CLIMER - Climatic, abiotic and biotic drivers of mercury in freshwater fish in northern ecosystems (completed)

This project explores how climate change and other long-term environmental changes can influence the transport, uptake and food web transfer of mercury in boreal lakes.

Langtjern catchment

About the project

This is a Project Financed by the Research Council of Norway and led by the Norwegian Institute of water research (NIVA) in which the participation by the Environmental Analysis Group is mainly related to Work Packadge (WP) 1: Process-oriented studies of catchment and in-lake Hg cycling.

The aim of this work packdage is to investigate factors driving catchment export and in-lake processing of Hg species to better assess catchment loading and future food web exposure to aqueous MeHg.

A Central theme in this WP is DOM, which is a transport vehicle, a limiting factor for in-lake retention processes and a promoter of food web Hg exposure. We will use existing research infrastructure (long-term ecological research site Langtjern and ‘intensive’ study sites, process-based models, laboratory studies and novel analytical methods.



The primary aim is to assess risks of elevated Hg in fish in boreal and subarctic lakes under interactions of climate change and deposition, and assess implications for ecosystem function from a toxicological and fisheries perspective

Secondary objectives

-To test effects of climate and deposition on catchment production, transport and in-lake processing of Hg species

-To test if long-term trends in MeHg in primary consumers and fish can be described by climate, deposition and water chemistry

-To test if spatial variation in Hg fish can be explained by climatic, physical, chemical and biotic factors

-To investigate of the role of dietary sources (bacterial, algal; littoral, pelagic) on food web exposure to MeHg

-To investigate factors driving variation in uptake and trophic magnification rates of MeHg in food webs

-To predict Hg concentrations in aquatic biota and associated ecosystem risk under realistic environmental change scenarios



Mercury (Hg) in freshwater fish, especially in its organic and most toxic form methyl-Hg (MeHg), has shown increases in recent decades, leading

to increased risk of Hg exposure for fish consumers (including wildlife andhumans). The provision of healthy and uncontaminated fish for humans

and wildlife by surface waters is under pressure. Key questions regarding Hg levels in biota relate to identification of driving factors of Hg in surface

waters such as catchment Hg export, factors stimulating or limiting MeHg production, degradation, transfer into the food web and trophic magnification.

Current trends of climate change, reduced sulphur deposition and surface water browning may have direct and indirect impacts on food web Hg

exposure and bioaccumulation. Here, we propose to investigate spatial patterns and temporal trends in Hg in freshwater food webs by 1) sampling

food webs (fish and lower trophic levels) gradients across boreal and subarctic lakes; 2) analyzing temporal trends in Hg in fish in existing

time-series (and adding to those time-series by targeted sampling) in relation to environmental drivers (climate, deposition, water chemistry); 3) studying

key processes in catchments, lakes and food webs in greater detail and transferring obtained insights to process-based modelling of catchment

and lake Hg cycling and trophic transfer of Hg; 4) building on expertise and existing data within the project international project consortium in order to

improve the quality and reliability of predictions of food web exposure to Hg and food web Hg levels in boreal lakes. The overarching aim of the project is

to better assess present and future risk of Hg levels in biota and Associated changes in ecosystem value from a toxicological and fisheries perspective.


  • WP1 Process-oriented studies of catchment and in-lake Hg cycling.

Task 1.1 Organic matter quality and transport and bio-availability of Hg species

Task 1.2 The role of photodemethylation in MeHg exposure

Task 1.3 Past and future projections of catchment and lake Hg processing

Task 1.4 Linking time series of MeHg in aquatic zoobenthos with process-based modelling


  • WP2: Spatial and temporal trends of Hg in freshwater lakes
  • WP3. Environmental drivers of Hg trophodynamics in freshwater ecosystems


Tags: DOM, Climate change, Water works
Published Oct. 13, 2015 11:23 AM - Last modified Oct. 26, 2020 3:36 PM