| What is the redifeld ratio?
How do you know whats limiting in the stream? | N and P interresting in streams.
Sometimes both sometimes one.
Demand is higher than availability
Redfield ratio: C:N:P = 106 : 16 : 1 these are moalr based.
If the N:P ratio deveates from 16:1 you can see what is limiting.
If you can see the C:N:P within the organism it reflects the availability in the system. Because looking in the system is not always the best because it goes up and down depending on precepitation etc. |
| Which forms of N and P do we work with in streams? | Nitrogen can be organic or inorganic. Can be dissolved or total.
Most we talk about nitrate and amonium for inorganic dissolved nitrogen.
Dissolveed organic can be part of enzymes or dna.
Particulate organic nitrogen (PON) can be part of phytoplankton
PO43- is the inorganic phosphor that we look at.
DOP - dissolved organic P
POP - particulate organic P
There is also particulate inorganic phosphorus. |
| How do dissolved nutrients enter the stream? | Upstream, precipitation, ground water, overland flow, subsurface flow (drainage etc) channel sources. Nitrogen is coming with the water (easily dissolved for instance nitrate)
Phosphurous comes with particles (soil etc) but also as free in the water. The more water the more total nutrients will be transported to and in the stream.
Also affected by processes in the bank, groundwater etc. |
| What are the main sources of P and N in danish streams? | See picture
Punktkilder = spildevadsrensning eller spredt bebyggelse. |
| N cycle:
What is assimiatory uptake and dissimilatory transformation?
How can a stream remove N? | Assimilatory (der hvor den optager N) og Dissimilatory (der hvor den bruger det i en elektrontransportkæde).
Dissimilatory = nitrification and denitrification.
Denitrification is the only process that removes nitrogen from the stream.
Happens in areas areas with slow moving water (no oxygen) or deeper in the sediment. Can also happen in thiick biofilm because there can be anoxic conditions.
Indirect nitrification - det har lige været en tur igennem en mikroorganisme først.
Direct betyder at det ikke har været assimileret først. |
| Where does most uptake of nutrients happen? | FBOM, roots, macrophytes, dead leaves, cobble and wood. These are sites if you want to measure uptake you would need to meassure these. |
| Fortæl lidt om phosphor cyklussen
Kan der også ske både dissimilatory og assimilatory?
Hvad sker der når der ikke er ilt? | Ilt til stede: phosphor er bundet jern - alle er glade.
Når ilt ikke er til stede bliver phosphor frigivet fra jern og gjort tilgeængeligt for mirkoorganismer.
Souluble p is what the organisms can use (phosphate or autophosphate). Some may be exchanged to sediment with oxygen it will will be sorbed to sediment particles in water column and surface. Desorbtion takes place with no oxygen. When no oxygen you have more solluble P. when the P enters oxygenated areas it can be taken u or sorbed again.
Its only used as assimilatory uptake. |
| What is nutrient spiraling? | Se billedet |
| What is the nutrient spiraling length | Nutrient spiriling length is how far is how far from it being turnt into ammonium then it is taken up again. The spiraling length s short if there is limitation of the nutrient. It is demand compared to availability.
If there is a high production the spiral length is short.
Low production long spiral length.
SW = uptake lenght how long it travels before it is taken up again.
The length in the biota = Sb.
Uptake length can be meassured |
| How do we determine nutrient retention in streams? | You add nutrient to the stream. Then you can meassure the concentration down stream.
You know how long time it takes until the water has been exchanged by doing the salt thing.
You can pump amonium together with the salt. |
| How can we determine nutrient uptake length (Sw) and nutrient uptake rate (U) and nutrient uptake velocity (Vf)?
What are these measures indicators of? | Sw is basicly how far the nutrients travel before taken up. grows with nutrient aailability. Sw is an indicator of retention efficiency. If length is shorter its more limited and better at retaining nutrients. Sw is influenced by discharge.
The uptake rate (black line) if theres a lot of nutrients aailable the uptake rate increases. Its an indicator of uptake capacity because it has a max where more nutrients doesnt mean a higher uptake.
Uptake velocity (red line) how fast an atom is mooving towards an uptake site. It shows demand/availability. If you have high demand vf is high or if you have high availability Vf is low. |
| How do we compare nutrient Sw accros different ecosystems? | If its a small stream the N is more probable to hit a macrophyte or something.
So you can only compare Sw of laeks in simiar sizes.
To compare different typees of streams then you use Vf (uptake velocity) instead.
If you want to compare different ecosystems the you use the real uptake rate (U). |
| How do we calculate uptake length (Sw)? | Sw = 1/K
K = longtitudinal loss rate. enheden er pr meter. |
| How do you calculate Uptake velocity (Vf)?
How about uptake rate= | First you calculate Sw and then you can calculate Vf and then you can calculate U |
| What controls nutrient uptake rates in streams? | Controls on nutrient uptake:
- Assimilation bu autotrophs
- Heterotrophic uptake or transformation
- Physical adsorption (especially P)
- Hydrolic storage (I transient zones går vanedt langsomt så her kan N nå at reagere piv meget. Så her kan der ske meget N transformation. )
- Ion exchange
Chemical complexation
High Q (vandføring) also means higher volume så er der mindre probability for cantact. Og vandet ryger hurtigt ud.
Stream size er også vigtig. jo større stream jo længere traveler nutrients så højere Sw |
| Forklar denne: | Direct and indirect effects of macrophytes.
Macrophytes can store nutrients.
They can both slow down water and increase surface transient storage (water column transient storage) and they can also uptake nutrients them selves.
There is a deposition of organic matter - oxygen is used and denitrification can increase in areas without oxygen. |
| How does the nutriet cycling differ between seasons? | Seasonality:
Demand / availability (V_f). There is a lot of removal of No3 in spring. They prefer ammonium but there is more nitrate. Removal is highest in spring.
Respiration is high in the autmn. Only net uptake of phosphurus here. There is a coupeling between high respiration and P uptake. |
| How come its important to have different species present in regards to nutrient uptake? | Not all macrophytes behave in the same way.
There is a variaty in uptake of amonium nitrate and phosphurus for both amphibius and submerged plants.
If you have many species you have bigger proability that uptake rate is high during the whoole season. Variability can give complementary effect. |
| Say some clever stuff about this graph in relation to biological control of nutrient uptake and seasonality | Assimilatory uptake - highest when there is high production (so in forrest when there is light and no leaves - spring)
Heterotrophic uptake - when a lot of stuff enters the stream - fall
When flood comes the biofilm is scoured.
Can be used to explain metabolism and relate it to nutrient uptake as well for exam. |
| What are some effects off land use on nutrients? | Land use - increased nutrients and decreased retention time when you straighten out the lake.
Nutrient uptake and metabolism can be used as a proxy for land use and the degree of agricultural landuse. |
