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Comprehensive exams > Comps > Flashcards

Comps Flashcards

1
Q

What are the major ions and what are their concentrations in sea water?

A 
Chloride (546 mM)
Sodium (469 mM)
Magnesium (52.8 mM)
Sulfate (28.2 mM)
Calcium (10.3 mM)
Potassium (10.2 mM)
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2
Q

What is the mixing time of the Ocean?

A

1000 years

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3
Q

What is the average temperature and salinity of the Oceans?

A

Average temperature = 3.5 C

Average Salinity = 34.7 ppt

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4
Q

When do we have the earliest record of Life?

A

3.9 billion years ago

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5
Q

What is the mean ocean depth?

A

4000 m

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6
Q

Describe the overall weathering process.

A

We have silicate rock up in the continent that react with carbonic acid (from CO2 + H2O), and start to alter the rock. The carbonic acid kicks out the Ca ions of the rock and dissolves the rock in some degree, producing Ca ions and Silica in solution and bicarbonate, abundant in river water. Drains into the oceans from the continents all the time. Those component run into the sea and build up and precipitate in the ocean biologically in the form of calcium carbonate and silica used for shells

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7
Q

What is production?

A

Production is an increase in biomass due to the addition of new organic matter into organisms

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8
Q

What is productivity?

A

Productivity is the RATE of production

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9
Q

What is the source of electrons for oxygenic photosynthesis?

A

WATER

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10
Q

What constitutes the “light reactions”?

A

The conversion of lift energy into ATP and NADPH

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11
Q

Do you get twice as much photosynthesis out of a blue photon than a red photon?

A

NO, the number of photons matters

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12
Q

Describe briefly the “light reactions”

A

At the thylakoid membrane, light comes to P680, water gets split, electrons go off through the b6f complex, along the way what it really happens is that protons get pumped across the membrane, to make a proton gradient. The electron comes to P700, there is more light energy, electrons get handed off to NADPH. These protons get formed in the lumen and are used by an ATPase to convert the energy that is in that proton gradient into ATP.

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13
Q

What other pigments other than chlorophyll are there and why are they so important?

A

Carotenoids and Phycobiliproteins. These are important because they can absorb green to orange light that dominates in natural waters. One advantage of having these pigments is that plankton can adjust how much antenna pigments it makes relative to each photosynthetic reaction center so it can adjust its ability to capture light to suit the environment

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14
Q

What is the main connection between light and dark reactions?

A

ATP and NADPH produced in the light reactions are used by the dark reactions to fix inorganic carbon to organic carbon

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15
Q

How does CO2 get fixed?

A

It gets fixed by being reduced and added to a sugar called Ribulose-1.5-biphosphate by the enzyme RuBisCO. The rest of the dark reaction cycle is to produce again that sugar. The cycle has to go 6 times to make 1 glucose molecule

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16
Q

Describe a typical P vs. E curve

A

-At zero light, zero photosynthesis
-As you add more light, the rate of photosynthesis increases, that part of the curve is where photosynthesis is light-limited
-The rate of the entire system is determined by the rate of the light reactions
-If we add more light, the curve starts to bend over, the rate does not longer increase with more light
-the dark section has hit their limit. The system goes as fast as it can, the dark reactions cannot use anymore ATP and NADPH than they can use
-If you keep adding more light the rate of photosynthesis starts to decline
-Photoinhibition occurs which happens because the light reactions are still capturing light, still trying to process electrons but there is nowhere for the electrons to go because the dark reactions are not using ATP and NADPH fast enough, so the electrons are backing up and they get handed off to an O2 molecule and make a reactive oxygen radical, that damages the cell.
More damage than more repair = Photoinhibition

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17
Q

Why is there a chlorophyll maximum?

A

A deep chlorophyll maximum is caused by the lack of light at depth, therefore the amount of chlorophyll produced by phytoplankton at that depth is maximized

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18
Q

What is the ionic strength of seawater?

A

0,7

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19
Q

What is a typical pH value at the surface of the ocean?

A

8.2

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20
Q

Why is the pH in the North Pacific lower?

A

pH gets lower because water is older and reactions, such as respiration has had more time time to be expressed

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21
Q

What is the relation between photosynthesis and respiration with pH?

A

Respiration brings pH down (more CO2)

Photosynthesis brings pH up (utilization of CO2)

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22
Q

What is the Michaelis-Menten kinetics?

A

It described enzymatic processes using two parameters Ks and Vmax

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23
Q

What is the Monod Kinetics?

