Research | IGB | 27-09-2018

When lakes start to sweat

Rising temperatures are a threat to the balance of lakes. In a new IGB Dossier, researchers provide a summary of the changes that lakes are already undergoing and of the scenarios that are likely to occur.

Lake Müggelsee is located in the southeast of suburban Berlin. Using its own monitoring station, IGB has been documenting changes in this shallow lake since the 1970s. | Photo: © stock.adobe.com – Maurice Tricatelle

The latest IGB Dossier explains the impact of climate change

Rising temperatures are a threat to the balance of lakes. Scientists at Berlin’s Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) are investigating the extent to which climate change is already affecting our freshwaters and whether it jeopardises their stability. In a new IGB Dossier, the researchers provide a summary of the changes that lakes are already undergoing and of the scenarios that are likely to occur. The IGB Dossier “Lakes under climate change: diagnosis and prognosis from long-term research" can now be downloaded free of charge from the institute’s website. The first few warm days of spring act as a stimulus to lake ecosystems. Underwater life awakens. The increase in light and warmth encourages algae and plants to thrive. These, in turn, are an essential source of food for aquatic creatures – from zooplankton to fish. And yet what would happen if the system “overheated”, upsetting the balance of this annual cycle long term?

Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB)
Johannes Graupner
Knowledge Transfer
Email graupnerigb-berlin.de
Phone+49 30 64181-703

Alarming increase in temperature in recent decades

In the new IGB Dossier, scientists warn that the general trend towards higher temperatures induced by climate change is a problem for our lakes. Since 1985, scientists have registered an average increase of 0.34°C per decade in the temperature of lakes throughout the world in summer. “Consequently, surface water temperatures have increased more considerably and rapidly than comparable air temperatures,” explained Rita Adrian, Head of IGB’s Department of Ecosystem Research and co-author of the Dossier.

The cycle of a typical dimictic lake: the water column mixes twice a year (spring and autumn circulation), which has a major impact on its oxygen concentration and its communities. Temperature differences between surface water and deep water that develop under ice, as well as in summer, prevent mixing.

Lakes under climate stress

Higher water temperatures and less winter ice formation, lasting for shorter periods, are direct consequences of climate change. “However, we are even more concerned about indirect effects, such as impacts on light, oxygen, and nutrient dynamics, which may have a major influence on lake ecosystems,” explained Tom Shatwell, co-author and IGB scientist. Greater inflow from the catchment area in high-precipitation areas also leads to an increase in the contamination of freshwaters with nutrients.

Depending on the type of lake and their catchment area, these waters react differently to such circumstances. “Lakes are ecosystems featuring complex interrelations and processes. In the new IGB Dossier, we therefore provide a universally comprehensible explanation of the underlying natural processes, highlighting how our freshwaters may change as a consequence of climate change,” added Rita Adrian.

Both authors agree that blanket statements are virtually impossible in this respect. One thing is for certain, however: besides rising water temperatures, there will primarily be lower oxygen concentrations and an altered stratification in summer, which, owing to “lake-internal fertilisation”, could lead to the release of even more nutrients. Such effects promote excessive growth of algae, especially the development of Cyanophyceae, commonly referred to as “blue-green algae”. Rising temperatures also cause heat-tolerant species to spread further north, displacing cold-adapted species.

IGB (ed.) (2018): IGB Dossier. Lakes under climate change. Diagnosis and prognosis from long-term research.
Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin.
Download dossier

Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB)
Prof. Dr. Rita Adrian
Head of Department "Long-term and Climate Impact Research of Lake Ecosystems"
Email adrianigb-berlin.de
Phone +49 30 64181-680

Comparison of the internally and externally caused fertilisation of lakes in the context of global warming: nutrient accumulation in water encourages the growth of algae, particularly the development of Cyanophyceae, which, owing to their ecology, are among the beneficiaries of climate change.

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