Plankton analysis

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Plankton analysis

• Song SUN and Ivan HEANEY

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Importance

• The base of marine food webs
• The base of marine biogeochemical cycling
• The biggest biomass in the oceans
• Shaping the structure of the marine ecosystem

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What information arewe concerned about?

• What lives in the ocean - species composition
• How many live in the ocean at a certain time -
  Biomass

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How do we get the information?

• traditional methods
• new technologies

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Observing and Counting
Optical Underwater Video Profiler (UVP)
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Observing and Counting
Optical Video Plankton Recorders (VPRs)
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Observing and Counting
Optical Optical plankton counters (OPCs) Laser
OPCs
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Observing and Counting
Optical Optical plankton counters (OPCs) Laser
OPCs
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Observing and Counting
Optical Satellite Remote Sensing
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Observing and Counting
Optical FlowCAM
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Observing and Counting
Acoustic technology

• Standard Multi-Frequency Echo Sounders
• Towed Arrays
• Side-scan SONAR
• ADCP

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Could we get enough information using the new
technology?

• No!
• Not enough information for species composition
  and biomass! Only estimates of taxa

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What we have to do
Take plankton samples
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Sample processing
Traditional methods

• Expert Microscope species composition
  Biomass
• It is the most reliable and it can not be
  substituted at present and in the near future
• Most of the new technology and new methods for
  the plankton analysis need traditional methods
  for calibrating.

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Sample processing
Traditional methods

• The problem for these methods is they are time
  consuming, labor intensive and require highly
  trained technical assistants (sorting centers).
• Quality control it depends on who does it-the
  knowledge and skill of the technicians.
• It is hard to meet the needs of marine ecosystem
  research, especially for processing of large
  numbers of samples and for providing real time
  information. When we get the results, the
  situation has changed already.

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Sample processing
Traditional methods

• For species identification, it is hard to
  distinguish between similar species, deferent
  stages and eggs.
• For biomass measurements, these are generally
  estimated as displacement volume or wet weight,
  and then converted into dry weight, organic
  matter, organic carbon or nitrogen using
  conversion factors, or through length weight
  relationships, but a lot of error resources .
• In general, the statistical relationships between
  the different biomass estimators depends on their
  analytical suitability, precision and accuracy

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Sample processing
Traditional methods

• The use of inadequate conversion factors relating
  organism dimensions or volume to other biomass
  indicators (dry weight, organic C and N, etc.)
  remains a source of error.

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Sample processing
OPC methods

• Easy to process large quantity samples, we can
  get biomass and size spectra almost
  immediately.
• It can meet the needs of ecosystem dynamics
  research and for developing models.

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Sample processing
OPC/LOPC methods

• We can get size spectrum information, but not the
  species included.
• It can not distinguish living plankton from
  detritus and other particles.

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Sample processing
OPC/LOPC methods

• Traditional methods can be used to calibrate the
  OPC information and estimate the dominant species
  and main function groups.
• It is more useful for simple cold water
  ecosystems than in complex warm water
  ecosystems.

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Sample processing
Image analysis methods

• A simple, non-destructive method that allows
  reliable estimates of biomass (individual
  numbers, zooplankton biovolume, volume-class
  distribution and organic C and N) to be obtained
  from preserved zooplankton samples.
• Avoids most of the variability sources due to
  sample manipulation when measuring zooplankton
  volume displacement, or to the presence of
  particulate material other than zooplankton.
• M. Alcaraz et al, 2003

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Sample processing
Image analysis methods

• Image analysis used to estimate individual
  volume. Digital images of aliquots of zooplankton
  samples, captured with a CCD camera attached to a
  stereomicroscope (A), are with grey-scale
  threshold (B). The images are numbered, and the
  major and minor axis of ellipses of the same area
  as the corresponding shadows (projections) of
  the organisms are automatically calculated (C),
  and thus the corresponding volumes of the
  revolution ellipsoids (D). Finally, the
  individual volumes are sorted into the
  corresponding volume-class octave. The individual
  volumes are integrated, and the sample volume
  (mm3 m)3) is related to the C and N contents of
  parallel triplicate aliquots
• M. Alcaraz et al, 2003

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Sample processing
Image analysis methods

• It can provide reliable estimations of the
  numbers, individual and integrated volume, and
  distribution into volume classes and fresh C and
  N zooplankton composition from the image analysis
  of formalin-preserved zooplankton samples.
• The image analysis is absolutely selective, so
  that the interference of alien particulate
  material (i.e. detritus, phytoplankton, etc.) can
  easily be avoided.
• M. Alcaraz et al, 2003

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Sample processing
Image analysis methods

• Some new technology and software have been
  developed to identify species automatically by
  computer.
• The software is still experimental and has not
  been much tested with real end-users or with the
  analyses of large amount of samples.

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Sample processing
DNA-Barcoding method

• Enable the discrimination of closely allied
  species.
• Easy to record and describe the known species.
• It can be applied where traditional methods are
  problematical, for instance identification of
  eggs and immature forms, and analysis of stomach
  contents or excreta to determine food webs.

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Sample processing
DNA-Barcoding method

• Only species composition, no quantity
  information.
• It is hard to process large quantity of samples.
• There is no suitable DNA Barcoding data base that
  can be employed at present.

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Sample processing
Protocol suggestion

• To meet the need for quick and real time
  information of biomass, dominant size group, the
  OPC can be used first. It is a fast way to get
  information and can be used for fresh samples and
  on board ship.
• The image analysis methods can be used to
  calibrate the OPC data as it can distinguish
  between detritus and plankton.

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Sample processing
Protocol suggestion

• Take images using a digital camera and microscope
  for identification of species and calibrate the
  size groups.
• Identify the species that cant be recognized by
  images under microscope.
• Use the DNA Barcoding method to identify
  zooplankton younger stages, eggs and closely
  allied species.
• Integrate all the information.

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What we should be concerned about

• How to take samples.
• The new technologies should be integrated with
  sampling methods.

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What is the best way?
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What is the best way?
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What is the best way?
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What is the best way?
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How to do it?

• Different country, different region have
  different problem, the most important is to get
  the valuable plankton information, they can
  choose one of the methods that fit their
  situation, but it must be a standard method and
  the data can be comparable.

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Thank you!