Job opportunity

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Job opportunity

• Falkowski lab seeks aquarist/ undergraduate
  assistant for the coral lab!
• If interested, contact Frank Natale
• fnatale_at_marine.rutgers.edu

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• Review
• Competition for nutrients
• Light
• Critical and Compensation Depths
• Seasonal cycle and spatial variation
• Food web and microbial loop
• Eutrophic vs. Oligotrophic food webs
• Biological pump

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Competition for nutrients
µmax1 µmax2 Ks1ltKs2 Sp. 1 wins except at very
high nutrients µmax2 gt µmax1 Equal Ks Sp. 2
wins, but not by much at low nutrients µmax2 gt
µmax1 Ks1ltKs2 At low N, Sp. 1 wins At high N, Sp.
2 wins
Species 1 Species 2
Specific Growth Rate µ
Max growth rate (a constant) Half-saturation
constant (a constant)
Nutrient Concentration N
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• Light attenuates with depth.
• Longer wavelengths have greater absorption by
  particles and attenuate more with depth.
• Too much light damages cells and reduces
  photosynthesis (photoinhibition).

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Compensation Critical Depth
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Definitions

• Autotrophs get their carbon and energy from
  inorganic sources. Phytoplankton are autotrophs
  because they get their carbon from CO2 and energy
  from light.
• Heterotrophs get their carbon and energy from
  pre-formed organic matter. Zooplankton are
  heterotrophs because they get carbon and energy
  by eating phytoplankton.

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Some marine heterotrophs (Zooplankton)
Protists - single cells Size range 1 to 1000
µm Life span days to week Crustaceans Size
range 0.01 to 10 cm Life span weeks to
years Gelatinous animals Size range mm to
m Life span months to year
ciliates
dinoflagellates
krill
copepods
salps
jellyfish
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Seasonal evolution of mixed layer
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Annual cycle in N. Atlantic
Nutrients
Light Temperature
Mixing
Mixing
Stratified
Relative increase
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Draw seasonal cycle of temperate and light
profiles with critical depth here
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Primary production and its seasonal cycle vary
greatly in space
Chl a from SeaWIFS satellite
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Mixed layer is deeper in Atlantic than in Pacific
Atlantic Ocean
Depth (m)
South pole Equator
North Pole
Pacific Ocean
Depth (m)
South pole Equator
North Pole
Temperature
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Nutrient limitation varies among oceans

• Mixed layer is deeper in Atlantic than in Pacific
• Remineralized nutrients accumulate in deep water,
  transported by ocean conveyer belt

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Atlantic vs. Pacific spring bloom
Winter Deep mixed layer, Production shuts
down Spring Phytoplankton bloom Zooplankton -
slow to catch up
Winter Shallower mixed layer, Continuous low
production Spring Phytoplankton
bloom Zooplankton - right there to eat the
bloom!
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Spring in the Arctic is darker colder than
winter at mid-latitudes
Also Irradiance
90oN N. Pole 60oN Anchorage,AK 30oN N.
Florida 0oN Equator
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Seasonal cycle varies with latitude
Nutrients
Nutrient
Light
Latitude
Light
Winter Spring Summer Autumn Winter
Lalli Parsons
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Annual cycles in other regions
Try this on your own Draw the vertical profiles
of temperature and light and the critical depth
for each region as we did in class for the North
Atlantic.
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Biological Pump
Photosynthesis
respiration
Chisholm, 2000
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Whats in a liter of seawater?

