SUPERVISOR: Thomas HEIN

PROJECT ASSIGNED TO: Dominik von Spinn

The transformation of river systems into industrialized riverine landscapes (IRL) has profoundly impacted ecosystem functions, biodiversity, and ecosystem services (Hein et al. 2021). While rivers remain among the most biodiverse ecosystems on Earth (Altermatt et al. 2020), they are also among the most endangered (Fryirs and Brierley 2016). Connectivity alterations play a pivotal role in the ongoing freshwater biodiversity crisis (Tickner et al. 2020; Dudgeon et al. 2006). Although connectivity is shaped by landscape features and the inherent dynamics of rivers, the establishment of societal infrastructure in riverine landscapes has changed connectivity properties on a global scale (Belletti et al. 2020; Dynesius and Nilsson 1994). Artificial barriers, such as dams and weirs disrupt longitudinal connectivity and cause fragmentation. Besides instream barriers, channelization and floodplain drainage are major anthropogenic interventions leading to ecological disconnectivity (Crook et al. 2015). 

Freshwater fish species are particularly threatened by connectivity changes (Liermann et al. 2012; Bellard and Hugueny 2020). Due to the high level of autecological diversity (Aarts and Nienhuis 2003) and continuous life-history transitions (Lucas 2001), fish depend on habitat diversity and corridors that allow movement between habitats. As a consequence, abundances are decreasing in impacted rivers (Schiemer et al. 2004) and species richness cannot be maintained because recolonization after local extinctions is inhibited in fragmented systems (Brauer and Beheregaray 2020; Carvajal‐Quintero et al. 2017). Due to the high sensitivity, ecosystem management and restoration of rivers will be of fundamental importance for the long-term persistence of freshwater fish communities. By reverse conclusion, fish can serve as excellent bioindicators for the ecological integrity of riverine ecosystems (Aarts and Nienhuis 2003). 

This PhD thesis is part of the FWF doc.funds project “Industrialized Riverine Landscapes” and linked to the Christian Doppler Laboratory for Meta Ecosystem Dynamics in Riverine Landscapes (MERI - https://cdl-meri.boku.ac.at). Selected fish species are used to investigate how man-made infrastructure and riverine network characteristics influence population connectivity, spatial genetic variation, and connectivity-dependent community turnover. Furthermore, the influence of dendritic network structure and the role of anthropogenic infrastructure in facilitating or hindering the spread of invasive species are studied. State-of-the-art molecular ecological methods are applied and combined with a network-analytic framework based on a meta-ecosystem approach (Bondar-Kunze et al. 2022; Erős and Lowe 2019; Loreau et al. 2003). The research is focused on the upper Danube which can be classified as heavily impaired due to the long-term exposure to socio-economic usage (Hein et al. 2019). In addition, research is conducted in the Vjosa River in southern Albania, one of Europe’s last free-flowing rivers (Schiemer et al. 2018), representing an ideal reference system for floodplain rivers (Schiemer et al. 2018; Schiemer et al. 2020). 

Restoring connectivity to mitigate the adverse effects of human interventions in riverine landscapes is embedded in several EU legislations, such as the European Water Framework Directive (European Commission 2000), the European Biodiversity Strategy (European Commission 2020), and the European Nature Restoration Law (European Commission 2023). The thesis aims to provide a more comprehensive understanding of connectivity in the context of the fundamental transformation river systems have undergone due to human interventions. The findings will support ecologists and conservation practitioners in the successful planning of conservation and restoration projects and help to identify locations with the highest potential for ecological improvement. Within the conceptual framework of HR21 the project is placed in the research cluster “connectivity” and addresses aspects of “vulnerability”. Resulting considerations for future management fall under the cluster “governance and planning”. Additionally, it contributes to the research field of “urbanization and infrastructure.” 

