Intensive agriculture poses a significant threat to global biodiversity. However, one aspect of biodiversity in farmland is little studied: algae. Most people have seen algae growing in streams, lakes or the sea. However, algae have also adapted to survive in dryer, harsher conditions on land. In fact, soil algae are thought to be responsible for about 6% of the vegetation production on Earth. This led a research team at the universities of Göttingen and Kassel to investigate the algae in the surface soils of farmland. Their pilot study revealed more than 100 different algae, likely to be made up of hundreds of individual species. Unlike most other microbes, these algae showed seasonal variation in their communities. These are the first steps towards understanding the factors that determine the diversity of these important microorganisms. The results were published in the Journal Frontiers in Microbiology.
The team examined soils from farmed wheat fields, managed by nearby Kassel University. Samples were collected from the topsoil of the fields in spring, summer and autumn representing different conditions of wheat fields throughout the year. Molecular methods – such as DNA Metabarcoding – enabled the analysis of many samples at once and the identification of the large diversity of soil algae with higher precision than previous studies.
The researchers discovered unexpectedly strong seasonal variation. A group of algae known as yellow-green algae (Xanthophyceae) was the most abundant when it was colder, at the time points in spring and autumn; whereas blue-green algae (Cyanobacteria) and green algae were prevalent shortly before crop harvest in summer. Cyanobacteria are often already used as a natural fertilizer in rice paddy fields in Asia. The researchers showed that many of these organisms could also be abundant in the fields of Central Europe. Additionally, researchers identified a large diversity of green algae, as well as diatoms – a common type of single-celled algae mostly known from marine or freshwater habitats.
"These organisms are critical to the soil microbiome. Soil health and fertility may depend on them," says Professor Thomas Friedl at the University of Göttingen. Although the microbiome of arable land has received increased attention from researchers in recent years, most studies focus on Bacteria and Fungi, not on soil algae. "Soil algae produce an array of substances and have many valuable effects, such as on texture and fertility. They can stimulate other organisms, improve nutrient cycling, and positively influence local water availability and quality. Their cell walls can act as reservoirs, absorbing essential nutrients, enhancing the soil's capacity to retain these substances," adds Friedl.
Professor Miriam Athmann at the University of Kassel explains, "Until now, neither researchers nor farmers were aware of how crop management affects the algae in their fields and many questions remain." For instance, the research found a huge diversity of algae in both organically and conventionally managed fields, with clear differences in species composition, however. How management affects soil algae is one of the issues that will be studied in follow-up research with over 300 samples from long-term field experiments, allowing a sound scientific evaluation. Athmann adds: "Future studies will bring insights into how farmers can protect algal diversity and potentially even profit from their benefits for crop growth."
Original publication: Barthel S, et al "Soil algae in arable land: changes in the genotypic community composition across time points and farming systems - a pilot study". Frontiers in Microbiology, 2026 DOI: 10.3389/fmicb.2026.1813833
