Phytoplankton

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Phytoplankton

• Photosynthetic autotrophs (algae) drifting
  passively in aquatic environments
• Some common phyla
• Euglenophyta (euglenoids)
• Pyrrhophyta (dinoflagellates)
• Bacillariophyta (diatoms)
• Chlorophyta (green algae)

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Absorption spectra for different algal pigments
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Plankton sampling techniques
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Plankton counting techniques
Sedgewick-Rafter Counting Cells
Palmer Counting Cells
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The number of species recorded from the same
water body depends on.

• Sampling method (net or water samples)
• Number and location of sampling stations
  (littoral vs. pelagic presence of floating
  macrophytes, etc.)
• Time span of the investigation
• Time of the year (and time of the day)

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Phytoplankton communities in the tropics

• Lack of comprehensive data on phytoplankton
  communities in the tropics.
• Even so, there seems no trend towards increased
  algal diversity towards the equator (applies to
  lakes, rivers, wetlands and reservoirs).

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Euglenophyta
Euglena
Phacus
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Dinoflagellates (Pyrrhophyta)
Ceratium
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Red Tide A bloom of dinoflagellates
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Swimming with bioluminescent dinoflagellates
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Diatoms (Bacillariophyta)
Cyclotella
Navicula
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Diatoms Diatom diversity (left), Pinnularia
(left)
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Diatom shell
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Single celled, colonial and multicellular
chlorophytes
Caulerpa
Volvox
Pediastrum
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Periphyton growing along rocks in mesotrophic
Lake Titicaca, Peru)
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N is more frequently limiting to freshwater
production in tropical lakes and rivers.
Source Downing et al. 1998

• N may be lost from aquatic systems more rapidly
• in the tropics than the temperate zone (e.g.
  through denitrification)

• P erosion from tropical landscapes and P
  mobilization
• in aquatic environments may be more rapid.

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Species Caulerpa taxifolia Division
Chlorophyta ClassUlvophyceae Native range
Hawaii, Brazil, SE Asia (i.e., tropical). Now
Worldwide distribution with large outbreaks after
accidental introduction in the Mediterranean,
Southern California and Australia. Successful
invader because (1) rapid reproduction/spread
with fragmentation, (2) lack of natural grazers,
(3) rapid growth, and (4) toxic to herbivores
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Lewis, 1990
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