Publication bibliography 

Aarts, Bram G.W.; Nienhuis, Piet H. (2003): Fish zonations and guilds as the basis for assessment of ecological [2pt] integrity of large rivers. In Hydrobiologia 500 (1-3), pp. 157–178. DOI: 10.1023/A:1024638726162. 

Altermatt, Florian; Little, Chelsea J.; Mächler, Elvira; Wang, Shaopeng; Zhang, Xiaowei; Blackman, Rosetta C. (2020): Uncovering the complete biodiversity structure in spatial networks: the example of riverine systems. In Oikos 129 (5), pp. 607–618. DOI: 10.1111/oik.06806. 

Bellard, Céline; Hugueny, Bernard (2020): Importance of metapopulation dynamics to explain fish persistence in a river system. In Freshwater Biology 65 (11), pp. 1858–1869. DOI: 10.1111/fwb.13571. 

Belletti, Barbara; Garcia de Leaniz, Carlos; Jones, Joshua; Bizzi, Simone; Börger, Luca; Segura, Gilles et al. (2020): More than one million barriers fragment Europe's rivers. In Nature 588 (7838), pp. 436–441. DOI: 10.1038/s41586-020-3005-2. 

Bondar-Kunze, Elisabeth; Funk, Andrea; Haidvogl, Gertrud; Unfer, Günther; Muhar, Susanne; Hohensinner, Severin et al. (2022): Der Meta-Ökosystem Ansatz in der Praxis – Integration von hydromorphologischen Veränderungen und menschlichen Eingriffen in die Meta-Ökosystem-Theorie zur Entwicklung eines nachhaltigen Flussmanagements an der österreichischen Donau. In Österr Wasser- und Abfallw 74 (11-12), pp. 501–509. DOI: 10.1007/s00506-022-00893-2. 

Brauer, Chris J.; Beheregaray, Luciano B. (2020): Recent and rapid anthropogenic habitat fragmentation increases extinction risk for freshwater biodiversity. In Evolutionary Applications 13 (10), pp. 2857–2869. DOI: 10.1111/eva.13128. 

Carvajal‐Quintero, Juan D.; Januchowski‐Hartley, Stephanie R.; Maldonado‐Ocampo, Javier A.; Jézéquel, Céline; Delgado, Juliana; Tedesco, Pablo A. (2017): Damming Fragments Species’ Ranges and Heightens Extinction Risk. In Conservation Letters 10 (6), pp. 708–716. DOI: 10.1111/conl.12336. 

Crook, David A.; Lowe, Winsor H.; Allendorf, Frederick W.; Erős, Tibor; Finn, Debra S.; Gillanders, Bronwyn M. et al. (2015): Human effects on ecological connectivity in aquatic ecosystems: Integrating scientific approaches to support management and mitigation. In The Science of the total environment 534, pp. 52–64. DOI: 10.1016/j.scitotenv.2015.04.034. 

Dudgeon, David; Arthington, Angela H.; Gessner, Mark O.; Kawabata, Zen-Ichiro; Knowler, Duncan J.; Lévêque, Christian et al. (2006): Freshwater biodiversity: importance, threats, status and conservation challenges. In Biological Reviews 81 (2), pp. 163–182. DOI: 10.1017/s1464793105006950. 

Dynesius, M.; Nilsson, C. (1994): Fragmentation and flow regulation of river systems in the northern third of the world. In Science 266 (5186), pp. 753–762. DOI: 10.1126/science.266.5186.753. 

Erős, Tibor; Lowe, Winsor H. (2019): The Landscape Ecology of Rivers: from Patch-Based to Spatial Network Analyses. In Curr Landscape Ecol Rep 4 (4), pp. 103–112. DOI: 10.1007/s40823-019-00044-6. 

European Commission (2000): European Commission, 2000. Directive 2000/60/EC of the European parliament and of the council of 23 October 2000 establishing a framework for community action in the field of water policy or, in short, the EU Water Framework Directive. Official Journal of the European Communities L 327. 

