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Mind Map by sebastian1862, updated more than 1 year ago
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Created by sebastian1862
almost 10 years ago
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The Marine Nitrogen Cycle
- REDOX reactions
- Loss of electrons is oxidation
- Gain of Electrons is reduction
- Ar ed = A ox + e-
- B ox + e- = B red
- B ox + e- = B red
- Ecell = Eright - E left
- More negative on top going backwards to write equation for electrode potentials
- Determines feasibility
- Determines feasibility
- More negative on top going backwards to write equation for electrode potentials
- Electron Donor: H2
- Electron Acceptor: O2
- Electron Acceptor: O2
- Loss of electrons is oxidation
- Marine Nitrogen Cycle and Oxidation States
- NH4+ = charge of 1+. Hydrogen is 1+, N will be -3 charge to match 1+ charge.
- The Nitrogen Cycle: the series of processes by which nitrogen and its compounds are interconverted
in the environment and in living organisms, including nitrogen fixation (The process of converting N2
into biologically available nitrogen) and decomposition.
- Nitrogen: Nitrogen is one of the primary nutrients critical for the survival of all living organisms.
Although nitrogen is very abundant in the atmosphere, it is largely inaccessible in this form to most
organisms.
- Nitrogen: Nitrogen is one of the primary nutrients critical for the survival of all living organisms.
Although nitrogen is very abundant in the atmosphere, it is largely inaccessible in this form to most
organisms.
- NH4+ = charge of 1+. Hydrogen is 1+, N will be -3 charge to match 1+ charge.
- Why the Nitrogen Cycle
- Efficiency of biological pump in C-export to deep ocean depends on
primary production which in turn is often regulated by th availiablity
of nitrate
- Most fixed N occurs as nitrate (NO03-) in the oceans, but mostly locked in deep ocean. Fixed Nitrogen = Reactive N = Bioavailable N)
- Most fixed N occurs as nitrate (NO03-) in the oceans, but mostly locked in deep ocean. Fixed Nitrogen = Reactive N = Bioavailable N)
- Efficiency of biological pump in C-export to deep ocean depends on
primary production which in turn is often regulated by th availiablity
of nitrate
- Redfield Ratio (C:N:P = 106:15:1)
- N*=(NO3-)-16(PO4 3-) + 2.9 umol kg-1 = overall budget ratio
- Relationship used to find deviation type and identify process of N.
- Positive Deviation (N*>0) = N is in excess, N gain process e.g. N2 fixation
- N2 Fixation
- N2+8H+ + 8e- + 16ATP = 2NH3 + H2 + 16ADP + 16Pi
- N2 unusable for most organisms due to high activation energy to break its triple bond.
- Mediated by enzyme nitrogenase, which needs Fe and often Mo (Molybdenum)
- Occurs in oligotrophic regions e.g. subtroical gyres (whirl), and upwelling regions
- Maybe limited by Fe or P or both (nutrient competition)
- Maybe limited by Fe or P or both (nutrient competition)
- Bloom forming cyanobacteria Trichodesmium and unicelluar cyanobacteria being
discovered. Including Heterotrophic and symbiotic bacteria
- Occurs in oligotrophic regions e.g. subtroical gyres (whirl), and upwelling regions
- Mediated by enzyme nitrogenase, which needs Fe and often Mo (Molybdenum)
- N2 unusable for most organisms due to high activation energy to break its triple bond.
- N2+8H+ + 8e- + 16ATP = 2NH3 + H2 + 16ADP + 16Pi
- N2 Fixation
- Negative Deviation (N*<0) = N deficit, N-loss process e.g. denitrification, anammox, N2O production
- Denitrification
- A step wise process: NO3- = NO2- = NO = N2O = N2
- Major remineralisation process in Oceans as NO3- is thermodynamically the
most favourable electron acceptor after O2
- Denitrifying organisms are diverse, usually facultative (capable of but not restricted to a particular
function or mode of life.) anaerobic microogranisms (bacteria, archaea) but also foraminifera.
- Only known since 1995
- Autotrophic (Plant) denitrification (e.g. coupled with sulphide oxidation) found to be important in
sulphidic water coloumn.
- Autotrophic (Plant) denitrification (e.g. coupled with sulphide oxidation) found to be important in
sulphidic water coloumn.
