Ancient plankton fossils are telling scientists about the longevity of Antarctica’s modern climate and its plankton ecosystem.
A Science journal study led by Alexander Houben from Utrecht University in the Netherlands, along with a team of researchers from around the world, found that cooling in Antarctica led to a restructuring of the area’s ecosystem, starting with plankton.
33 million years ago, when the Oligocene epoch was first beginning, temperatures in Antarctica dropped. The first major Antarctic glaciation occurred: ice sheets expanded and icebergs formed in the sea.
Due to the cooling, the diversity of dinoflaggates—tiny photosynthetic plankton—decreased. The study found that right before the Oligocene cooling, plankton diversity was high. But fossil evidence from 33.6 million years ago shows after this period, a drop in plankton diversity occurred— concurrently with the drop in temperatures.
At this point when plankton diversity fell, the scientists found the modern-day freeze-melt cycle, characteristic of Antarctica, began. Antarctica freezes over in the fall and winter, but come spring, the ice sheets melt and as a result nutrients are released from their frozen prisons and plankton dive in to feed on them. The plankton convert these into organic compounds, which are then available for organisms higher up the food chain. The melting ultimately results in a period of intense feeding in all areas of the Antarctic food web.
Scientists think the climate cycle and the resulting plankton ecosystem change that began 33 million years ago may have resulted in the evolution of whales and penguins as we know them today.
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