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Freshwater mussels are the industrious cleaners of lakes and rivers, filtering small algae out of the water and keeping it clear. This positive image has suffered since the spread of the invasive quagga mussel. The voracious appetite of this newly introduced species means that fish in Lake Constance and other water bodies are deprived of plankton as a source of food. Keeping them in check also costs a lot of money: masses of quagga mussels clog up pipes and boats. We put five questions to IGB researchers to find out more about these industrious filter feeders.

Two recent studies highlight the profound impacts of hydropower on biodiversity in river channels and at the land-water surface. The studies demonstrate that these effects arise from impoundment upstream of the dams, disruptions to the natural flow, sediment, and thermal regimes in downstream channels and floodplains, altering habitat conditions and environmental cues vital for many species to complete their life cycles. 

Aquatic fungi are among the least studied organism groups on Earth, yet they play a vital role in our waters. Hans-Peter Grossart cultivates fungal cultures from lakes to better understand their role in nutrient cycles – and to make them visible. High-resolution images of his work now form the basis of an extraordinary art project at Expo 2025 in Osaka.

Today on Earth Day, the 19 National Champions of the Frontiers Planet Prize, a globally significant research prize for sustainability, were announced. Robert Arlinghaus, Professor of Fisheries at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) and the Humboldt Universität zu Berlin, and his team are recognized for their groundbreaking publication in Science on the effectiveness of habitat improvement on fish populations in lakes.

How do invasive species change the use of food resources? A meta study reveals that the maximum consumption rates of the invasive species are on average 70 percent higher than those of their native counterparts. This phenomenon is particularly pronounced in freshwater species and could be a major reason for the strong impact of invasive species on biodiversity.

Light pollution, which illuminates the night sky, promotes the growth of cyanobacteria (often called blue-green algae) and stimulates metabolic processes in lakes. This is shown by a recent study by the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) in the largest field experiment to date on the effect of light pollution on lakes. The results have been published in the scientific journal Water Research.

To survive as a species, aquatic organisms have developed a wide variety of strategies. Millions of years ago, sturgeons used their bony shells to fend off predators and relocate their habitats, sulphur mollies survive in toxic, almost oxygen-free water, and fish stocks in the River Oder are gradually recovering from the 2022 disaster. However, there are limits to the resilience of organisms, and these can be seen even in the tiniest single-celled creatures.

Without algae, little would function in aquatic ecosystems: they are a key component of the aquatic food web and provide oxygen for respiratory animals. But there is ample evidence that their abundance and composition are shifting as a result of climate change. This often has alarming consequences for the communities that live in rivers and lakes – and for us humans.