title: Global spread of hypoxia in freshwater ecosystems during the last three centuries is caused by rising local human pressure.
abstract: The spread of hypoxia is a threat to aquatic ecosystem functions and services as well as to biodiversity. However, sparse long-term monitoring of lake ecosystems has prevented reconstruction of global hypoxia dynamics while inhibiting investigations into its causes and assessing the resilience capacity of these systems. This study compiles the onset and duration of hypoxia recorded in sediments of 365 lakes worldwide since AD 1700, showing that lacustrine hypoxia started spreading before AD 1900, 70 years prior to hypoxia in coastal zones. This study also shows that the increase of human activities and nutrient release is leading to hypoxia onset. No correlations were found with changes in precipitation or temperature. There is no evidence for a post-1980s return to well-oxygenated lacustrine conditions in industrialized countries despite the implementation of restoration programs. The apparent establishment of stable hypoxic conditions prior to AD 1900 highlights the challenges of a growing nutrient demand, accompanied by increasing global nutrient emissions of our industrialized societies, and climate change.
authors.affiliation: Centre Eau Terre Environnement, INRS, Québec, QC, Canada, G1K9A9.|GEOTOP Research Center, Montreal, QC, Canada, H3C 3P8.|EDYTEM, Université de Savoie, CNRS, 73376, Le Bourget du Lac Cedex, France.
authors.forename: Jean-Philippe
authors.identifier: http://orcid.org/0000-0002-2740-174X
authors.initials: JP
authors.lastname: Jenny
authors.affiliation: Centre Eau Terre Environnement, INRS, Québec, QC, Canada, G1K9A9.|GEOTOP Research Center, Montreal, QC, Canada, H3C 3P8.
authors.forename: Pierre
authors.initials: P
authors.lastname: Francus
authors.affiliation: Department of Geography and Planning, Queen's University, Kingston, QC, Canada, ONK7L3N6.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Normandeau
authors.affiliation: Centre Eau Terre Environnement, INRS, Québec, QC, Canada, G1K9A9.|GEOTOP Research Center, Montreal, QC, Canada, H3C 3P8.
authors.forename: François
authors.initials: F
authors.lastname: Lapointe
authors.affiliation: INRA UMR 42 CARRTEL, Université de Savoie, 74203, Thonon-les-bains Cedex, France.
authors.forename: Marie-Elodie
authors.initials: ME
authors.lastname: Perga
authors.affiliation: Geological Survey of Finland, P.O. Box 96, 02151, Espoo, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Ojala
authors.affiliation: Department of Geological Sciences, Indiana University, Bloomington, IN, 47405, USA.
authors.forename: Arndt
authors.initials: A
authors.lastname: Schimmelmann
authors.affiliation: GEOPOLAR, Institute of Geography, University of Bremen, D-28359, Bremen, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Zolitschka
mesh_terms: D057231:Climate Change; D017753:Ecosystem; D019015:Geologic Sediments / Q000032:analysis; D006801:Humans; D060106:Lakes / Q000032:analysis*; D010100:Oxygen / Q000032:analysis*; D011156:Population Density; D013696:Temperature
chemical_list: D010100:Oxygen
keywords: anoxic conditions; aquatic transition; global change; lake ecosystem; local human pressure; varved sediment