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Nutrient Cycles
NITROGEN MOLECULES TO
KNOW
N2 - Nitrogen Gas
NO2 – Nitrite
NO3 – Nitrate
NH4 – Ammonia
Nitrogen Cycling
Nitrogen Fixation
aka nitrification
• To be useful to plant organisms nitrogen
must be supplied in the form of the Nitrate
ion NO3 –
• NITROGEN FIXATION is a series of
processes when Nitrogen gas from the
atmosphere (N2) is converted into Nitrate
ions
• Nitrogen fixation can occur through
lightning or through special bacteria
Fixation by Lightning
• Energy in lightning causes Nitrogen gas to
combine with Oxygen gas to for Nitrates
• The Nitrates dissolve in rain and move into
plants through their roots
• Plants use these nitrates to make amino
acids (proteins)
Nitrogen Fixation by Bacteria
• Special bacteria are responsible
for creating most of the Nitrates
plants need.
• Bacteria nodules form on the roots of
legumes (beans, peas, alfalfa) to supply
them with usable nitrogen
• Excess nitrates move into the soil to help
other plants
Decomposing Nitrogen
• When organisms die decomposers break
Nitrogen containing molecules into simpler
chemicals like ammonia (NH3)
AMMONIFICATION
• Some bacteria convert Ammonia into nitrites
(Nitrification)
Some bacteria can turn nitrites into nitrates
(Nitrification)
• With the right bacteria decaying matter like
manure can be turned into usable nitrates
Denitrification
• When there is low oxygen in the soil
bacteria can remove oxygen turning
nitrates (NO3) back into nitrites (NO2) and
then back into Nitrogen Gas (N2)
• Denitrification usually occurs in bogs
leaving the soil low in usable nitrogen.
Phosphorous Cycle
• Phosphorous is a key element in ATP,
DNA and the Calcium Phosphate in bones.
• Phosphorous is cycled between living
organisms by decomposers
• Phosphorous is also found in Bedrock in
Phosphate ions. Phosphates can dissolve
out of rocks and can be absorbed by
plants
Human Effects on Cycling
• Fertilizers are materials used to restore
nutrients like nitrogen and phosphorous
that have been removed from the soil.
• Runoff from fields carries extra nutrients
into streams. This can cause
Eutrophication
• Eutrophication is the over concentration of
nutrients in an ecosystem
• Eutrophication can also be caused by
municipal or industrial sewage deposit.
Eutrophication
(to much of a good thing)
• Causes overgrowth of algae (Algal Bloom)
which may block out sunlight
• Nitrates in water are dangerous for
animals that have hemoglobin in their
blood
• Increased numbers of decomposing algae
and animals reduces the amount of
oxygen in the water causing even more
species death
• Sea of Azov
In Ukraine
Caspian Sea