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The Role
of Temperature
Blue light containes more energy per proton than red light
-
280 –
320 nm: UV-B
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320 –
400 nm: UV-A
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400 –
700 nm: PAR – Photosynthetically Active Radiation
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> 700
nm: IR (Infrared Radiation)
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Light
decreases exponentially with depth
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Blue light
penetrates deepest into the ocean, red light is absorbed fastest (Consequences:
Live seems more ‘colorless’ with depth)
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Optical
classes of water (Jerlov):
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Coastal
oceans: stronger light absorption, brownish to greenish due to shift in
spectral absorbance
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Open oceans:
clearest water, deep euphotic zone, blue color
Photosynthesis
and Light
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P vs.
I curves (photosynthesis versus light intensity):
shows photosynthetic adaptation
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Gross
production = total production; net
production = gross prod. – respiration
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Compensation
point: photosynthesis = respiration,
net
production = 0
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Pmax
= maximum production; depends on dark reaction (unlimited growth) or limiting
resources
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Initial
slope a:
photosynthetic
efficiency (how good is low light used), also
quantum
yield f
= D P/DI;
depends on light reaction
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Ik:
summarizes key characteristics Pmax and a in one term; shade-adapted
cells have lower Ik than high-light cells
Note: Species (1) and (2) have the same Ik despite different
Pmax and a. The lower Ik
of (1) and (2) as compared to (3) reveals them as shade-adapted species.
The depth of maximum phytoplankton abundance is a compromise between
light and available nutrients; often near the thermocline
Blown
with the winds: Turbulence and upwelling
Water
movements by wind and currents affect plankton distributions
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Langmuir
circulation: lines of concentrations
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Wind-driven
surface flows
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Eddy
formation: Gulf Stream rings
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Coastal
upwelling: Eckman transport
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