A

It describes growth in terms of outside nutrient concentration

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24
Q

What can a phytoplankton do to increase nutrient acquisition?

A

Phytoplankton could express genes encoding enzymes required to use a different form of the nutrient (e.g ammonium, urea, organic N instead of nitrate, organic Pninstead of phosphate)

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25
Q

Describe the Michaelis-Menten curve

A
  • The rate increases with increasing substrate concentration for a while, therefore in the first part of the reaction the is a substrate concentration limitation
  • At some point the curve starts to bend over and the rate of the reactions starts reaching a maximum. This is limited by the amount of enzyme
  • Ks is often described as the affinity of an enzyme for its substrate
  • The lower the Ks, the lower the half-saturation concentration, THE HIGHER THE AFFINITY THE ENZYME HAS FOR ITS SUBSTRATE.
  • A lower Ks means a higher affinity
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26
Q

In the Nitrogen cycle what is the most reduced and most oxidized molecule?

A

Most reduced = NH4

Most oxidized = NO3

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27
Q

What happens in nitrification?

A

Nitrifiers use NH4 for energy and produce NO3

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28
Q

What does a dinitrifier do?

A

Uses NO3 as an electron acceptor and goes from NO3 to N2 gas

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29
Q

What are the necessary properties for an ion to behave as a conservative component in seawater?

A

Ions behave as a conservative component if they do not react or are being taken up in biological or physical processes. We know if they are conservative if their residence time is longer than the mixing time of the ocean (around 1000 years)

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30
Q

How are Zooplankton categorized by size?

A
  • Femptoplankton =
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31
Q

What is the solubility pump?

A

Physical interactions between the Ocean and CO2 gas (e.g. Temperature)

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32
Q

Gases tend to be more soluble is cold water. (True/False)

A

TRUE

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33
Q

What are the typical concentrations of oxygen in the surface water of the ocean?

A

Between 200 and 400 umols per liter depending on the temperature. Higher temperature lower oxygen concentration

34
Q

What happens with the oxygen, phosphate and DIC as we move out of the North Atlantic to the North Pacific following the global circulation?

A

As we move from a high oxygen to a low oxygen (oxygen is being used up), stoichiometrically I’m producing phosphate. The same for DIC although DIC is not only respiration but also calcium carbonate dissolution.

These are stoichiometric models that we use together with the circulation has model.

35
Q

How does molecular weight of a gas affect its solution?

A

Solubility increases with molecular weight! The bigger and heavier the gas the more of it goes into solution

36
Q

How does salinity affect solubility?

A

Gases are less soluble in a solution when there is salt in the solution

37
Q

Where is CO2 coming out and coming in, in the global oceans?

A

Coming out in upwelling regions, specially the cold water tongue in the eastern tropical pacific and the tropics. Coming in at higher latitudes. Lots of temporal variability due to seasonality (winter vs summer)

BUT OVERALL ITS COMING IN AT 1 Pg C/yr

38
Q

What is alkalinity?

A

Is a measure of how the water and its composition can neutralize protons, neutralize acids that are introduced into the system

39
Q

How does carbonate alkalinity work as a buffer in the ocean?

A

As you add acid the pH of the water stays constant (8.2). That is because the acid you are adding is interacting with HCO3 and CO3. And then as you use up the last carbonate and bicarbonate ions in the solution, the pH changes fast.

40
Q

Does photosynthesis affect alkalinity?

A

No, photosynthesis affects pH by taking up CO2 but not alkalinity since it does not involve a CHARGED species

41
Q

Where is total CO2 lower and higher in the oceans and why?

A

Total CO2 is lower in the Atlantic below 1000 m depth, compared to theories oceans, with the Pacific having the highest total CO2.

Atlantic water is the youngest and Pacific the oldest, which means all the reactions that are occurring in the oceans tend to be expressed more dominantly at the bottom of the Pacific.

42
Q

How does the biological pump work?

A

For the top to the bottom, the biological pump is taking up CO2, putting it into particles, those particles are falling through the water, being remineralized, CO2 is being released back into solution, but it can’t go out, because it is not near the surface so it just builds up in the water

43
Q

How does alkalinity go up at the same time total CO2 goes up?

A

Because of the carbonate part of the system!!! That is the CaCO3 coming from the surface and dropping through the water column and dissolving, releasing charged species, therefore increasing alkalinity!

44
Q

During CaCO3 precipitation, what happens to the alkalinity, SumCO2, pCO2 and pH?

