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Marine Chemistry Flashcards

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1
Q

Name 7 physical properties of H2O and their importance!!!

A

Polarity: relatively high // strong dissolver of polar substances

Heat capacity: highes of all liquids (except NH3) // prevents rapid fluctuations in T

Latent heat of fusion: Highest of all solids & liquids except liquid NH3 // Heat transfer at poles

Latent heat of evaporation: highest of all substances // heat transfer & precipitation

Thermal expansion: 15% greater than mercury // sea level rise

Suface tension: highest of all liquids // capillarity in plants & trees, drop formation

Transparency: High // Photosynthesis

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2
Q

What are five effects of adding salt to H2O?

A
  • increases density (from 1gxcm-3 -> 1.028gxcm-3)
  • lowers freezing point (from 0°C to -1.9°C)
  • elevates boiling point (100 -> 100.6°C)
  • increases electrical conductivity
  • increases its viscosity
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3
Q

In one kilogram seawater, whats the salinity?

What is the range?

A

34.8 g salinity + 965.2 g seawater

34 - 37 ppt

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4
Q

What are the major constituents of water?

A

Chloride (Cl-) - 19.2 g

Sodium (Na+) - 10.62 g

  • Sulfate (SO42-) - 2.66 g
  • Magnesium (Mg2+) - 1.28 g
  • Calcium (Ca2+) - 0.40 g
  • Potassium (K+) - 0.38 g
  • Other - 0.25 g
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5
Q

How can you measure the salinity?

A
  • By measuring the density with floating hydrometers
  • Measure Chlorinity = measures. directly proportional to salinity
  • measured by no. mol Ag1+ required to precipitate Cl-, Br-, I- in 1kg seawater x atomic mass Cl-*
  • CTDs: conductivity / temp / depth
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6
Q

Which factors influence salinity?

A
  • evaporation + freezing increase salinity
  • rainfall + runoff + snowmelt reduce salinity
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7
Q

Define chemical equilibrium

A

there is no net change over time in the chemical activities or concentrations of reactants and products.

The point at which this occurs is influenced by salinity

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8
Q

Define Ionic strength

A

influence of ions in a solvent on solubility
= total concentration of ions i n a solution

I = 0.5 Summe ( mi zi2 )

M = molality; concentration in mol x kg<sup>-1</sup>
z = ion charge / valence
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9
Q

What is the importance of the ionic strength?

A

Ionic Strengh increases = increase in charged particles in H2O

–> solubility of polar substaces and proteins increases (to a point)

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10
Q

Difference between chemical equiibrium dependent on ionic strength

A

Ionic Strength = 0
K can be determined from concentrations of products & reactants. dissolved substances behave “ideally”: aA + bB ⇔ cC + dD
can ignore influence of dissolved ions + determine equilibirum pointas Keq = [C]c[D]d / [A]a[B]b

Ionic Strength > 0
{} = ion activity, total concentrations must be corrected by ionic strength effects to work out the equilibrium point
Keq = {C}c{D}d / {A}a{B}b

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11
Q

Define the term photic zone

A

part of the water colun which is illuminated by sunlight

–> upper 100-200 m depending on water clarity.

all photosynthesis occurs within this zone

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12
Q

What are the light zonations in the ocean?

A
  • photic zone: enough light to support photosynthesis
  • 100-200m*
  • disphotic: measurable levels of light, insufficient for PS
  • 200m - 1000m*
  • aphotic: no measurable light
  • > 1000m*
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13
Q

Different wavelength penetrate to different depth

-> effect on color visiblity?

A

first: red

orange

yellow

green

violet

blue

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14
Q

What is the “Gran method” 1920’s

A

test for primary production in dependence of light availablity.

Have clear/ dark bottles in different depths to check net PS measured by O2 gain and respiration by O2 loss

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15
Q

Without accounting for scattering:

What is the light attenuation in seawater?

A
  • light is attenuated exponetially thorugh the water columns

IZ = I0 exp(-Kd dz)
– Iz [W m-2] is the light at a depth z, dz [m] below I0
– I0 [W m-2] light at top of the water column
– Kd [m-1] is the attenuation coefficient
What are the light levels at depths of 1, 10 and 100
metres if the surface light is 100 W m-2, and the
attenuation coefficient, Kd is 0.1 m-1 ?

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16
Q

How much of the red light is absorbed in the top 1m ?

A

45%

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17
Q

different wavelength have different attenuation coefficients Kd

what is the attenuation coefficient dependent on?

A
  • attenuation of pure water
  • concentration of total suspended solids
  • concentration of chlorophyll
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18
Q

How can the light attenuation be measured?