- Only known since 1995
- Denitrifying organisms are diverse, usually facultative (capable of but not restricted to a particular
function or mode of life.) anaerobic microogranisms (bacteria, archaea) but also foraminifera.
- Major remineralisation process in Oceans as NO3- is thermodynamically the
most favourable electron acceptor after O2
- A step wise process: NO3- = NO2- = NO = N2O = N2
- Anammox
- NH4+ + NO2- = N2 + 2H2O
- Performed by a group of chemolithoautotrophic bacteria that belong to planctomycetales
- Marine sediment evidence 2002, now global in suboxic water and sediments
with distribution of marine anammox bacteria
- Marine sediment evidence 2002, now global in suboxic water and sediments
with distribution of marine anammox bacteria
- Performed by a group of chemolithoautotrophic bacteria that belong to planctomycetales
- NH4+ + NO2- = N2 + 2H2O
- Nitrification
- Nitrification is the process that converts ammonia to nitrite and then to nitrate. Mostly
carried out by yprokaryotes. Two steps of nitrification that are carried out by distinct types of
microorganisms.
- The second step in nitrification is the oxidation of nitrite (NO2-) to nitrate (NO3-). This step
is carried out by a completely separate group of prokaryotes, known as nitrite-oxidizing Bacteria.
- First step is the oxidation of ammonia to nitrite, carried out by microbes known as
ammonia-oxidizers. Aerobic ammonia oxidizers convert ammonia to nitrite via the intermediate
hydroxylamine, a process that requires two different enzymes, ammonia monooxygenase and
hydroxylamine oxidoreductase.
- The second step in nitrification is the oxidation of nitrite (NO2-) to nitrate (NO3-). This step
is carried out by a completely separate group of prokaryotes, known as nitrite-oxidizing Bacteria.
- Nitrification is the process that converts ammonia to nitrite and then to nitrate. Mostly
carried out by yprokaryotes. Two steps of nitrification that are carried out by distinct types of
microorganisms.
- Denitrification
- N loss in Indian and Pacific Ocean, Gain in Atlantic Ocean
- Positive Deviation (N*>0) = N is in excess, N gain process e.g. N2 fixation
- Relationship used to find deviation type and identify process of N.
- N*=(NO3-)-16(PO4 3-) + 2.9 umol kg-1 = overall budget ratio
- Anthropogenic (human activity) impact
- Haber Bosch, fossil fuel consumption, nitrogen-based fertilizers, N fixation cultivation ,etc
- nearly 80% of the nitrogen found in human tissues originated from the Haber-Bosch process
- nearly 80% of the nitrogen found in human tissues originated from the Haber-Bosch process
- Human activity with N is increasing with 4x increases added to atmosphere depostion.
- Terrestrial ecosystems, the addition of nitrogen can lead to nutrient imbalance in trees, changes in
forest health, and declines in biodiversity.
- Nearshore marine systems, increases in nitrogen can often lead to anoxia (no oxygen) or hypoxia (low oxygen),
altered biodiversity, changes in food-web structure, and general habitat degradation. One common consequence
of increased nitrogen is an increase in harmful algal blooms . Toxic blooms of certain types of dinoflagellates
have been associated with high fish and shellfish mortality in some areas. Also increased acidity in freshwater
systems.
- Eutrophication of water - leads to blue baby syndrome East Anglia, and links to cancer
- Eutrophication of water - leads to blue baby syndrome East Anglia, and links to cancer
- Terrestrial ecosystems, the addition of nitrogen can lead to nutrient imbalance in trees, changes in
forest health, and declines in biodiversity.
- Haber Bosch, fossil fuel consumption, nitrogen-based fertilizers, N fixation cultivation ,etc
- see http://www.nature.com/scitable/knowledge/library/the-nitrogen-cycle-processes-players-and-human-15644632 for more detail
- Summary: REDOX. Nitrogen has numerous oxidation states and gaseous forms lead to Nitrogen cycle. Nitrogen enters ocean via atmosphere, rivers and nitrogen fixation.
Nitrogen lost by denitrification and anammox, and some as N2O via denitrification and nitrification. Anthropogenic impact has significantly perturbed the marine N-cycle
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