EcosystemsEcosystems

Ecosystem Ecosystem

An association of organisms and their An association of organisms and their

physical environment, interconnected physical environment, interconnected

by ongoing flow of energy and a by ongoing flow of energy and a

cycling of materialscycling of materials

Modes of NutritionModes of Nutrition

AutotrophsAutotrophs Capture sunlight or chemical energyCapture sunlight or chemical energy

ProducersProducers

HeterotrophsHeterotrophs Extract energy from other organisms or Extract energy from other organisms or

organic wastesorganic wastes

Consumers, decomposers, detritivoresConsumers, decomposers, detritivores

Simple Simple EcosysteEcosystem Modelm Model

energy input from sun

nutrientcycling

PHOTOAUTOTROPHS(plants, other producers)

HETEROTROPHS(consumers, decomposers)

energy output (mainly heat)

Consumers Consumers

Herbivores Herbivores

Carnivores Carnivores

ParasitesParasites

Omnivores Omnivores

DecomposersDecomposers

Detritivores Detritivores

SPRING

rodents, rabbits

fruits

insects

birds

SUMMER

rodents, rabbits

fruits

insects

birds

Seasonal variation in the diet of an omnivore (red fox)

Trophic LevelsTrophic Levels

All the organisms at a trophic level are All the organisms at a trophic level are

the same number of steps away from the the same number of steps away from the

energy input into the systemenergy input into the system

Producers are closest to the energy input Producers are closest to the energy input

and are the first trophic leveland are the first trophic level

Trophic Levels in Trophic Levels in PrairiePrairie

5th

4th

3rd

2nd

1st

Fourth-level consumers (heterotrophs):

Top carnivores, parasites, detritivores, decomposers

Third-level consumers (heterotrophs):Carnivores, parasites, detritivores, decomposers

Second-level consumers (heterotrophs):

Carnivores, parasites, detritivores, decomposers

First-level consumers (heterotrophs):

Herbivores, parasites, detritivores, decomposers

Primary producers (autotrophs):

Photoautotrophs, chemoautotrophs

Food ChainFood Chain

A straight line A straight line

sequence of who sequence of who

eats whom eats whom

Simple food chains Simple food chains

are rare in natureare rare in nature

MARSH HAWK

UPLAND SANDPIPER

GARTER SNAKE

CUTWORM

FoodFoodWebWeb

Energy Losses Energy Losses

Energy transfers are never 100 percent Energy transfers are never 100 percent

efficientefficient

Some energy is lost at each stepSome energy is lost at each step

Limits the number of trophic levels in an Limits the number of trophic levels in an

ecosystem ecosystem

Two Types of Food WebsTwo Types of Food Webs

Producers (photosynthesizers)

Producers (photosynthesizers)

herbivores

carnivores

decomposers

decomposers

detritivores

ENERGY OUTPUT ENERGY OUTPUT

Grazing Food Web Detrital Food Web

Biological MagnificationBiological Magnification

A nondegradable or slowly degradable A nondegradable or slowly degradable

substance becomes more and more substance becomes more and more

concentrated in the tissues of concentrated in the tissues of

organisms at higher trophic levels of a organisms at higher trophic levels of a

food webfood web

DDT in Food WebsDDT in Food Webs

Synthetic pesticide Synthetic pesticide banned in the United banned in the United States since the 1970sStates since the 1970s

Birds that were top Birds that were top carnivores accumulated carnivores accumulated DDT in their tissuesDDT in their tissues

BioaccumulationBioaccumulation

Primary ProductivityPrimary Productivity

GrossGross primary productivity is ecosystem’s primary productivity is ecosystem’s

total rate of photosynthesistotal rate of photosynthesis

NetNet primary productivity is rate at which primary productivity is rate at which

producers store energy in tissues in producers store energy in tissues in

excess of their aerobic respirationexcess of their aerobic respiration

Primary Productivity Primary Productivity VariesVaries

Seasonal variationSeasonal variation

Variation by habitatVariation by habitat

The harsher the environment, the The harsher the environment, the

slower plant growth, the lower the slower plant growth, the lower the

primary productivity primary productivity

Silver Springs StudySilver Springs Study

Aquatic ecosystem in FloridaAquatic ecosystem in Florida Site of a long-term study of a grazing food webSite of a long-term study of a grazing food web

5

decomposers, detritivores(bacteria, crayfish)

1.5

1.1

37

third-level carnivores(gar, large-mouth bass)

second-level consumers(fishes, invertebrates)

first-level consumers(herbivorous fishes,turtles, invertebrates)

809 primary producers (algae,eelgrass, rooted plants)

Biomass pyramid

Pyramid of Energy FlowPyramid of Energy Flow

Primary producers trapped about 1.2 Primary producers trapped about 1.2 percent of the solar energy that entered the percent of the solar energy that entered the ecosystemecosystem