A

- light meter

- Secchi disk
kreisförmige Blechscheibe mit vier Sektoren schwarz und weiß. An der Oberseite wird im Mittelpunkt ein Seil mit einer Längenmarkierung befestigt. Diese Scheibe wird in waagrechter Lage im Gewässer abgesenkt und dabei bis zu ihrem visuellen Verschwinden beobachtet. Die Tiefe des Verschwindens wird an der Maßteilung des Seiles abgelesen und als „Sichttiefe“ oder „Secchi-Tiefe“ zs registriert.
In ungefähr doppelter Sichttiefe ist vielfach die Grenze der positiven Photosynthesebilanz erreicht (Assimilation > Dissimilation)

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19
Q

Define Biogeochemical Cycle

A

transport and transformation of elements or compounds as a result of biological, chemical and geological processes.

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20
Q

definition closed system

A

new nutrients are not added to the system and must be recycled

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21
Q

3 facts about the global carbon cycle

A
  1. predominantly a gaseous cycle
  2. CO2 the main vector linking atmosphere, oceans and terrestrial habitats
  3. Carbon is the currency in which energy is stored in food webs
    predominantly enters food webs from bottom up (used in photynthesis)
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22
Q

Draw a simplified version of the global carbon cycle

A

red: annual changes

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23
Q

Name two carbon pumps

A
  • biological pump
  • physical pump
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24
Q

where are the largest carbon depots

A
  1. deep ocean inorganic: 37’890
  2. soil: 1’500
  3. upper ocen inorganic: 920
  4. atmoshpere: 750
  5. deep ocean organic: 700
  6. terrestrial vegetation: 610
  7. shelf and slope waters: 310
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25
Q

where do we have negative carbon fluxes

A

negative flux = sink = more in than out:

  1. athomsphere: +3.3
  2. deep ocean inorganic: +1.6
  3. Upper Ocean inorcanic: +0.4
  4. terrestrial vegetation: +0.1
  5. shelf and slope waters +0.05
  6. sediments +0.05
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26
Q

What’s the percentage in the atmosphere / sobulity (ml/L) / seawater concentration

N2

O2

Ar

CO2

A
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27
Q

On which two processes relies the physical carbon pump on?

A

is the movement of C between the deep and shallow open water

  • enhanced solubility of CO2 in cold water
  • upwelling of deep water at the equator

• CO2 more soluble in cold than warm water (i.e. more soluble at the poles than the tropics)
• At the poles CO2 is ‘pumped’ from atmosphere to ocean
• Cold, dense water sinks taking CO2 to the deep ocean
& flows at depths to equatorial latitudes (thermohaline
circulation)
• Deep water up-wells in equatorial latitudes, as it warms
CO2 solubility drops and outgases to the atmosphere

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28
Q

Explain the biological pump

A
  • changes in the biological pump = 0
  • biological carbon linkage between ocean surface and deep ocean

in upper ocean biology: photosythetic planktion fix carbon

  • in deep ocean: dead planktion with organic c arbon sinks to the seafloor
29
Q

What are the interactions between the biological & physical pump

A

upper ocean: CO2 incorporated into food chains via PS (pfeile gegenseitig)

deep ocean: dead organic matter is remineralized by bacteria
einseitiger pfeil in richtung physical pump.

30
Q

Continental shelf-pump

A

• Shallow waters tend to be cooler than the open ocean (due to evaporation etc.)

• CO2 is more soluble in cool, dense water (remember the solubility
pump)

• Dissolved CO2 is incorporated into food webs

• Organisms die & sink to seafloor, organic C carried offshore
(remember the biological pump)

• Estimated global capacity ~ 1 Gt C.yr-1

31
Q

What is the antrhopogenic input?

A

coal deposits = C sink

but through human activities this C is liberated from this sink and pumped into the atmosphere

32
Q

what is the potential human impact on biological pump?

A
  • increase T of ocean surface –> less ocean mixing
  • less ocean mixing –> less nutrients brought up from deep water
  • less strength of biological pump removing CO2 from atmosphere
  • A positive feedback as more CO2 also increase rate of this process
  • Warmer planet will have more droughts.
  • More dust with trace nutrients gets from land gets to ocean
  • more trace nutrients –> more strength of biological pump removing more CO2 from atmosphere.
  • more CO2 results in more CO2 uptake into biological pump
  • A negative feedback
33
Q

what is the potential human impact on solubility pump?

A
  • *-> global warming predicte to**
  • increase SST
  • slow the thermo-haline circulation
  • -> solubility pump dependent on
  • -> CO2 more soluble in cold water
  • -> thermo-haline circulation

• CO2 released into atmosphere eventually enters ocean
• Saturation predicted by 2100 (Cox et al 2000)
• Saturation combined with reduced strength of
solubility pump could have huge consequences for
ability of ocean to store CO2
• Uncertainty surrounds predictions of fate of solubility
pump, but none of the possible outcomes look
particularly good…

34
Q

define pH

A

pH is equal to the negative logarithm of the concentration of hdrogen ions:

pH = -log10 [H+]

–> pH = 7 –> [H+] = 10-7 mol L-1

35
Q

How is Alkalinity measured?