European Commission (2020): European Commission, 2020. Communication from the comission to the European parliament, the European council, the European economic and social committee and the committee of the regions, EU Biodiversity Strategy for 2030 – Bringing nature back into our lives. 

European Commission (2023): European Commission, 2023. Proposal for a regulation of the European parliament and of thecouncil on nature restoration. Available online at environment.ec.europa.eu/publications/naturerestoration-%20law_en. 

Fryirs, Kirstie A.; Brierley, Gary J. (2016): Assessing the geomorphic recovery potential of rivers: forecasting future trajectories of adjustment for use in management. In WIREs Water 3 (5), pp. 727–748. DOI: 10.1002/wat2.1158. 

Hein, T.; Funk, A.; Pletterbauer, F.; Graf, W.; Zsuffa, I.; Haidvogl, G. et al. (2019): Management challenges related to long‐term ecological impacts, complex stressor interactions, and different assessment approaches in the Danube River Basin. In River Research & Apps 35 (5), pp. 500–509. DOI: 10.1002/rra.3243. 

Hein, Thomas; Hauer, Christoph; Schmid, Martin; Stöglehner, Gernot; Stumpp, Christine; Ertl, Thomas et al. (2021): The coupled socio-ecohydrological evolution of river systems: Towards an integrative perspective of river systems in the 21st century. In The Science of the total environment 801, p. 149619. DOI: 10.1016/j.scitotenv.2021.149619. 

Liermann, Catherine Reidy; Nilsson, Christer; Robertson, James; Ng, Rebecca Y. (2012): Implications of Dam Obstruction for Global Freshwater Fish Diversity. In BioScience 62 (6), pp. 539–548. DOI: 10.1525/bio.2012.62.6.5. 

Loreau, Michel; Mouquet, Nicolas; Holt, Robert D. (2003): Meta‐ecosystems: a theoretical framework for a spatial ecosystem ecology. In Ecology Letters 6 (8), pp. 673–679. DOI: 10.1046/j.1461-0248.2003.00483.x. 

Lucas, Martyn C. (2001): Migration of freshwater fishes. With assistance of Etienne Baras. Oxford: Blackwell Science. 

Rabitsch, W.; Milasowszky, N.; Nehring, S.; Wiesner, C.; Wolter, C.; Essl, F. (2013): The times are changing: temporal shifts in patterns of fish invasions in central European fresh waters. In Journal of Fish Biology 82 (1), pp. 17–33. DOI: 10.1111/j.1095-8649.2012.03457.x. 

Schiemer, F.; Guti, G.; Keckeis, H.; Staras, M.; RAP; International Symposium on the Management of Large Rivers for Fisheries, 2, Phnom Penh, 11-14 Feb 2003 (2004): Ecological status and problems of the Danube River and its fish fauna: a review. Available online at agris.fao.org/search/en/providers/122415/records/647367f553aa8c89630cf40c.

Schiemer, Fritz; Beqiraj, Sajmir; Drescher, Anton; Graf, Wolfram; Egger, Gregory; Essl, Franz et al. (2020): The Vjosa River corridor: a model of natural hydro-morphodynamics and a hotspot of highly threatened ecosystems of European significance. In Landscape Ecol 35 (4), pp. 953–968. DOI: 10.1007/s10980-020-00993-y. 

Schiemer, Fritz; Drescher, Anton; Hauer, Christoph; Schwarz, Ulrich (2018): The Vjosa River corridor: a riverine ecosystem of European significance (155). Available online at www.researchgate.net/profile/anton-drescher/publication/329687235_the_vjosa_river_corridor_a_riverine_ecosystem_of_european_significance.

Tickner, David; Opperman, Jeffrey J.; Abell, Robin; Acreman, Mike; Arthington, Angela H.; Bunn, Stuart E. et al. (2020): Bending the Curve of Global Freshwater Biodiversity Loss: An Emergency Recovery Plan. In BioScience 70 (4), pp. 330–342. DOI: 10.1093/biosci/biaa002