It's an ingredient found in dandruff shampoos and, if you're a movie buff, you also know it was used to help fight off alien invaders in the film "Evolution."

Scientists at the University of Leicester are now using selenium as a tool in investigating how the oxygen content of the oceans has changed over geologically recent time.

Selenium is an anti-oxidant and an essential trace nutrient in our diet. It belongs to a group of elements whose behavior is controlled by the concentration of oxygen in the environment. Now scientists are using selenium as part of a research project to measure the isotopic ratios of selenium in sediments.

One possible outcome of the project is that the results could give scientists a global picture of the changing oxygen content of the oceans through time. Previous studies have tended to focus on local variations in ocean oxygen content.

The oxygen content of oceans can also be used as an indicator of the "overall health" of the oceans. The recent report from the Intergovernmental Panel on Climate Change (IPCC) states changes in fish populations are "associated with changes in oceanic oxygen levels." Therefore an understanding of oxygen in the oceans is not only important for the past but also for the future.

"We are using samples from an ocean basin off the Venezuelan coast which previous studies have shown to have changed its oxygen content over the last 500,000 years," explained Andrew Shore, PhD student on the project.

Without oxygen living things suffocate. Six hundred million years ago, the only life that could survive was tiny single-celled organisms. Then suddenly 540 million years ago complex life began to thrive, possibly as the "miracle molecule", oxygen, became abundant on Earth.

Andrew added: "Our understanding of the changes in atmospheric oxygen is good, but our planet is 70% covered by oceans. Determining the oceanic oxygen content is very difficult - it is linked to the atmosphere, plankton growth, and ocean circulation patterns."

This research is funded by the Petroleum Research Fund of the American Chemical Society and is in collaboration with Dr Gawen Jenkin, University of Leicester, and Dr Tom Johnson, University of Illinois at Urbana-Champaign.

Andrew did his first degree at the University of East Anglia, studying Environmental Sciences. While there, he became interested in oceanography, geochemistry and quaternary sciences. It was during a year abroad, studying at the University of Illinois, he first became involved with this research.

The research is being presented to the public at the University of Leicester on Thursday 26th June. The Festival of Postgraduate Research introduces employers and the public to the next generation of innovators and cutting-edge researchers, and gives postgraduate researchers the opportunity to explain the real world implications of their research to a wide ranging audience.