Global atlas of thermal tolerance provides heat check for freshwater organisms

Lisa Lock
scientific editor

Robert Egan
associate editor

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 at the University of Duisburg-Essen has published the largest openly accessible collection of data on the thermal tolerance of freshwater organisms to date. This data helps water management and government authorities to enact preventive measures to protect animals living in and around water.
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. The work is in the journal Scientific Data.
"With our global compilation of thermal tolerance, we can much more precisely assess which species are particularly at risk when water temperatures rise," emphasizes ecotoxicologist Helena Bayat, a doctoral researcher in the RESIST Collaborative Research Center 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 in domestic waters
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.
"If their populations decline, entire food chains and nutrient cycles are disrupted, and the ecosystem can eventually collapse," explains Bayat. "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 and planning
The openly accessible ThermoFresh database, available on , 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, recognize 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 (e.g., from thermal power plants or industrial facilities).
More information: Helena S. Bayat et al, Global thermal tolerance compilation for freshwater invertebrates and fish, Scientific Data (2025).
Journal information: Scientific Data
Provided by University of Duisburg-Essen