Great Fishing Grounds: How Turbulent Mixing Works

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Great Fishing Grounds How Turbulent Mixing Works
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• huge shallow area off Newfoundland, extension of
  the continental shelf which extends offshore
• less than 200 metres deep after that you are on
  the continental slope
• this is the area where turbulent mixing occurs,
  and it is this turbulent mixing that is
  responsible for the huge fish populations

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• The cold Labrador Current and the warm Gulf
  Stream meet off the east coast over the Grand
  Banks
• Cold Labrador Current plunges beneath warmer Gulf
  Stream (it is denser)
• Because the water is shallow, the descending
  Labrador Current water "displaces" bottom water
  and pushes or stirs it up (this is the "turbulent
  mixing")

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• this bottom water is rich in nutrients from all
  the organisms that live in the sea and die and
  sink
• the nutrient rich bottom waters are brought up
  into the photic zone (the part of the surface
  water where sunlight reaches - about 50m)

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• The combination of sunlight and nutrients cause
  there to be a "phytoplankton bloom" - countless
  billions of microscopic green plants ("phyto"
  refers to plankton that needs sunlight, that is,
  green plants)

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• The phytoplankton feed the zooplankton
  (microscopic animals), which in turn feed larger
  organisms, which feed little fish which feed
  bigger fish, etc.

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