This summary includes all the content that is needed for the "Chemical Oceanography" exam II of paleoceanography. It includes all lectures, online materials, and Archer. All lectures are given by Prof. Caroline Slomp
Paleoceanography summary exam II
Spatial and temporal variability → be careful when extrapolating from sediment core to whole
ocean. Differences in paleogeography and types of organisms (evolution)
CaCO3 = calcium carbonate (solid phase)
HCO3- = bicarbonate (dissolved)
CO32- = carbonate (dissolved)
H2CO3 = carbonic acid
NO3- = nitrate
NH3 = ammonium
CaSiO3 = silicate bedrock
H4SiO4 = Si(OH)4 = dissolved silica = silicic acid
SiO2nH2O = Biogenic silica = biogenic opal
Si = silicate (element)
Silicate = compound/ion containing SiO4
Organic matter production
- Production in the surface ocean
- Sinking flux of OM into deeper waters
- Dissolved OM: leaks from organisms, acts as a solute
- Photosynthesis in Euphotic zone = layer where light is present
- All phytoplankton need N and P
In sea water: ammonium (low C, converts to nitrate) and nitrate
Depth profiles
- Low but important concentrations
- Low in surface waters → there they are taken up
- Higher in intermediate→ flux of OM into deep water, nutrients released again
- Less release in the deepest areas
Biological pump = biological processes bringing carbon to the ocean’s interior
,Degradation of OM = remineralization and regeneration
Euphotic zone:
- inorganic carbon → OM : nutrient consumption and oxygen production.
- OM degrades below euphotic zone, little OM makes it to the sea floor
- Some OM recycled in euphotic, some settles (by gravity) to ocean interior
Ocean’s interior:
- recycled in thermocline and deep waters : oxygen consumption and CO2
- Some buried as OM, some released as CO2 in deep waters.
OM recycling
Average Marine OM
Redfield ratio 106:16:1
Redfield composition (CH2O)106(NH3)16H3PO4
Phytoplankton build in N and P in OM at a constant ratio
This is average, can vary depending on species and environmental conditions
Redfield ratio of sea water
Stoichiometry of OM production
Stoichiometry = quantitative relationship between elements in reactions or materials
, - Including nutrients, more water is taken up and more oxygen is produced
- Conversion of nitrate into ammonia → produces oxygen.
- OM more complex than CH2O → need less water and produce more oxygen when OM is
formed.
- True average: Ratios differ per carbohydrate → lipids and proteins have different ratios
Know simplified by heart, complicated ones not.
Phytoplankton = micro-organisms capable of photosynthesis
Primary producers → fix carbon.
Not secondary producers = heterotrophs (produce OM based on uptake of OM)
Separation → metabolism
- Autotrophs = harvest light or chemical energy to produce OM (and release oxygen)
- Photo(auto)trophs = use light
- Chemoautotrophs = use chemical energy (e.g. sulphite and oxidize)
Separation → size
>20k species
- Pico : 0.2-2 μm
- Nano : 2-20 μm
- Micro : 20-200 μm
Size matters:
- Living
o Small: few nutrients. Open gyres. Oligotrophic ocean. Warm water. Low production.
o Nano and micro: high nutrient availability, high production, coastal zone, upwelling
- Sinking speed
o Larger : sink out of euphotic zone more easily, less recycling
- Eat:
o Smaller → more easy to eat
Picophytoplankton
- Very small, important, efficient nutrient uptake
- Live at low nutrient concentrations, open ocean, cannot fix nitrogen from atmosphere
, - Unicellular autotrophic cyanobacteria: Synechococcus and Prochlorococcus
Larger algae → need to know these!!!! (nano and micro, large, inefficient nutrient uptake)
responsible for much OM production
Diatoms
- Silicate shield: SiO2
- First to bloom
Coccolithophorids
- CaCO3 shields
- Reduced light, later blooms, warmer waters
Dinoflagellates
- Cellulose (theca)
- Motile, coastal areas, red tides, mixo and heterotrophs (no theca)
Phaeocystis
- Massive blooms in e.g. north sea
- Produce dimethyl sulphide (DMS) → gas released in atmosphere.
- Climate impact → forming cloud condensation nuclei
- Foam on beaches upon decay of the algae after a bloom
Cyanobacteria: Trichodesmium
- Lives in solitude or colonies
- Diazotroph: Fixes N from atmosphere and convert to NH3, does not need nitrate
- Nutrient-depleted environments in open ocean: important in (sub)tropical regions
Zooplankton grazing
- Impact amount of phytoplankton
- Waste products → droppings can sink → important for biological pump
- Release of ammonium
- Prefer nitrate instead of ammonium → less energy (no conversion needed). Help recycling of
nutrients
Pteropods : aragonite (CaCO3)
Foraminifera : calcite (CaCO3)
Ciliates : eat pico
Copepods : eat micro (couple of mm large)
Factors governing OM production
P = R B f (nutrients, CO2) f (light)
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