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Epipelagic Zone
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Major Ocean Currents4
Surface Winds
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Currents
• The surface currents are caused by the winds
• Only a small amount of energy is transferred (2%), so even fast, hard winds don’t get the currents moving too fast.
• But things don’t necessarily move in the way you would expect…
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2
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Ekman Spiral
• Just like wind, water is deflected by the Coriolis effect
• As energy goes down, water is bent towards the right (in N. Hemisphere)
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Upwelling
Coastal-
Equatorial
9 10Deep Ocean Currents
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Figure 15.02PELAGIC ANIMALS
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3
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The Microbial Web14
Primary Productivity• 6CO2 + 6H2O = C6H12O6 + 6O2• With rare (relatively)
exceptions, all energy comes into the system via this pathway.
• Gross PP – respiration = Net Production
• Many different measurement techniques for PP
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Phytoplankton Production
What determines the productivity of an area? Two things…
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Physical- Light
• Variation in wavelengths through water
Compensation Depth ≈ 1% surface intensity
PAR-Photosynthetically Available Radiation
Count available photons, not just all wavelengths
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Where does the light go?• Light is Scattered by:
– Suspended particles (Sediment “soil”, plankton, etc.)
– Dissolved material• Light is Absorbed by:
– Phytoplankton: used in photosynthesis, converted to chemical energy
– Water molecules: converted to heatThis scattering and absorption
impact the colors differently
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Measuring Water Clarity
•Secchi Disk•Other more complicated methods
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• So…Why is the ocean blue?– The rates of scattering and absorption are
LOWEST for blue, so blue light makes it down to greater depths and is more available for reflecting back to the surface.
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Importance of light in the sea• Sunlight absorbed by the water is converted to
heat.– This heat warms the upper portions of the water.– It also provides the energy for evaporation and the
winds.• Photosynthesizing organisms (“plants”) are
the main source of the food in the ocean!– The depth at which light penetrates the ocean
controls the depth to which these organisms can occur.
– This zone is called the Photic Zone.
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Other biological impacts of light• Light influenced movement
– Daily Vertical Migration• Many different groups of animals migrate up and
down in the water with the changing light intensity. • They typically come up to the surface to feed at
night, then swim back down at dawn to escape their predators.
• Many swim 100s of meters a night.
• Coloration of animals– In the open ocean there is no where to hide! – Many animals have evolved interesting ways to
deal with this issue using color.
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Intensity changesWith time of day
With other biomass
With turbidity
With season
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Seasonal Cycles in Primary Productivity
Winter Spring Summer Fall
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Seasonal Cycles in Primary Productivity
Winter Spring Summer Fall
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Seasonal Cycles in Primary Productivity26
What is the midwater?
• All pelagic or open water environments
• Largest and least known habitat on earth!
6000 m
4000 m
200 m
Oceansurface
Abyssal plain
Continental shelf
Land
Trench
Hadal-pelagic
Mesopelagic
Bathypelagic
Epipelagic
Abyssopelagic
1000 m
Continental slope and rise
10,000 m
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Oxygen Minimum Zone
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Deepsea Fish30
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Feeding32 Avoiding Predation
There is nowhere to hide!
• Be big/mean or small/hidden• Transparency• Bioluminescence• Mucus• Counter-shading• Low Carbon value
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Big and/or Mean...34
…or Small...
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…or Hidden!36
Counter Shading
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Counter shading38
Bioluminescence
??
?
39 40
?
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Bioluminescence
Photoproteins- modify/control the reaction
Coelenterazine
Dinoflagellate
Firefly
General reaction•Communication
•Protection
•Hiding
•Hunting
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“Milky Seas”
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43Dark Guts to Hide Luminescent Prey
“Burglar Alarm” Hypothesis
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