Sediment-Bound Fossil Specimens Suggest Effects of Ocean Acidification


Scanning electron microscope image of rock surfaces collected from the Bass River core in New Jersey.

Paleontologists have discovered micrometer-scale fossils of plankton from the Palaeocene-Eocene Thermal Maximum, a period of rapid ocean warming and acidification that occurred 55 million years ago, during the Paleogene Period. The tiny plankton will allow researchers to study how the marine organisms coped with the rising acidity of the oceans.

The discovery of intact specimens of coccolithophores, micrometer-sized marine plankton encased in discs of carbonate, is somewhat rare, since most that are found are just fossilized remains of partial skeletons. This has allowed scientists to image them, right to their intracellular vesicles, using an electron scanning microscope. The images were presented at the Third International Symposium on the Ocean in a High CO2 World in Monterey, California.


Close-up of intact micron-sized calcite plates that surround coccolithophores embedded in clay.

There is a growing concern that the current acidification of the oceans, which is driven by climate change, will reduce the abundance of calcium carbonate in the waters, making it difficult for algae to form microscopic plating, which is essential to their survival.

Intact fossils allow researchers to compare the size, shape, thickness, and growth rates of ancient and modern coccolithophores. They are hoping to find clues about the past adaptations of the coccolithophores. Preliminary indications show that the growth rates of the ancient coccolithophores were sensitive to rapid changes in the chemistry of the oceans.


Reticulofenestra umbilicus and Reticulofenestra minuta demonstrate the range in size and calcification seen in coccolithophores found in the fossil record. Scale bar = 1 micron.

The specimens were collected bay palaeocoeanograrpher Samantha Gibbs, from the University of Southampton, UK, in California, New Jersey, and Tanzania.

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