Pollution neutralises improved heat tolerance in water fleas

Researchers at KU Leuven studied the impact of pollution on evolutionary reactions of organisms that adapt to global warming. The research, published in , shows that pollution, specifically metal pollution, can neutralise the advantage of a fast evolution of heat tolerance in water organisms.

Revived water fleas provide unique new insights

The research focused on the water flea (Daphnia magna), a crucial element in freshwater ecosystems. The water flea eats algae and helps to keep the waters in shallow lakes clear. Dormant eggs of this water flea can survive for decades in sediment layers and can be revived under the right circumstances.

The Daphnia Magna water flea
©Marlies Van de Maele

By comparing two subpopulations of the water flea from the same lake with 40 years difference, the study confirms that these organisms have adapted to an increase in the number of heat waves over the course of these 40 years, and have managed to better endure the rising heat stress.

This quick evolution sounds like good news. But this study also investigated what happens if the organisms are exposed to pollution, specifically zinc pollution.

The improved heat tolerance in the recent subpopulation reduced considerably. So much so that the evolutionary advantage of a higher heat resistance completely disappeared because of the adverse effects of pollution.

Researcher Ying Dong: 'We have revived Daphnia magna water fleas out of sediment layers from different periods in time (1955-1965 and 1995-2005) and exposed them to different levels of heat and zinc pollution. The results were clear: while the recent subpopulation showed improved heat tolerance, this advantage was lost when zinc was introduced, which led to a similar vulnerability to heat compared to the older subpopulation.'

The results support a crucial evolutionary approach. The capacity to better endure heat leads to an increased sensitivity to polluting components. This interaction between multiple stress factors is probably common because dealing with stress factors always has a high energy cost. This highlights the complexity of ecological reactions in quickly evolving climate and environmental conditions.

'Our results show that, even though some species can quickly adapt to increasing temperatures, the presence of polluting components can completely undermine these adaptations. This interaction between rising temperatures and pollution should therefore be included in climate strategies and estimates of ecological risks,' concluded professor Stoks.

Public link

Please use the above public link if you want to share this noodl on another website.