SUPERVISOR: Wolfram GRAF

PROJECT ASSIGNED TO: Lana ŽIDAK

Intermittent streams are estimated to account for over 50% of the global river network, which highlights their significance (Datry et al., 2014; Messager et al., 2021). These systems are commonly associated with Mediterranean river systems. But nowadays, due to climate change and human activities, such flow regimes can also be found in Central Europe (Datry et al., 2014; Skoulikidis et al., 2017; Straka et al., 2021; Piniewski et al., 2022). As the spread of intermittent flows is strongly connected to climate change, the number of these systems is expected to increase due to the frequency of extreme events such as droughts (Dai, 2011; Prudhomme et al., 2014). These shifts in hydrological systems present challenges for dynamic systems like intermittent flows, as drought's immediate and long-term ecological impacts still remain under-researched in Central Europe, particularly in lowland areas where their presence increases (Bogan et al., 2014; Verdonschot et al., 2015; Stubbington et al., 2018). As the number of intermittent flows grows (Datry et al., 2014), changing the way how they are studied and managed is important. This includes understanding their unique ecological characteristics on the one hand and their role in socioeconomics like human water supply and food production.

All those changes in the global water cycle majorly impact how we manage water resources. Intermittent rivers are very important for nutrients cycle, maintaining biodiversity, and supporting ecosystem services, but they are often left out of traditional monitoring systems. Biomonitoring frameworks are primarily designed for rivers with perennial flow (Reyjol et al., 2014; Stubbington et al., 2018). They need to be improved to better handle the specific hydrological and ecological features of intermittent flow systems so their ecological health under anthropogenic impact can be properly assessed (Prat et al., 2014; Soria et al., 2020). Currently, they do not detect ecological impacts like pollution in intermittent flow systems (Munné & Prat, 2011; Mazor et al., 2014; Stubbington et al., 2018; Messager et al., 2021).

Macroinvertebrates play a crucial role in assessing the ecological quality of water bodies by analyzing their taxonomic richness and abundance. They are used as bioindicators in ecological assessments of water bodies due to their high sensitivity to environmental changes and ability to reflect the effects of different pressures (Stoica et al., 2014; Ramos-Merchante & Prenda, 2017; Miliša et al., 2022). Their responses to different pressures and hydrological changes have been used to develop indices like the Biodrought Index (BI), which assesses drought impacts on benthic communities using taxa traits, abundance, and drying tolerance (Straka et al., 2019). Furthermore, indices like The Drought Effect of Habitat Loss on Invertebrates (DEHLI) index (Chadd et al., 2017) and The Monitoring Intermittent Streams (MIS) index (England et al., 2019), which evaluate species' resilience and habitat preferences under varying drought conditions (Chadd et al., 2017; Straka et al., 2019) were developed.

This research will focus on understanding the ecological impacts of intermittent flow in river systems through field sampling, laboratory analysis, and statistical modelling. Fieldwork will be conducted in Styria on several case-study sites, where macroinvertebrate and eDNA (environmental DNA) samples will be collected to evaluate their community structure, functional traits, and biodiversity assessment.

The main research questions of this PhD thesis are: 

  1. How do drought conditions and aquatic systems' connectivity and fragmentation patterns affect benthic communities' diversity and functional metrics related to resistance and resilience, including biological assessment indices?

  2. What are the seasonal patterns of organismic responses and linked metrics (for example, taxonomic richness and abundance, the proportion of indicator taxa, body flexibility, and feeding type) to hydrological cycles, and how do these patterns enhance our understanding of resilience and resistance strategies in aquatic ecosystems?

  3. How do the connectivity of gene flow and interconnections within metapopulations differ between selected species typical of intermittent and permanent flow?

  4. Can indicative macroinvertebrate communities be effectively screened and tested as early warning indicators for drought-risk assessment in smaller catchments, where drying phenomena are largely unknown? Moreover, can this biological classification be validated by hydrological data?

Within the HR21 framework, this research positions itself in the research field of extreme events. It most strongly relates to research clusters of “vulnerability” by identifying thresholds at which benthic communities and ecosystem services are compromised under drought stress, providing tools for early-warning indicators of drought conditions. In addition, this research connects with the research cluster “connectivity” by assessing fragmentation and its impact on biodiversity and gene flow in intermittent systems. Furthermore, during extreme events, the metabolic processes of ecosystems, such as nutrient cycling and primary production, are disrupted, aligning this research within the “metabolism” cluster (Hein et al., 2021).

 

Bogan, M.T., Boersma, K.S. and Lytle, D.A., 2015. Resistance and resilience of invertebrate communities to seasonal and supraseasonal drought in arid‐land headwater streams. Freshwater Biology, 60(12), pp.2547-2558.

Chadd, R.P., England, J.A., Constable, D., Dunbar, M.J., Extence, C.A., Leeming, D.J., Murray-Bligh, J.A. and Wood, P.J., 2017. An index to track the ecological effects of drought development and recovery on riverine invertebrate communities. Ecological Indicators, 82, pp.344-356.

Chessman, B.C., Metzeling, L. and Robinson, D.P., 2022. Development of a flow‐sensitive macroinvertebrate index for Australian rivers. River Research and Applications, 38(5), pp.846-862. 

Dai, A., 2011. Drought under global warming: a review. Wiley Interdisciplinary Reviews: Climate Change, 2(1), pp.45-65.

Datry, T., Larned, S.T. and Tockner, K., 2014. Intermittent rivers: a challenge for freshwater ecology. BioScience, 64(3), pp.229-235.

