Global chlorophyll concentrations

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Global chlorophyll concentrations (low in
subtropics, high in upwelling and subpolar
regions)
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(Pinet, P.)
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(Pinet, P.)
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North Atlantic Spring Bloom
March 1999 April 1999 May 1999 June 1999
http//daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/nab.
html
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UV and IR quickly scattered and absorbed
(Pinet,
P.)
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Visible spectrum 400-700nm penetrates deeper in
the ocean. These are the same wave- lengths used
by plants in photosynthesis
Open Ocean
100m
Coastal ocean
20m
(Pinet, P.)
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Blue light most readily transmitted (where
chlorophyll-a peak is).
Max absorption Chl-a
(Lalli and Parsons)
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Light absorbance by phytoplankton between 400
and 700 nm
(Lalli and Parsons)
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Light intensity with depth for ocean vs coastal
water
1 light level
20m
200m
(Lalli
and Parsons)
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and photosynthesis levels
(Pinet, P.)
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Photosynthesis is enhanced at greater light
levels up to a maximum
(Lalli and Parsons)
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Photosynthesis curve follows light curve
Respiration constant with depth
(Lalli and Parsons)
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Respiration
Due to reduced mixing and stratification, cells
remain above Critical Depth
Photosynthesis
Compensation Depth Critical Depth
Cells mixed below Critical Depth
Winter Summer
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Bloom off of Norway note shoaling of mixed
layer, increase in critical depth
Onset of bloom when mixed layer is less than
critical depth
(Mann and Lazier)
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photoinhibition
(or photosynthesis)
Where vertically averaged photosynthesis equals
average respiration is called the CRITICAL
DEPTH
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Photosynthesis is enhanced at greater light
levels up to a maximum
(Lalli and Parsons)
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Northward Bloom Migration
April June/July August/September
(Mann and Lazier)
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Theoretical progression at temperate latitudes
Primary production
nutrients
biomass
(Lalli and Parsons)
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Spring Warming weather Reduced mixing
Thermocline growing Autumn Cooling
weather Increased mixing Thermocline decaying
Winter Cold, windy Well
mixed No thermocline Summer Warmest
weather Little mixing Strong thermocline
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(Pinet, P.)
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Seasonal-latitudinal variation in phyto- plankton
blooms in the Atlantic
(Lalli and
Parsons)
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In tropical waters primary production is
typically nutrient limited and a subsurface
chlorophyll maximum is commonly observed
(Mann and Lazier)
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That is thought to be the result of a weak
nutrient flux through the base of the mixed layer
Turbulence levels
(Mann and Lazier)
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Zooplankton seasonal migration.
Re-enter diapause
Feeding and reproduction
Diapause (hibernation)
(Lalli and Parsons)
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Variations in blooms between ocean regions
Phytoplankton
Zooplankton
(Lalli and Parsons)
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Coccolithophorid bloom around the British Isles
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Tidal mixing fronts on shelf seas zones of high
productivity
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Basic structure and nutrient distribution at a
shelf front
Stratified
Mixed
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Chlorophyll-a concen- tration sections in the
Celtic Sea in mg/m3. Well-mixed layer to the
right. With time, nutrients are depleted in the
surface layers of the stratified side of the
front. Vigorous mixing on the mixed side of the
front supplies nutrients to the
front. Pycnocline receives injection of
nutrients from mixed side of front with
stability and proximity to surface resulting in
production.
Chl
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Georges Bank in early summer well-mixed region
shows up as a Chlorophyll-a maximum