lec 14 Flashcards
how can we measure phytoplankton growth as a function of P input? ie what do we measure instead of biomass bc that’s tuff
we measure chlorophyll a, which is pretty much universally used by photosynthesizers
how can we classify a lake as a function of productivity (4 categories)
total conc of of P in the water column
- oligotrophic (>10 micrograms P/L)
- mesotrophic (10 - 35 micrograms P/L)
- eutrophic (35 - 100 micrograms P/L)
- hypertrophic (>100 micrograms P/L)
this isn’t a perfect classification and can vary from lake to lake
in Schindler et al experiment, they added C+N to one side of a lake and C+N+P into the other side. what were the results?
C+N+P had significantly higher algal bloom
why do high levels of productivity result in anoxia?
oxygen gets used up in the hypolimnion as phytoplankton and decomposers respire
what is orthophosphate? what is its significance?
orthophosphate is an inorganic form of phosphorus, which can be taken up quite easily
what is the main source of phosphorus in aquatic environments?
rocks :)
what is the pathway from dissolved organic P to dissolved inorganic P?
enzymes - specifically phosphatases, which cleave inorganic P from the organic molecule
inorganic phosphate has a charge. what does this mean for free floating inorganic phosphates in oxic waters?
inorganic phosphate may bind w iron to form the precipitate FePO4, also called pyrite :)
how do u analyze the amount of phosphorus?
molybdate is added to a sample of lake water. this molybdate binds to orthophosphates and turns to a specific wavelength of blue, the saturation of which denotes the amount of P.
(also technically molybdate binds to Soluble Reaction Phosphate, which is an analog of orthophosphate)
which weather faster to provide P? igneous, sedimentary, or metamorphic rocks?
sedimentary rocks weather faster and also just tend to have higher P conc anyways
in the presence of iron (Fe3+) phosphate can undergo one of two reactions. what are these conditions, and what are the products?
the condition is pH
in acidic conditions (pH < 7) we get FePO4
in basic conditions (pH > 7) we get (Fe)x(OH)y(PO4)z
where x, y, and z represent different values idk
in oligotrophic lakes, the stratification graph and subsequent oxygen and phosphorus graphs are relatively standard.
conversely, in more productive lakes, what happens to P?
in more productive lakes, P levels incr as u go deeper bc P is remineralized in sediments
[what about this has to do with productivity causing this?]
what is oxic internal loading? what are two ways this may occur?
oxic internal loading refers to when sediments get stirred up, mixing nutrients into the water column
oxic internal loading can result from bioturbation (living things moving around) or turbulence from wind
in the presence of oxygen, how do phosphates behave? conversely, in anoxic conditions, how do phosphates behave?
in the presence of oxygen, phosphate precipitates
conversely under anoxic conditions phosphates dissociate
phosphorus can become apatite when two conditions are met. what are these conditions?
high pH and presence of calcium (apatite precipitate is CaPO4)
this pH is usually caused by macrophytes [doing what?]
