Lecture 5 cards Flashcards
Formula for photosynthesis
6 CO2 + 6 H2O = C6H12O6 + 6 O2
How do we measure primary productivity
O2 evolution or C14 uptake
Which increases more with temperature, photosynthesis or respiration?
Respiration, resulting in decrease in net productivity and more carbon dioxide, negative feedback loop, decreased biomass in terrestrial systems also
Expected effect of 4C increase in temperature
20% increase in net primary production and 43% increase in oxygen consumption
Redfield ratio
106 C : 16 N : 1 P
Monod relationship
Formula for direct growth on substrate
Michaelis-Menten relationship
General enzyme relationship, how rapidly nutrients get into the cells
Droop relationship
Growth on internal substrate
Variable internal stores model
2 steps, uptake and utilization (view slide 34)
DIP
Dissolved inorganic phosphotous, HPO4(2-). This is what algae use.
N2
Dissolved nitrogen gas in equilibrium with the air
DIN
Dissolved inorganic nitrogen, NH4(+), NO2(-), NO3(-). Algae use these ions.
Nitrate assimilation
NO3(-) to NH4(+), requires energy and nitrate reductase
Nitrification
NH4(+) to NO3(-), energy source for bacteria
Denitrification
NO3(-) to NO2(-) to N2O to N2. Anaerobic, requires energy-rich organics
Nitrogen fixation
N2 to NO3(-), anaerobic, reduced to oxidized form, cyanobacteria
Ammonification
Organic matter to NH4(+)
Amino acid synthesis
NH4(+) to amino acids
Trichodesmium thiebautii
Cyanobacterium in the open ocean, requires moderately warm temperature and non-rough seas. Fixes nitrogen, does not have heterocysts, requires a lot of iron to fix.
Sources of nitrogen
Uptake into phytoplankton and bacteria, regeneration of N from food web, upwelling from below mixed layer, primary production
Old production of nitrogen
Recycling and regeneration
New production of nitrogen
Upwelling and N2 fixation
Losses of nitrogen to the atmosphere
Volatilization, denitrification, sedimentation
Volatization of nitrogen
NH3
HNLP areas
High nutrients low production. Eg gulf of alaska, equatorial pacific ocean, antarctic ocean
Critical depth
Point at which total gross photosynthesis of the phytoplankton in the water column equals total respiration
Compensation depth
Depth at which the rate of photosynthesis equals the rate of respiration
PAR
Photosynthetically active radiation
Spring bloom
Caused by increases in light, abundant nutrients that have accumulated over winter period, shallower critical depth. Brought to an end by nutrinet limitation and increases in grazing.
Summer recycling
Summer period dominated by recycling
Fall bloom
May occur because of breakdown of thermocline and deeper mixing bringing nutrients to the euphotic zone
Low light
Declining growth because of declining light
