The Antarctic continental ice cap came into existence during the Oligocene epoch,
some 33.6 million years ago, according to data from an international
expedition led by the Andalusian Institute of Earth Sciences (IACT)—a Spanish National Research Council-University of Granada
joint center. Before the ice covered Antarctica, the Earth was a warm
place with a tropical climate. In this region, plankton diversity was
high until glaciation 33.6 million years ago reduced the populations
leaving only those capable of surviving in the new climate.
Seasonal primary productivity of plankton communities appeared with the
first ice. This phenomenon, still active today, influences global food
webs. These findings, reported in the journal Science, are based on
fossil records in sediment cores at different depths. The study was led
by the Andalusian Institute of Earth Sciences, a Spanish National
Research Council-University of Granada joint center.
The Integrated Ocean Drilling Program international
expedition has obtained this information from the paleoclimatic history
preserved in sediment strata in the Antarctic depths. IACT researcher
Carlota Escutia, who led the expedition, explains that “the fossil
record of dinoflagellate cyst communities reflects the substantial
reduction and specialization of these species that took place when the
ice cap became established and, with it, marked seasonal ice-pack
formation and melting began."
The appearance of the Antarctic polar icecap marks the beginning of
plankton communities that are still functioning today. This ice-cap is
associated with the ice-pack, the frozen part that disappears and
reappears as a function of seasonal climate changes.
As Antarctic summer approaches, this marks the increase in primary
productivity of endemic plankton communities. When it melts, the ice
frees the nutrients it has accumulated and these are used by the
Since ice first expanded across Antarctica and caused the
dinoflagellate communities to specialize, these species have been
undergoing constant change and evolution. However, the IACT researcher
thinks “the great change came when the species simplified their form and
found they were forced to adapt to the new climatic conditions”.
Pre-glaciation sediment contained highly varied dinoflagellate
communities, with star-shaped morphologies. When the ice appeared 33.6
million years ago, this diversity was limited and their activity
subjected to the new seasonal climate.
The image below shows A simple dinoflagellate associated with the
early Oligocene epoch and found in 33 million year-old sediments.
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