Infrastructure

We operate a modern laboratory for the determination of stable isotope ratios of the elements carbon⁽¹³C) and nitrogen⁽¹⁵N) in solids. Furthermore, measurement the stable isotope ratio of sulphur⁽³⁴S) will be established in the future. For the analysis we run the EcovisION IRMS system (Elementar) for ecological research, which combines elemental analysis (EA) with isotope ratio mass spectrometry (IRMS) in a compact, automated system. In the first step of the measurement, the samples are first burned in the EA module under controlled conditions and converted into the measuring gases (i.e.CO₂, N₂), which are then analyzed with high precision in the IRMS for their isotope ratio.

Usally, we analyze bulk samples with natural isotope ratios, but it is also possible to measure traced samples with enriched isotope ratios. However, the latter is only carried out by arrangement and not routinely. We use the data obtained in particular in research projects to investigate food webs, material cycles and biogeochemical processes.

Selected publications using stable isotope analysis:

• Koester, M., C. Frenzel, G. Becker & R. Sahm (2022). Food spectrum of the Chinese mitten crab(Eriocheir sinensis): insights from the Lower River Rhine comparing stable isotope mixing models and genetic gut content analyses. Aquatic Invasions 17: 560-576. https://doi.org/10.3391/ai.2022.17.4.06
• Sahm, R., E. Sünger, L. Burmann, J.P. Zubrod, R. Schulz & P. Fink (2021). Compound-specific ^δ15Nanalyses of amino acids for trophic level estimation from indigenous and invasive freshwater amphipods. International Review of Hydrobiology 106: 41-47. https://doi.org/10.1002/iroh.202002058
• Koester, M., B. Bayer & R. Gergs (2016). Is Dikerogammarus villosus (Crustacea, Gammaridae) a 'killer shrimp' in the River Rhine system? Hydrobiologia 768: 299-313. https://doi.org/10.1007/s10750-015-2558-9

The Department has a modern experimental facility for simulating streams consisting of 16 stainless steel channels with a volume of approx. 80 liters. Arranged in two rows, which are accessed independently of each other by a separate motor, a water flow is generated in each flume by means of a paddle wheel, simulating natural flow conditions. The systems are illuminated by two separate LED units (Neptun, Roschwege company), each of which controls 8 of the channels. Using four independently controllable light channels per LED unit (UV-A + blue light [430 nm] // white light with a high proportion of blue light // white light with a high proportion of red light // far red), special wavelength distribution scenarios can be mapped, covering almost the entire natural light spectrum and thus ideally supporting the growth of aquatic plants and various algae as well as controlling physiological regulators. Furthermore, both diurnal and seasonal lighting patterns can be simulated. This makes the system equally suitable for short-term experiments as well as studies lasting several months, in which complex stream ecosystems with water, sediment, macrophytes and various invertebrate species can be mapped and investigated.