• 1 Liter of seawater contains
• 1-10 trillion viruses
• 1-10 billion bacteria
• 0.5-1 million phytoplankton
• 1,000 zooplankton
• 1-10 small fish or jellyfish
• Maybe some shark, sea lion, otter, or whale poop

This basking shark can filter 25 million L
seawater per day!
The bigger you are, the fewer you are
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Assume a trophic transfer efficiency of 10
Biomass 10 100 1000
Efficiency 0.1 0.1
fish
zooplankton
phytoplankton
Trophic transfer efficiency fraction of biomass
consumed that is converted into new biomass of
the consumer
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Traditional view of simple food webSmall things
are eaten by (10x) bigger things
Heterotrophs Autotrophs
20,000
2,000
200
20
2
0.2
Size (µm)
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Have to add heterotrophic bacteria, heterotrophic
protists, autotrophic microbes
Heterotrophs Autotrophs
20,000
2,000
200
20
2
0.2
Size (µm)
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Bacteria absorb organic molecules leaked by
microbes and phytoplankton. This creates a
microbial loop.
Heterotrophs Autotrophs
20,000
2,000
200
20
2
0.2
Size (µm)
Dissolved organic matter
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Zoom in on Biological Pump
Photosynthesis
respiration
Chisholm, 2000
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Phytoplankton are eaten by zooplankton
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Plankton size structure is important
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Importance of microbial loop depends on
environmental conditions.
Microbial loop
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Definitions

• Eutrophic environments have high nutrient
  concentrations and high productivity. Coastal
  upwelling regions and estuaries are Eutrophic.
• Oligotrophic environments have low nutrients and
  low productivity. Subtropical gyres (open ocean)
  are Oligotrophic.
• It takes a lot of mixing or a big nutrient influx
  to make an environment eutrophic. Stratified
  systems eventually must become oligotrophic.

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Eutrophic -coastal -estuaries -upwelling Oligotr
ophic -open ocean -central gyres
Diatom bloom in Barents Sea
Transparent L. Tahoe
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In eutrophic systems, large phytoplankton
(diatoms) dominate and more biomass goes directly
to large plankton and fish.
Temp.
Depth
Dcr
Microbial loop is less important
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In oligotrophic systems, small phytoplankton
(e.g. cyanobacteria) dominate and biomass goes
through more levels of plankton to get to fish.
Dcr
Microbial loop is key
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Open Ocean Tuna Carniv. Fish Carniv. Plankton
Herbiv. Plankton Phytoplankton 5 Levels 10
Efficiency
Coastal Ocean Carniv. Fish Carniv. Plankton
Herbiv. Plankton Phytoplankton 4
Levels 15 Efficiency
Upwelling Zone Anchovies Phytoplankton 2
Levels 20 Efficiency
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Area Total Plant Production Transfer Efficiency Trophic Levels Estimated Fish Production
(x109 metric tons carbon per year) (x106 metric tons per year)
Open Ocean 39 10 5 4
Coastal Ocean 8.6 15 4 29
Upwelling Zones 0.23 20 2 46
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109 metric tons C per year 109 metric tons
fish per year
Open ocean Coastal ocean Upwelling zones
5 Trophic levels 10 Efficiency
4 Trophic levels 15 Efficiency
2 Trophic levels 20 Efficiency
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How does food-web structure affect the export of
carbon to deep ocean?
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How does organic matter get to the bottom of the
ocean ?

• Dead cells and fecal pellets (plankton poop)
  sink. Big ones sink faster.
• Dissolved organic matter, pieces of gelatinous
  animals etc. stick together and form bigger
  marine snow that sinks.

Organic debris is collectively known as Detritus.
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Bigger plankton sink faster. They also have
bigger, faster-sinking fecal pellets.
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In eutrophic conditions, there are more, larger
particles that sink into deep ocean.
Temp.
Depth
Dcr

Large fecal pellets
Large Marine snow
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In oligotrophic conditions, there are fewer,
smaller particles that sink more slowly into deep
ocean.
Dcr
small fecal pellets
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Eutrophic vs. Oligotrophic summary
Eutrophic Oligotrophic
Mixed layer More mixing Cooler More stratified Warmer
Nutrients High concentration Newer Low concentration More recycled
Plankton Larger Smaller
Particles Larger Faster-sinking Smaller Slower-sinking
Carbon Export More Less