Ecology 13Ecology 13

Ralph KirbyRalph Kirby

AllAll nutrients follow biogeochemical cycles nutrients follow biogeochemical cyclesTwo types of cycleTwo types of cycle

– GaseousGaseousMajor reservoirs are atmosphere and oceansMajor reservoirs are atmosphere and oceansGlobal in natureGlobal in nature

– OxygenOxygen– NitrogenNitrogen– Carbon of carbon dioxideCarbon of carbon dioxide

– SedimentarySedimentaryMajor reservoirs are soil rock and mineralsMajor reservoirs are soil rock and mineralsRock and salt solution phasesRock and salt solution phasesSalt solution is the available formSalt solution is the available form

– PhosphorusPhosphorus– Metals, eg Calcium, Magnesium, etcMetals, eg Calcium, Magnesium, etc

Some cycles are hybridSome cycles are hybrid– SulphurSulphur

Nutrients enter the ecosystem via inputsNutrients enter the ecosystem via inputs– Gaseous cycle from atmosphereGaseous cycle from atmosphere– Sedimentary from rocks and mineralsSedimentary from rocks and minerals

Nutrients are recycled within the Nutrients are recycled within the ecosystemecosystem

– Internal recycling important within Internal recycling important within ecosystemecosystem

– Some systems have large amount of short Some systems have large amount of short term recyclingterm recycling

LakesLakes– Other have most stored as biomassOther have most stored as biomass

ForestsForests– Long term storage in water systems is in Long term storage in water systems is in

the sedimentthe sediment

System dependent on primary production System dependent on primary production and decompositionand decomposition

– Without latter, everything will become Without latter, everything will become locked uplocked up

Each ecosystem Each ecosystem varies in balance varies in balance of primary of primary production and production and decompositiondecompositionThere is feedback There is feedback between the twobetween the twoHigh primary High primary productionproduction– High level of High level of

nutrients in leavesnutrients in leaves– High return to litterHigh return to litter– High High

mineralizationmineralization– High nutrient High nutrient

availabilityavailability

Low primary Low primary productionproduction– ConverseConverse

Thus climate, Thus climate, plants, etc affect plants, etc affect nutrient recyclingnutrient recycling

There are also outputs to the There are also outputs to the biogeochemical cyclesbiogeochemical cycles– Carbon to carbon dioxideCarbon to carbon dioxide– Nitrogen to ammoniaNitrogen to ammonia– Loss of organic matter from Loss of organic matter from

ecosystem by washoutecosystem by washout– Herbivores between aquatic and Herbivores between aquatic and

terrestrialterrestrialMooseMooseHippopotamusHippopotamus

See effect of logging in above two systemsSee effect of logging in above two systemsPrimary production and decomposition are usually in Primary production and decomposition are usually in two separate zonetwo separate zone– Can be linked in terrestrial systemsCan be linked in terrestrial systems– Usually not linked in aquatic systems Usually not linked in aquatic systems

Note that all ecosystems such alinkNote that all ecosystems such alink

Link for terrestrial systemsLink for terrestrial systems– Plants bridge systems and move mineralsPlants bridge systems and move minerals

Link for aquatic systemsLink for aquatic systems– ShallowShallow

PlantsPlants– DeepDeep

Physical separationPhysical separationNeed for a transport systemNeed for a transport system

Static deep water forms three Static deep water forms three layerslayers– Surface warm oxygen rich layerSurface warm oxygen rich layer– Deep cold oxygen poor layerDeep cold oxygen poor layer– Narrow transition zone or Narrow transition zone or

thermoclinethermocline

Mixing from weather does not Mixing from weather does not affect hypolimnionaffect hypolimnion

However in winter, However in winter, thermocline disappearsthermocline disappears

Mixing verticallyMixing vertically– Thus winter replenishes the Thus winter replenishes the

Epilimnion’s nutrientsEpilimnion’s nutrients– While summer depletes the While summer depletes the

Epilimnion’s nutrientsEpilimnion’s nutrients

Seasonality those Seasonality those affects productivity affects productivity and decomposition and decomposition in open waterin open water

Effect is called Effect is called turnoverturnover

Flowing systems are Flowing systems are differentdifferent– Inputs from terrestial Inputs from terrestial

systems are systems are significantsignificant

Leaves, seepage, etcLeaves, seepage, etc

– SpirallingSpirallingVaries with speed of Varies with speed of waterwaterVaries with biological Varies with biological system holding system holding nutrientsnutrients

– Retention of detritus Retention of detritus can results in tighter can results in tighter spiralspiral

– Woodland streamWoodland streamP moves 10.4 m/dP moves 10.4 m/dP cycles once every P cycles once every 18.4 d18.4 dOne spiral was 190 mOne spiral was 190 m

