Inconspicuous, hardly researched – but ecologically enormously important: Researchers draw attention to the importance of aquatic fungal species and are committed to their investigation and protection. Accordingly, these organisms form an important part of the “digestive apparatus” of water bodies and thus of the food web. The aquatic fungi are threatened, among other things, by fungicides from agriculture that are introduced into water bodies, the scientists report.
In addition to plants and animals, they lead a shadowy existence: many people often only associate the term mushroom with mushrooms and the like. But in addition to these so-called pillar fungi with their eye-catching fruiting bodies, the gigantic realm of these organisms has many other subgroups with different ways of life and appearances to offer. As ecosystem engineers, symbiosis partners or pathogens, they fulfill a variety of roles in nature. They also have a special meaning for us humans: without mushrooms there would be no penicillin, no beer and no yeast braid. An international team of researchers is now focusing on a group of fungi that has so far remained particularly unknown: species that live in water.
Part of the aquatic “digestive system”
In their publication, the scientists first clarify the great ecological importance of these organisms. Because they form networks and cell structures in all types of water – from small puddles to the oceans and even in ice and snow, they occur. According to the researchers, there are only rough estimates of the proportion of fungi in the microorganisms in different bodies of water, but this can apparently be significant: In freshwater, they could make up up to 50 percent of the microorganisms with a cell nucleus. Their importance is correspondingly great.
“The aquatic fungi are tiny, can be found everywhere and form an important part of the ‘digestive system’ in water bodies,” says co-author Hans-Peter Grossart from the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB). Because, as he and his colleagues explain, these organisms chew up food, so to speak: They break down sometimes stubborn substances from dead plant material and therefore make them more available to other creatures in the water. There are also species that infest certain creatures such as water fleas and thereby affect their populations. Ultimately, the aquatic fungal species are therefore an important factor in the complex system of the climate-relevant carbon cycle. There is also scientific evidence that they play an important role in breaking down pollutants in water.
“Microbial Black Matter”
Despite the complex and great importance, however, hardly any other group of organisms on our planet has remained as unknown as this group of fungi, the researchers show. In professional circles, the aquatic fungi are therefore also referred to as microbial black matter. According to the team, this also means that these important organisms are not in focus as potential conservation targets. “To date, the International Union for Conservation of Nature (IUCN) Red List of Threatened Species only includes assessments for a small number of fungi, and all of the assessed fungi also include only terrestrial macrofungi,” says co-author Mariyana Vatova of the University of Algarve in Portugal.
However, it is already becoming apparent that aquatic fungi could also be severely affected by man-made threats to aquatic ecosystems: Studies have already provided evidence that pesticides used against fungal pathogens in agriculture damage aquatic fungal communities. The substances introduced into water bodies therefore have a negative effect on fungal biomass and diversity. “On the other hand, we still know next to nothing about the other dangers to which they are also likely to be exposed. Many other pollutants could affect fungi and their delicate networks, such as pharmaceuticals, metals, microplastics and nutrients,” says Grossart.
exploration and protection
However, if you basically know hardly anything about these organisms, you cannot really recognize the losses and their basis, emphasizes co-author Ivan Jarić from the Biology Center of the Czech Academy of Sciences in České Budějovice: “Unfortunately, many effects probably remain undiscovered due to the gaps in knowledge . Such hidden losses of ecosystem functions are problematic as they hamper our ability to carry out timely and effective conservation measures.” The adverse impacts could lead to the decline of fungal species in aquatic communities and thus the loss of their key ecosystem functions, which can ultimately cause cascade effects in aquatic food webs .
“The protection of water fungi must therefore urgently be recognized as a priority for the management of water bodies,” says Grossart. However, such measures may need to be adapted to the specifics of fungi. Therefore, there is a need for research, emphasizes the scientist: “It would therefore be important not only to work towards the adoption of strict measures against sources of pollution, but also to develop and apply new, standardized fungal bioassays,” says Grossart.
Source: Leibniz Institute for Freshwater Ecology and Inland Fisheries