Nutrient Cycles

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Nutrient Cycles

• Nitrogen and Phosphorus

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WHY DO WE NEED NITROGEN??

• Nitrogen is needed to make up DNA and protein!
• In animals, proteins are vital for muscle
  function.
• In plants, nitrogen is important for growth.

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NITROGEN

• Nitrogen stores
• Largest store atmosphere (N2)
• Also stored in....
• Oceans
• Organic matter (in soil)

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NITROGEN
PROBLEM!

• 78 of the planets Nitrogen is N2 (atmosphere)
• there are 3 main ways that nitrogen is made
  available to plants/ animals....

Most organisms CANNOT use N2!
SOLUTION
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1 Nitrogen Fixation

• This is a process that changes N2 into forms that
  plants can use!

N2
NO3-
NH4
(nitrate)
(ammonium)
Happens in atmosphere... LIGHTNING!
Happens in soil, and in water bodies
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N2
NO3-
Lightning provides the energy for nitrogen to
react with oxygen in the atmosphere!
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N2
NH4
Nitrogen-fixing cyanobacteria in water can
also do this!

• Nitrogen-fixing bacteria in the soil can
  convert (fix) N2 to ammonium.
• Usually live on roots of legumes
• and other plants.

In the water
In the soil
Rhizobium
Video
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Nitrogen fixing bacteria

• In the soil are an example of SYMBIOSIS!!
• These bacteria grow on the root nodules of
  legumes like peas.
• The plants provide sugars, while bacteria provide
  nitrogen ions.

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2 Nitrification and 3- Uptake

• In the soil, nitrifying bacteria convert
• NH4 ? NO2- ? NO3-

Nitrate can be taken up by plant roots! (Uptake)
So, plants that dont live with nitrogen fixing
bacteria, can also get nitrogen from the soil.
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The Nitrogen Cycle

• How does N2 get back to the atmosphere?
• Denitrification changes NO3- back to N2
• This occurs in aquatic and land
  ecosystems by denitrifying bacteria

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• Excess nitrogen dissolves in water, enters the
  waterways, and washes into lakes and oceans.

The nitrogencompoundseventually becometrapped
insedimentary rocksand will not bereleased
againuntil the rocksundergo hundredsof years
ofweathering.
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The Nitrogen Cycle
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• Human activities can also affect the nitrogen
  cycle.
• Due to human activities, the amount of nitrogen
• in the ecosystem has doubled in the last 50
  years.
• Burning fossil fuels and treating sewage releases
  
• nitrogen oxide (NO) and nitrogen dioxide (NO2).
• Burning also releases nitrogen compounds that
  increase acid precipitation in the form of
  nitric acid (HNO3).

Acid rain damaged these trees
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• Agricultural practices often use large amounts of
  nitrogen-containing fertilizers.
• Excess nitrogen is washed away, or leaches, into
  the waterways.
• This promotes huge growth in aquatic algae called
  algae blooms.
• Algae blooms use up all CO2 and O2
• and block sunlight, killing many aquatic
  organisms.
• Algae blooms can also produce neurotoxins that
  poison animals.

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A nice summary...
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The Phosphorus Cycle

• Phosphorus is essential for life processes in
  plants and animals.
• Phosphorus is a part of the molecule that carries
  energy in living cells ATP (cellular
  respiration)!!

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The Phosphorus Cycle

• How do plants and animals use phosphorus?
• Plants Animals (humans)

Developing healthy seeds, root growth, and stem
strength!
Developing healthy bones (works with Ca to build
bone tissue)
Corn with a Phosphorus deficiency
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Where do we find P?

• It is not stored as a gas in the atmosphere like
  C and N....
• P is stored in phosphate rock and sediments on
  the ocean floors
• (Phosphates PO43-, HPO42-, and H2PO4-)

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How it gets from rock ? soil

• Phosphorus is released from rock into the soil by
  a process called weathering

CHEMICAL
PHYSICAL

• Acid rain
• Chemical in
• lichens

• Wind, rain,
• freezing

Weathering rock breaks down into smaller
pieces. These pieces make their way into the
soil.
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The Land Cycle

• Plants take up phosphate through their roots
• Animals eat the plants (get phosphate)
• Decomposers return it to the soil

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The Aquatic Cycle

• Phosphate gets into the water by erosion,
  leaching, run-off
• Most settles at the bottom (turns into sediment)
• Some phosphate is taken up by aquatic plants

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Geological Uplift

• Mountains and hills are created when rock gets
  uplifted
• The earths crust folds (very slowly) and deeply
  buried rock layers rise up

Mt. Everest is made of limestone that must have
originally formed on ancient sea floor. It
contains fossils of marine creatures.
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This is a rock in Scotland. Below the yellow line
was once horizontal rock. It has been uplifted
over time. It has now started to erode due to
weathering.
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Human Activity the P Cycle

• We affect the P cycle by
• Mining phosphate rock (for fertilizers and
  detergents)
• Making fertilizers and detergents (industrial
  waste)
• Applying fertilizer to land
• Fishing (remove aquatic organisms small effect)

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A Nice Summary
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How Changes in Nutrient Cycles Affect
Biodiversity

• Any significant changes to any of these nutrients
  (C, H, O, N, or P) can greatly affect
  biodiversity.
• Carbon cycle changes contribute to climate change
  and global warming.
• Slight temperature fluctuations and changes in
• water levels can drastically change ecosystems.
• Changes influence other organism in the
• food webs.

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How Changes in Nutrient Cycles Affect
Biodiversity

• Increased levels of nitrogen can allow certain
  plant species to outcompete other species,
  decreasing resources for every species in the
  food webs.
• Decreased levels of phosphorus can inhibit the
• growth of algae that are very important
• producers in many food chains.

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