The Phosphorus Cycle

1
The Phosphorus Cycle

• All organisms require phosphorus because it forms
  part of life-sustaining molecules like DNA/RNA
• Not very common in the biosphere

2
A Erosion by Rock

• Sedimentary rocks act like a sink, conserving
  much of the phosphorus for future eons.
• When rock erodes away, the phosphorus is released
  into water where it is carried away and deposited
  as phosphate (combined with oxygen).

3
B Absorption by Plants

• Plants absorb phosphorus from water and soil into
  their tissues, tying them to organic molecules.

4
C Concentration in Plant Tissue

• Dissolved phosphates are readily absorbed by
  plants and accumulate in their tissues.
• These phosphates are then used in the production
  of vital organic molecules (like DNA and RNA).

5
D/E Plant Consumption/Grazing

• Once taken up by plants, phosphorus is available
  for animals when they consume the plants.

6
F Plant Waste

• When plants die, bacteria decompose their bodies,
  releasing some of the phosphorus back into the
  soil.

7
G Animal Waste

• Animal wastes along with the remains of dead
  animals is also released back into the soil.

8
H Runoff to Oceans

• Since phosphate can be dissolved in water and
  carried away, it will eventually reach the
  oceans.
• There the phosphates are incorporated into the
  tissues of fish and other marine organisms.

9
I Marine Sediment

• Scales, bones, etc.
• Can be returned to the land when a marine
  organism is consumed and that consumers waste (or
  dead body) is deposited on the land again.

10
J Geologic Upthrust

• Over time, ocean sediments that are made up of
  dead organisms that contain the phosphates become
  exposed through plate movement and upthrusts.
• Erosion of these sedimentary rocks begins the
  process again.