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)