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Lecture 9

BIO220H1 Lecture Notes - Lecture 9: Guano Islands Act, Intact Forest Landscape, Orogeny

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John Stinchcombe

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Lecture 9: Biogeochemical cycles
Role of atomic bombs in our understanding of geological cycles
Connection between nuclear weapons and ecological research?
Cold war after 1945
oBoth US and USSR expected to use nuclear weapons
oRadionuclide fallout would enter food chains
Where is the radio-active material going to go?
How will they affect organisms?
In 50s had dummy cover drills (duck-and-cover drill)
oSchool children drilled to hide under desk for H bomb attack….
Not really helpful
US National Labs (U of T) researched radiation effects on organisms & Ecosystems
People wanted to know how radio-active compounds would affect organisms: (because
people knew that nuclear conflict was inevitable)
oBiological effects of deuterium
oRadiation Protection in Mammals
oPictures shows Old Pine Oak forest in Long Island
People would release some radio-active substance
Studied effects of gamma radiation
Radiation scorched bit where everything turned into sand
Nuclear research also gave ecology tools and a model
oGave ecology tools for how world worked
oGave research model to follow and emulate
Radioactive isotopes became tracers that we could follow through ecosystems
oFollow them as they were taken up by plants, as herbivores eat plants, as
predators eat herbivores
oGives you trace of energy flow through ecosystem
Manhattan Project were classic models for Big Science
oGovernment set out goal and expected all of scientific community to work on goal
oEcologists have tried to follow, but has limited success
oEX: Human genome project was one of these projects
Overall goal, then rest of community organizes to meet goals
Aspects of selected biogeochemical cycles
Carbon cycle
Nitrogen cycle
oMostly a gas cycle
oHumans have intervened with HB process to convert N2 to products for fertilizer
Phosphorus cycle
oRock-base (sedimentary) cycle
oHuman interventions (mining P rich deposits for agriculture, pollution)

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Hydrologic cycle pools and fluxes
oHuman intervened by diverting freshwater for agriculture
Chemistry of the natural world
Large organic molecules constantly synthesized, and broken down
oWhen organisms die, those compounds break down
o= production and decomposition components of ecosystem
These chemical elements aren’t created or destroyed, they are cycled
oCan also change oxidation states
Cycles made of pools and fluxes
oPool: Compartment that is a storage (large amount of carbon, nitrogen,
oFluxes: Movements between compartments
Stable long-lived compounds (like water + some pollutants) can persist (like some
oBut might have phase changes
C, N, & P cycles
All tied to hydrological cycle
Carbon cycle encompasses all trophic food webs
N and P = 2 elements most likely to limit plant productivity
oWhich is why they’re usually in fertilizers
In next few graphs:
oSolid black lines = strong natural fluxes
oSolid red lines = strong human fluxes
oDashed black lines = weaker natural fluxes
C cycle
CO2 is usually gaseous
Much of carbon is in actual living beings
Some inactive sedimentary pool of carbonates in form of rock
Arrows = fluxes
Processes include:
oPhotosynthesis (CO2 into carbohydrates)
Bring C from atmosphere into terrestrial landscape
CO2 released back into atmosphere
oHuman activities through combustion of fossil fuels have put terrestrial carbon
back into atmosphere really fast
Burn wood/fossil fuels
Accelerate movement of CO2 from terrestrial ecosystem back into
In general human intervention: Combustion of fossil fuel + land conversion
Agricultural impacts on carbon
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