England, J., Chadd, R., Dunbar, M.J., Sarremejane, R., Stubbington, R., Westwood, C.G. and Leeming, D., 2019. An invertebrate-based index to characterize ecological responses to flow intermittence in rivers. Fundamental and Applied Limnology, 193(1), pp.93-117.

Hein, T., Hauer, C., Schmid, M., Stöglehner, G., Stumpp, C., Ertl, T., Graf, W., Habersack, H., Haidvogl, G., Hood-Novotny, R. and Laaha, G., 2021. The coupled socio-ecohydrological evolution of river systems: Towards an integrative perspective of river systems in the 21st century. Science of The Total Environment, 801, p.149619.

Mazor, R.D., Stein, E.D., Ode, P.R. and Schiff, K., 2014. Integrating intermittent streams into watershed assessments: applicability of an index of biotic integrity. Freshwater Science, 33(2), pp.459-474.

Messager, M.L., Lehner, B., Cockburn, C., Lamouroux, N., Pella, H., Snelder, T., Tockner, K., Trautmann, T., Watt, C. and Datry, T., 2021. Global prevalence of non-perennial rivers and streams. Nature, 594(7863), pp.391-397.

Miliša, M., Stubbington, R., Datry, T., Cid, N., Bonada, N., Šumanović, M. and Milošević, D., 2022. Taxon-specific sensitivities to flow intermittence reveal macroinvertebrates as potential bioindicators of intermittent rivers and streams. Science of the total environment, 804, p.150022.

Munné, A. and Prat, N., 2011. Effects of Mediterranean climate annual variability on stream biological quality assessment using macroinvertebrate communities. Ecological Indicators, 11(2), pp.651-662.

Piniewski, M., Eini, M.R., Chattopadhyay, S., Okruszko, T. and Kundzewicz, Z.W., 2022. Is there a coherence in observed and projected changes in riverine low flow indices across Central Europe?. Earth-Science Reviews, 233, p.104187.

Prat, N., Gallart, F., Von Schiller, D., Polesello, S., García‐Roger, E.M., Latron, J., Rieradevall, M., Llorens, P., Barberá, G.G., Brito, D. and De Girolamo, A.M., 2014. The mirage toolbox: an integrated assessment tool for temporary streams. River research and applications, 30(10), pp.1318-1334.

Prudhomme, C., Giuntoli, I., Robinson, E.L., Clark, D.B., Arnell, N.W., Dankers, R., Fekete, B.M., Franssen, W., Gerten, D., Gosling, S.N. and Hagemann, S., 2014. Hydrological droughts in the 21st century, hotspots and uncertainties from a global multimodel ensemble experiment. Proceedings of the National Academy of Sciences, 111(9), pp.3262-3267.

Ramos-Merchante, A. and Prenda, J., 2017. Macroinvertebrate taxa richness uncertainty and kick sampling in the establishment of Mediterranean rivers ecological status. Ecological Indicators, 72, pp.1-12.

Reyjol, Y., Argillier, C., Bonne, W., Borja, A., Buijse, A.D., Cardoso, A.C., Daufresne, M., Kernan, M., Ferreira, M.T., Poikane, S. and Prat, N., 2014. Assessing the ecological status in the context of the European Water Framework Directive: where do we go now?. Science of the Total Environment, 497, pp.332-344.

Skoulikidis, N.T., Sabater, S., Datry, T., Morais, M.M., Buffagni, A., Dörflinger, G., Zogaris, S., del Mar Sánchez-Montoya, M., Bonada, N., Kalogianni, E. and Rosado, J., 2017. Non-perennial Mediterranean rivers in Europe: status, pressures, and challenges for research and management. Science of the Total Environment, 577, pp.1-18.

Soria, M., Gutiérrez‐Cánovas, C., Bonada, N., Acosta, R., Rodríguez‐Lozano, P., Fortuño, P., Burgazzi, G., Vinyoles, D., Gallart, F., Latron, J. and Llorens, P., 2020. Natural disturbances can produce misleading bioassessment results: Identifying metrics to detect anthropogenic impacts in intermittent rivers. Journal of Applied Ecology, 57(2), pp.283-295.

Stoica, C., Gheorghe, S., Petre, J., Lucaciu, I. and Nita-Lazar, M., 2014. Tools for assessing Danube Delta systems with macro invertebrates. Environmental Engineering & Management Journal (EEMJ), 13(9). 

Straka, M., Polášek, M., Syrovátka, V., Stubbington, R., Zahrádková, S., Němejcová, D., Šikulová, L., Řezníčková, P., Opatřilová, L., Datry, T. and Pařil, P., 2019. Recognition of stream drying based on benthic macroinvertebrates: A new tool in Central Europe. Ecological Indicators, 106, p.105486.

Straka, M., Polášek, M., Csabai, Z., Zweidick, O., Graf, W., Meyer, E.I., Elexová, E.M., Lešťáková, M. and Pařil, P., 2021. Stream drying bioindication in Central Europe: A Biodrought Index accuracy assessment. Ecological Indicators, 130, p.108045.

Stubbington, R., Chadd, R., Cid, N., Csabai, Z., Miliša, M., Morais, M., Munné, A., Pařil, P., Pešić, V., Tziortzis, I. and Verdonschot, R.C., 2018. Biomonitoring of intermittent rivers and ephemeral streams in Europe: Current practice and priorities to enhance ecological status assessments. Science of the total environment, 618, pp.1096-1113.

Verdonschot, R.C., van Oosten‐Siedlecka, A.M., ter Braak, C.J. and Verdonschot, P.F., 2015. Macroinvertebrate survival during cessation of flow and streambed drying in a lowland stream. Freshwater Biology, 60(2), pp.282-296.