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EOSC 372 > 3B Light Availability of Phytoplankton > Flashcards

3B Light Availability of Phytoplankton Flashcards

1
Q

what are the main reasons light reaching the earth varies

A

latitude
season
time of day
day length
atmospheric conditions

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2
Q

how does latitude impact light reaching earth

A

poles receive less solar energy cus sun is on horizon, therefore larger impact patch

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3
Q

impact patch

A

solar rays hitting the earth
smaller impact patch means more solar energy per unit area (vice versa)

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4
Q

how does season impact light reaching earth

A

tilt of the earth causes size of impact patch to change
summer/winter solstice receives most solar energy at 23.5 degrees N/S

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5
Q

what is the is the tilt of the earth’s rotation axis

A

23.5 degrees

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6
Q

how does time of day impact light reaching earth

A

maximum solar energy occurs at noon when it is directly over head
function of time of day for the Equinox

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7
Q

how does day length impact light reaching earth

A

longer days get more sun; more solar energy
poles in summer have longer days and vice versa

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8
Q

what is one mole of photons called

A

Einstein (E)

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9
Q

what is photosynthesis dependent on

A

number of photons in the right wavelength reaching the chlorophyll

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10
Q

what is heating in the water column dependent on

A

light’s energy (short wavelength heats more)

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11
Q

what do we usually use to measure light

A

irradiance Watts (Joules/s)

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12
Q

watt is the conversion between Watt and Einsteins usually

A

1 Watt = 4.4 microE/s

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13
Q

what is low, optimal, and high light for a phytoplankton

A

< 100 microE/m^2 s
150-200 microE/m^2 s
2000 microE/m^2 s

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14
Q

how does atmospheric conditions affect amount of light reaching earth

A

clear sky lets more light in vice versa
scattering, absorption prevent light from reaching the surface

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15
Q

what percent of solar radiation reaches the surface on a clear day

A

80

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16
Q

what percent of solar radiation reaches the surface on a cloudy day

A

25

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17
Q

what is albedo

A

fraction of light reflected from a surface
average sinced different wavelengths reflect differently
large for light surfaces, vice versa

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18
Q

what does ocean water albedo depend on

A

surface roughness
sun light angle
sediment concentraion
chl concentration

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19
Q

do open ocean or coastal ocean have higher albedos

A

coastal oceans

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20
Q

what happens to light as it moves through water

A

phons scatter/ get absorbed

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21
Q

what is the attenuation coefficient

A

measure of how clear the water is
larger k is coastal water

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22
Q

what wavelengths does water absorb more

A

longer wavelengths

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23
Q

what kind of light is found in deeper water

A

blue

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24
Q

what is photosynthesis

A

fixation of CO2 into sugars
releases O2

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25
Q

what is respiration

A

suagrs being ‘burned’ with O2 to release energy (ATP) for cellular metabolism
CO2 and H2O are released

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26
Q

who uses respiration

A

all aerobic organisms

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27
Q

what percentage of carbon gets fixed annually by phytoplankton??

A

50%

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28
Q

how did the creation of phosynthesis change the earth’s evolution?

A

oxygen level increased from <1% to 20%
CO2 levels fell from >10% to 0.03%

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29
Q

how is phytoplankton biomass measured in the ocean?

A

hyperspectral radiometer- measures light reaching down the water column, temperature and salinity
clamps shut at a certain depth in the ocean
filter water to measure phytoplankton

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30
Q

primary production definition

A

stock/biomass of phytoplankton
measure of chl a or C over volume (mg chla/ml)

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31
Q

what is PAR

A

photosynthetically active radiation
400-700 nm wavelength

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32
Q

primary productivity definition

A

rate of fixation of organic carbon from inorganic carbon
photosynthesis
in mole CO2 comsumed/ml h or O2 produced/ml h or organic C produced/ml h

