M2-3 Flashcards
what are the different forms of phos
TP
dissolved
particulate
organic (can particulate or dissolved)
inorganic (can be particulate or dissolved)
dominant forms of phos in a lake
PO4 3- or FePO4
(freeform)
most P is tied up in org tissues
internal vs external loading of phos into a lake
external loading: often sourced from the weathering of rocks, atmos deposits , streams or rivers into a lake
PO4 or org P detritus
internal loading: from lake sediment at the bottom of a lake and in decaying OM. the conditions at the sed-water interface are critical
role of O2 and iron in the phos cycle
P is relsease 1000 faster in ANOXIC conditions. in oxic conditions, PO4 is bound to iron.
what is excessove phos linked to
cyanobacteria blooms and eutrophication
what % of TP is Solubale reactive phos
0.2. note that is is the ofrm of P that plant need to growth
is particulate organic phos or particulate inorganic phos more abundant (give %) and explain why
POP (98.5%) as most of it is retained in living organisms
algal mechanisms for phos uptake
1) luxury consumption- store P in tissues when very abundant
2) ability to use P at low conc lvl- alter energy budget
3) phosphatase production - some orgs will have enzymes that break the bond between P and org moles in the water, triggered by low P
where are the major zones for P cycling in lakes
Sed-water interface
open water in the pelagic zone (uptake and sedimentation)
littoral zone (uptake and plant decomp)
vertical P dist in oligo lakes
Low soluble and total phos. O2 follows ortho pattern
vertical P dist in eutroph lakes
Low soluble P and total P in epi and meta. Sig increase in the hypo fpr both.
O2 follows clino
human impacts on P cycle and eutroph
Cultural eutroph
agricultural input- excess run off of alot of fertilizers (has P)
speeds up the rate- from 1000’s of years to just a few decades
natural eutroph
often due to the age of a lake
nautral accumulation of P in a system- often takes 1000s of years
N and productivity
N has the ability to limit plant growth- trophic status depends partially on the N content
range of P and N to define lake prod
TP:
diff forms of N
N2
TN
Dissolved and inorg (NH4+, NO3-, No2-)
in organic compounds
N fixation
assimilation of N2 in NH4 via nitrogenase enzyme or lightning
occurs in anoxic environ only
may use heterocycts
denitrification
conversion of inorg N (NO3) into N2
less energy mase when comped to the conversion of Org Carbon to CO2
occur in anoxic
possible solution to dec N in water
heterocysts and their function.
a strucutire to protect the nitrogenase enzyme from oxygen)
nitrification
NH4 to NO2 to NO3 and energy
NH4 in water w/ DO, it will have more energy than NO species
done by bActeria, fungi or other autotroph
nitrosomonas
conver NH4 to NO2
nitrobacter
convert NO2 to NO3
what form of N is easiest to take up
NH4 is easiest to tke up from water colomn. from here plant and orgs have metabolic oircesses to convert into useful forms
nitrate reductase
Nirtate to nitrite. this can be limiting
this is an oxic process
