NITROGEN CYCLE

Nitro

• Composes about four-fifths (78.03 percent) by volume of the atmosphere

• an essential part of the amino acids. It is a basic element of life.

• is an important element in plant nutrition• in the form of protein is an important constituent

of animal tissue.

Cyclegen

Nitrogen Cycle• natural cyclic process in the course of which

atmospheric nitrogen enters the soil and becomes part of living organisms

Nitrogen Cycle

Amounts of NitrogenNitrogen Reservoir Metric tons nitrogen

Atmosphere 3.9*1015

Land organic matter Biota

1.1*1011

2.5*1010

Ocean soluble saltsBiomass

6.9*1011

5.2*108

Forms of Nitrogen in OceanForm Formula Function Pathway Habitat

Nitrate NO3 _ Electron acceptor,

nitrogen sourceNitrogen assimilation,dissimilatory nitratereduction anddenitrification

Coastal upwelling zones, deepocean

Ammonium NH4+ Electron donor, energysource, nitrogen source

Nitrogen assimilation,ammonia oxidation(aerobic), and anaerobicammonia oxidation

Important, rapidly recycled pool inopen ocean, intermediate indecomposition of organic matter

Nitrite NO2- Electron donor andacceptor, energy source,nitrogen source

Nitrification (nitriteoxidation), denitrification

Found at margins of oxic/anoxicregions, intermediate in oxidationand reduction pathways

Dinitrogen N2 Nitrogen source _______ High concentration in equilibriumwith atmosphere, available toN2-fixing microorganisms

Nitrous oxide N2O Trace gas, electronacceptor, electron donor

End or by-product ofnitrification anddenitrification

Intermediate in reductive pathway,also formed in nitrification and atoxic/anoxic interfaces and anoxicor suboxic zones

Urea CH4N2O Nitrogen source Nitrogen assimilation Decomposition product,potentially important nitrogensource in water column

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Nitrogen Fixation• Nitrogen gas is converted into

inorganic nitrogen compounds. It is mostly (90 percent) accomplished by free-living, nitrogen-fixing bacteria.

Nitrogen-Fixing Bacteria• symbiotic bacteria living on the roots of

plants (mostly legumes and alders)• cyanobacteria (formerly known as blue-

green algae) • archaebacteria (also known as archaea)

in deep-sea hydrothermal vents

Nitrogen Fixation by Lightning• The high energies provided by lightning

and cosmic radiation serve to combine atmospheric nitrogen and oxygen into nitrates, which are carried to the Earth’s surface in precipitation.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Nitrogen Assimilation• are assimilation of nitrates and ammonia

resulting from nitrogen fixation into the specific tissue compounds of algae and higher plants. Animals then ingest these algae and plants, converting them into their own body compounds.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Ammonification• The remains of all living things—and their

waste products—are decomposed by microorganisms which yields ammonia.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Nitrification• a process carried out by nitrifying

bacteria, transforms soil ammonia into nitrates, which plants can incorporate into their own tissues.

1rst step catalyzed by Nitrosomonas2 NH4

+ + 3 O2 2 NO2

- +2 H2O+ 4 H+

2nd step catalyzed by Nitrobacter2 NO2

- + O2 2 NO3

-

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Denitrification• The process where nitrates are

metabolized by denitrifying bacteria to free nitrogen and returned to the atmosphere

Nitrogen Cycle in Ocean• In groups construct a poster or drawing

diagram about how the Nitrogen Cycle would work in the ocean

• Label steps (Nitrogen Fixation, Nitrogen Assimilation, Ammonification,

Nitrification, Denitrification)

Nitrogen Cycle In Ocean

Nitrogen Cycle in Fish Tanks