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BIOL311 > Primary production: light and nutrients > Flashcards

Primary production: light and nutrients Flashcards

1
Q

primary production is measured as the rate of?

A

CO2 uptake or O2 production

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2
Q

primary productions tells you the rate of what?

A

rate at which phytoplankton biomass is growing or turning over

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3
Q

gross primary production (GPP):

A

Total primary production per unit time

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4
Q

net primary production (NPP)

A

GPP - loss to respiration

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5
Q

New production:

A

production “fueled” by “new” nutrients brought in from outside local system

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6
Q

regenerated production

A

fueled by nutrients recycled within the local system

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7
Q

is photosynthesis endothermic or exothermic?

A

endo (light energy input)

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8
Q

is respiration endothermic or exothermic?

A

exo (heat energy released)

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9
Q

Does respiration occur in light or dark?

A

both

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10
Q

high -> low primary productivity for various ecosystems

A

upwelling zone&raquo_space; continental shelf&raquo_space;> open ocean

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11
Q

What is the Gran method?

A

light and dark bottles at different depths
- Excess O2 produced in light bottle represents net primary production
- Measure how much O2 decreases in dark bottle. Adding that to O2 produced in light bottle gives gross primary production

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12
Q

What happens in the light bottles in the Gran method?

A

both respiration and photosynthesis occur so O2 is being produced and consumed

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13
Q

What happens in dark bottles in gran method?

A

only respiration is occuring so O2 is consumed

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14
Q

What is the 14C method?

A

Water collected at depths representing 100%, 50%, 25%, 10%, 5%, and 1% of surface illumination
- Samples “spiked” with radioactive 14C and incubated for 6-12hrs
- Filter samples and use a scintillation counter to measure how much 14C has been taken up from the seawater and incorporated into C6H12O6
- Knowing the total amount of labeled 14 C in the original sample, net primary production can be estimated

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15
Q

what does 14C provide you with an estimate of?

A

net primary production by all phytoplankton

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16
Q

what does 15NO3 provide you with an estimate of?

A

“new production”

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17
Q

what does 15NH4+ provide you with an estimate of?

A

“regenerated production”

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18
Q

what does 32Si provide you with an estimate of?

A

diatom productivity

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19
Q

How do remotely sense ocean colour techniques work?

A
  • Various satellite sensors measure subtle changes in ocean color resulting from differences in the amount of Chlorophyll in the water.
  • From this, it is possible to estimate primary production on global scales. But still requires calibration against in situ measurements of primary production made from ships
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20
Q

Can we predict PP from measurements of Chlorophyll concentration?

A

not always –> phytoplankton biomass can be very low even though pp is high

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21
Q

3 factors regulating primary production:

A
  1. light
  2. nutrient availability
  3. grazing pressure (from meso and microzooplankton)
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22
Q

How much of the solar energy that reaches Earth makes it to the ocean surface

A

50%

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23
Q

what does PAR stand for

A

photosynthetically active radiation (400nm-760nm)

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24
Q

Euphotic zone:

A

upper surface of the water column where theres enough light for photosynthesis

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25
Q

Base of the euphotic zone is where __% of surface light remains

A

1%

26
Q

where is light penetration usually deepest?

A

in offshore waters (open ocean with less productivity)

27
Q

What does the light extinction coefficient k represent?

A

how rapidly light is diminished in the water column
- k is higher in coastal waters than offshore (gets diminished faster)

28
Q

Estimating k by secchi disk:

A
  • lower disc into water and record depth where disk dissapears/reappears –> known as Secchi depth (Ds)
    k = 1.7/Ds
29
Q

what did long-term secchi depth measurements show?

A
  • a shallowing of the euphotic zone (lower secchi depth)
  • increase in k
30
Q

why is fish biomass positively correlated with Ds?

A

Shallow D s indicates high primary production, but also indicates reduced light penetration, making it harder for fish to find prey at depth (so they come up)

31
Q

what must accessory pigments do?

A

transfer their energy to chloropyll a since its the only one used directly in photosynthesis

32
Q

Picophytoplankton (1μm) can grow at depths where other species can’t… how?

A

they have an accessory pigment that is tuned to absorb blue light

33
Q

why is there a layer of high Chl water at 100m depth in a tropical gyre?

