Access to fresh water is absolutely vital for our survival. Without it, we would suffer from a lack of drinking water, fish to eat and the ability to irrigate the fields. Lakes, rivers and ponds are also home to countless species. But the structure of these sensitive ecosystems is not fully known.
“Freshwater environments are among the most threatened environments on the planet,” says Jennifer Anderson, who conducts research in the Department of Organismal Biology. “About one in three freshwater organisms is threatened. If we look at the International Union for Conservation of Nature Red List, we know the status of many fish in Europe. But when I say one in three species is threatened, I’m referring to the organisms we’ve studied. This does not include the great diversity of species that we have not even developed tools or methods to assess.
Pollution and land use
The greatest threats to freshwater environments are directly related to humans, such as pollution, land use change, water abstraction, and the release of pharmaceutical residues from wastewater. But temperature changes and drought, which are becoming more common with climate change, also impact freshwater environments.
“We put enormous pressure on this very small asset,” Anderson says. “Fresh water makes up 2.5% of all water on earth and most of it is ice-bound or exists underground, so very little water is surface water.”
enlarged freshwater mushroom spores and a fish.
Anderson is one of the few researchers in the world to study freshwater fungi. These microscopic fungi perform a very important function by breaking down dead organic matter and making nutrients available to other organisms.
“Fungi are the dominant microbial decomposers in streams and rivers,” says Anderson, “and they are an extremely important link between carbon and nutrients that end up in streams and other stream food webs. They are therefore absolutely crucial. Organisms that live in a waterway are a lot like us – they lack the enzymes to digest tough plant fibers. So that’s what mushrooms do.
Symbiosis and decomposition
In terms of lifestyle, these mushrooms show great variation, to say the least. Within the same species, some fungi can live as decomposers in a watercourse and others live in the roots of plants in symbiosis with their host plant.
“It’s not unheard of in fungi,” says Anderson. “They may have these dual lifestyles, but we don’t know much about it. There is another example of fungi that live in plants and at the same time cause disease in insects. Thus, they can be connected to an insect they have killed and transfer nutrients from it to the plant.
cladium setigerum, which have been found in the Fyris
River. Photo: Jennifer Anderson
Knowledge gaps regarding freshwater fungi are significant because very little research has been done on them. Because of this, no one knows how common they are and how threatened they are. None of them have been assessed for conservation status.
“We can at least learn to understand the biodiversity that we actually have,” says Anderson, “and that doesn’t just include beautiful fish. We can start looking at what actions improve or worsen the biodiversity of our freshwaters.
Asa Malmberg
