lec 16 Flashcards
in the presence of oxygen, how does Fe3+ behave? when oxygen is not available, what happens? [REVIEW]
in oxygen, Fe3+ forms insoluble oxides
in anoxia, Fe3+ is reduced to Fe2+ which will come together with sulfur (returns to Fe3+ when oxygen returns)
how do iron, sulfur, and phosphorus come together?
in the oxygenated water column, Fe3+ combines w orthophosphate and falls into anoxic sediments. at that point, Fe3+ is reduced to Fe2+, releasing the orthophosphate and picking up a sulfur instead to form pyrite
what is the difference between natural and cultural eutrophication?
natural eutrophication occurs naturally w the ebb and flow of nutrients. cultural eutrophication occurs specifically due to anthropogenic inputs
looking at irl examples, chlorophyll a, canthaxanthin, and zeaxanthin are important to note. what do they indicate?
chlorophyll a is a general indicator of cyanobacteria, while canthaxanthin indicates nuisance cyanobacteria and zeaxanthin indicates other cyanobacteria!
what happens to hydrogen sulfide in different pH conditions?
in acidic conditions turns into a gas, in basic conditions turns into S2- ions (protons get neutralized so ur left w the anions)
sulfur + O2 = ? how have bacteria adapted this ?
sulfur can become OXIDIZED in the presence of oxygen (REDOX) for a huge release of potential energy - some bacteria use sulfur for chemosynthesis
what is the process of Sulfur disproportionation?
thiosulfate –> sulfate –> sulfides under anoxic conditions to prod energy
pyrite has low solubility, which can be bad for locking up iron in aq ecosystems. certain bacteria can be used to free up this iron, but there is a drawback. what is it?
the process produces a lot of sulfuric acid which, if returned to the aq ecosystem, can acidify an environment or result in things like acid rain
some bacteria have adapted to use sulfur, such as Beggiatoa. tell me what those funky dudes do
store nitrates in oxic areas, then travel to anoxic sediments that are rich in sulfur. nitrates are oxidized, releasing lots of energy
what is anoxygenic photosynthesis?
a form of photosynthesis where sulfate is broken up for oxygen instead of water :)
iron is very important in many process (list 3)
key element in ETC prot, hemoglobin, a bunch of enzymes
what is the difference between ferric and ferrous iron? where can either be found?
ferric iron is Fe3+, and is found in oxic conditions. ferric iron gives electrons (gets oxidized easily)
ferrous iron is Fe2+ and is found in anoxic conditions. ferrous iron accepts electrons (gets reduced easily)
can think of ferrous as ferr-US (us being 2 people :D)
what are chelators? what are organic instances of them?
chelator is a type of bonding. organisms maintain high conc of iron in oxic environ by briefly binding iron to prevent it from turning into precipitates like ferric hydroxide
dystopic wetlands are unproductive because a lack of light, but iron might also play a role. what is this role?
humic material (that dead/decomposing shit) can complex with iron, such that organisms are unable to use it. if enough humic material is around, no iron is left available –> nothing can survive
is it ferric or ferrous iron that precipitates phosphorus?
ferric (Fe3+) iron - the dude in the oxic environment
