Nannoplankton Coccolithophores

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Nannoplankton Coccolithophores
Kingdom Protista Division Chrysophyta Class
Coccolithophyceae
Introduction

• They are unicellular marine planktonic protists
  (algae) with photosynthetic pigments and two
  flagella and haptonema (whip-like organ). It is
  surrounded by scales (plates) called COCCOLITHS.
• Size 5-60 µm, plate size 10 µm

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Live coccolith cell surrounded by scales after J.
Young, NHM.
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Coccoliths morphology

• Plate (coccolith) consists of shields, plates,
  central area with or without bars, spine, distal
  side (outward) and proximal side

Morphological components of coccoliths
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Emiliana huxleyi
Reticulofenestra sessilis
Gephyrocapsa oceanic
Some common recent coccoliths. From The Natural
History Museum, London
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Coccolith Life-Style, Ecology and Reproduction

• Coccolithophores live in the photic zone (the
  surface waters, where sunlight reaches) and are
  photosynthesising (autotrophic) so are at the
  bottom of the marine food chain, excellent food
  for herbivorous bacteria.
• Some have flagella (whip-like appendages) so
  unlike plants, are capable of movement
  furthermore, they don't simply float around, but
  can swim.
• Although they are photosynthesising, some have
  been known to eat bacteria.
• Reproduction is asexual-----simple division.
• Sensitive for temprature, more abundant at the
  tropics 100 000 cells/l.

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Coccoliths and Sedimentation

• After death, they sink by rate of 15 cm/day.
• Factors of dissolution
• They form high proportion
• of carbonate in the sediments
• Recent 26
• Chalk (Cretaceous) 26
• Eocene 90
• They are largest producers of calcium carbonate
  on Earth today, and probably have been since the
  Late Jurassic. They dump about 1.5 million tons
  yearly of limestone to the ocean floor.

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Geologic history of coccoliths
Abundance of coccoliths in the stratigraphic
column (Brasier, 1980).
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Important coccoliths in the geologic history
a-b) Cyclococcolithina (Oligocene-Recent), c-d)
Pseudoemiliania (Pliocene-Pleistocene), e)
Helicopontosphaera (Eocene-Recent), f) Zygodiscus
(U. Cret-Eocene), g) Prediscosphaera
(Cretaceous), h) Braarudosphaeara (Cret-Recent),
j) Rhabdosphaeara (Pliocene-Recent) and k)
Discoaster (Mio-Pliocene). From Brasier 1980.