1.6 - Phosphorus Cycle

Question 1

What is the phosphorus cycle?

Answer 1

The movement of Phosphorus particles through sources and sinks/reservoirs

Question 2

What are phosphorus’ major reserves

Answer 2

Rocks and sediment

Question 3

Why is phosphorus the slowest cycle?

Answer 3

• Phosphorus is formed as phosphate so it takes a long time for Phosphorus minerals to be weathered out of rocks & carried into soil/bodies of water
• No gas phase of Phosphorus (doesn’t enter atmosphere)
• Because it cycles so slowly, it is a limiting nutrient, meaning plant growth in ecosystems is often limited by Phosphorus availability in soil/water - meaning phosphorus has to be given as nutrients in a limited manner then decomposed in that limited quantity (very slow)

Question 4

Why is phosphorus important?

Answer 4

Phosphorus is needed by all organisms for DNA, ATP (energy), bone & tooth enamel in some animals

Question 5

What is a major natural source of phosphorus

Answer 5

Weathering of rocks

Question 6

Explain the phosphorus cycle through the weathering of rocks

Answer 6

• Wind & rain break down rock & phosphate (PO4-3)
• released and dissolved into water
• rain water carries phosphate into nearby soils & bodies of water

Question 7

What happens because the phosphorus cycle is so slow?

Answer 7

Weathering is so slow that P is often a limiting nutrient in aquatic & terrestrial ecosystems

Question 8

What are synthetic sources of phosphorus

Answer 8

mining phosphate minerals & adding to products like synthetic fertilizers & detergents/cleaners

Question 9

Explain what happens with synthetic sources of phosphorus

Answer 9

• Synthetic fertilizers containing phosphates are added to lawns or ag. Fields; runoff carries P into nearby bodies of water
• Phosphates from detergents & cleaners enter bodies of water via wastewater from homes

Question 10

Assimilation in phosphorus cycle

Answer 10

• Just like N, P is absorbed by plant roots & assimilate into tissues
• animals assimilate P by eating plants or other animals

Question 11

Decomposition in phosphorus cycle

Answer 11

Animal waste, plant matter & other biomass is broken down by bacteria/soil decomposers that return phosphate to soil

Question 12

How does Decomposition and Assimilation relate

Answer 12

They create a loop within the phosphorus cycle

Question 13

Explain sedimentation in the phosphorus cycle

Answer 13

• Phosphate doesn’t dissolve very well into water; much of it forms solid bits of phosphate that fall to the bottom as sediment (sedimentation)
• P sediments can be compressed into sed. rock over long time periods by pressure of overlying water

Question 14

What is geological uplift

Answer 14

• tectonic plate collision forcing up rock layers that form mountains
• allows for the phosphorus cycle to start again with wethering and release of phosphate from rocks

Question 15

What causes eutrophication

Answer 15

extra input of Nitrogen and phosphorus into aquatic ecosystems

Question 16

What is fueled by extra nitrogen and phsophorus

Answer 16

algae blooms

Question 17

Explain the process of eutrophication

Answer 17

• Algae bloom covers surface of water, blocking sunlight & killing plants below surface
• Algae eventually die-off; bacteria that break down dead algae use up O2 in the water (b/c decomp. = aerobic process)
• Lower O2 levels (dissolved oxygen) in water kills aquatic animals, especially fish
• Bacteria use up even more O2 to decompose dead aq. animals
• Creates pos. feedback loop: less O2 → more dead org. → more bacterial decomposition → less O2

Question 18

What can eutrophication occur from

Answer 18

Can occur from fertilizer runoff, human/animal waste contamination

Question 19

Simple Photos explanation of eutrophication

Answer 19

1. nutrient load up - excessive nutrients from fertilizers are flushed from land into rivers or lakes by rainwater
2. plants flourish - these pollutants cause aquatic plant growth
3. algae blooms, oxygen is depleted - algae blooms preventing sunlight reaching other plants. The plants die and oxygen in the water is depleted
4. Decomposition further depletes oxygen - dead plants are broken down by bacteria decomposers, using even more oxygen in the water
5. death of the ecosystem - oxygen levels reach a point where no life is possible. Fish and other organisms die