A

Alkalinity of a solution is a measure of the negative ions present that can neutralise H+

36
Q

Alkalinity in seawater (include main ions in alkalinity equation)?

A

Seawater has a strong buffering capacity:

  • HCO3- = bicarbonate ion

CO32- = carbonate ion

OH- = hydroxide ion

H2CO3 = carbonic acid

–> Alkalinity = [HCO3-] + 2[CO32-] + [OH-] - [H+]

37
Q

Carbonate buffering system:

what happens if too acidic?

what happens if too basic?

A

too acid: CO32- + H+ → HCO3-

too basic: HCO3- → CO32- + H+

38
Q

What happens when CO2 is dissolved in seawater?

A

2 reactions:

  1. CO2 + H2O ⇔H2CO3
  2. H2CO3 ⇔ H+ + HCO3-

–> so if more CO2 is solved in the seah, the initial reaction is a drop in pH (due to more H1 ions)

Reaction to more H+ ions:

H+ + CO32- ⇔HCO3-

–> a drop in pH and reduction in carbonate. buffers the pH reduction, leading to only a small shift towards a lower pH.

39
Q

What heapens in ocean with rising atmospheric concentrations to

  • bicarbonate
  • carbonate
  • carbonicc acid
A
  • bicarbonate : HCO32- rises
  • carbonate: CO32- sinks
  • carbonic acid: H2CO3 rises
40
Q

What was the averag pH of surface oceans pre-industrial, what is it nowadays?

A

8.18 –> 8.07

41
Q

Estimation, if we do nothing to reduce carbon emissions

how much will the CO2 in atmosphere rise, how much will carbonate decrease and how much will the pH decrease

A

CO2: from 280 1750 -> 380 now -> 2001: **700 - 750 µatm **

  • *–> 50% decrease in carbonate
  • -> pH drop by 0.35
  • -> increase of 124% increase in H+**
42
Q

What are the consequences of a drop in pH?

A

1. animals that synthesis calcium caronate (CaCO3)

corals (10%)

* coccolithophores (70%)
= unicellular, eukaryotic phytoplankton (alga)*

–> major photosynthetic & calcifying systems in the ocean

  1. fish r**ely on CaCO3 otoliths (earstones)
    * **to navigate towards reef habitats -> struggle to find suitable reef habitats*
  • *3. predator-prey interaction**
  • limpets would produce thicker shells, when they sense preadators. not possible with low pH, so they run away*
43
Q

What is CO2 connected to calcification?

A

Calcification: drop in carbonate (as it is used as buffer to bicarbonate),

**Ca2+(aq )+ CO32-(aq) ⇔CaCO3 (s) **

–> acidification decreases amount of carbonate, slowing rate of calcification.

44
Q

what is the residence time?

A

the residence time is the amount of time an element spends in a given pool

residence time = (size reservoir) / (rate of addition by all processes)

45
Q

What is the residence time of atmosphreic CO2 and what of deep ocean inorganic CO2?

A

atmospheric CO2 = 4.6 years

deep ocean inorganic CO2 = 372.9 years

46
Q

Nitrogen Cycle:

  • where is N used
A

N used in AS, proteins, DNA / RNA

incorporated into chlorophyll used in photosynthesis

limiting nutrient, particularly in temperate marine ecosystems

complex biogeochemical cycle (as N can be found in many forms)

47
Q

What is the major sink for nitrogen?

A

the atmosphere in form of N2(g)

N2 compromises ~79% of gas in atmosphere

48
Q

Different forms of Nitrogen

A
49
Q

Which forms of N are available to organisms?

A

Nitrite NO2-

nitrate NO32-

ammonia NH3

50
Q

What is meant by nitrogen bottleneck?

A

that only few bacterial species can process N to usable forms

51
Q

what is nitrogen fixation?

how can it be achieved?

A

process of converting nitrogen to a useful form.

1. biotic: performed by bacteria

2. abiotic: lightning strikes

3. anthropogenic: haber process

52
Q

Elaborate on abiotic N-fixation

A

by lithning

responsible for ca. 8% global N fixation

N2(g) + O2(g) → 2 NO

53
Q

Elaborate on biotic N-fixation

A

mostly by bacteria on land - yet some species of cyonbacteria in oceans

→ bacteria associated with plant roots convert Nitrate to Ammonia NH3 and then to nitrates and nitrites

Nitrosomonas: NH3 → NO2

Nitrobacter: NO2 → NO3

54
Q

How are decompising plants used in N cycle?

