The nexus among long-term changes in lake primary productivity, deep-water anoxia, and internal phosphorus loading, explored through analysis of a 15,000-year varved sediment record

Tu, Luyao; Gilli, Adrian; Lotter, André F.; Vogel, Hendrik; Moyle, Madeleine; Boyle, John F.; Grosjean, Martin (2021). The nexus among long-term changes in lake primary productivity, deep-water anoxia, and internal phosphorus loading, explored through analysis of a 15,000-year varved sediment record. Global and planetary change, 207, p. 103643. Elsevier Science 10.1016/j.gloplacha.2021.103643

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Increased cultural eutrophication since the 20th century, caused by phosphorus (P) enrichment, has become a major problem worldwide. In deep, stratified lakes, eutrophication-induced hypolimnetic anoxia often stimulates the release of labile P from the sediment into the water column. This positive feedback, termed internal P loading, maintains or even accelerates eutrophication. However, most studies on internal P loading have focused on recent times. Little is known about whether such positive feedbacks caused by labile P release from sediments also played a role under natural conditions with little or no human impact. We investigated a high-resolution 15,000-year sediment record of paleoproduction, anoxia, and five sedimentary P fractions from a small, deep lake, Soppensee, on the Swiss Central Plateau. We estimated long-term qualitative internal P loading by comparing the Holocene record of diatom-inferred epilimnetic total P (DI-TP) concentrations with labile P fraction (Fesingle bondP) concentrations in sediments under changing trophic state, redox, and lake mixing regimes. Intensified P cycling from sediments into the water column (enhanced internal P loading) apparently occurred as a positive feedback to natural eutrophication with persistent bottom-water anoxia during the early to mid-Holocene (~9000–6000 cal BP). However, this positive feedback was not inferred for other eutrophic phases. Fe-rich layers formed during seasonal mixing of the lake in the late Holocene (~2000–200 cal BP) and magnetite-type minerals produced by magnetotactic bacteria (MTB) internal P loading during anoxic phases in the mid- to late Holocene (~6000–2000 cal BP) appeared to prevent internal P loading. MTB presence resulted in high concentrations of potentially labile Fesingle bondP in sediments. Our study demonstrates the potential contribution of internal P loading during long-term natural eutrophication of deep stratified lakes and has wide implications for lake management and restoration. Our results highlight the importance of the coupled geochemical cycles of P and Fe in the long-term trophic state evolution of stratified, ferruginous, low-sulfate-water lakes, conditions that have been reported to serve as analogs for the Archaean Ocean.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Paleolimnology
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geological Sciences > Quaternary Geology
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Palaeoecology
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Tu, Luyao; Lotter, André Franz; Vogel, Hendrik and Grosjean, Martin

Subjects:

500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel
500 Science > 580 Plants (Botany)

ISSN:

0921-8181

Publisher:

Elsevier Science

Funders:

Organisations 200021 not found.; Organisations 0 not found.; [UNSPECIFIED] Chinese Scholarship Counsel

Language:

English

Submitter:

Luyao Tu

Date Deposited:

22 Oct 2021 14:03

Last Modified:

18 Nov 2021 12:12

Publisher DOI:

10.1016/j.gloplacha.2021.103643

Uncontrolled Keywords:

Internal phosphorus loadings, Natural eutrophication, Anoxia, Late glacial/Holocene, Paleolimnology, Switzerland

BORIS DOI:

10.48350/160199

URI:

https://boris.unibe.ch/id/eprint/160199

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