6-16% passed on to next level6-16% passed on to next level

detritivores

21

383

3,368

20,810 kilocalories/square meter/year

top carnivores

carnivores

herbivores

producers

decomposers

All Heat in the EndAll Heat in the End

At each trophic level, the bulk of the At each trophic level, the bulk of the energy received from the previous level energy received from the previous level is used in metabolismis used in metabolism

This energy is released as heat energy This energy is released as heat energy and lost to the ecosystemand lost to the ecosystem

Eventually, all energy is released as heatEventually, all energy is released as heat

Biogeochemical CycleBiogeochemical Cycle

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

environment to living organisms and environment to living organisms and

back to the environmentback to the environment

Main reservoir for the nutrient is in the Main reservoir for the nutrient is in the

environmentenvironment

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 Cycle

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

Atmosphere

Oceans Land

Hubbard Brook Hubbard Brook ExperimentExperiment

A watershed was experimentally stripped A watershed was experimentally stripped

of vegetationof vegetation

All surface water draining from watershed All surface water draining from watershed

was measuredwas measured

Removal of vegetation caused a six-fold Removal of vegetation caused a six-fold

increase in the calcium content of the increase in the calcium content of the

runoff waterrunoff water

Hubbard Brook Hubbard Brook ExperimentExperiment

losses fromdisturbed watershed

time ofdeforestation

losses fromundisturbed watershed

Phosphorus CyclePhosphorus Cycle

Phosphorus is part of phospholipids and Phosphorus is part of phospholipids and

all nucleotidesall nucleotides

It is the most prevalent limiting factor in It is the most prevalent limiting factor in

ecosystems ecosystems

Main reservoir is Earth’s crust; no Main reservoir is Earth’s crust; no

gaseous phasegaseous phase

Phosphorus CyclePhosphorus Cycle

GUANO

FERTILIZER

ROCKS

LAND FOOD WEBS

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

excretion

weathering

mining

agriculture

uptake by autotrophs

death, decomposition

sedimentation setting out leaching, runoff

weathering

uplifting over geolgic time

DISSOLVED IN SOILWATER,

LAKES, RIVERS

uptake by autotrophs

death, decomposition

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

Carbon CycleCarbon Cycle

Carbon moves through the atmosphere Carbon moves through the atmosphere

and food webs on its way to and from and food webs on its way to and from

the ocean, sediments, and rocksthe ocean, sediments, and rocks

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

reservoirreservoir

Carbon CycleCarbon Cycle

photosynthesisTERRESTRIAL

ROCKS

volcanic action

weathering

diffusion

Bicarbonate, carbonate

Marine food webs

Marine Sediments

Atmosphere

TerrestrialRocks

Soil WaterPeat, Fossil

Fuels

Land Food Webs

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, Aerobic respiration, volcanic action,

burning fossil fuels burning fossil fuels

Removed by photosynthesisRemoved by photosynthesis

Greenhouse EffectGreenhouse Effect

Greenhouse gases impede the escape Greenhouse gases impede the escape

of heat from Earth’s surfaceof heat from Earth’s surface

Global WarmingGlobal Warming

Long-term increase in the temperature Long-term increase in the temperature

of Earth’s lower atmosphereof Earth’s lower atmosphere

Carbon Dioxide IncreaseCarbon Dioxide Increase

Carbon dioxide levels fluctuate Carbon dioxide levels fluctuate

seasonally seasonally

The average level is steadily increasingThe average level is steadily increasing

Burning of fossil fuels and deforestation Burning of fossil fuels and deforestation

are contributing to the increaseare contributing to the increase

Other Greenhouse GasesOther Greenhouse Gases

CFCs - synthetic gases used in plastics CFCs - synthetic gases used in plastics

and in refrigerationand in refrigeration

Methane - produced by termites and Methane - produced by termites and

bacteria and cow burpsbacteria and cow burps

Nitrous oxide - released by bacteria, Nitrous oxide - released by bacteria,

fertilizers, and animal wastesfertilizers, and animal wastes

Store Liquid COStore Liquid CO22 on on Ocean Bottom?Ocean Bottom?

““At shallow depths liquid carbon dioxide will At shallow depths liquid carbon dioxide will rise to the surface. But based on laboratory rise to the surface. But based on laboratory experiments with carbon dioxide hydrates, experiments with carbon dioxide hydrates, researchers imagined that liquid carbon researchers imagined that liquid carbon dioxide put deep in the ocean would form a dioxide put deep in the ocean would form a stable layer on the seafloor with a skin of stable layer on the seafloor with a skin of solid hydrate as a boundary, like a pond solid hydrate as a boundary, like a pond covered by ice in winter.” from the Monterey covered by ice in winter.” from the Monterey Bay Aquarium Research InstituteBay Aquarium Research Institute

http://www.cnn.com/NATURE/9905/10/oceans.enn/

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 Cycle

NO3-

IN SOIL

NITROGEN FIXATION

by industry for agriculture

FERTILIZERS

FOOD WEBS ON LAND

NH3-, NH4

+

IN SOIL

1. NITRIFICATION

loss by leaching

uptake by autotrophs

excretion, death,

decomposition

uptake by autotrophs

NITROGEN FIXATION

loss by leaching

AMMONIFICATION

2. NITRIFICATION

NITROGENOUS WASTES, REMAINS IN SOIL

GASEOUS NITROGEN (N2)

