Pioneering database charts how freshwater wildlife respond to rising temperatures

Researchers studying the effects of climate change on freshwater wildlife have published the world’s largest database of how river, lake and stream species respond to rising temperatures.

Climate change not only causes temperatures on land and in the sea to rise, but also leads to warming rivers, lakes, and streams – with serious consequences for the animals living within them.

A research team led by the University of Duisburg-Essen, that included Dr. Noël Juvigny-Khenafou from the University of Stirling’s Institute of Aquaculture, has published the largest openly accessible collection of data on the thermal tolerance of freshwater organisms to date.

They hope that the data will support water management and government authorities to enact preventive measures to protect animals living in and around water.

Valuable tool

Dr. Noël Juvigny-Khenafou, Lecturer in Aquatic Environmental Science at the University of Stirling, said: “Temperature is one of the most studied parameters in biology, and not all species respond in the same way to fluctuations in temperature, many have different tolerance thresholds.

“Our rivers, lakes and streams are disproportionately biodiverse and are exposed to rapid temperature changes. As the impacts of global change on the thermal regime of natural systems intensify, it is important to quickly access species-specific data so we can better predict which species might be more susceptible and the resulting impact on ecosystems.

“This database is unique as it draws on the knowledge from multiple languages, and we believe that it will prove to be a valuable tool for the management of freshwater resources, the animals living in them, as well as the industries depending on them."

The new ThermoFresh database comprises 6,825 entries on 931 species from 572 studies conducted worldwide between 1900 and 2023. In addition to data on fish, it also includes data for numerous invertebrate species such as insect larvae, crustaceans and planarians in one place for the first time.

These are particularly important in the context of climate change because they keep water bodies clean and functioning, serve as the basis of food webs, and act as biological indicators for water quality.

“With our global compilation of thermal tolerance, we can much more precisely assess which species are particularly at risk when water temperatures rise,” said ecotoxicologist Helena Bayat, a doctoral researcher in the RESIST Collaborative Research Centre at the University of Duisburg-Essen.

“Our rivers serve as early warning systems for the effects of climate change. When species such as burbot or gammarids disappear, it warns us that water quality is also at risk for us humans."

Endangered species

The burbot (Lota lota), which is considered endangered in Germany, is particularly sensitive to heat. The freshwater amphipod (Gammarus fossarum) and European planarian flatworm (Dugesia gonocephala) are also heat sensitive and only occur in clean waters with a good ecological status.

Helena Bayat added: “If their populations decline, entire food chains and nutrient cycles are disrupted, and the ecosystem can eventually collapse.

“For humans, the waters then not only lose their recreational value, but also their use as cooling water for industry or as drinking water.”

Benefits for authorities

The openly accessible ThermoFresh database aims to prevent this from happening. It contains data in English, German, French, Spanish and Chinese and, in addition to temperature tolerances, data on other stress factors such as oxygen deficiency or pollutants. 

Researchers and practitioners can use it to identify sensitive species, recognise danger zones and plan targeted measures. This enables authorities to set priority areas for nature restoration projects, better assess the spread of invasive species in the context of climate change, and better evaluate the risks of cooling water discharges (such as from thermal power plants or industrial facilities).

Global thermal tolerance compilation for freshwater invertebrates and fish has been published in the journal Scientific Data.