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Research article - Peer-reviewed, 2021

Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

Wu, Pianpian; Kainz, Martin J.; Valdes, Fernando; Zheng, Siwen; Winter, Katharina; Wang, Rui; Branfireun, Brian; Chen, Celia Y.; Bishop, Kevin


Climate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (<40 mu m) and larger sized plankton (microplankton; 40-200 mu m), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels.

Published in

Scientific Reports
2021, volume: 11, number: 1, article number: 16859

Authors' information

Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Dartmouth College
Kainz, Martin J.
WasserCluster Lunz
Valdes, Fernando
Uppsala University
Zheng, Siwen
Tongji University
Winter, Katharina
WasserCluster Lunz
Wang, Rui
Tongji University
Branfireun, Brian
Western University (University of Western Ontario)
Chen, Celia Y.
Dartmouth College
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment

Associated SLU-program

Non-toxic environment
Lakes and watercourses

Sustainable Development Goals

SDG6 Clean water
SDG13 Climate action

UKÄ Subject classification

Climate Research
Environmental Sciences

Publication Identifiers


URI (permanent link to this page)