Download Circulation of Nutrients

Circulation of Nutrients
Provides:
essential elements for processes like photosynthesis,
building amino acid and nucleic acids etc
decomposition releases minerals and nutrients for
metabolic processes
Decomposition
•Dead or waste organic matter converted to inorganic
nutrients
•Un-decomposed material is litter
•fully decomposed material is humus
•physical and biological process
•detritovores - detritus eating invertebrates
•microbial decomposers - bacteria/fungi
•fixed, lost and transformed nutrients
Detritus converted to humus (small pieces of
material more easily broken down by microbes
Decomposition rates influenced by:
type of detritus
type / abundance of decomposers
environmental conditions e.g. temp, moisture,
aeration, nutrient availability
Mineralisation – release of minerals essential for life
Nutrient Cycling
nutrients required by living organisms
plants from soil
animals from ingested material
nutrients can be macro or micro
macro nitrogen, carbon, phosphorus, (sulphur)
micro
trace elements, zinc, magnesium, iron, etc.
Nutrient Cycling
nutrients in biogeochemical cycles
fixed in biotic and abiotic components
taken up or lost by absorption or leaching
chemically transformed by biological or environmental
processes
Nitrogen cycle (80% stable)
converted by redox reactions to useful compounds
5 main steps
1. Biological nitrogen fixation
•
gaseous nitrogen converted to ammonia
•
Rhizobium bacteria (free living or symbiotic in
nodules in legumes)
•
prokaryotic bacteria or cyanobacteria
1. Biological nitrogen fixation
•
anaerobic conditions, needs energy
•
enzyme nitrogenase.
•
leghaemoglobin in nodule bacteria fixes oxygen
giving anaerobic conditions
2. Nitrification
ammonia converted to nitrates by soil involves
many bacterial groups
Nitrosomonas/Nitrococcus convert ammonia to nitrites
Nitrobacter oxidises nitrites to nitrates (energy release)
3. Assimilation
Initial uptake of ammonia/nitrates by primary producers
to make protein/nucleic acids.
Consumers eating at various trophic levels
4. Ammonification
Decomposition to produce ammonia by bacteria
in soil and aquatic ecosystems
5. Denitrification
Nitrates converted to nitrogen gas by free living
anaerobic denitrifyng bacteria
(agrobacterium and psuedomonas)
Loss of soluble nutrients
Loss of soluble nitrates by leaching and run-off
Limits to nitrogen in environment
Water saturation creating anaerobic conditions
reduces nitrification
Tropical rainforest decomposition is rapid but soil
quality is poor due to scarcity of humus and litter,
leaching removes nutrients quickly
Temperate forest decomposition slower, soil quality
is good as litter and humus in plentiful supply
Crop rotation and addition of fertilizers
Carbon cycle
Phosphorus cycle
Phosphorus
nucleic acids, phospholipids, ATP, minerals in bones and teeth
local cycling of phosphate bound by humus and soil particles
occurs as phosphates in soils from weathered rocks
plants take up phosphates and assimilate it
animals consume phosphorus and assimilate it
animals excrete, organisms die and decomposition
returns phosphorus to soil
Eutrophication
Results from too much phosphorus or nitrogen in aquatic
ecosystems
plants and algae grow rapidly and die
decomposition of plant material uses lots of oxygen from
water
other organisms e.g. fish unable to survive low oxygen
levels