more nuts Flashcards
lec 14
photosynthesis limited by what nutrients
mostly N or P
but sometimes S, Si or Fe
most common form of nitrogen in atmosphere
N2
inorganic forms of nitrogen
nitrate NO3-
ammonium NO4+
nitrite NO2-
nitrous oxide N2O
organic forms of nitrogen
amino acids, nucleic acids, proteins, urea
dissolved and particulate forms
fish, insects and mammals can only consume ____ nitrogen
organic
aquatic plants get most of their nitrogen through roots or leaves?
roots
primary producers love ______ (form of inorganic nitrogen), why?
ammonium because it’s less energy to process
cyanobacteria fix nitrogen in certain situations. why
to fix nitrogen, use enzyme nitrogenase which is very energetically exhausting to use so they prefer not to use it unless absolutely necessary
nitrogenase is inactivated by _____. what do bacteria have to get around this neucence?
oxygen
use special heterocyst cells to protect enzyme from oxygen
nitrification in one senteance
oxidize ammonium to nitrate
NH4+ -> NO3-
nitrification requirements
specific bacteria for ammonium and nitrate oxidation
oxygen must be present
denitrification in one sentence
reduce nitrate to N2
______ removes inorganic nitrogen from water
denitrification
phosphorus dominant form
phosphate (PO4)-3
how does phosphorus appear in water
breaking down rocks
organic phosphorus forms
lipids, nucleic acids
in oxic environment, phosphate is typically
bound to iron and not bioavailable
in anoxic conditions, phosphate is typically
freely floating (not bound to iron) and available
sulfur cycle is driven by
redox states that sulfur can exist as
abundance of silicon in water depends on ________. give an example of an environment with high si and low si
geology/weathering
high silicon near volcano
low silicon near limestone area
diatoms love silicon because
use it to make frustules (specialized cell wall)
what is the dominant form of iron in oxic and anoxic conditions
oxic = Fe3+
anoxic = Fe2+
trace metals important to life but toxic if…
present in ridiculously high amounts
lots of Si movement into water during which season. why?
spring and fall because lots of runoff at this time
describe how sulfur influences phosphate bioavailability
competition between S and P for Fe. but S has stronger binding affinity to Fe, so it outcompetes P.
only occurs in anoxic conditions because when oxygen present, Fe is always bound to oxygen. so when no oxygen around, Fe is free to bind to either ((S)) or P
