In a laboratory experiment, Eawag ecologists studied how the pond snail Lymnaea stagnalis is affected by heatwaves, which are expected to become more frequent as a result of climate change. Snails exposed to temperature stress showed a greater investment in reproduction, egg production increasing by 60 per cent on average. However, a trade-off was observed with immune defence: the activity of phenoloxidase – an enzyme offering protection against parasites – was reduced by 36 per cent. Stress responses were also investigated in snails concomitantly exposed to low concentrations of micropollutants – and the combined effects of high temperature and chemicals were mainly additive.. As the effects observed were transient, the researchers conclude that pond snails are highly resilient to environmental changes – but this finding is not automatically applicable to other aquatic organisms.