A

Alkalinity DECREASES (you’re taking charged species out HCO3-)

SumCO2 DECREASES

pCO2 INCREASES (forms CO2 gas)

pH DECREASES

45
Q

During calcium carbonate dissolution, what happens to alkalinity, pH, SumCO2 and pH?

A

Alkalinity INCREASES (releasing charged species)

SumCO2 INCREASES (produced 2 HCO3-)

pCO2 DECREASES (using CO2)

pH INCREASES

46
Q

How does temperature and salinity affect solubility of aragonite and calcite?

A

As it gets warmer the solubilities of calcite and aragonite go down!!

They are more soluble when is colder! At the bottom is colder so they become more soluble as they go down in the after column.

Also, as salinity goes up, solubility of calcium carbonate goes up due to ion pairing

47
Q

Does pressure affect dissolution of calcite and aragonite?

A

YES, the higher the pressure the more soluble they are. So as they go down and temperatures go down and pressure goes up, they really become soluble, specially the aragonite which is 2.5 times more soluble than calcite

48
Q

Explain what happens to calcium carbonate in the water column in terms of precipitation/dissolution..

A

The surface ocean is warm and supersaturated with CaCO3. So, it is easy to precipitate for organisms. As it falls out through the water column, as part of the biological pump, the carbonate minerals get to colder water, higher pressure, and the CO2 is going up because of the aerobic metabolism, so the pH is getting lower. Carbonate minerals her under saturated at depth. As we get into the bottom sediments it gets supersaturated again due to high alkalinity through the release of HCO3 by bacteria

49
Q

What is the Carbonate Compensation Depth?

A

Carbonate Compensation Depth: rate of supply = rate of dissolution

50
Q

What Kong of Important reactions occur is the hydrothermal vents?

A

Redox reaction! For example Mg is taking up by reaction with basalt and water, protons are being used, alkalinity is decreasing since HCO3- is being used up

51
Q

What is the intermediate disturbance hypothesis?

A

The Intermediate Disturbance Hypothesis (IDH) suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct.

52
Q

What are the environmental conditions at the deep sea benthos?

A

Conditions have been constant over the las 8000 years.

Temperatures are below 3C but not below 0C.

Oxygen usually near saturation >4mg/L

Pressure between 300 and 600 atmospheres

53
Q

How does the deep sea benthos depend on surface production?

A

Deep sea benthos depend on food falling from productive layers.

Only 1-2% of surface production reaches abyssal plains, but accumulates at the sediment-water interface providing a relatively rich resource

54
Q

Why does biodiversity matter?

A

Ecosystem characteristics (e.g. Biomass) will tend to be more stable as biodiversity increases

Ecosystem functions (e.g. Primary production) will tend to be greater and less variable as biodiversity increases

Ecosystem functions depend not only on biodiversity in one part of a community, but also on interactions between communities within the same system

55
Q

What is the ecosystem function of bacteria?

A

Getting DOC back into the system!

56
Q

What is the respiratory quotient?

A

CO2 released per oxygen consumed

57
Q

In terms of CO2 gas exchange at the surface, what are the consequences of having wi d at the surface?

A

More CO2 uptake because boundary layer gets thinner

Entrainment of water due to waves, bringing Gas into solution with depth

Latent heat loss, so water gets colder increasing gas solubility

Piston velocity increases

58
Q

Does salinity affect gas solubility?

A

YES! Gases are less soluble at higher salinities

59
Q

How do chemolithoautotrophs work?

A

They use energy from oxidizing sulfide and other reduced compounds to produce ATP and NADPH. And then they use ATP and NADPH to fix carbon in a system that is analogous to the dark reactions

60
Q

What is bacterial growth efficiency?

A

It is defined as:

Bacterial production/total production and respiration

50% of growth efficiency means that half the C taken up is incorporated into new biomass, and the other half is respites back to inorganic C

61
Q

What is the Burial Efficiency?

A

Is the proportion of POC arriving at the bottom that gets sequestered below the bioturbation limit

13% near continental margins

2% in the open, oligotrophic oceans

62
Q

What are the electron acceptors below the oxic zone in the sediments?

A

Nitrate

Manganese

Iron

Sulphate

Methane

63
Q

What happens when organic carbon reaches the bottom?

A

Organic C reaching the sediment-water interface it’s being broken down while it is in the bioturbation zone. If it gets below that, then it gets deposited. Oxygen respiration using O2 near the surface. Then there is a variety of different electron acceptors ending up with the major one, SO4 respiration in the reduced zone of the sediment.

