Climate change and risks 3 min

Widespread decline of oxygen in lakes caused by climate change

PRESS RELEASE - Oxygen conditions in lakes of temperate regions are decreasing faster than in oceans. Climate change has been the main driver of this decline in lakes during the last four decades, threatening biodiversity and drinking water quality. These are the conclusions of an international study published on 2 June in Nature which was led by the Rensselaer Polytechnic Institute (USA) and involved INRAE scientists. Since 1980, the oxygen concentrations in these aquatic systems have fallen by 5.5% in surface waters and 18.6% in bottom waters. This overall decline of dissolved oxygen in lakes has potential impacts on ecosystems, particularly habitats of complex life such as fish. Oxygen decline can also alter biogeochemical cycles*, notably by increasing the release of nutrients into water and greenhouse gases such as methane into the atmosphere. However, these impacts are site-dependent, and some lakes may not be significantly impacted.

Published on 03 June 2021

illustration Widespread decline of oxygen in lakes caused by climate change
© INRAE - Guillaume Thirel

Although they only cover 3% of the world’s land surface, lakes are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. Smaller than seas and oceans, they react more rapidly to the effects of environmental changes. They thus represent excellent sentinels for the impacts of climate change on ecosystems. For this reason, an international team from the Global Lake Ecological Observatory Network (GLEON) ** conducted a study based on more than 45,000 samples of water from 400 lakes in temperate regions of the globe, mainly in North America and Europe; the oldest samples dated from 1941 and the most recent from 2019. INRAE contributed by supplying data from its Alpine Lake Observatory, OLA. The scientists analysed temporal trends on oxygen dissolved in surface and deep waters in addition to temperature profiles and analysed causes of change in oxygen fluctuations.

An overall decline of lake oxygen levels since the 1980s

The results showed an overall decrease in oxygen in lakes since 1980. Oxygen conditions in the lakes studied have decreased by an average of 5.5% in surface waters and 18.6% in deep waters. These rates of decline are 3 to 9 times faster in lakes than in oceans. The main driver of oxygen losses in surface water was attributed to the global rise in water temperatures, which caused a reduction in oxygen solubility in waters. With the rise in atmospheric temperatures since 1980, the overall temperature of lake surface waters increased by 0.38°C per decade, while oxygen concentrations decreased by 0.11 mg/l per decade. In deep waters, temperatures remained relatively stable but the rise in surface water temperatures increased the difference in density with deep waters, thus hampering the mixing of waters from different lake strata and hence the renewal of oxygen in deep waters. It is this increase in thermal stratification in terms of both intensity and duration that led to a decrease in oxygen conditions in deep lake waters.  

A positive feedback loop for eutrophication and a risk for increasing greenhouse gas emissions

Dissolved oxygen is a fundamental parameter of lakes that regulates numerous characteristics of the ecological quality of waters. Most complex life in lakes, such as fish, needs well oxygenated conditions. However, poor oxygen conditions can favour micro-organisms, such as certain bacteria that produce methane, a strong greenhouse gas. A decrease in oxygen conditions can also increase the release of pollutants from sediments such as metals and nutrients such as phosphorus, which in turn induce major changes in aquatic community structure of waters and foster eutrophication phenomena***.

Rapid changes observed in lakes in recent years provide new evidence of the effects of climate change on ecosystems on a global scale. Based on these observations, INRAE’s OLA Observatory is currently developing models to assess and forecast oxygen conditions in lake ecosystems in order to support their management.


Jane, S.F., Hansen, G.J.A., Kraemer, B.M. et al. Widespread deoxygenation of temperate lakes. Nature 594, 66–70 (2021). DOI:



In 2016, two studies based on sediment archives from lakes in Europe and throughout the world, conducted by the National Institute for Scientific Research in Quebec and involving INRAE, demonstrated that lakes were tending to lose their oxygen because of rises in nutrient release. These nutrients were notably due to an increase in human pressures, particularly in Europe following an increase in urban areas. This new study shows that during recent decades, climate change and rising temperatures have become the principal causes of lake deoxygenation, while the historical cause was the increase in nutrient supplies from watersheds. The question is now to determine how these two pressures (climate and nutrients) interact, and whether residual concentrations of phosphorus (nutrient elements for micro-organisms) in lakes and inherited from the 1950s in Europe, might amplify the impacts of climate change. These issues are currently being addressed by modelling, using data from sediment archives (long time scale) and the monitoring of lakes (recent data and the seasonal monitoring of lake waters).  

  • Jean-Philippe Jenny, Alexandre Normandeau, Pierre Francus, Zofia Ecaterina Taranu, Irene Gregory-Eaves, François Lapointe, Josue Jautzy, Antti E. K. Ojala, Jean-Marcel Dorioz, Arndt Schimmelmann, and Bernd Zolitschka. Urban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes. PNAS first published October 24, 2016, DOI: 10.1073/pnas.1605480113
  • JeanPhilippe Jenny, Pierre Francus, Alexandre Normandeau, François Lapointe, MarieElodie Perga, Antti Ojala, Arndt Schimmelmann and Bernd Zolitschka. Global spread of hypoxia in freshwater ecosystems during the last three centuries is caused by rising local human pressure. Global Change Biology (2016), DOI: 10.1111/gcb.13193

* A biogeochemical cycle is the process that concerns the transport and cyclical transformation of an element or chemical compound between the main reservoirs which are the geosphere, atmosphere and hydrosphere, in which the biosphere is situated.
** Le Global Lake Ecological Observatory Network (GLEON) is formed of a voluntary international network of scientists which aims to understand, predict and communicate on the role and responses of lakes to global environmental changes. The GLEON draws strength from more than 60 lake observatories worldwide, with more than 850 members from 62 countries. 
***Imbalance of aquatic ecosystems triggered by an excessive input of nutrients, often of human origin. The best known indicators are the appearance of toxic cyanobacteria in lakes and water courses, and macroalgal blooms in coastal regions. 


Learn more


Scott McCairns, an environmental explorer

When he discusses his career studying the ecological evolution of aquatic ecosystems, Scott McCairns, researcher at INRAE Brittany-Normandy, affirms that both luck, and timing, have been on his side. His recipe for success shines through his contagious enthusiasm: a curious scientific mind and a continual drive to expand his field of research.

21 December 2019

Climate change and risks

What we don't know (about lakes) could harm us

PRESS RELEASE - While extreme weather events are increasing in intensity and frequency due to climate change, an international research team warned that lakes around the world could change dramatically, placing both ecosystem health and water quality at risk. They also noted the lack of information about the biological impact that strong storms have on lakes, particularly on phytoplankton, which are the base of food webs.

04 March 2020


Biodiversity: microorganisms in lakes have been markedly impacted during the past century

PRESS RELEASE - Aquatic microorganisms are important actors in the ecosystems and biodiversity of lakes. However, we still have little understanding of the degree to which they have been affected by climatic and anthropogenic pressures. In a study published in Nature Communications on 31 July, a research team from INRAE, Université de Savoie Mont-Blanc, CNRS, Université Clermont-Auvergne and Université de Toulouse studied the DNA preserved in sediments from 48 lakes in order to compare the current diversity of microorganisms with that at the end of the 19th century, before the impact of human activities on ecosystems started to accelerate. Their results demonstrate drastic changes in the biodiversity of aquatic micro-organisms and a homogenisation of their diversity between lakes.

31 July 2020