biogeochemical cycles

BIOGEOCHEMICAL BIOGEOCHEMICAL

CYCLESCYCLES

General Ecology Lecture 3b General Ecology Lecture 3b

Instructor: ANGELI VALERA- MAG-ASO

Objectives::

�� Identify and describe Identify and describe the flow of nutrients in the flow of nutrients in each biogeochemical each biogeochemical cycle. cycle. cycle. cycle.

�� Explain the impact Explain the impact that humans have on that humans have on the biogeochemical the biogeochemical cycles.cycles.

What Sustains Life on Earth?What Sustains Life on Earth?

�� Solar Solar energy, the energy, the energy, the energy, the cycling of cycling of matter, and matter, and gravity sustain gravity sustain the earth’s life.the earth’s life.

Figure 3Figure 3--77

Two Secrets of Survival: Energy Two Secrets of Survival: Energy

Flow and Matter RecycleFlow and Matter Recycle

�� An ecosystem survives by a An ecosystem survives by a combination of energy flow and combination of energy flow and matter recycling.matter recycling.matter recycling.matter recycling.

� Sources and sinks: domination of storage or release process of a specific material within a reservoir

� FLUX: exchange between two between two reservoirs

� CYCLE: system of connected reservoirs that transfer and conserve a specific material

D. T. Krohne, General Ecology

Fig .Idealized diagram of the geologic cycle, which includes the tectonic, hydrologic, rock and biogeochemical cycles.

© 2003 John Wiley and Sons Publishers

PrecipitationPrecipitation

Transpiration

Condensation

EvaporationTranspiration from

plants

Precipitation

to land

Evaporation

from land Evaporation

from ocean Precipitation

to ocean

Rain clouds

RunoffSurface runoff

(rapid)

WATER CYCLE

Ocean storage

Groundwater movement (slow)

to ocean

Infiltration and

Percolation

Surface

runoff

(rapid)

Water’ Unique PropertiesWater’ Unique Properties

�� There are strong forces of attraction between There are strong forces of attraction between

molecules of water.molecules of water.

�� Water exists as a liquid over a wide temperature Water exists as a liquid over a wide temperature

range. range.

�� Liquid water changes temperature slowly.Liquid water changes temperature slowly.

�� It takes a large amount of energy for water to It takes a large amount of energy for water to

evaporate.evaporate.

�� Liquid water can dissolve a variety of compoundsLiquid water can dissolve a variety of compounds..

�� Water is the medium by which elements and other Water is the medium by which elements and other

materials move through the ecosystemmaterials move through the ecosystem

�� Water expands when it freezes.Water expands when it freezes.

Effects of Human Activities Effects of Human Activities

on Water Cycleon Water Cycle

�� We alter the water cycle by:We alter the water cycle by:

�� Withdrawing large amounts of freshwater.Withdrawing large amounts of freshwater.

�� Clearing vegetation and eroding soils.Clearing vegetation and eroding soils.�� Clearing vegetation and eroding soils.Clearing vegetation and eroding soils.

�� Polluting surface and underground water.Polluting surface and underground water.

�� Contributing to climate change.Contributing to climate change.

15%/year

CO2 & CH4

Modified from D. T. Krohne, General Ecology

THE CARBON CYCLE



on Carbon Cycleon Carbon Cycle

�� We alter the We alter the carbon cycle by carbon cycle by adding excess COadding excess CO22

to the atmosphere to the atmosphere to the atmosphere to the atmosphere through:through:�� Burning fossil fuels.Burning fossil fuels.

�� Clearing vegetation Clearing vegetation faster than it is faster than it is replaced.replaced.


Fig 4.17 Global flux of carbon, 1850-1990.


Idealized diagram illustrating photosynthesis for a green plant (tree) and generalized reaction.


OXYGEN CYCLE

�� Major sources: Major sources: photodissociationphotodissociation of water of water vapor and photosynthesisvapor and photosynthesis

�� Comines with a wide range of substancesComines with a wide range of substances�� Comines with a wide range of substancesComines with a wide range of substances

�� Ozone Ozone –– produced by photochemical produced by photochemical reactions in the reactions in the atmophereatmophere; essential to ; essential to reduce influx of UV radiation to Earthreduce influx of UV radiation to Earth

FORMS OF NITROGEN

50% fertilizer

(Bacteria)


NITROGEN CYCLE

Nitrogen fixers:Nitrogen fixers:

�� CyanobacteriaCyanobacteria

�� FreeFree--living soil bacterialiving soil bacteria

�� Bacteria associated Bacteria associated

with roots of with roots of

leguminous plantsleguminous plants

�� ActinomycetesActinomycetes

fungi, associated with fungi, associated with

roots of alders and roots of alders and

other species of woody other species of woody

plantsplants


on the Nitrogen Cycleon the Nitrogen Cycle

�� We alter the nitrogen cycle by:We alter the nitrogen cycle by:

�� Adding gases that contribute to acid rain.Adding gases that contribute to acid rain.

�� Adding nitrous oxide to the atmosphere through Adding nitrous oxide to the atmosphere through �� Adding nitrous oxide to the atmosphere through Adding nitrous oxide to the atmosphere through

farming practices which can warm the farming practices which can warm the

atmosphere and deplete ozone.atmosphere and deplete ozone.

