The invisible helpers in lakes and rivers

The invisible helpers in lakes and rivers

Aquatic fungi occur in virtually all bodies of water, but until now they have been largely unexplored. Now researchers want to discover which habitats are particularly important for organisms and how they can be better protected.

The threads of an aquatic mushroom under the scanning electron microscope.

The threads of an aquatic mushroom under the scanning electron microscope.

Dennis Kunkel Microscopy / Scientific Photo Library / Keystone

Aquatic mushrooms are small, tiny and invisible to the naked eye. And even under the microscope, only graphic patterns are revealed to the layman’s eye. They belong to the same phylum of fungi that we see on the forest floor, but they are adapted to life in water and are found in all bodies of water. In the seas, in lakes, in streams, but also in the water that accumulates in the hollows of trees.

To date, aquatic fungi have remained largely unexplored. “Very few research groups around the world deal with aquatic fungi in depth, perhaps because they are not very iconic compared to other organisms,” says Andreas Bruder, who researches aquatic fungi at the University of Applied Sciences of Southern Switzerland (SUPSI). , in Mendrisio.

And although research into these fungi is still at an early stage, scientists already agree that they play a fundamental role in the health of ecosystems. “You can actually imagine that their role is similar to that of forest mushrooms,” says Bruder. According to the ecologist, aquatic fungi have enzymes that they use to decompose leaves or wood in water and make them available to other species as their main food. Aquatic insects, for example, that feed fish and birds. “They are at the base of the food chain and take on extremely important tasks for the community of a body of water,” says Bruder.

Threatened by pesticides

Research suggests that waters with high biodiversity are healthier and therefore less vulnerable to disturbances and invasive species. Or put another way: without aquatic fungi, there would be no healthy ecosystems or clean water.

The researchers agree on one more point: aquatic fungi are threatened. For example, through fungicides and pesticides ending up in the water, through the loss of habitat diversity or through climate change that warms or dries out water bodies. The protection of aquatic fungi is, therefore, one of the main objectives of the research project that started this summer and in which SUPSI is one of eight international partners.

But: you can only protect what you really know. “That’s why we first have to fill big gaps in our knowledge,” says Bruder, talking about “biogeography,” about figuring out where suitable habitats are for aquatic fungi and what sets them apart. “On the one hand, we must collect and evaluate existing information on the biodiversity and distribution of aquatic fungi. On the other hand, we have to use new measurements to discover where the biodiversity hotspots are.”

Researchers are trying to understand whether existing protected areas – for birds or amphibians, for example – also benefit aquatic fungi or whether separate protected areas with specific properties are needed.

A team from the International Union for Conservation of Nature (IUCN), one of the oldest and most comprehensive species protection authorities in the world, is therefore also represented in the project. One of its areas of responsibility is the maintenance of red lists. The IUCN headquarters are in Gland, Switzerland. The recently founded group of aquatic fungi experts accompanying the project works in several countries.

To date, more than 5,700 species of aquatic fungi are known worldwide – around 1,900 coming from marine ecosystems and the rest from inland waters. “Until now, however, not a single species of aquatic mushroom has been subject to a risk assessment – ​​for example, according to the Red List,” says Isabel Fernandes, who researches at the University of Minho in Portugal and directs this IUCN. group of experts.

Things that are invisible are quickly forgotten

“The Red List of Threatened Species and its categories generally work for all organisms – with the exception of microorganisms. With aquatic fungi, we are advancing precisely in the area of ​​microorganisms”, says Monika Böhm, who works at the Indianapolis Zoo in partnership with the IUCN in the area of ​​protection of freshwater and marine species and is also involved in the research project. “Now it is important to find out which aquatic fungi can be evaluated based on existing criteria and which cannot,” she says.

Cooperation with the IUCN involves more than just formal inclusion on a list. “With inclusion in the IUCN species protection program, the protection of aquatic fungi would gain a social context”, says Andreas Bruder. Because even though aquatic fungi are ecologically important, they are invisible. And what is invisible is quickly forgotten or receives no attention at all – “one of the biggest challenges”, says Fernandes.

Science is also left to its own devices here – unlike terrestrial mushrooms, for example, which have already been included in the Red Lists and which can also be identified by laypeople thanks to their fruiting bodies. These, in turn, help assess mushroom populations. For example, how hundreds of amateur ornithologists support science with voluntary bird counts. On the other hand, laypeople cannot detect aquatic mushrooms without prior knowledge and tools. And they can’t count them.

The research project on aquatic fungi will last three years. It is very possible that unknown species will also be discovered.

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