IN ATMOSPHERE

NO2-

IN SOIL

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

DiazotrophsDiazotrophs

Soil bacteria that fix nitrogenSoil bacteria that fix nitrogen Most famous: Most famous: RhizobiaRhizobia Rhizobia lives in a symbiotic relationship Rhizobia lives in a symbiotic relationship

with legumeswith legumes

Nitrogen Fixation videoNitrogen Fixation video

http://www.youtube.com/watch?v=k3TrdF-PWNg

NHNH44 ++ to NO to NO33 - Nitrofication- Nitrofication

““NitrificationNitrification is the biological oxidation is the biological oxidation of ammonia with oxygen into nitriteof ammonia with oxygen into nitrite

Followed by the oxidation of these nitrites Followed by the oxidation of these nitrites into nitratesinto nitrates

Nitrification is an important step in the Nitrification is an important step in the nitrogen cycle in soil “nitrogen cycle in soil “

Important bacteria: Important bacteria: NitrosomonasNitrosomonas and and NitrobacterNitrobacter http://en.wikipedia.org/wiki/Nitrification

Sea Battle South AmericaSea Battle South America

Ammonification & Ammonification & NitrificationNitrification

Bacteria and fungi carry out Bacteria and fungi carry out

ammonification, conversion of ammonification, conversion of

nitrogenous wastes to ammonianitrogenous 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 ecosystemsNitrogen is often a limiting factor in ecosystems

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 gas (often occurs in water nitrites to nitrogen gas (often occurs in water

logged soil)logged soil)

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

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

Sewage spill hits Peachtree Sewage spill hits Peachtree Creek, Chattahoochee Creek, Chattahoochee

Over a million gallonsOver a million gallons of raw sewage poured into of raw sewage poured into a creek Monday just upstream of the Chattahoochee a creek Monday just upstream of the Chattahoochee River and near the spot where Atlanta draws its River and near the spot where Atlanta draws its drinking water.drinking water.

Before a collapsed 36-inch sewer pipe was repaired, Before a collapsed 36-inch sewer pipe was repaired, sewage flowed into Peachtree Creek at the rate of sewage flowed into Peachtree Creek at the rate of 10,000 gallons a minute for two hours, said Janet 10,000 gallons a minute for two hours, said Janet Ward, a spokeswoman for Atlanta's Watershed Ward, a spokeswoman for Atlanta's Watershed Management Department. Management Department. The incident occurred The incident occurred near the Chattahoochee Water Treatment near the Chattahoochee Water Treatment Plant off Bolton Road, where the city gets Plant off Bolton Road, where the city gets drinking water.drinking water.

The Atlanta Journal-ConstitutionPublished on: 11/29/05

Dead WatersDead Waters Massive oxygen-starved zones are Massive oxygen-starved zones are

developing along the world's coastsdeveloping along the world's coasts

““Summer tourists cruising the waters Summer tourists cruising the waters off Louisiana or Texas in the Gulf of off Louisiana or Texas in the Gulf of Mexico take in gorgeous vistas as Mexico take in gorgeous vistas as they pull in red snappers and blue they pull in red snappers and blue marlins. Few realize that the lower half marlins. Few realize that the lower half of the water column below them may of the water column below them may lack fish, despite the piscine bounty lack fish, despite the piscine bounty near the surface.”near the surface.”

Nitrates and Phosphates Nitrates and Phosphates Contributions from Contributions from FertilizersFertilizers

““Typically, they appear where a river Typically, they appear where a river spews rich plumes of nutrients into water spews rich plumes of nutrients into water that's stratified because of either that's stratified because of either temperature or salinity differences temperature or salinity differences between the bottom and the top of the between the bottom and the top of the water column. If the water doesn't mix, water column. If the water doesn't mix, oxygen isn't replenished in the lower oxygen isn't replenished in the lower half.” half.”

Eutrophication Leads to Eutrophication Leads to Oxygen DepletionOxygen Depletion

Bacteria Use Up Most of Bacteria Use Up Most of the Othe O22

““the Mississippi River deposits water that is the Mississippi River deposits water that is heavily enriched with plant nutrients, principally heavily enriched with plant nutrients, principally nitrate. This pollutant fertilizes the abundant nitrate. This pollutant fertilizes the abundant growth of tiny, floating algae. As blooms of the growth of tiny, floating algae. As blooms of the algae go through their natural life cycles and algae go through their natural life cycles and die, they fall to the bottom and create a feast die, they fall to the bottom and create a feast for bacteria. Growing in unnatural abundance, for bacteria. Growing in unnatural abundance, the bacteria use up most of the oxygen from the bacteria use up most of the oxygen from the bottom water.” the bottom water.”

http://www.sciencenews.org/articles/20040605/bob9.asp

Black SeaBlack Sea