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Freshwater biodiversity and community composition in a changing climate: from ecosystem manipulation to biogeographical patterns

Final Report Summary - FRESHCLIM (Freshwater biodiversity and community composition in a changing climate: from ecosystem manipulation to biogeographical patterns)

FRESHCLIM has three research objectives: i) assess climate change and nutrient effects on phenology, biodiversity, and community composition, ii) assess the importance of connectivity for species diversity and community composition under climate change, iii) predict the geographic range of individual species as a function of climate and other environmental variables including forecast range shifts of organisms due to climate change and identify potential climate change sensitive (species) indicators. Objective I of the project was studied in 24 shallow lake mesocosms mimicking climate change and nutrient perturbation. These were sampled for benthic macroinvertebrates (e.g.insect larvae and snails) where both sediment- and hard substratum (wall) samples were taken. One major sampling campaign was undertaken in the autumn of 2011 (with a very high number of samples within each mesocosm). The newly collected data were sorted and identified (both sediment and wall samples). Water chemistry samples for the period of interest for the mesocosm study has also been analysed e.g. for nutrients and chlorophyll a. The existing data on macroinvertebrate sampling as well as insect emergence have also been analysed. Analyses were also done on different existing datasets including benthic invertebrate and climate/environmental variables. Metabolic rates (respiration rates) of individual snails, taken from a temperature gradient in the field (the Hengill area in Iceland) as well as from the 24 mesocosms in Jutland have been examined.
Riverine organism diversity in relation to river network topology has been analysed as well as riverine habitat heterogeneity in relation to human induced stressors and riverine organism biodiversity. The project focused on predicted (geographical) range shifts as well as potential climate change indicators for freshwater biota. The necessary climate data were finalised and a potential indicator tool for climate change effects on riverine ecosystems developed as well as a comparison of different predictive models in relation to dispersal of aquatic organisms. Lake benthic macroinvertebrate communities in relation to spatial and hydromorphological variables has been analysed and potential indicators of change identified.

Training has included the participation in two statistics courses: one on Structural Equation Modelling, and one on using the R statistical environment in Macroecology. The fellow has also taken an advanced course in Danish for Scandinavians and participated in a leadership course in Plymouth, UK ”The challenge of science leadership” a leadership and communications course for mid-career scientists organised by Plymouth University. I have also participated in a three day symposia at Lund University on the topic ” Causes and Consequences of Organism Dispersal” and finally a week long course on ”Species Distribution Modelling” in Amsterdam, The Netherlands.

Transfer of knowledge has taken numerous forms, both through seminars at both host departments, as well as the participation in three conferences “Science for the Environment” in Aarhus, Denmark (October 2011), “Water bodies in Europe: Integrative Systems to assess ecological status and Recovery” in Tallinn, Estonia (January 2012), 7th Annual Meeting of the Specialist Group on Macroecology of the Gesellschaft für Ökologie in Göttingen, Germany (March 2013), and publications mentioned above. I have participated in a climate change research workshop in London, UK, presenting results from the FRESHCLIM project at Queen Mary University of London ”Thermal physiological responses in stream benthic invertebrates”. Results from the project has also been presented at the following conferences: (i) EcoSummit, Ecological sustainability – Restoring the Planet's Ecosystem Services conference, Columbus USA (speaker), (ii) INTECOL meeting, London, UK: “Long-term effects of warming and nutrients on the invertebrate community in a lake mesocosm experiment” (speaker), (iii) BES-YESI Global Change and Biosphere Interactions conference, York, UK: “Long-term effects of warming and nutrients on the invertebrate community in a lake mesocosm experiment” (poster). I have also given a departmental seminar at the Ecology Department, Lund University, where I was invited to talk about ”Effects of climate change on freshwater organisms”.

The main results of the project includes: new knowledge of the interaction effects between eutrophication and warming on aquatic bottom living organisms in a unique large-scale mesocosm set-up, individual responses of aquatic organisms by warming in relation to temperature gradients (potential future changes in climate), the importance of riverine network typology (mainly stream size and connectivity within the network) on organismal diversity and function, identification of potential climate change indicators based on aquatic organisms, as well as indicators of human induced stressors on lake littoral ecosystems.

Given the alarming rate of loss of biodiversity and the high potential of climate change effects on aquatic ecosystems the assessment of effects of climate change, in concert with other stressors, on freshwater organisms has been highly timely and relevant. The improved understanding of how climate interact with e.g. eutrophication to affect aquatic biodiversity, how the metabolic activities of individual organisms are affected by temperature, depending on at what temperature they live, as well as the importance of landscape connectivity in the riverine ecosystem has strong implications for potential future changes in aquatic ecosystem structure, and function as well as adaptation, mitigation, and understanding how management of these important ecosystems should be done in the future.