Chapter 10 Biological Productivity in the Ocean

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It is possible to estimate plant and fish
productivity in the ocean.
10-3
Global Patterns of Productivity

• The size of the plankton biomass is a good
  indicator of the biomass of the remainder of the
  food web.
• Annual primary production (APP) is equal to
  primary production rate (PPR) times the area for
  which the rate is applicable.
• APP PPR x Area (to which applicable )
• Transfer efficiency (TE) is a measure of the
  amount of carbon that is passed between trophic
  levels and is used for growth.
• Transfer efficiency varies from 10 to 20 in most
  food chains.

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10-3
Global Patterns of Productivity

• Potential production (PP) at any trophic level is
  equal to the annual primary production (APP)
  times the transfer efficiency (TE) for each step
  in the food chain to the trophic level of the
  organism under consideration.
• PP APP x TE (for each step)
• Although rate of productivity is very low for the
  open ocean compared to areas of upwelling, the
  open ocean has the greatest biomass productivity
  because of its enormous size.
• In the open ocean the food chains are longer and
  energy transfer is low, so fish populations are
  small.
• Most fish production is equally divided between
  area of upwelling and coastal waters.
• Calculations suggest that the annual fish
  production is about 240 million tons/yr.
• Over-fishing is removing fish from the ocean
  faster than they are replaced by reproduction and
  this can eventually lead to the collapse of the
  fish population.

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Upwelling of deep, nutrient-rich water supports
large populations of phytoplankton and fish.
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Biological Productivity of Upwelling Water

• The waters off the coast of Peru normally is an
  area of upwelling, supporting one of the worlds
  largest fisheries.
• Every three to seven years warm surface waters in
  the Pacific displace the cold, nutrient-rich
  water on Perus shelf in a phenomenon called El
  Nino.
• El Nino results in a major change in fauna on the
  shelf and a great reduction in fishes.
• This can lead to mass starvation of organisms
  dependent upon the fish as their major food
  source.

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The waters of the neritic zone are fertile and
support a rich community of organisms.
13-1
Biology of the Continental Shelf

• The plankton are floaters and weak swimmers which
  are helplessly transported by ocean currents.
• Nekton have the ability to swim against currents
  and actively search for a more hospitable
  environment.
• Many fish display schooling, another form of
  patchiness.

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The open ocean is the largest habitat on Earth,
but life is sparse because of low nutrient
concentration and great depth.
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Biology of the Open Ocean and the Deep Sea

• In the open ocean, diversity is high but the
  number of individual per species is low.
• The only seaweed in the open ocean sea is
  Sargassum gulfweed.
• The major phytoplankton are diatoms,
  dinoflagellates and coccolithophores and the
  major zooplankton are foraminifera and
  radiolaria.
• Diatoms dominate the shallow coasts, but decrease
  in abundance seaward.
• Top predators are mackerel, squid, jellyfish,
  tuna, porpoise, shark and man.

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The biomass on the sea floor tends to decrease
with depth faster than it does with distance from
shore.
13-2
Biology of the Open Ocean and the Deep Sea

• The benthic food chains largely depend upon food
  from the surface which reaches the bottom.
• Characteristics of the benthic organisms include
  year-round reproduction, smaller broods, slow
  growth, and longer life.
• Diversity of the benthos is greater than expected
  because the high predation rate prevents any
  group from dominating through competitive
  exclusion (when one group out-competes most
  others and drives them to extinction).

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13-2
Biology of the Open Ocean and the Deep Sea

• Four traits common to all abyssal depths are
  perpetual darkness., low temperature, high
  hydrostatic pressure, and sparse food supply.
• Rate of bacterial decay is greatly reduced under
  high hydrostatic pressure.
• This means that organic material that settles
  onto the sea floor remains for a long time before
  it decays and is thus more likely to be consumed.

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