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TitleUrban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes
AuthorJenny, J P; Normandeau, AORCID logo; Francus, P; Taranu, Z E; Gregory-Eaves, I; Lapointe, F; Jautzy, JORCID logo; Ojala, A E K; Dorioz, J M; Schimmelmann, A; Zolitschka, B
SourceProceedings of the National Academy of Sciences of the United States of America vol. 113, no. 45, 2016 p. 12655-12660, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20160242
PublisherProceedings of the National Academy of Sciences
Mediapaper; on-line; digital
File formatpdf
AreaEurope; United Kingdom of Great Britain and Northern Ireland; Spain; Portugal; Italy; Greece; Germany; Austria; Croatia; Serbia; Slovakia; Finland; Norway; Sweden; Ireland; Belgium
Lat/Long WENS -10.0000 31.0000 70.0000 35.0000
Subjectslake water; lakes; phosphorus; limnology; environmental impacts; lacustrine environments; phosphate, fertilizer; Anthropocene
Illustrationslocation maps; graphs
Released2016 10 24
AbstractEnhanced phosphorus (P) export from land into streams and lakes is a primary factor driving the expansion of deep-water hypoxia in
lakes during the Anthropocene. However, the interplay of regional scale environmental stressors and the lack of long-term instrumental
data often impede analyses attempting to associate changes in land cover with downstream aquatic responses. Herein, we performed a
synthesis of data that link paleolimnological reconstructions of lake bottom-water oxygenation to changes in land cover/use and climate
over the past 300 years to evaluate whether the spread of hypoxia in European lakes was primarily associated with enhanced P exports from growing urbanization, intensified agriculture, or climatic change. We showed that hypoxia started spreading in European lakes around CE 1850 andwas greatly accelerated after CE 1900. Socioeconomic changes in Europe beginning in CE 1850 resulted in widespread urbanization, as well as a larger and more intensively cultivated surface area. However, our analysis of temporal trends demonstrated that the onset and intensification of lacustrine hypoxia weremore strongly related to the growth of urban areas than to changes in agricultural areas and the application of fertilizers. These results suggest that anthropogenically triggered hypoxia in European lakes was primarily caused by enhanced P discharges from urban point sources. To date, there have been no signs of sustained recovery of bottom-water oxygenation in lakes following the enactment of European water legislation in the 1970s to
1980s, and the subsequent decrease in domestic P consumption.
Summary(Plain Language Summary, not published)
Using a compilation of data arising from over 1,500 European watersheds, we have identified the relative role of different drivers affecting lake health. In particular, our regional synthesis of lake sediments indicated a significant acceleration in the spread of hypoxia (lack of available oxygen) in lakes in the 1900s, which occurred well before the general use of commercial fertilizers in the mid-20th century and the onset of climate warming in the 1970s. The spread of hypoxia was best explained by urban expansion and the associated increase man-made sources of phosphorus, such as discharge of nutrients from treated and raw sewage, which led to enhanced lacustrine biological productivity.

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