Where terrestrial and Where terrestrial and open water system joinopen water system join– Influenced by both Influenced by both

systemssystems

Meeting of fresh and salt Meeting of fresh and salt waterwater– Creates nutrient trapCreates nutrient trap– Limits release of nutrients Limits release of nutrients

into seainto sea

Coastal areasCoastal areas– UpwellingUpwelling

EquatorialEquatorial– Coriolis force causes by Coriolis force causes by

counter currents at counter currents at equatorequator

– Upwelling betweenUpwelling between

CoastalCoastal– Coriiolis force wind Coriiolis force wind

causes offshore causes offshore currents and upwelling currents and upwelling at continental edgeat continental edge

Carbon CycleCarbon Cycle

Tightly linked to Tightly linked to energy flowenergy flowThus different Thus different between between production and production and loss loss – Net ecosystem Net ecosystem

productivityproductivityVaries dailyVaries dailyVaries Varies seasonallyseasonallyNote storageNote storage– CarbonatesCarbonates

Coral reefsCoral reefsLimestoneLimestone

– CoalCoal– OilOil– GasGas– PeatPeat

Note temporal Note temporal cyclescycles– DailyDaily– AnnuallyAnnually

InvolvementInvolvement– LandLand– SeaSea– AirAir

Most generalMost generalNote size of Note size of poolspoolsNote size of Note size of fluxesfluxes

Nitrogen cycleNitrogen cycleNitrogen is essental to lifeNitrogen is essental to lifeStarts with nitrogen fixation from Starts with nitrogen fixation from atmosphereatmospherePlants can only utilize nitrate or Plants can only utilize nitrate or ammoniaammonia

– Atmospheric depositAtmospheric deposit– Nitrogen fixationNitrogen fixation

High energyHigh energyBiologicalBiological

– BacteriaBacteria

– NitrificationNitrification– BacteriaBacteria

– DenitrificationDenitrification– BacteriaBacteria

– Loss by washoutLoss by washout

Phosphorus cyclePhosphorus cycle

No atmospheric reservoirNo atmospheric reservoirPermanent loss of phosphorus to oceansPermanent loss of phosphorus to oceansInput limited to weathering of rocksInput limited to weathering of rocksTerrestrial systems can be limited by phosphorus availabilityTerrestrial systems can be limited by phosphorus availabilityPhosphorus is more abundant in marine and freshwater systemsPhosphorus is more abundant in marine and freshwater systems– ParticularParticular– Dissolved organic phosphorusDissolved organic phosphorus

Rapidly utilized by zooplankton\Rapidly utilized by zooplankton\Secrete inorganicSecrete inorganic

– Dissolved inorganic phosphorusDissolved inorganic phosphorusRapidly utilized by phytoplanktonRapidly utilized by phytoplankton

Phosphorus can sink as particulate phosphorus and become locked in botomn Phosphorus can sink as particulate phosphorus and become locked in botomn sedimentsediment– Depletion of surface layersDepletion of surface layers

Sulphur cycleSulphur cycle

Gaseous and SedimentaryGaseous and SedimentaryPoorly understoodPoorly understood

Oxygen cycleOxygen cycleCreated by biologyCreated by biologyUnder biological Under biological controlcontrolInputsInputs– Breakup of waterBreakup of water– PhotosynthesisPhotosynthesis– Now in balanceNow in balance– Not alwaysNot always

Many other formsMany other forms– CarbonatesCarbonates– NitratesNitrates– SulphatesSulphates– OxidesOxides

Thus all cycles are Thus all cycles are linkedlinked– ChemicallyChemically– EnergeticallyEnergetically– BiologicallyBiologically

Humans have changed and are Humans have changed and are changing the biogeochemical cycleschanging the biogeochemical cycles

CarbonCarbon– Burning of fossil fuelsBurning of fossil fuels– Clearing of forestsClearing of forests– Greenhouse effectGreenhouse effect

NitrogenNitrogen– AgricultureAgriculture

Clearing of forestsClearing of forestsFertilizersFertilizers

– IndustryIndustry– Motor carsMotor cars– Increased nitrogen in nitrogen poor areasIncreased nitrogen in nitrogen poor areas

Algal bloomsAlgal blooms

SulphurSulphur– Natural 60%Natural 60%– Human 40%Human 40%

Fossil fuelsFossil fuels

Acid rain Acid rain from excess from excess depositing of depositing of sulphur and sulphur and nitrogen as nitrogen as acidsacidsSome Some systems are systems are more acid more acid sensitive sensitive than othersthan othersReduction in Reduction in available available phosphorusphosphorusReduction in Reduction in nitrogen nitrogen fixationfixation

New cycles established for xenobioticsNew cycles established for xenobioticsEffect on ozone layer of chlorohydrocarbonsEffect on ozone layer of chlorohydrocarbons– Increased skin cancerIncreased skin cancer

Effect on bird reproduction of DDTEffect on bird reproduction of DDT– Loss of birds of preyLoss of birds of prey

Effect on shellfish consumption of heavy metalsEffect on shellfish consumption of heavy metals– Mercury poisoning in JapanMercury poisoning in Japan

Effect on human reproduction of non-ionic detergents (Triton)Effect on human reproduction of non-ionic detergents (Triton)– Form compounds similar to human reproductive hormones on breakdownForm compounds similar to human reproductive hormones on breakdown