A

photosynthetic bacteria have carotenoids which can take advantage of light that penetrates low

34
Q

Compensation depth:

A
  • Depth at which rate of carbon fixation (via photosynthesis) balances the rate at which carbon is lost via respiration
  • In other words, depth at which NPP = 0
35
Q

what determines compensation depth?

A

light penetration

36
Q

in general, compensation depth (Dc) is where?

A

at the base of the euphotic zone

37
Q

mixing depth:

A

How deep phytoplankton are mixed in the water column, due to surface wind mixing

38
Q

critical depth:

A

Depth at which total production in the water column = total respiration in the water column ( i.e. , Pwc = Rwc or Pwc - Rwc = 0)

39
Q

If mixing depth is shallower than the critical depth…

A

phytoplankton can bloom

40
Q

If mixing depth is deeper than the critical depth

A

no phytoplankton bloom (not enough time in the light)

41
Q

once warm whether and sunlight comes in spring phytoplankton kick off before zooplankton… why?

A
  • zooplankton depend on phytoplankton so they start growing later than phyto
  • also phytoplankton turnover in about a day whereas zooplankton take weeks
42
Q

some essential elements for phytoplankton growth:

A

carbon, hydrogen, oxygen, nitrogen, phosphorus, magnesium, iron, copper, manganese, zinc, molybdenum

43
Q

which nutrients are often in short supply?

A

N, P, Si, Fe

44
Q

Which nutrient is most often cited as causing limitation of phytoplankton biomass and primary production in marine ecosystems

A

NITROGEN

45
Q

Why do inorganic nutrients have a nutricline below the surface?

A

-Most inorganic nutrient concentrations are low near the surface ( i.e., where phytoplankton are!)
- Most inorganic nutrient concentrations are high at depth bc organic matter gets re-mineralized by bacteria (i.e. in the microbial loop) as it sinks → bacteria break them down for their own metabolism
- No phytoplankton at depth to utilize them

46
Q

why are nutrient levels higher at depth in the pacific than the atlantic?

A

water is hundred of years older (see conveyer belt) and has had hundreds of more years to gather nutrients

47
Q

How long does a complete circuit of the conveyer belt take?

A

1000 yrs

48
Q

What converts atmospheric nitrogen into inorganic forms (e..g NO3) for phytoplankton to use?

A

nitrogen fixing bacteria

49
Q

Processes that bring nitrogen into euphotic zones:

A
  1. upwelling
  2. atmospheric imputs
  3. rivers and runoff
  4. new nitrogen (NO3 form)
  5. regenerated nitrogen (ammonium form)
  6. sinking of dead plankton
  7. denitrification (formation of reduced N compounds from NO3)
50
Q

Most common mechanism to get nitrogen across membranes

A

active transport

51
Q

what is Ks in terms of enzyme saturation curve

A
  • half-saturation constant (concentration of S where V is 1/2 of Vmax)
52
Q

what does lower K2 indicate?

A

higher affinity of the substrate

53
Q

if Both species have the same K S but Species 1 has a higher μ max than Species 2… who will be outcompeted?

A

at low [N] both grow equally well. However, at higher [N], Species 1 will always dominate because of its higher μ(max)

54
Q

what does ammonium presence do to nitrate uptake?

A

inhibits it

55
Q

primary production in polar oceans

A
  • Very strong seasonality
  • Nutrients: always high
  • Light: only in spring-summer
  • Primary Production: light limited → increases during light period
56
Q

Primary production in tropical oceans

A
  • No seasonality
  • Nutrients: always low - strong thermocline
  • Light: abundant
  • Primary Production: nutrient limited; at steady, low rate
  • Nutrient recycling: important
57
Q

Productivity in mid-latitude (temperate) oceans

A

Winter PP: light limited, abundant nutrients, deep mixing
Spring PP: adequate light, phytoplankton blooms
Summer PP: nutrient limited by stratification
Autumn PP: nutrients replenished (windy) and see a small phytoplankton bloom

58
Q

main drivers of spring bloom timing in strait of georgia?

A

The main drivers of bloom timing were winter/early spring windspeeds and cloud Cover

59
Q

why are food chains longer in open ocean?

A

open oceans dominated by picoplankton because there are low mixing rates and low nutrients
- picoplankton are <2um and too small to be grazed on my zoop or fish –> adds extra steps to food chain

60
Q

longer food chain = _____(more/less) energy at the top of the food chain?

A

less –> less productive

BIOL311 (4 decks)

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