carbon and nitrogen cycles

stages of the nitrogen cycle

nitrogen fixation

nitrification

assimilation

ammonification (decomposition)

dentrificaton

nitrogen fixation

converstion of atmospheric nitrogen into ammonia by nitrogenase enzymes. the microorganisms involved in this are nitrogen fixing organisms such as rhizobium. this provides nitrogen organisms can use

nitrification

oxidaton of ammonia to nitrite using AOB(nitrosomonas) and then oxidizing nitrite to nitrate using NOB (nitrobacter) which plants can then assimilate

assimilation

uptake of ammonium nitrite or nitrate by plants to synthesize organic nitrogen compounds

ammonification (decomposition)

microbial breakdown of organic nitrogen from dead organisms and waste products back into ammonium

denitrification

reduction of nitrate back to nitrogen gas using denitrifying bacteria such as pseudomonas and returning it to the atmosphere which prevents a nitrogen build up

stages of the carbon cycle

photosynthesis respiration decomposition sedimentation combustion

photosynthesis

plants, algae and cyanobacteria convert atmospheric CO2 into organic matter using sunlight

respiration

organisms release CO2 back into the atmosphere by metabolising organic matter using sunlight

decomposition

microbes break down dead organic material, releasing carbon back into the soil and atmosphere

sedimentation

over geological timescales, organic matter can become buried and transformed into fossil fuels

combustion

burning of fossil fuels and biomass releases stored carbon as CO2

microbial roles in the carbon cycle

decomposers

methanogens

methanotrophs

human impact on the carbon cycle

burning fossil fuels

deforestation

farming animals

human impact on the nitrogen cycle

nitrogen-rich fertilizers

burning fossil fuels

livestock farming

Health issues

anammox

ammonium is directly converted into nitrogen gas using nitrite. this is carried out by planctomycetes bacteria. this process removes excess nitrogen from oxygen-limited environments and is used in water treatment plants

DNRA

converts nitrate into ammonium keeping nitrogen in the ecosystem

methanotrophs

bacteria that consume methane and convert it into CO2. found in wetlands, rice fields and landfill sites