nitrogen fixation in the sea

8/6/2019 Nitrogen Fixation in the Sea

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Nitrogen Fixation InNitrogen Fixation InThe SeaThe Sea

Genevive Marston & JessicaGenevive Marston & Jessica M. OsmondM. Osmond


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Nitrogen FixationNitrogen Fixation

Nitrogen is the common element in all amino acids and is therefore essentialNitrogen is the common element in all amino acids and is therefore essentialfor the growth and survival of all organisms.for the growth and survival of all organisms.

Animals are unable to use the inorganic N2 gas that is present in theAnimals are unable to use the inorganic N2 gas that is present in theatmosphere, they must rely on nitrogen fixing organism calledatmosphere, they must rely on nitrogen fixing organism called diazotrophsdiazotrophs

(organism that fixes nitrogen)(organism that fixes nitrogen) such as some forms of bacteria and bluesuch as some forms of bacteria and blue--green algae (ex; phytoplankton) for their source of N.green algae (ex; phytoplankton) for their source of N.

These organisms possess nitrogenase a enzyme that fix's nitrogen intoThese organisms possess nitrogenase a enzyme that fix's nitrogen intousable from like nitrate, nitrite and ammonia.usable from like nitrate, nitrite and ammonia.

Nitrogen fixation is the conversion of molecular N2 into one or another ofNitrogen fixation is the conversion of molecular N2 into one or another ofthe chemically combined forms.the chemically combined forms.

Most nitrogen fixation occurs on land, but some does happen in the sea (thisMost nitrogen fixation occurs on land, but some does happen in the sea (thismay not be true).may not be true).


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Nitrogen FixationNitrogen Fixation

NN22 + 8 H+ 8 H++ + 8 e+ 8 e 2 NH2 NH33 + H+ H22

The enzymes that are associated with nitrogenase areThe enzymes that are associated with nitrogenase are

easily destroyed by O2, for this reason anaerobiceasily destroyed by O2, for this reason anaerobicconditions are ideal, in fact many diazotrophs onlyconditions are ideal, in fact many diazotrophs onlyexist in anaerobic conditions.exist in anaerobic conditions.


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Organic MatterOrganic Matter

ProductionProductionNitrogen availability on land is much greater than in the ocean, plants haveNitrogen availability on land is much greater than in the ocean, plants haveaccess to about 0.5% nitrogen in the soil and this allows them to producedaccess to about 0.5% nitrogen in the soil and this allows them to producedabout 50kg of organic materialabout 50kg of organic material

However in the ocean there is only 0.00005% present for phytoplankton toHowever in the ocean there is only 0.00005% present for phytoplankton to

produce, they however can access a larger volume of the water.produce, they however can access a larger volume of the water.

The phytoplankton are limited in depth by light, it is calculated that theyThe phytoplankton are limited in depth by light, it is calculated that theywould have access to about 100m^3 giving a production of 500g. This is notwould have access to about 100m^3 giving a production of 500g. This is notthe case, it is shown that they may only produce about 25g of organicthe case, it is shown that they may only produce about 25g of organicmaterial This discrepancy is explained by a number of factors such as varyingmaterial This discrepancy is explained by a number of factors such as varyingamounts of nitrogen across the sea (not equally spread out), concentrationamounts of nitrogen across the sea (not equally spread out), concentrationalso vary at different debts. Also due only to light absorptions by water,also vary at different debts. Also due only to light absorptions by water,

production is better at 10m rather than 100m. phytoplankton growth alsoproduction is better at 10m rather than 100m. phytoplankton growth alsoaffects the absorption, as growth increases in the uppers parts of the sea,affects the absorption, as growth increases in the uppers parts of the sea,the light can not penetrate as well threw the thinker phytoplankton.the light can not penetrate as well threw the thinker phytoplankton.


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Conversion of NConversion of N22

4 ways to convert N2 to a organic useable form4 ways to convert N2 to a organic useable form

1.1. Biological fixationBiological fixation Symbiotic bacteria, like diazotrophsSymbiotic bacteria, like diazotrophs(primary producers)(primary producers)

2.2. Industrial NIndustrial N--fixationfixation Under high pressure and temperatureUnder high pressure and temperature(600 C), combined with the use of an iron catalyst, atmospheric(600 C), combined with the use of an iron catalyst, atmosphericnitrogen and can be combined to form ammonia (NHnitrogen and can be combined to form ammonia (NH33).).

3.3. Combustion of fossil fuelsCombustion of fossil fuels automobile engines and thermalautomobile engines and thermal

power plants, which release various nitrogen oxides (NOpower plants, which release various nitrogen oxides (NOxx).).

4.4. Other processesOther processes The formation of NO from NThe formation of NO from N22 and Oand O22 due todue tophotons and especially lightning.photons and especially lightning.


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Nitrogen CycleNitrogen Cycle

Is the cycle of nitrogen from inorganic from to organicIs the cycle of nitrogen from inorganic from to organicand back to inorganicand back to inorganic

This cycle is essential part of lifeThis cycle is essential part of life


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Nitrogen CycleNitrogen Cycle


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Nitrogen Cycle In The SeaNitrogen Cycle In The Sea


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Primary Produces in ThePrimary Produces in The

SeaSea


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Cyanobacteria (Blue-Green

Algae)include unicellular and colonial species

colonies may form filaments, sheets or hollow balls

include a type of cell called a heterocyst

a heterocyst is a nitrogen-fixing cell that usesnitrogenase to provide the filament with nitrogen forbiosynthesis

nitrogenase is activated by oxygen, so the heterocystmust create a microanaerobic environment


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Rivularia

a filamentous blue-green algae

form colonies of densely arranged trichromes (the

mutlicelluar filaments)that aggregate intohemispherical colonies

often found on pebbles and soil

heterocysts are oriented at the base on the substrate


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Anabaena

heterocysts form at semi-regular intervals along thefilament


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Nostoc

form colonies composed of thousands of filaments ina gelatinous sheath


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Gleocapsa

a few cells inside clear matrix


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Oscillatora (unsheathed) &

Phormidium (inside sheath)filaments can slide back and forth across one anotheruntil the whole mass is reoriented into its lightsource.

Reproduces by fragmentation

nitrogen fixation in the sea

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