The open ocean is a biological desert.

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The open ocean is a biological desert.
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Primary Production
Global chlorophyll concentrations for Oct. 2000
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Feb 5, 1998 uniformly low pigment concentrations
during all seasons
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Primary productivity

• Primary productivity is the amount of carbon
  (organic matter) produced by organisms
• Mostly through photosynthesis
• Energy source solar radiation
• Also includes chemosynthesis
• Energy source chemical reactions

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Photosynthetic productivity
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Primary Producers
Common Name Blue-green algae (cyanobacteria) Red
algae Brown algae Green algae Coccolithophorids Di
noflagellates Diatoms Seagrass
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Oceanic photosynthetic productivity

• Controlling factors affecting photosynthetic
  productivity
• Availability of nutrients
• Nitrates
• Phosphates
• Iron
• Amount of sunlight
• Varies daily and seasonally
• Sunlight strong enough to support photosynthesis
  occurs only to a depth of 100 meters (euphotic
  zone)

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Locations of maximum photosynthetic productivity

• Coastlines
• Abundant supply of nutrients from land
• Water shallow enough for light to penetrate all
  the way to the sea floor
• Upwelling areas
• Cool, nutrient-rich deep water is brought to the
  sunlit surface

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Upwelling
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Coastal upwelling
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The electromagnetic spectrum and light
penetration in seawater
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Water color and life in the ocean

• Ocean color is influenced by
• The amount of turbidity from runoff
• The amount of photosynthetic pigment, which
  corresponds to the amount of productivity
• Yellow-green highly productive water
• Found in coastal and upwelling areas (eutrophic)
• Clear indigo blue low productivity water
• Found in the tropics and open ocean (oligotrophic)

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Table 1. Average net primary production and
biomass of aquatic habitats. Data from R.H.
Whittaker and G.E. Likens, Human Ecol. 1
357-369 (1973).
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• Productivity varies TEMPORALLY and SPATIALLY
• generally highest over continental shelves over
  the shelf itself it is highest just offshore
• seasonality more pronounced at high latitudes
• at mid latitudes, productivity peaks both spring
  and fall

Observations from September 1997 through July
2005
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Thermocline
depth
Temperature profile
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Regional productivity

• Photosynthetic productivity varies due to
• Amount of sunlight
• Availability of nutrients
• Thermocline (a layer of rapidly changing
  temperature) limits nutrient supply
• Examine three open ocean regions
• Polar oceans (gt60 latitude)
• Tropical oceans (lt30 latitude)
• Temperate oceans (30-60 latitude)

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Productivity in tropical, temperate, and polar
oceans
Zooplankton
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Productivity polar oceans
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Productivity in tropical oceans
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Productivity in temperate oceans
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Plankton Sampling
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Plankton Size
Picoplankton (.2-2 µm) Nanoplankton (2 - 20
µm) Microplankton (20-200 µm) Macroplankton
(200-2,000 µm) Megaplankton (gt 2,000 µm)
microplankton
picoplankton
nanplankton
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RP
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Primary Productivity

• Gross Primary Productivity (GPP)
• The rate of production of organic matter from
  inorganic materials by autotrophic organisms
• Respiration (R)
• The rate of consumption of organic matter
  (conversion to inorganic matter) by organisms.
• Net Primary Productivity (NPP)
• The net rate of organic matter produced as a
  consequence of both GPP and R.

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Primary Productivity

• NPP GPP - R

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Light Dark Experiments
zooplankton
phytoplankton
Respiration C6H12O6 6O2
6CO2 6H2O
decomposition
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dark bottle
light bottle
photosynthesis respiration
respiration
weight
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Calculating Primary Productivity
Assume that our incubation period was 1 hour.
Measured oxygen concentrations Initial bottle
8 mg O2 /L Light bottle 10 mg O2 /L Dark
bottle 5 mg O2 /L
(Light - Initial) (10 - 8) 2 mg/L/hr (GPP -
R) NPP (Initial - Dark) (8 - 5) 3 mg/L/hr
Respiration (Light - Dark) (10 - 5) 5
mg/L/hr (NPP R) GPP
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Environmental Factors Affecting Primary Production
(eutrophication)
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Inquiry

• Why is the open ocean a biological desert?
• Where are the most productive regions located?
• Describe productivity in temperate, polar and
  tropical water.
• Why does the zooplankton lag behind the
  phytoplankton?
• If you want to catch microplankton, what size
  mesh net do you need?
• Why cant plants grow below the compensation
  depth?
• Why does eutrophication sometimes result in mass
  fish kills?