A

decomposing plant material: batcteria produce ammonia

ammonia is then converted by bacteria back to nitrite and nitrate

or: plant tissues consumed by ^herbivores and enter food web

55
Q

What is meant by Nitrification + Denitrification?

A

Conversion of ammonia to nitrite and then to nitrate by microbes:

N2→ NH3 → NO2-→ NO3-

Denitrification:

NO3- → N2(g)

56
Q

Name a denitrifying bacteria species

A

Pseudomonas

57
Q

Explain the Haber-Bosch Fixation

A
  • carried out at high pressure & Temperature
  • fertilizer produced using catalysed reaction

N2(g) + 3H2(g) ==> 2NH3(g)

then NH3(g) is converted to a crystalline form.

58
Q

How many % of the world’s population is alive because of the Haber Bosch process?

A

40%

59
Q

Define Eutrophication

A

**Eutrophication **- “Eutrophication is defined as an increase in the rate of supply of organic matter in an ecosystem.” - Nixon, 1995

**Eutrophication **- “The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These typically promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Eutrophication is a natural, slow-aging process for a water body, but human activity greatly speeds up the process.” - Art, 1993

Eutrophication - “The term ‘eutrophic’ means well-nourished; thus, ‘eutrophication’ refers to natural or artificial addition of nutrients to bodies of water and to the effects of the added nutrients….When the effects are undesirable, eutrophication may be considered a form of pollution.” - National Academy of Sciences, 1969

Eutrophication – “The enrichment of bodies of fresh water by inorganic plant nutrients (e.g. nitrate, phosphate). It may occur naturally but can also be the result of human activity (cultural eutrophication from fertilizer runoff and sewage discharge) and is particularly evident in slow-moving rivers and shallow lakes … Increased sediment deposition can eventually raise the level of the lake or river bed, allowing land plants to colonize the edges, and eventually converting the area to dry land.” - Lawrence and Jackson, 1998

Eutrophic – “Waters, soils, or habitats that are high in nutrients; in aquatic systems, associated with wide swings in dissolved oxygen concentrations and frequent algal blooms.” - Committee on Environment and Natural Resources, 2000

60
Q

What is the result of excess N in estuaries?

A
  • *Eutrophication!**
  • accelerated production of organic matter (esp. algae) in a water body as a result of increasing nutrient inputs*

  • -> result in harmful algal blooms
  • > algaae consume dissolved oxygen leading to anoxic conditions
  • > fish kills
  • > destroy coral reefs*
61
Q

What is the coral-algal phase shift?

A

nutrient enrichment may lead to coral-algal phase shifts on tropical reefs:

  1. macroalgae are fast-growing species which typically benefit from increases in nutrients
  2. algae are able to grow rapidly by acquiring excess nutrients and may out-compete corals
62
Q

In which ways differs the phosphous cycle from the N and C cycle?

A

1. one of the slowest biogeochemical cycles
so slow that except across long time-scales P does not really cycle:
land → ocean → seafloor

2. phosphorus not found in atmosphere

3. bacteria do not play a major role…

63
Q

the phosphorus cycle, some main points

  • 4 to be precise -
A
  1. P often the ultimately limiting nutrient in marine and feshwater ecosystems
  2. essential nutrient for plants and animals
  3. used in photosynthesis (ATP and ADP)
  4. component of fats, cell membranes, bones and teeth
64
Q

in what form is phosphorus liberated from rocks?

A

as inorganic phosphate

PO43-

65
Q

Why is the phosphorus cycle slow?

A

due to the gelogical fluxes

-> phosphates from decomposing organisms in ocean is taken up within minutes by plankton!

66
Q

What are the sources of oceanic P?

A
  • *1. riverine inputs**
    • dominant source of inputs to ocean
  • mostly P2O4 from weathering of rocks
  • land use changes greatly increase riverine P*
  • *2. Atmosphere:**
    • accounts for < 1% P input
  • more important offshore away from rivers
  • no precise estimates of exact quantities*
  • *3. Volcanic processes**
    • eruptions release P4O10 and PO4
  • localized importance only*
67
Q

Sinks of oceanic P

A
  • *1. organic matter in sediments**
  • major sink is seafloor, reliant upon upwelling and gelogical uplift to return to surface waters*
  • *2. adsorption to iron particles**
  • complex chemical interaction with iron and colloidal material in estuaries. P absorbs to small iron particles making it un-available as nutrient. as ionic strength increases, P starts to redissolve maktin it available to organism*
  • *3. hydrothermal vents**
  • fluid coming from vents contains lots of iron -> binds P and takes it to the seaflor.*
68
Q

What have fish farms to do with phosphorus?

A

fish farms introduce much P to underlying sediments

-> eg 1 g fish tissue prodcued by 11 mg phosphorus

69
Q

What is the redfield ratio?

A

Ratio from N: P = 16:1

Marine Biology (3 decks)

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