in soil

Elevation of the water table and Elevation of the water table and

waterloggingwaterlogging

Depletion of aquifersDepletion of aquifers

Aquifer ProblemsAquifer Problems

Figure 47-19 Page 855

Carbon CycleCarbon Cycle

Carbon moves through the Carbon moves through the

atmosphere and food webs on its atmosphere and food webs on its

way to and from the ocean, way to and from the ocean,

sediments, and rockssediments, and rocks

Sediments and rocks are the main Sediments and rocks are the main

reservoirreservoir

Figure 47-20 Page 856

diffusion between atmosphere and ocean

bicarbonate and carbonate in ocean water

marine food webs

marine sediments

combustion of fossil fuels

incorporation into sediments

death, sedimentation uplifting

sedimentation

photosynthesis aerobic respiration

Carbon Cycle - MarineCarbon Cycle - Marine

Carbon Cycle - LandCarbon Cycle - Land

photosynthesis aerobic respirationterrestrial

rocks

soil water

land food webs

atmosphere

peat, fossil fuels

combustion of wood

sedimentation

volcanic action

death, burial, compaction over geologic time

leaching, runoff

weathering

combustion of fossil fuels

Figure 47-20 Page 856

Carbon in the OceansCarbon in the Oceans

Most carbon in the ocean is dissolved Most carbon in the ocean is dissolved carbonate and bicarbonatecarbonate and bicarbonate

Ocean currents carry dissolved carbon Ocean currents carry dissolved carbon

Carbon in AtmosphereCarbon in Atmosphere

Atmospheric carbon is mainly carbon Atmospheric carbon is mainly carbon dioxidedioxide

Carbon dioxide is added to atmosphereCarbon dioxide is added to atmosphere Aerobic respiration, volcanic action, burning Aerobic respiration, volcanic action, burning

fossil fuels fossil fuels

Removed by photosynthesisRemoved by photosynthesis

Nitrogen CycleNitrogen Cycle

Nitrogen is used in amino acids and Nitrogen is used in amino acids and

nucleic acidsnucleic acids

Main reservoir is nitrogen gas in the Main reservoir is nitrogen gas in the

atmosphereatmosphere

Nitrogen CycleNitrogen Cyclegaseous nitrogen (N2)

in atmosphere

NO3-

in soil

nitrogen fixationby industry

fertilizers

NH3-,NH4

+

in soil

1. Nitrification leaching

uptake by autotrophs

excretion, death, decomposition

uptake by autotrophs

nitrogen fixation

leaching

ammonification 2. Nitrification

dentrification nitrogenous

wastes, remains

NO2-

in soil

food webs on land

Figure 47-25Page 860

Nitrogen FixationNitrogen Fixation

Plants cannot use nitrogen gasPlants cannot use nitrogen gas

Nitrogen-fixing bacteria convert Nitrogen-fixing bacteria convert

nitrogen gas into ammonia (NHnitrogen gas into ammonia (NH33))

Ammonia and ammonium can be Ammonia and ammonium can be

taken up by plantstaken up by plants

Ammonification & NitrificationAmmonification & Nitrification

Bacteria and fungi carry out Bacteria and fungi carry out

ammonificationammonification

conversion of nitrogenous wastes to ammoniaconversion of nitrogenous wastes to ammonia

Nitrifying bacteria convert ammonium to Nitrifying bacteria convert ammonium to

nitrites and nitratesnitrites and nitrates

Nitrogen LossNitrogen Loss

Nitrogen is often a limiting factor in Nitrogen is often a limiting factor in

ecosystemsecosystems

Nitrogen is lost from soils via leaching and Nitrogen is lost from soils via leaching and

runoff runoff

Denitrifying bacteria convert nitrates and Denitrifying bacteria convert nitrates and

nitrites to nitrogen gasnitrites to nitrogen gas

Human EffectsHuman Effects

Humans increase rate of nitrogen loss by Humans increase rate of nitrogen loss by clearing forests and grasslandsclearing forests and grasslands

Humans increase nitrogen in water and air Humans increase nitrogen in water and air by using fertilizers and by burning fossil by using fertilizers and by burning fossil fuelsfuels

Too much or too little nitrogen can Too much or too little nitrogen can compromise plant healthcompromise plant health

guano

fertilizer

terrestrial rocks

land food webs

dissolved in seawater

marine food webs

marine sediments

excretion

weathering

mining

agricultureuptake by producers

death, decomposition

sedimentation settling out

leaching, runoff

weatheringuplifting over geologic time

dissolved in soil water,

lakes, rivers

uptake by autotrophs

death, decomposition

Phosphorus cycle

Fig. 47-27, p.862

Phosphorus CyclePhosphorus Cycle

Phosphorus is part of Phosphorus is part of

phospholipids and all nucleotidesphospholipids and all nucleotides

It is the most prevalent limiting It is the most prevalent limiting

factor in ecosystems factor in ecosystems

Main reservoir is Earth’s crust; Main reservoir is Earth’s crust;

no gaseous phaseno gaseous phase

Phosphorus CyclePhosphorus Cycle

GUANO

FERTILIZER

TERRESTRIAL ROCKS

LAND FOOD WEBS

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

excretion

weathering

mining

agricultureuptake

by autotrophs

death, decomposition

sedimentationsettling

out leaching, runoff

weathering

uplifting

over geologic time

DISSOLVED IN SOILWATER,

LAKES, RIVERS

uptake by

autotrophs

death, decomposition

Figure 47-27, Page 862

Human EffectsHuman Effects

In tropical countries, clearing lands for In tropical countries, clearing lands for

agriculture may deplete phosphorus-agriculture may deplete phosphorus-

poor soilspoor soils

In developed countries, phosphorus In developed countries, phosphorus

runoff is causing eutrophication of runoff is causing eutrophication of

waterwayswaterways