Nannoplankton Coccolithophores
Kingdom: Protista
Division: Chrysophyta
Class: Coccolithophyceae
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
Introduction
Live coccolith cell surrounded by scales after J. Young, NHM.
Plate (coccolith) consists of shields, plates, central area with or
without bars, spine, distal side (outward) and proximal side
Coccoliths morphology
Morphological components of coccoliths
Emiliana huxleyi
Reticulofenestra sessilis Gephyrocapsa oceanic
Some common recent coccoliths. From The Natural History Museum, London
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.
Coccolith Life-Style, Ecology and Reproduction
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.
Coccoliths and Sedimentation
Geologic history of coccoliths
Abundance of coccoliths in the stratigraphic column (Brasier, 1980).
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.