�� Contaminating ground water from nitrate ions in Contaminating ground water from nitrate ions in

inorganic fertilizers.inorganic fertilizers.

�� Releasing nitrogen into the troposphere through Releasing nitrogen into the troposphere through

deforestation.deforestation.


on the Nitrogen Cycleon the Nitrogen Cycle

�� Human activities Human activities such as such as production of production of fertilizers now fix fertilizers now fix more nitrogen more nitrogen than all natural than all natural sources sources combined.combined.


Critical Thinking Issue Critical Thinking Issue –– How are Human How are Human Activities Affecting the Nitrogen Cycle?Activities Affecting the Nitrogen Cycle?

Effects of increased use ofnitrogen fertilizer:


• Increased nitric acid in soil:

• Leaching of magnesium and

potassium

• Increased aluminum levels

• Plant root damage

• Changes in microbe communities

• Fish kills

• Eutrophication of water bodies

• Nitrates in drinking water

• Global effects on plant based CO2 uptake

nitrogen fertilizer:

D. T. Krohne, General Ecology D. T. Krohne, General Ecology

Gaseous

phase

D. T. Krohne, General Ecology D. T. Krohne, General Ecology


Dissolvedin Ocean

LandFood

Dissolvedin Soil Water,

uptake by

autotrophs

agriculture

leaching, runoff

uptake by

autotrophs

excretion

mining Fertilizer

weathering

Guano

MarineFood

PHOSPHORUS CYCLE

Dissolvedin Ocean

Water

Marine Sediments Rocks

uplifting over

geologic time

settling out weatheringsedimentation

LandFoodWebs

in Soil Water,Lakes, Rivers

death,

decompositiondeath,

decomposition

MarineFoodWebs

PHOSPHORUS CYCLE



on the Phosphorous Cycleon the Phosphorous Cycle

�� We remove large amounts of phosphate from We remove large amounts of phosphate from the earth to make fertilizer.the earth to make fertilizer.

�� We reduce phosphorous in tropical soils by We reduce phosphorous in tropical soils by �� We reduce phosphorous in tropical soils by We reduce phosphorous in tropical soils by clearing forests.clearing forests.

�� We add excess phosphates to aquatic We add excess phosphates to aquatic systems from runoff of animal wastes and systems from runoff of animal wastes and fertilizers.fertilizers.

Animals

Plants

Industries

Volcano

Hydrogen sulfide

Oxygen

Dimethyl sulfide

Ammonium

sulfate

Ammonia

Acidic fog and precipitationSulfuric acid

WaterSulfur

trioxide

Sulfur dioxide

SULFUR CYCLE

Hydrogen sulfide

Sulfur

Sulfate salts

Decaying matter

Ocean

Metallic

sulfide

deposits


on the Sulfur Cycleon the Sulfur Cycle

�� We add sulfur dioxide to the atmosphere by:We add sulfur dioxide to the atmosphere by:

�� Burning coal and oilBurning coal and oil

�� Refining sulfur containing Refining sulfur containing petroleumpetroleum�� Refining sulfur containing Refining sulfur containing petroleumpetroleum

�� Convert sulfurConvert sulfur--containing metallic ores into free containing metallic ores into free

metals such as copper, lead, and zinc releasing metals such as copper, lead, and zinc releasing

sulfur dioxide into the sulfur dioxide into the environment environment –– produce produce

acute toxicity and major damage to vegetation acute toxicity and major damage to vegetation

(bleaching, defoliation and reduced growth); (bleaching, defoliation and reduced growth);

significant part of acid rain; irritates respiratory significant part of acid rain; irritates respiratory

tracttract

Ecosystems and the Gaia Hypothesis

Ecosystem defined: a community

of organisms and it’s corresponding abiotic

environment through which matter cycles

and energy flows

• Wide variation in ecosystems• Wide variation in ecosystems

• Boarders can be well defined or vague

• Can be natural or artificial, managed or

wild

• Wide range in scale

• Common to all ecosystems: energy flow

and cycling of matter

Gaia Hypothesis(es)

• Life has greatly affected the planetary

environment

• This alteration has allowed life to persist

• The Earth is a “super-organism” - Life controls • The Earth is a “super-organism” - Life controls

the environment in a fashion that is equivalent to

the way an organism controls its various systems

•Has not been accepted by all ecologists and

atmospheric scientists, but helps us to

understand the behavior of ecosystems and the

interaction of biogeochemical cycling.

The Gaia Hypothesis:The Gaia Hypothesis:

Is the Earth Alive?

�� Some have proposed that the earth’s various Some have proposed that the earth’s various forms of life control or at least influence its forms of life control or at least influence its chemical cycles and other earthchemical cycles and other earth--sustaining sustaining processes.processes.processes.processes.

�� The strong Gaia hypothesis: life The strong Gaia hypothesis: life controlscontrols the the

earth’s lifeearth’s life--sustaining processes.sustaining processes.

�� The weak Gaia hypothesis: life The weak Gaia hypothesis: life influencesinfluences the the

earth’s lifeearth’s life--sustaining processes.sustaining processes.

biogeochemical cycles

Education

water cycleon water

ecosystem water

underground water

molecules of water

wide temperature water

matter recycling

reservoirs cycle

combination of energy