Ann-Kristin Bergström

Climate change induced regime shifts in Northern lake ecosystems

Sunset over lake Törnetrask (as seen from the Abisko Scientific Research Station)

Sunset over lake Törnetrask (as seen from the Abisko Scientific Research Station)

Climate change induced regime shifts in Northern lake ecosystems

Project Summary

A present major scientific challenge is to understand and predict effects of climate change on lake ecosystems and the services they deliver. Globally, lakes are concentrated at northern latitudes where the magnitude of climate change is expected to be strongest. Recent advances in lake research suggest that responses of Northern lakes to global warming are fundamentally different from the expectations based on conventional knowledge. This project brings together new tools and concepts in biogeochemistry and ecology, with the aims of understanding and predicting the effects of climate change on the delivery of two major ecosystem services, fish production and the net greenhouse gas balance of Northern lakes.

Specific objectives include:

  1. Assessment of long vs. short term effects of climate change;

  2. Assessment of nonlinear dynamics and regime shifts; and,

  3. Projection of responses to future climate conditions.

The project’s core is made up of a multi-scale (pond to whole-lake) experimental test of ecosystem responses to increases in temperature and precipitation/runoff. Further, we will use aDNA techniques to address past regime shifts and ecosystem resilience to climate change from paleolimnological sediment records. Finally, the project will develop process-based models to be used in the projection of future conditions in lakes at the whole ecosystem scale.

Project Dates: 2017-2021

Funding Organizations

Knut and Alice Wallenberg Foundation

Collaborators

David Bastviken, Linköping University
Ann-Kristin Bergström, Umeå University
Christian Bigler, Umeå University
Richard Bindler, Umeå University
Åke Brännström, Umeå University
Pär Byström, Umeå University
Sebastian Diehl, Umeå University
Isabelle Domaizon, French National Institute for Agricultural Research
Göran Englund, Umeå University
Cristian Gudasz, Umeå University
Dag Hessen, Oslo University, Norway
Jonatan Klaminder, Umeå University
Sally MacIntyre, University of California Santa Barbara, USA
Frank Peeters, University of Konstanz, Germany
André de Roos, University of Amsterdam, The Netherlands
Martin Rosvall, Umeå University
David Seekell, Umeå University
Ryan Sponseller, Umeå University
Xiau-Ru Wang, Umeå University
Marcus Klaus, Umeå University

Monitoring and management of Arctic lakes in a changing climate

Jan Karlson monitoring Arctic lakes

Monitoring and management of Arctic lakes in a changing climate

Project Summary

There is a lack of scientific based monitoring and management strategies of Arctic lakes where climate change effects are expected to be especially pronounced. The purpose of this study is to improve knowledge and monitoring of climate impacts on Arctic lakes. Specific aims include to quantify and provide threshold variables for climate change induced regime shifts in fish resource use and production, and to develop tools and guidelines to be used in monitoring programs. By experimental and comparative studies across climate gradients we test predictions of rapid changes in fish production and resource use with climate change, and by developing new analytical and statistical tools we test predictions that changes in lake function following climate change could be rapidly detected using automatized and cost efficient methods suitable for use in monitoring. Based on the results we will develop methods and guidelines together with stakeholders for use in monitoring of Arctic lake ecosystems. The outcome of the project will be of fundamental importance for society as this will provide knowledge and tools for sustainable management of a unique and attractable resource sensitive to environmental perturbations. The project is financed by FORMAS and carried out in collaboration with the county boards in Northern Sweden.

Project Dates: 2016 to 2018

Funding Organization

FORMAS (2015-723)

Collaborators

Jan Karlsson, Umeå University
Jens Andersson, Jämtland County Administrative Board
Ann-Kirstin Bergström, Umeå University
Pär Byström, Umeå University
Sally MacIntyre, University of California Santa Barbara, USA
David Seekell, Umeå University

The invisible carbon: an early indication of ecosystem change!

The invisible carbon: an early indication of ecosystem change!

Project Summary

Streams are sensitive sentinels for environmental change by their integration of processes in terrestrial and aquatic systems. Upland headwater streams in the north Swedish tundra show seasonally exceptional high concentrations of uncolored dissolved organic carbon (DOC) and high CO2 concentrations. We suggest that this reflects on-going changes in the terrestrial environment responding in their delivery of carbon (C) to the recipient aquatic systems. This is a hitherto unknown effect of a changing tundra landscape that will have large implications for the positive feedback on the global climate warming because of the large quantities of C that is stored in tundra soils. Current climate change mobilizes the stored C in upland tundra soils and cause a substantial increase in headwater stream C emissions and water-borne C losses.

We are studying stream CO2 fluxes mainly across a 42-km long stream network in the Miellajokka catchment near Abisko to better understand how stream functional traits and landscape features affects CO2 emissions. We are amongst others using different isotopic approaches (13C, 15N, 87Sr/86/Sr, 34S18O4 and water isotopes) and high-resolution measurements of stream CO2 and oxygen to disentangle different sources and processes that affects stream CO2 concentrations and emissions. We are also studying spatiotemporal variations in stream DOC across different tundra streams to unravel how different landscape features and hydrological conditions affect stream DOC concentrations, its degradability and qualitative characteristics. We are particularly interested in pulses of high stream DOC concentrations that has occurred irregularly during early autumns.

Collaborators

Carl-Magnus Mörth, Stockholm University
Steve Lyon, Stockholm University
Ann-Kristin Bergström, Umeå University
Ryan Sponseller, Umeå University
Jan Karlsson, Umeå University
Martin Berggren, Lund University
Gerard Rocher Ros, Umeå University

Funding organizations

The Swedish Research Council (VR) 2013-5001
FORMAS 2014-970

Global Nitrogen Enrichment Experiment (AGNEE)

Global Nitrogen Enrichment Experiment (AGNEE) - Role of nitrogen deposition on nutrient limitation of phytoplankton and zooplankton in low productive lakes

Project Summary

Variation in atmospheric nitrogen (N) deposition due to anthropogenic activities have profound effects on the chemistry and biology of lake ecosystems worldwide. Our previous research has shown that there are dramatic variations in productivity, nutrient biogeochemistry, and food chain structure among low productivity lakes in the Northern biosphere. This research program assess on a global scale two critical knowledge gaps: (1) How rates of N deposition control lake dissolved inorganic N (DIN):total phosphorus (TP) stoichiometry, nutrient limitation of phyto- and zooplankton, and the consequence of these biogeochemical changes on the nutritional quality of the food web; and (2) How catchment structure and function may serve to mitigate unwanted changes in lake ecosystem stoichiometry. The research is conducted on low productive lakes in Sweden and Canada/US along a similar climate and wet DIN deposition gradient (<1 to 8-10 kg N/ha/yr). In Sweden sampling is conducted in three areas: Värmland, Västerbotten and in Norrbotten (i.e. in the Abisko region). We use N deposition, satellite remote sensing- and GIS data to determine the influence of catchment structure in regulating DIN:TP ratios in lakes. We aim to establish how DIN:TP ratios influence biomass, composition and elemental stoichiometry of phyto- and zooplankton communities; and we perform bioassay enrichment experiments to determine nutrient limiting factors of phytoplankton and consumer driven nutrient regeneration responses.

Collaborators

Irena Creed, Western University, Canada
Anders Jonsson, Umeå University
Peter Isles, Umeå University
Danny Lau, Umeå University
Tobias Vrede, Swedish of Agricultural Sciences, Uppsala

Funding organizations

Swedish Research Council (VR)