lec 21 (MIDTERM REVIEW)

Question 1

what is an orthograde curve? what do we expect to see in oligo- and eu- lakes

Answer 1

orthograde curve refers to when there is a relatively straight line in terms of (x) levels

in oligo, its low amts but incr slightly at meta- + hypolimnion; there is an orthograde

in eu, its high in epi- but falls off in metalimnion; there is a clinograde (GRADIENT)

Question 2

what are heterograde curves? when do they occur? what does it mean for it to be positive? negative?

Answer 2

heterograde curves refer to when there is an excess deficit of oxygen in the thermocline. they arise when there light penetration > mixing depth

[+] occurs when there is photosynth in the thermocline that isnt dispelled due to being in the metalimnion

[-] occurs when there is denser water that delivers anoxic water to the metalim, and stratification prevents mixing beyond the metalim.

Question 3

anaerobic respiration and chemosynthesis can cycle into each other via redox. explain this

Answer 3

anaerobic respiration is a process to use organic carbon to ‘create’ energy. chemosynthesis is a process used to use energy from breaking chemical bonds to produce organic carbon. in this sense they are cyclic.

in terms of redox, at anaerobic respiration, an oxidized compound (ex. SO42-) becomes reduced (GER) to get energy (H2S). alternatively, in chemosynthesis, this reduced compound becomes oxidized (LEO) for energy.

Question 4

P is thought to be the main limiting factor in most cases. why then has it been documented that microcystin conc decreases as the N:P ratio incr?

Answer 4

if the N:P ratio incr, the relative amt of P decr –> more N facilitates more growth but relative amt of P cannot support it

Question 5

QUICK! WHAT DO THE GRAPHS LOOK LIKE IN OLIGO- AND EU- LAKES FOR DO

Answer 5

DO oligo: relatively orthograde, incr a bit at the bottom since cold water can hold more O2

DO eu: high in epi (prim prods), falls off in meta (dominated by decomposers)

Question 6

QUICK! WHAT DO THE GRAPHS LOOK LIKE IN OLIGO- AND EU- LAKES FOR DOC

Question 7

QUICK! WHAT DO THE GRAPHS LOOK LIKE IN OLIGO- AND EU- LAKES FOR N (AMMONIA AND NITRATES)

Answer 7

oligo: nitrates are high, there is relatively no ammonia (no one around to prod it)

eu: nitrates are high in epilim since nitrifying bacteria are nitrifying; ammonia is high in hypolim (bacteria nitrify in anaerobic conditions)

Question 8

QUICK! WHAT DO THE GRAPHS LOOK LIKE IN OLIGO- AND EU- LAKES FOR P

Answer 8

oligo: P doesnt really change idk

eu: phosphates incr in hypo since it gets bound up w iron etc

Question 9

in moderate areas, CaCO3 dominate; in arid and tropical regions, NaCl dominate. why is this?

Answer 9

in moderate areas, the process of weathering is giving consistent CaCO3

in arid regions, evap > precip – there is not enough water to do a lot of weathering

in tropical regions, precip > evap – there is so much water, weathering has alr run its course, so all that’s left is salts that consistently cycle

Question 10

how does buffering work?

Answer 10

when CO2 gets hydrated (add H2O) u get carbonic acid, which dissociates to bicarbonate (HCO3) and then carbonate (CO3)

bicarbonate and carbonate form OH- ions that counteract acid input

using CO2 is smart bc animals naturally produce CO2 as a byproduct of respiration