A recently published study on Diktar-Eriks sjö, a lake situated between Abisko and Riksgränsen in Sweden, provides a detailed picture of how climate change has influenced its biodiversity and food web.
- How food webs and biodiversity have changed due to historical climate changes provides us with knowledge that helps us to understand how lake ecosystems may be affected by ongoing climate change, says Simon Belle, researcher at the Department of Aquatic Sciences and Assessment.
Lake sediments can function as archives, as remains of animals and plants are stored in the sediments over the centuries. By analysing samples from the sediments in Diktar-Eriks sjö, researchers can now show how the community of planktonic and benthic water fleas has changed over the past 5700 years. The study revealed that the diversity of water fleas in Diktar-Eriks sjö decreased substantially, starting around 3500 years ago. At that time, the climate became colder and wetter, causing the number of species to drop species from 18 to 7.
- Climate change affects the aquatic food web. A direct effect is a warmer temperature in the lake, but we can also show that changes in the landscape surrounding the lake have a clear impact on aquatic biodiversity, says Tobias Vrede, researcher at the Department of Aquatic Sciences and Assessment.
The study also showed that the complexity of the food web decreased as it became shorter, and species with specialised ecological niches were replaced by generalists. These changes coincide with alterations in the vegetation surrounding the lake and changes in the composition of the algal community within the lake. The reduction in biodiversity and ecosystem complexity is crucial to understand as biodiversity provides resilience and stability to an ecosystem. A stable ecosystem, in turn, is essential for sustaining the ecosystem services that humans rely on.
Subarctic lakes as climate change indicators
Lakes in the subarctic, such as Diktar-Eriks sjö, are among the most vulnerable ecosystems to climate change. Arctic regions are warming faster than the global average, making these ecosystems particularly sensitive. As a result, such lakes act as sentinels, offering insights into how both terrestrial and aquatic environments respond to climate shifts. Scientists view them as key indicators that can help predict how other lakes may be affected in the future.
Water fleas: tiny crustaceans with great importance
Water fleas play an important role in lake ecosystems, making them of particular interest to study. These small crustaceans feed on phytoplankton and benthic algae, yet others are predators. In turn, the water fleas serve as an important food source for larger organisms, like fish. Water fleas leave fossilised remains, such as carapace shields and claws, in lake sediments. As these parts remain, this characteristic makes them invaluable for studying historical shifts in biodiversity and the structure of food webs over time.
The changes in diversity as observed in the lake sediment samples highlight how sensitive these ecosystems are to temperature changes and alterations in the surrounding landscape. Given the rapid pace of global warming, it is crucial to continue studying the links between climate, land, and water in order to better understand and manage future changes.
