CYCLING OF PHOSPHORUS ATOMS

Energy Flow & Nutrient Cycling Life on Earth depends upon one–way flow of high–quality energy from sun & cycling of crucial elements.

Nitrogen and Phosphorus…These elements are essential to function and productivity of ecological systems.

Importance of Phosphorus (P) Like nitrogen, phosphorus (P) is an essential part of the process of photosynthesis. Involved in the formation of all oils, sugars, starches, etc. Helps with the transformation of solar energy into chemical energy; proper plant maturation; withstanding stress.

Importance of Phosphorus (P) Effects rapid growth. Encourages blooming and root growth. Phosphorus originates from rocks

Phosphorus Cycle (P)

Layers of the Earth Hydrosphere- water layer. Liquid, Ice, Vapor. Lithosphere- Earth’s crust and upper mantle. - Fossil fuels, minerals, soil chemicals. Biosphere- biotic & abiotic factors.

Phosphorous Cycle Atmosphere Biosphere Lithosphere Hydrosphere Never enters the atmosphere Atmosphere Biosphere Absorption Waste & Decomposition Weathering & Erosion Lithosphere Hydrosphere Absorption Sedimentation

Phosphorous Cycle Human Impacts Biosphere Net Effect: Increase in phosphorous in water & “algal blooms”; Depletion in soils Mining, use (fertilizer, detergent, etc.) & increased runoff Lithosphere Hydrosphere More Phos. for organisms

Background The phosphorus cycle does not have a gas phase, but small amounts of phosphoric acid rise into the atmosphere, contributing to acidic precipitation.

Background The water, carbon, and sulfur cycles all include at least one phase in which the element is in its gaseous state. The largest reservoir of phosphorus is in sedimentary rock.

The Cycle

Description of Cycle Simplest of the cycles Phosphorus has only one form – phosphate Always part of an organism, dissolved in water, or in the form of rock

Description of Cycle Phosphorus enters environment from rocks or deposits Apatite is the phosphate rock where phosphate is available Weathering and erosion releases phosphate ions that are soluble in water

Description, cont. Phosphate then acts as fertilizers or nutrients for land plants It gets incorporated into molecules essential for life like ATP, adenosine triphosphate – this is important in storage and use of energy

Description, cont. Phosphate is in backbone of DNA and RNA When animals and plants die, phosphates will return to the soils or oceans again during decay

Description, cont. Phosphorus cycles through plants and animals much faster than it does through rocks and sediments.. A lot of phosphate goes into the water from erosion and leaching Water plants use this phosphate as nutrients

Description, cont. Phosphate is the limiting agent in growth of plants and algae If there is a lack of phosphate, plants grow slowly or are stunted If too much, excess growth may occur

Description, cont. Phosphate in water is precipitated from water as ion phosphate (insoluble) Phosphate in shallow sediment may be recycled into water In deep sediment in water, it is available as part of as part of rock formations for cycle to repeat

Description, cont. After that, phosphorus will end up in sediments or rock formations again, remaining there for millions of years. Eventually, phosphorus is released again through weathering and the cycle starts over.

Major components of aquatic ecosystems. Fig. 4–11

Major components of terrestrial ecosystems. Fig. 4–12

Human Influences on Cycle Human influences on phosphate cycle mostly comes from introduction & use of commercial synthetic fertilizers. Phosphate obtained by mining at certain deposits of calcium phosphate called apatite.

Influences cont. Phosphate rock and sulfuric acid are combined to make a fertilizer called “super phosphate.” There are many negative effects of using this fertilizer.

Influences cont. A lot of the fertilizer is lost through the water run-off because plants aren’t able to use up all of it. Eventually the wasted phosphate in the water is precipitated as it settles at the bottom of the body of water.

The Phosphorus Cycle Crop Atmospheric harvest deposition Animal Component Input to soil Loss from soil The Phosphorus Cycle Crop harvest Atmospheric deposition Animal manures and biosolids Mineral fertilizers Plant residues Runoff and erosion Primary minerals (apatite) Organic phosphorus Microbial Plant residue Humus Plant uptake Mineral surfaces (clays, Fe and Al oxides, carbonates) Weathering Adsorption Immobilization Mineralization Soil solution phosphorus HPO4-2 H2PO4-1 Desorption Secondary compounds (CaP, FeP, MnP, AlP) Dissolution Leaching (usually minor) Precipitation

Phosphorus Cycle

The Phosphorus Cycle How and in what form(s) does phosphorus enter and leave the cycle? How do the roles of autotrophs and heterotrophs differ? What are the human impacts on the cycle?