The effect of rising water temperatures on ecosystems will likely interact with pre-existing pressures, such as excess nutrients from pollution, leading to a dangerous combination, according to a new study. New international research, carried out by the University of Sheffield, University of Oxford, University of Savoie Mont Blanc and the French National Research Institute for Agriculture, Food and Environment, has found that food webs become less complex in warmer, nutrient-rich waters. This simplification means shorter food chains and a poorer functioning ecosystem. The urgent global need to reduce river pollution levels was recognized internationally when Olympic open water swimming events, due to take place on the Seine in Paris, had to be postponed due to harmful bacteria levels.
Scientists previously thought that global warming due to climate change and increased nutrient levels due to pollution could offset each other’s impact on aquatic life. However, a new study has shown that warming waters and nutrient overload are a dangerous combination that threatens our rivers and lakes.
The research, carried out by an international team of scientists from the University of Sheffield, the University of Oxford and the University of Savoie Mont Blanc and the French National Research Institute for Agriculture, Food and the Environment, examined hundreds of lakes and streams and analyzed the complex relationships between fish species.
Researchers found that food webs, the intricate networks of who eats whom, become less complex in warmer, nutrient-rich waters. This simplification means shorter food chains and an ecosystem with reduced functioning. Top predators are particularly vulnerable to these changes, but they are essential to the functioning and stability of ecosystems.
Less than three percent of our planet’s water is fresh, yet freshwater habitats are home to nearly 10 percent of all known animals and nearly half of all known fish species. Freshwater ecosystems not only help maintain the water quality of the land and sea, but also allow wildlife such as eels and salmon to travel great distances to complete their life cycles, and act as conveyor belts that transport nutrients that keep the soil well for growing food.
The far-reaching impact of the need to reduce pollution levels in our rivers was felt worldwide when the Olympic open water swimming events such as the triathlon, which were due to take place in the River Seine in Paris, had to be postponed due to harmful bacteria levels. The study highlights that this need is even more urgent as the effects of warming climate change continue to worsen, but also suggests that reducing pollution levels is a promising way to mitigate the effects of climate change.
Alain Danet, postdoctoral research fellow at the University of Sheffield and co-first author of the study, said: “The eyes of the world are on the Seine this summer for the Olympic Games. The challenges facing Paris demonstrate how important it is to reduce pollution levels in our rivers and lakes, not only for our own health, but also for the health of our ecosystems.
“Our rivers, lakes, wetlands and underground water supplies store and purify the water that is crucial for people and wildlife. From providing drinking water to providing essential resources to terrestrial and marine ecosystems, healthy freshwater systems are essential.
“These vital ecosystems also protect us from flooding, filter pollution and support countless plants and animals.”
Willem Bonnaffé, postdoctoral research fellow at the University of Oxford and co-first author of the study, said: “Lake and river animals are like the kidneys of our planet. They purify water and prevent the bloom of toxic algae and bacteria. Keeping them safe keeps us safe.
‘Climate change and pollution are not isolated problems for our rivers and lakes, as scientists previously believed. Our research has shown that they interact in complex ways, threatening the balance of life in our waters.
“By reducing greenhouse gas emissions and improving water quality, we can help protect the health of our rivers and lakes for future generations.”
Camille Leclerc, postdoctoral research fellow at the French National Research Institute for Agriculture, Food and Environment and co-first author of the study, said: “This important research has shown what a dangerous combination of warming water caused by climate change and increased nutrient levels was causing. due to pollution.
“On a more positive note, this study shows that if we can reduce pollution in our lakes and rivers, this will better protect them from the impacts of climate change and warmer waters.”
