Innovative Ideas for Using Midge Larvae in Climate Research

The paleoecologist Oliver Heiri has been awarded funding of two million Swiss francs from the European Research Council. With an innovative approach, the funded project aims to reconstruct the emission of the greenhouse gas methane in lakes at the end of the last ice age.

Any young researcher seeking to impress the European Research Council (ERC) needs one thing above all else: revolutionary new ideas. Which is exactly what the biologist and paleoecologist, Oliver Heiri has to offer. He was recently awarded a prestigious starting grant for outstanding young scientists by the ERC. He will now receive a total of 1.5 million Euros over five years and establish a new research team at the Oeschger Centre for Climate Change Research. Until recently, Oliver Heiri worked at Utrecht University in the Netherlands. The outstanding scientific milieu at the Oeschger Centre prompted his move to Bern. "Working with specialists in various areas benefits my project enormously – that is what persuaded the people responsible at the ERC to consent to the transfer to another university".

Oliver Heiri has devoted several years to the reconstruction of past climates. To be specific, he investigates fossil chironomids (non-biting midges). Or to be more precise, the chitin-containing heads of midge larvae. Non-biting midges are well-known environmental indicators as the distribution of many species is strongly related to water temperature and quality. This applies equally well to the past as to the present and this circumstance is taken advantage of by climate researchers. Microscopic examinations of individual lake sediment layers reveal when certain groups of midge were most abundant and, based on this information, and with the help of mathematical models, summer temperatures in the past can be reconstructed.

Measuring isotopes in fossil skeletons

This sums up the conventional procedure. The innovative young researcher Heiri, however, intends to take a whole new approach to analysing micro-fossils. Not content to simply determine the various chironomid species, distinguishing characteristics of which include the number and arrangement of their teeth, he goes on to conduct chemical examinations of the fossil skeletons. As Oliver Heiri explains, "Our new approach consists of measuring isotopes directly in parts of the skeleton. We've already managed to do this with oxygen, and now we're trying out carbon isotopes as well". Particularly interesting about the latter measurements is that they supply indirect information about the methane levels of lakes in the past. Lakes are important sources of the greenhouse gas methane, and reconstructing their changing activity is vital to climate research. "We want to find out whether climate changes in the past also had an impact on methane production".

Isotope measurement is a proven and important method in climate reconstruction. It has been used, for instance, to investigate ice cores and to reconstruct past temperatures based on air bubbles in the Greenland ice. Leading the international field are the researchers from the Climate and Environmental Physics department at the Physics Institute of the University of Bern, part of the Oeschger Centre. Based on ice cores from the Antarctic, climate physicists have been able to reconstruct temperatures and CO2 and methane concentrations going back 800,000 years.

The Oeschger centre is a magnet for top researchers

This expertise in isotope measuring was one of the reasons why Oliver Heiri decided to conduct his ERC project at the University of Bern. "The experience in Bern with these measurements on ice cores and other climate archives will improve our own measuring method and hopefully take our approach to a whole new level". The researcher, recently arrived from Utrecht – incidentally, he studied and completed his doctorate in Bern before continuing his scientific career in Norway and the Netherlands – now works at the Institute of Plant Science. At the moment he is putting together his team of two doctoral students and a post doctoral researcher, and field work is already due to start this summer with sediment corings in lakes in Sweden, Finland and Switzerland. Based on these campaigns, he aims to refine the isotopic approach. Then comes the centrepiece of the project, namely the reconstruction of the methane level in Lake Rotsee near Lucerne for the period between 15,000 and 11,000 years ago. This period marks the end of the last ice age, a particularly interesting phase in terms of understanding climate change.

The young paleoecologist's research project sounds fascinating and has obviously also impressed the selection committees of the European Research Council. Yet how certain is it that the method that worked so well with ice cores will also be a success with non-biting midges? "There are no guarantees and my financial backers are also aware of this", comments Heiri, " but, after all, the ERC grants are awarded according to the high risk – high gain principle".

Whether the project "Reconstruction of methane flux from lakes: development and application of a new approach " will lead to a scientific breakthrough or not – the Oeschger Centre for one will benefit from Oliver Heiri's new ideas in any case. In the person of Oliver Heiri, returned from the Netherlands, with his excellent reputation and multidisciplinary network, it has trawled a promising catch.