M2-3

Question 1

what are the different forms of phos

Answer 1

TP
dissolved
particulate
organic (can particulate or dissolved)
inorganic (can be particulate or dissolved)

Question 2

dominant forms of phos in a lake

Answer 2

PO4 3- or FePO4
(freeform)
most P is tied up in org tissues

Question 3

internal vs external loading of phos into a lake

Answer 3

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

Question 4

role of O2 and iron in the phos cycle

Answer 4

P is relsease 1000 faster in ANOXIC conditions. in oxic conditions, PO4 is bound to iron.

Question 5

what is excessove phos linked to

Answer 5

cyanobacteria blooms and eutrophication

Question 6

what % of TP is Solubale reactive phos

Answer 6

0.2. note that is is the ofrm of P that plant need to growth

Question 7

is particulate organic phos or particulate inorganic phos more abundant (give %) and explain why

Answer 7

POP (98.5%) as most of it is retained in living organisms

Question 8

algal mechanisms for phos uptake

Answer 8

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

Question 9

where are the major zones for P cycling in lakes

Answer 9

Sed-water interface
open water in the pelagic zone (uptake and sedimentation)
littoral zone (uptake and plant decomp)

Question 10

vertical P dist in oligo lakes

Answer 10

Low soluble and total phos. O2 follows ortho pattern

Question 11

vertical P dist in eutroph lakes

Answer 11

Low soluble P and total P in epi and meta. Sig increase in the hypo fpr both.
O2 follows clino

Question 12

human impacts on P cycle and eutroph

Answer 12

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

Question 13

natural eutroph

Answer 13

often due to the age of a lake
nautral accumulation of P in a system- often takes 1000s of years

Question 14

N and productivity

Answer 14

N has the ability to limit plant growth- trophic status depends partially on the N content

Question 15

range of P and N to define lake prod

Answer 15

TP:

Question 16

diff forms of N

Answer 16

N2
TN
Dissolved and inorg (NH4+, NO3-, No2-)
in organic compounds

Question 17

N fixation

Answer 17

assimilation of N2 in NH4 via nitrogenase enzyme or lightning

occurs in anoxic environ only
may use heterocycts

Question 18

denitrification

Answer 18

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

Question 19

heterocysts and their function.

Answer 19

a strucutire to protect the nitrogenase enzyme from oxygen)

Question 20

nitrification

Answer 20

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

Question 21

nitrosomonas

Answer 21

conver NH4 to NO2

Question 22

nitrobacter

Answer 22

convert NO2 to NO3

Question 23

what form of N is easiest to take up

Answer 23

NH4 is easiest to tke up from water colomn. from here plant and orgs have metabolic oircesses to convert into useful forms

Question 24

nitrate reductase

Answer 24

Nirtate to nitrite. this can be limiting

this is an oxic process

Question 25

nitrites reductase

Answer 25

nitrite to Ammonium (NH4) for AA prod
this is an oxic process

Question 26

ammonification

Answer 26

org compunds are broken down by bacteria/ fungi and converted to ammonium

occurs in sediments and upper waters

oxic process

Question 27

vert dist of N (eutroph)

Answer 27

NO3 start high and dec w/ depth (to 0)
NH4 starts low and inc w/ depth (to mid)
O2 content is a large factor

Question 28

vert dist of N (oligo)

Answer 28

NH4 is low all the way down
NO3 is mid low w/ sligh inc w/ depth
O2 content is a large factor