Terrestrial diatoms as bioindicators for the soil ecological status (SoilDiatoms)

• Applicants: Professor Dr. Ulf Karsten; Dr. Jonas Zimmermann
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549124826

Soils play a key role for the functioning of terrestrial ecosystems such as C storage, nutrient cycling and being the habitat of an overwhelming biodiversity. Thus, soils and their good ecological status are essential for human society. Soil degradation and therefore the loss of intrinsic physical, chemical, and/or biological properties by either natural or anthropogenic processes/stressors definitely results in the decline of important soil ecosystem functions. Terrestrial diatom communities or “soil diatoms” are those diatoms living on and between substrate particles moistened mainly by atmospheric water supply. The biodiversity of these diatoms is far from being as well studied and understood as their aquatic counterparts, even though they are widespread and ubiquitous in many terrestrial habitats. Therefore, we propose to evaluate for the first time the biodiversity of soil diatom communities and pedological parameters on long-term agricultural field sites, which were established in 1998 with a focus on different phosphorus (P) management strategies. Natural soil diatom communities will be correlated with all available soil parameters using advanced statistics to outline the key factors for species composition, abundance and frequency. The site-specific soil diatom community structure will be a new and powerful tool for the bioindication of the soil ecological status on short to long temporal scales, reflecting soil P conditions and pH. Selected terrestrial diatom species will be isolated from the agricultural field sites and established as clonal cultures to study their autecological requirements under controlled conditions. Such experimental data are the backbone to confirm and validate their bioindicative value for soil P load and pH. The main goals of the project SoilDiatoms are 1.) to identify the almost unknown soil diatom biodiversity in fine-grained taxonomic depth using a combination of field, culture as well as culture-independent methods for phenotypic and genotypic identification; 2.) to establish a taxonomically validated reference library for soil diatoms with comprehensive information on habitat, morphology and DNA barcoding for unambiguous identification; 3.) to apply this new taxonomic reference library on soil diatoms for environmental DNA (eDNA) metabarcoding to access the concealed biodiversity and assess the status of the taxonomic coverage of different diatom groups; 4.) to establish clonal cultures of soil diatoms and to evaluate their autecological requirements for definition of tolerance ranges against soil P load and pH, thereby experimentally validating species-specific bioindicator values from the previous correlation analysis; 5.) to develop a new soil diatom index (SDI) for the soil ecological status, thereby providing fundamental information for the recently proposed EU Soil Monitoring Law directive. The results will allow to link biodiversity and functional data of soil diatoms to some soil properties.

• DFG Programme: Research Grants