The returned products to the water column are N2 gas from dinitrification, and all the other products of remineralization, CO2, NH4+ and HPO4, which contribute to the enriched waters in the deep ocean. Ammonium gets converted to NO3-

64
Q

If you mensure C14 of a plankton sample and it has a positive value, what does it mean? What does it mean if it is negative?

A

It means it was formed after the bombs were set off, it has bomb carbon in it

If the value is negative, it was formed either from old carbon or it is “repackaged” carbon

65
Q

What does it mean if a sample has a -100 C14 value?

A

It means it was formed either from old carbon or is repackaged carbon

66
Q

Why did we have, after 1800, lower values of C14 than most of the time before?

A

Because of the burning of very old carbon and fossil fuels!

If you take carbon from coal and oil there is no C14 in it, it is millions of years old. The C14 has since decayed away. And now you burn that, and you add that “dead carbon” into the ecosystem, into the atmosphere, and it dilutes the natural C14, makes it look like it has decayed a little bit, but it did not decay at all, it just got diluted

67
Q

Why did we start to have high values of C14 after 1960s?

A

C14 reintroduced by bomb carbon

68
Q

Why is the C14 value of coral lower (older) than in the atmosphere?

A

The ocean’s CO2 in the surface is a little bit old, it has a residence time there, so it is always a little bit offset. There is a time of mixing and a time of residence, there is upwelling, bringing up deep water that has lower C, etc

69
Q

Why did the C24 value in the atmosphere go down so fast after he bombs were set off?

A

Because he ocean is up taking it in through the solubility and biological pumps.

70
Q

Tules of Isotope Fractionation

A
  • Bonds formed by light isotopes are more readily broken than bonds involving the heavy isotope
  • Molecules involving the light isotope react more readily than those involving the heavy isotope
  • For a given energy of the system, molecules with the light isotope (lower mass) have higher translational velocities than those with the heavy isotope and so diffuse preferentially in solution, in a gas across a membrane
  • in a phase change, molecules with the light isotope favor the higher energy phase (gas>liquid>solid)
71
Q

Is there any isotope fractionation of Carbon by aerobic respiration and CaCO3 precipitation?

A

Respiration has no Carbon fractionation and CaCO3 has almost no fractionation as well

72
Q

How is the isotope fractionation with water evaporation/precipitation?

A

When we precipitate water from the atmosphere as rain it is heavier and when we evaporate it is lighter (+-9)

73
Q

Is there isotope fractionation of Oxygen during respiration?

A

During respiration there is a fractionation of Oxygen of -20 which mean that aerobic organisms preferentially use the light oxygen molecule

74
Q

What happens with fractionation during the hydrological cycle?

A

As we move for the low latitudes (tropics) to high latitudes the hydrological cycle supplies lighter and lighter precipitation to the places that are away from the source

75
Q

What is the Reyleigh destilation?

A

Lighter isotopes evaporate faster than heavy isotopes. In the ocean, the water gets heavier when rain gets stores as ice on lansheets

76
Q

What happens when you measure &O18 in the oxygen minimum zone?

A

In the minimum oxygen zone, the &O18 gets heavier, because organisms use preferentially lighter oxygen isotopes. Thus, the concentration of Oxygen in the gas phase in the ocean and the &O18 values are a mirror image

77
Q

What happens with the &C13 values in the water column?

A

The &13C composition starts at a high value because at the surface photosynthesis uses preferentially lighter isotopes. Then it gets lighter during respiration in the water column, specially in the O2 minimum zone. It gets a little higher deeper due to CaCO3 dissolution

78
Q

What are the sources of Iron in the ocean?

A

Rivers and Groundwater

Resuspension of particles from sediments

Upwelling deep water

Hydrothermal and tectonic activity

Atmosphere deposition (les than 10% is soluble)

79
Q

What are the main heat fluxes at the surface?

A

Shortwave Radiation (coming in)

Longwave Radiation (going out)

Latent heat (going out)

Sensible heat (in and out)

80
Q

Where are the different heat fluxes maximum and minimum?

A

Shortwave radiation is maximum at the tropics and minimum at the poles

Longwave is always negative (out) and is most negative at the tropics and subtropics

Latent is always negative (out) and the the most negative of all (highest heat loss). It is the most negative in the subtropics

The net heat flux is positive in the tropics (heating) and mostly negative anywhere else

Comprehensive exams (2 decks)

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