Chapter 13 Biological Productivity and Energy Transfer

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Chapter 13 Biological Productivity and Energy
Transfer

• Essentials of Oceanography
• 7th Edition

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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
Figure 13-1
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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

• Margins of the oceans
• Abundant supply of nutrients from land
• Water shallow enough for light to penetrate all
  the way to the sea floor
• Upwelling areas
• Currents hoist cool nutrient-rich deep water to
  the sunlit surface

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Coastal upwelling
Figure 13-3
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The electromagnetic spectrum and light
penetration in seawater
Figure 13-4
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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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Satellite view of world productivity
Figure 13-6
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Photosynthetic marine organisms Plants

• Seed-bearing plants
• Eelgrass (Zostera)
• Surf grass (Phyllospadix)

Surf grass
Figure 13-7
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Photosynthetic marine organisms Macroscopic algae

• Brown algae
• Sargassum (top left)
• Macrocystis (top right)
• Green algae
• Codium (bottom left)
• Red algae
• Lithothamnion (bottom right)

Figure 13-8
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Photosynthetic marine organisms Microscopic algae

• Microscopic algae include
• Golden algae
• Diatoms (silica test resembles a pillbox)
• Coccolithophores (calcite plates form a spherical
  test)
• Dinoflagellates
• Produce a test made of keratin
• Posses a whip-like flagella
• Bioluminescence
• Exist in great abundance creating red tides
  (harmful algae blooms)

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Dinoflagellates and red tides
Figure 13C
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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 polar oceans

• Sunlight peaks in summer
• Nutrients available nearly year-round (only weak
  seasonal thermocline develops)
• Productivity
• Peaks in spring
• Limited by sunlight

Figure 13-10a
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Productivity in tropical oceans

• Sunlight strong year-round
• Nutrients limited by strong permanent
  thermocline
• Productivity
• Steady low rate
• Limited by nutrients
• Exceptions
• Upwelling areas
• Coral reefs

Figure 13-11
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Productivity in temperate oceans

• Sunlight varies seasonally
• Nutrients limited by thermocline
• Productivity
• Spring bloom limited by nutrients
• Fall bloom limited by sunlight

Figure 13-12
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Productivity in tropical temperate and polar
oceans
Figure 13-13
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Energy flow in marine ecosystems

• Categories of organisms
• Producers
• Consumers
• Decomposers

Figure 13-14
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Biogeochemical cycling of matter
Figure 13-16
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Ecosystem energy flow and efficiency

• Energy is passed between trophic (feeding) levels
• Transfer efficiencies
• Algae 2
• Other levels 10

Figure 13-18
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Comparison between a food chain and a food web
Figure 13-19
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Biomass pyramid

• At each step up the pyramid there is/are
• Larger organisms
• Fewer individuals
• A smaller total biomass

Figure 13-20
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Ecosystems and fisheries

• Fishery fish caught from the ocean by
  commercial fishers
• Largest proportion of marine fish are taken from
  shallow shelf and coastal waters

Figure 13-21
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Fisheries and overfishing

• World total marine fish production has increased
  dramatically
• Overfishing occurs when adult fish are harvested
  faster than their natural rate of reproduction

Figure 13-22
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Fisheries and bycatch

• Some fishing practices produce large amounts of
  incidental catch (bycatch)
• Purse seine nets set for tuna can trap dolphins
• Driftnets (gill nets) take many unwanted species

Spotted dolphin
Figure 13-23
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Fisheries management

• Fisheries management seeks to maintain a
  long-term fishery by
• Assessing ecosystem health
• Determining fish stocks
• Analyzing fishing practices
• Enforcing catch limits
• Fisheries management does not regulate the number
  of fishing vessels

Figure 13-25
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End of Chapter 13

• Essentials of Oceanography
• 7th Edition