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33
Q

do phytoplankton use respiration or photosynthesis

A

both
respire all the time, photosynthesize in the day

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34
Q

Gross primary productivity definition

A

rate of PS without accounting for R (total C fixed)

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35
Q

net primary productivity

A

gross PP - rate of respiration

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36
Q

what can we determing from net PP

A

amount of C available for phytoplankton growth in higher trophic levels**

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37
Q

how can we measure net PP with a pure phytoplankton culture

A

bottle exposed to sunlight

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38
Q

how can we measure gross PP with a pure phytoplankton culture

A

use bottle kept in the dark to measure repiration, add that value to the value obtained from the light bottle measuring net PP

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39
Q

how come the light/dark bottle method doesn’t work for measuring phytoplankton net PP in situ?

A

because the respiration occuring is not only coming from phytoplankton, it also includes plankton respiration

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40
Q

how can we measure PP at sea?

A

adding radioactive carbon 14C to the bottle at a given ratio to C
phytoplankton become labelled with 14C

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41
Q

why do we let bottle sit for 24 hours when measuring net PP with 14C?

A

to allow for some respiration of organic 14C to occur

42
Q

how can we measure net PP at sea?

A

radioactive carbon insert left for 24 hours
can keep at different light intensities

43
Q

how can we measure gross PP at sea?

A

radioactive carbon insert left for 4 hours
can keep at different light intensities

44
Q

why do we let bottle sit for only 4 hours when measuring gross PP with 14C?

A

to avoid respiration of organic 14C fixed

45
Q

how do we measure phytoplankton respiration at sea

A

hourly gross PP - hourly net PP

46
Q

what is the usual unit used when considering gross/net PP and respiration

A

mol C/ L h

47
Q

what units does depth integrated net PP use

A

mol C/m^2 time

48
Q

how is photosynthesis divided into two reactions?

A

light reaction
dark reaction

49
Q

light reaction definition and formula

A

generates energy and O2
2H2O + light <—> H(ATP) + e-(NADPH) + O2

50
Q

dark reaction definition and formula

A

uses energy to fix inorganic carbon into useful molecules (sugar)
CO2 + H(ATP) + e-(NADPH) <—-> CH2O +H2O

51
Q

characteristics of light reaction?

A

light dependent
water splitting
O2 releasing
high energy electron transfer
NADPH and ATP producing

52
Q

characteristics of dark reaction?

A

light independent
uses ATP and NADPH
fixes CO2 to form carbohydrates htrough the calvin cycle
endergonic, reduction reaction

53
Q

where does photosynthesis occur in the cell?

A

chloroplasts

54
Q

where does respiration occur in the cell?

A

mitochondria

55
Q

where do light reactions happen in the chloroplast?

A

lumen of the thylakoids

56
Q

what is a granum

A

stack of thylakoids

57
Q

where do dark reactions happen in the chloroplast?

A

stroma

58
Q

what is the stroma?

A

fluid inside chloroplasts but outside the thylakoids

59
Q

what structures does the light reaction use in the chloroplast?

A

photosystem II then I

60
Q

what structures does the dark reaction use in the chloroplast?

A

calvin cycle
RubisCO

61
Q

how does the lumen facilitate light reactions?

A

with high [H] concentration creating electro and chemical gradient

62
Q

in what order are light reaction products occuring?

A

oxygen (water splitting) —-> ATP (PS II) —-> NADPH (PS I)
lower to higher energy

63
Q

what wavelengths do phytoplankton prefer absorbing? why?

A

shorter wavelengths (blue, green), means higher energy
because there is more of it that penetrates into the ocean

64
Q

main photosynthetic pigments?

A

chlorophylls
carotenoids

65
Q

what light do cartenoids absorb/transmit?

A

blue/green —–> yellow/orange/red

66
Q

what light do chlorophylls absorb/transmit?

A

red/blue —-> green

67
Q

how is photon energy released/transformed by phytoplankton?

