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KLIMAFORSK-Stort program klima

Effects of climate change on boreal lake ecosystems: Productivity and community responses

Awarded: NOK 11.1 mill.

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2013 - 2017

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The ECCO-project ended by summer 2016. The project has provided fundamentally new insights into the impacts of climate change on freshwaters as well as on processes linking impacts on terrestrial to aquatic (freshwater and coastal) ecosystems. The core issue has been to understand the determinants of the export of dissolved organic matter (DOM, including dissolved carbon, phosphorus with impacts also on iron, silicate and calcium)) to water, and the physical, chemical and biological responses. The project has analyzed processes and responses at various scales, from large-scale assessment at the regional catchment scales by remote sensing and statistical analysis, time series analysis of long term impacts, spatial analysis or large datasets in catchments and lakes to biological responses from the community level to the genome. As part of the project, predictions has been made for future responses in temperature, ice-duration and mixing in 200 000 statistically selected Northern lakes by use of the MyLake model. This is indeed novel work and approaches, and a paper on this is in prep for nature Climate Change. This is also coupled to works on climate gas production, oxygen saturation and biotic responses, and also a separate paper on greenhouse gas emissions from Nordic lakes is published (Biogeocemistry), while additionally 2-3 papers in this area in in progress. Another major work is in press (Scientific Reports), based on time-series analysis over 30 years in 80 Norwegian lakes where the drivers of the current browning (increased DOM) is analyzed. Increased forest growth and reduced sulphur deposition are the main drivers, but there is also a significant contribution from clime (both temperature and runoff). The same data is also explored to assess the dramatic decline in calcium in Norwegian watersheds, and the same drivers cause the reduced Ca (Limnology and Oceanography in press). Currently the levels are becoming critically low for many taxa and species, notably in southern watersheds. Most of the efforts has been based on existing data and have been methodological groundbreaking, serving as points of departure for further projects and applications. There are also almost finalized efforts to upscale this for Fennoscandia as a whole, and even the entire boreal zone for some parameters. The ECCO project has also provided models for linking light in lakes (and costal waters) related to DOM and further to primary and secondary production (one paper in Ecosystems and PlosOne, others are in progress). Also a paper on the couplings between DOM and fisk production has been published (Ecology Letters) and also here more work are in progress. In very nutrient-poor lakes a small increase of DOM stimulated productivity, but above ca 5 mg dissolved organic carbon, the effects are productivity becomes negative at all trophic levels. Finally, a series of experiments are conducted to test the direct responses of DOM on phyto- and zooplankton. One published papers demonstrate negative impacts of browning (elevated DOM) in alpine ponds, others demonstrates the production of free radicals in the presence of UV and DOM and how it may cause DNA-damage. There has ben an active popular dissemination from the projects both in leading newspapers (Aftenposten, 2 articles), other popular science outlets, and also the popular science book C. Carbon, an unauthorized biography (Cappelen Damm) has acknowledged the insights from ECCO. In total, the project should be seen as highly successful, it will continue to generate papers and propsals in the years to come.

Climate change is expected to affect lake ecosystems in many ways. In boreal systems, changes in dissolved organic matter and nutrients will affect light levels, thermal regimes, productivity and community structure. This project will address these respon ses by use of existing databases, refinement and integration of existing models and by experiments and field studies. The multidisciplinary project group will build on the extensive databases on lakes and boreal catchments in Norway, Sweden and Finland co mbined with predictive steady-state (space-for-time) models that have recently been developed and tested for Norwegian catchments as well as existing, dynamic, process-oriented models. The goal is to establish causal links between the drivers climate chan ge and N+S deposition and catchment properties on export fluxes of dissolved organic carbon (DOC), and the key nutrient elements nitrogen (N) and phosphorus (P). Projections will be made driven by various scenarios of future climate change and N+S deposit ion. The work will build on statistical tools, GIS-information and climate-related statistical modelling both at the catchment and lake level. These tools will be used to estimate lake ecosystem responses. The focus will be on: 1. Effects on primary prod uction due to changed loads of DOC (determining light climate), changed inputs of nutrients and changed N-deposition. 2. Effects on net ecosystem heterotrophy (and thus CO2 export) related to the same changes. 3. Effects on nutrient limitation (N vs. P) r elated to changed loads of nutrients and changed N-deposition. 4. Effects on phytoplankton cell size related to changed temperature and nutrients. 5. Community effects focusing on selected species susceptible to DOC and temperature.

Publications from Cristin

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KLIMAFORSK-Stort program klima