Nannoplankton Coccolithophores Kingdom: Protista Division: Chrysophyta Class: Coccolithophyceae They are unicellular marine planktonic protists (algae)

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.