A

fluorescence
resonance transfer
photochemistry (reduction/oxidation)

68
Q

why does chl a have two absorbance peaks at blue and red?

A

blue photons captured are re-emitted in fluorescence as red, chla can capture these red photons again

69
Q

what pigment do all phytoplankton have?

A

Chl a

70
Q

what are accessory pigments?

A

allow phytoplankton to use a broader range of the light spectrum

71
Q

what is a PU

A

photosynthetic unit

72
Q

what does a photosynthetic unit do?

A

antenna harvests light with pigment molecules and funnels energy to the chlorophyll a (and protein complex) molecule in the reaction center

73
Q

what pigment is the only one involved in electron transfer?

A

chla, that’s why it’s in all phytoplankton

74
Q

what are some functions of accessory pigments?

A

allow use of broader spectral range
funnel energy to the reaction center and harvest more light
some deal with excess energy and prevent photo oxidation

75
Q

how can phytoplankton adjust to low light?

A

increase size of antenna
increase numbe rof photosynthetic units (

76
Q

what phytoplankton typically have more accesory units?

A

low light adjusted ones

77
Q

what is a PE curve

A

photosynthesis as function of light intensity
AKA irradiance curve

78
Q

why does net PP PE curve not pass through the origin?

A

since respiration is included, there is a compensation light intensity

79
Q

what is a compensation ligh intensity (Ic)

A

intensity of light where we see equal levels of photosynthesis and respiration, therefore Net PP = 0

80
Q

what ligh intensity is the compensation ligh intensity usually?

A

10 microE/m^2 s

81
Q

what type of PP PE curve crosses through the origin? why?

A

gross PP, no respiration is considered, so when there’s no light, there’s no photosynthesis

82
Q

how can we represent the rate of photosynthesis?

A

slope of the PE curve
photosynthesis change / irradiance change = alpha

83
Q

how do we normalize photosynthetic efficiency to chla biomass?

A

divide it by amount of chla

84
Q

what is the maximum rate of photosynthesis?

A

light intensity where rate of photosynthesis levels of (Pmax)

85
Q

what is photoinhibition?

A

when phytoplankton get too much light and begins to damage photosystems (beta)

86
Q

what is Ki

A

light irrandiance at 50% of max rate of photosynthesis

87
Q

what is common in irradiance curves of phytoplankton adapted to low light

A

higher photsynthetic rate at low light (higher slope)
lower maximum rate of photosynthesis

88
Q

what happens to Pmax at higher temperatures?

A

increases

89
Q

what happens to Pmax at higher nutrient levels?

A

increases

90
Q

what happens to photosynthetic rate (a) at higher nutrient levels?

A

increases

91
Q

what happens to photosynthetic rate (a) at higher light levels?

A

decreases

92
Q

what ocean do we usually see higher levels of photosynthetic rate (a)

A

temperate and polar regions** (check polar part)

93
Q

what is the depth integrated Net Primary Productivity?

A

equation for finding productivity anywhere in the ocean using satellits and argo floats

94
Q

what is compensation depth?

A

depth where we find the compensation light intensity

95
Q

what can we observe happening above the compensation depth?

A

positive net PP, R is lower than PS

96
Q

what can we observe happening below the compensation depth?

A

negative net PP, R is higher than PS

97
Q

what allows phytoplankton to experience a range of light intensities?

A

movement through the mixed layer

98
Q

what is Id

A

average light level experienced by the cells as they move in the mixed layer

99
Q

what is the critical depth? (Dcr)

A

the depth at which the light that mixed phytoplankton are experiencing is equal to the compensation light level
zero net PP

100
Q

what causes phytoplankton biomass to increase in terms of their mixing depth?

A

when the mixing depth is higher than the critical depth

101
Q

what do we need to know in order to predict a spring bloom?

A

temperature
salinity and density
light levels
all in the mixed layer

102
Q

what machine allows us to predict a spring bloom

A

argo floats, satellites

EOSC 372 (5 decks)

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