ICBM PhD student Sebastian Neun has won the City of Wilhelmshaven's Science Award 2024 in the “Students” category. He convinced the jury with his scientific work “Living in a rainbow”, which investigates the interplay of light and the ecological interactions between phytoplankton and zooplankton. In a field experiment at the lake Schortens, Sebastian Neun investigated the influence of the light spectrum on phytoplankton - in terms of its biomass, its quality as food and its composition. He showed that with limited light intensity (and unlimited nutrients) the colour spectrum is decisive for growth. These effects also impacted zooplankton (daphnia) by influencing their food quality and quantity. “I am delighted that this outstanding work has been honoured with the Wilhelmshaven Science Prize,” says ICBM scientist Dr. Maren Striebel, who supervised Neun's work. At the ICBM, Sebastian Neun is continuing this work as part of his doctoral thesis in a project funded by the German Research Foundation (DFG) and in collaboration with scientists from the University of Greifswald.

The Wilhelmshaven Science Prize was awarded for the first time this year. The award recognizes outstanding scientific work by scientists, students and pupils and will be awarded every two years in future, alternating with the city's Innovation Award.
 

Every lake, regardless of its size, is a highly complex ecosystem that serves as a habitat for many organisms. All lakes are characterised by a tightly linked network of food chains and phytoplankton forms the basis of almost all of these, even though most species are so small that they are invisible to the human eye. To provide this service, phytoplankton requires the sufficient availability of nutrients and light for photosynthesis. However, a special feature underwater is that, unlike air, water strongly influences the availability of light. Roughly half of the light reaching the water surface is attenuated in the top few centimetres. In addition, the visible spectrum of solar light is composed of different light colours: violet, blue, green, yellow, orange and red (the typical colours of the rainbow). Phytoplankton possesses a variety of light-absorbing molecules, so-called pigments, but the ability to absorb the different light colours varies greatly from species to species. Therefore, not only the intensity but also the spectrum of light is important for phytoplankton, although comparatively little is known about the role of light spectrum in ecological processes.

This study therefore investigated the ecological significance of the light spectrum and how it influences the community structure and chemical composition of phytoplankton. Since the uptake of light and nutrients in phytoplankton are loosely coupled, the ratio of fixed carbon to nutrients in their cells can vary greatly and depends critically on the environmental conditions, as does the production of more complex molecules.