phosphorus cycle

Question 1

phosphorus facts

Answer 1

• no gaseous forms in nature
• highly reactive - not found in elemental form
• a small amount is transported attached to dust particles
• overall pH of an environment changed depending on what anion is present

Question 2

why is the partial dissociation of phosphoric acid important

Answer 2

because it can donate up to 3 protons

Question 3

inorganic phosphorus

Answer 3

• in over 300 naturally occurring minerals (e.g. apatite)
• lost of mining of sedimentary rocks
• found in bird dropping - Guano

Question 4

Phosphorus containing minerals

Answer 4

• apatite
• vivionite
• struvite
• manazite

Question 5

phosphorus as a vitamin

Answer 5

• essential for healthy teeth
• protects and rebuilds enamel
• helps the body absorb and use Ca
• this helps with bone strength

Question 6

Phosphorus involvement in cellular functioning

Answer 6

• DNA/RNA
• phospholipids
• ATP
• cell signalling and gene regulation

Question 7

organic phosphorus

Answer 7

• plants cannot take up this form
• phosphate undergoes esterification with carboxylic acids
• COP bond
• phosphotriesters
• phosphonates

Question 8

what are phosphotriesters

Answer 8

possibly newly evolved marine bacteria capable of degrading anthropogenic pollutants

Question 9

what are phosphonates

Answer 9

• found in outer membrane of polysaccharides and can replace lipids in the bilayer
• have a CP bond
• abundant in plant tissue and the ocean

Question 10

liable Phosphorus

Answer 10

• insoluble
• found in soils
• only bioavailable form of P
• orthophosphate

Question 11

how do organisms release liable P from complexes

Answer 11

1. solubilisation
   - chemical process that manipulates metabolism
   - more important in soil than sea water
2. mineralization
   - enzymatic process that degrades organic P

Question 12

how do phosphatase drive remineralisation

Answer 12

• in response to love P availability microbes release enzymes called phosphatases
• there is a huge range of them
• have both a promiscuous and specific substrate range
• have different cellular locations

Question 13

terrestrial phosphorus cycle

Answer 13

1. rock weathering
2. incorporation and return of P into/from organisms
3. exchange between soil and groundwater
4. freshwater lake cycling
5. transport to sea

Question 14

rock weathering

Answer 14

transport down rivers as dissolved and particulate PO43-
(much stays in river systems to transport to sea)

Question 15

incorporation and return of P into/from organisms

Answer 15

• 5% of weathered P is available
• P availability limits growth - controls other biogeochem cycles
• cell division
• atp
• DNA
• gene regulation

Question 16

exchange between soil and groundwater

Answer 16

• 5% of weathered P available
• inorganic reactions with minerals are important
• pH dependant

Question 17

freshwater lake cycling

Answer 17

• stratification of lake water in summer reduced p availability near surface - verticel mixing of nutrients is prevented so P is trapped deeper cooler layers where is is less accesibly to plants and algae
• this limits surface water productivity
• sensitive to anthropogenic inputs
• in winter P cycles better in lakes as there is no stratification but because there is less sunlight productivity is limited

Question 18

transport to sea

Answer 18

• change of pH within estuaries as seawater is approached is important
• dissolved P may precipitate (higher pH more precipitation)
• P may be dissolved from particulates
• difficult to generalise as dependent on many different factors

Question 19

oceanic P cycle

Answer 19

1. upwelling of nutrient rich waters
2. biological productivity, sinking of biogenic particles
3. regeneration of P by decomposition of organics
4. decomposition of particles below thermocline
5. slow exchange between surface and deep waters
6. P incorporation into deep sediments

Question 20

how does depth affect temperature and P content

Answer 20

• have reversed patterns with depth
• warm at the top with low P
• cold at bottom with high P

Question 21

upwelling of nutrient rich waters

Answer 21

• N, P, Fe
• zones of upwelling have high biological activity - e.g. coast of peru
• phytic zone
• cold waters with less stratification have higher P return to surface

Question 22

incorporation and return of P into/from organisms

Answer 22

• photosynthesis incorporates P into biota in photic zone
• some sinks can be traces using P isotopes

Question 23

loss and decomposition of particles below thermocline

Answer 23

• most P is recycled into water and returns by either upwelling or exchange

Question 24

slow exchange of P across deep water/surface water divide (thermocline)

Answer 24

• an extremely slow process
• temperature changes very rapidly

Question 25

incorporation of P as particles (organic/inorganic) into marine sediments as

Answer 25

- organic P - authigenic apatite - P associated with other mineral phases - CaCO3 and FeOOH - P loosely sorbed onto solid phases

Question 26

residence times

Answer 26

- atmosphere - 5h - ocean biota - 16-30d - surface ocean - 2.6y - land biota - 16y - land water - 950y - deep ocean - 1420y - sediments - 180my

Question 27

eutrophication

Answer 27

- N and P in waterways - cause increase in phytoplankton - overgrowth of algae occurs - this blocks sunlight and causes deoxygenation - other animals and plants cant survive

Question 28

p cycle between soil and plants

Answer 28

see diagram