Diatoms: tiny creatures telling us a big climate change story

Microscopy of diatom frustules (Image: microscopy-uk.org.uk)

Microscopy of diatom frustules (Image: microscopy-uk.org.uk)





Diatoms are micro-organisms, phytoplankton, a type of algae.

Diatoms are important in our marine and freshwater environments.

They produce energy through photosynthesis, providing almost a quarter of the oxygen we breath.

In the Southern Ocean alone, they constitute almost 75% of total primary productivity.

Diatoms and their tiny silica shells are important indicators of environmental change

Each tiny diatom produces a microscopic shell, to house its unicellular body in.

These shells are usually bilaterally symmetrical, hence the organism's name, diatom (di meaning “two” in Greek).

The shell the organism produces is called a frustule, and is composed of silica.

These frustules contain oxygen isotopes that can be sampled and interpreted. The information received from such analyses provide very specific and insightful paleoclimate data. This data can tell us exactly what a climate was like, during a certain period of time in the Earth’s geological history.

By analysing samples taken from the ocean floor, scientists from the University of Sydney have recently created the first map of the Earth’s ocean floor and associated sediments.

The ocean floor provides a rich history of the Earth’s climate through sedimentation including the frustules of historic diatoms

The world's first map depicting the ocean floor geology (Image: http://geology.gsapubs.org)

The first map depicting the ocean floor geology of Earth (Image: http://geology.gsapubs.org)

The information obtained through nearly 14, 500 acquired ocean floor samples is crucial for understanding biogeochemical cycles.

Diatoms congregate on the water surface, where they bask in the sunlight (required for their photosynthesis). When the diatoms die, their frustules sink to the sea floor.

There seems to be a slight disconnect between surface productivity and accumulation of diatom shells in the ocean’s sediments.

This information suggests that frustule accumulation is a useful indicator of sea-surface oceanographic variables including temperature, salinity and nutrient levels.

The humble diatom and its shell remains can potentially tell us a great deal about how our oceans have responded to climate change throughout history. And thus, how they may respond in the near future.

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