Nutrient Circulation Waste is in the form of
dead organisms: animals/ plants/ leaves faeces urine
All can contain nutrients and/or energy If the nutrients are not made available again, the
ecosystem will decline Open ocean productivity is low
Any dead organisms are removed from the ecosystem
sink to ocean floor Failure to recycle nutrients, reduces future
growth within an ecosystem. Farmers need to replace harvested nutrients with
fertiliser
Nutrient Circulation
During degradation wastes are decomposed to release inorganic ions
This is called - Mineralisation Can be absorbed by plants and used
for growth Circulation depends on activities of 2
groups Detritivores Decomposers
Detritivores
Detritivores = detritus eating invertebrates e.g Earthworms, woodlice
Turn large pieces of organic waste into small pieces (gain energy & nutrients for growth in doing so)
Make humus (important soil constituent –for aeration, water retention/ drainage)
Because they in turn enter food chains by being eaten by other animals (e.g birds), they recycle the nutrients (and energy) back into the ecosystem.
Also increase the surface area of the detritus, so that decomposers can act more quickly
Decomposers
These are bacteria and fungi Saprophytic (obtain nutrients and
energy directly from dead or decaying matter) A range of microbes found within soil Can secrete enzymes which degrade
molecules e.g cellulase External digestion, forming a soluble soup
easily absorbed Vital in e.g Nitrogen cycle, carbon cycle
Decomposers live freely in soil or can be found in detritivore digestive tracts
Rate of Decomposition
Type of detritus (coniferous litter is slower than deciduous)
Type and abundance of decomposers Abiotic factors
temperature moisture (humus) aeration (humus) nutrient availability (nitrogen)
Nutrient Cycling
Animals gain nutrients from food birds, some animals go to salt licks
Plants/ microbes gain nutrients from soil Macronutrients
required in large amounts e.g N, P, S
Micronutrients required in smaller amounts e.g Se, Mo, Mn
All nutrients need to be soluble before they can be absorbed
Lack of water can lead to nutrients not being available
Biogeochemical Cycles
Minerals can be part of living world (biota) or non living environment (abiota) e.g. nitrogen as protein or atmospheric gas chemically transformed by e.g. lightning or biologically fixed by e.g. Rhizobium
Soluble so often removed by leaching
Three cycles: Carbon cycle Nitrogen Cycle Phosphorous cycle
Nitrogen Cycle
Ammonium
nitritenitrification
nitrification
denitrification
fixation
assimilationammonification
Nitrogen Cycle
Ammonium
nitrite
Nitrosomonas
Nitrococcus, Nitrobacter
Thiobacillus denitrificans,Pseudomonas,Clostridium
Rhizobium sp.
Fungi & bacteriauptake by plant roots of
soluble nitrates
converted into plant protein, nucleic acids
etc.
converted into animal protein, nucleic acids
etc.
Carbon cycle
Phosphorous Cycle
Phosphorous Cycle
Phosphorous essential to cell biochemistry Phosphorous minerals are rel. insoluble Continuously weathered from rocks Solubility pH dependent
Plants obtain phosphorous from soil Phosphorous absorption often aided by
mycorrhizal associations (mutualism) Animals obtain phosphorous from plants Phosphorous availability often limits growth Hence use of NPK fertilisers Algal blooms induced by detergent effluent
Nitrogen Cycle 5 major processes:
Fixation converting atmospheric nitrogen into soluble nitrate rhizobium bacteria (free or in nodules), lightning
Assimilation uptake of nitrate into plant roots, incorporation into nitrogen
containing molecules (protein/ nucleic acid) In the cycle this is animal’s source of nitrogen
Ammonification breakdown of dead/ waste materials to give ammonia bacteria & fungi (saprotrophic)
Nitrification conversion of ammonia into nitrates 2 step process ammonia to nitrite (nitrosomonas; nitroso species) nitrite to nitrate (nitrococcus, nitrobacter; nitro species)
Denitrification fixed nitrate lost by bacterial reduction to gaseous oxides of nitrogen
(pseudomonas, clostridium) or nitrogen gas (thiobacillus dentirificans)