Effects of Bank Filtration on Lake Ecosystems
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Title page Effects of bank filtration on lake ecosystems vorgelegt von Master of Science Mikael Gillefalk ORCID iD 0000-0002-7642-776X von der Fakultät VI – Planen Bauen Umwelt der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktor der Naturwissenschaften - Dr. rer. nat. - genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr. Reinhard Hinkelmann Gutachter: Prof. Dr. Mark Gessner Gutachter: Prof. Dr. Christopher Soulsby Gutachterin: PD Dr. Sabine Hilt Tag der wissenschaftlichen Aussprache: 19. Juni 2019 Berlin 2019 A worker may be the hammer's master, but the hammer still prevails. A tool knows exactly how it is meant to be handled, while the user of the tool can only have an approximate idea. Milan Kundera, The book of Laughter and Forgetting (1978) The master's tools will never dismantle the master's house. Audre Lorde (1984) i Preface I am grateful for the opportunity to conduct research that was given to me in 2015. Since then, I have had the privilege to dive deep into one subject and spend a lot of time focussing both on big questions and small details. This was especially valuable for me after having worked for two years delivering results at a high pace as a consultant. It goes without saying that the work would not have been possible without the help and support of many people. First and foremost, I want to express my sincere gratitude to Sabine Hilt. She is a formidable scientist and supervisor, giving support both on a professional and personal level, whenever it was needed. I couldn’t have been more lucky in this regard. I also want to thank other past and present members of my working group: Marta Alirangues, Simon Asmus, Amir Bazyar, Spencer Froelick, Alexis Guislain, Liang He, Garabet Kazanjian, Julia Kionka, Anna Lena Kronsbein, Cécile Périllon, Simon Pötter, Anna Stelmecke and Benjamin Wegner, as well as other members of department II at IGB: Rita Adrian, Thomas Hintze, Katrin Lehmann, Jürgen Schreiber and Barbara Stein. There are many more people at IGB that helped me throughout the years, like the members of the chemical lab: Christiane Herzog, Hans-Jürgen Exner, Jörg Gelbrecht, Tobias Goldhammer, Sylvia Jordan, Antje Lüder, Thomas Rossoll and Elisabeth Schütte, but also other people who helped with big and small issues regarding for example field equipment or statistical analysis: Pascal Bodmer, Christof Engelhardt, Jörg Friedrich, Grit Siegert and Gabriel Singer. I am also grateful for the supervision of Mark Gessner, Reinhard Hinkelmann, Michael Hupfer and Wolf M. Mooij. Wolf’s invitation for a research stay at the Netherlands Institute of Ecology in Wageningen gave me the opportunity to work with the highly talented and generous PCLake team: Manqi Chang, Annette B.G. Janssen, Jan H. Janse and Sven Teurlincx. Thank you also to the other co-authors Jan Köhler, Gudrun Massmann and Gunnar Nützmann. Kyle Pipkins, Benjamin Kraemer and Spencer Froelick all helped to improve the language in article manuscripts and this thesis, thank you! My work on this thesis was part of the DFG research training group “Urban Water Interfaces” (UWI, GRK 2032/1). The benefits were manifold: the interdisciplinarity helped to view challenges from multiple points of view, UWI enabled my research stay in the Netherlands as well as my participation in international conferences. The doctoral candidates were able to give each other support, both scientifically and socially and the reoccurring reviews of the individual projects facilitated the structuring of my work and helped me reflect on my research. We all were also assisted by the core of UWI: Tosca Piotrowski and Gwendolin Porst. I also want to thank people that supported me and the project from the outside: Eckhard Scheffler, Thomas Petzoldt, the Berlin Senate Department for the Environment, Transport and Climate Protection, especially Antje Köhler, Alexander Limberg, Benjamin Creutzfeldt and Daniel Brüggemann, and the Berliner Wasserbetriebe, especially Dörte Siebenthaler. Finally, I want to express my gratitude for my family and say gracias to Marta for her continued love and support. Berlin, March 28, 2019 ii Publications of cumulative doctoral thesis First author publications (in chronological order): 1. Gillefalk, M., Massmann, G., Nützmann, G., Hilt, S. 2018. Potential impacts of induced bank filtration on surface water quality: a conceptual framework for future research. Water 10, 1240. https://doi.org/10.3390/w10091240 2. Gillefalk, M., Mooij, W.M., Teurlincx, S., Janssen, A.B.G., Janse, J.H., Chang, M., Köhler, J., Hilt, S. 2019. Modelling induced bank filtration effects on freshwater ecosystems to ensure sustainable drinking water production. Water Research 157, 19-29. https://doi.org/10.1016/j.watres.2019.03.048 3. Gillefalk, M., Herzog, C., Hilt, S. 2019. Phosphorus availability and growth of benthic primary producers in littoral lake sediments: are differences linked to induced bank filtration? Water 11, 1111. https://doi.org/10.3390/w11051111 An overview of supplementary scientific work is given in chapter 6. This thesis was carried out as project N5 of the Research Training Group “Urban Water Interfaces” (UWI) (GRK 2032/1), which is funded by the German Research Foundation (DFG). iii Abstract With ongoing population growth and increasing urbanisation the pressure on urban water bodies increases. In 2015 four billion people, more than half of the world’s population, lived in cities. The task to provide them with safe drinking water is massive. In case of severe pollution the production of drinking water using surface water can be risky and expensive. The preferred raw water source is therefore groundwater. But groundwater resources are often scarce; groundwater depletion is increasing every year with consequences like salt water intrusion, soil surface subsidies and loss of wetlands. Many methods therefore exist to recharge the groundwater aquifer, each of them with advantages and disadvantages. One of the techniques is induced bank filtration (IBF), used worldwide for more than a century. When installing and operating groundwater wells close to a surface water body, the groundwater level drops below the surface water level and infiltration is induced. The water passage through the sediment and the subsurface provides a cost-efficient pre-treatment step for drinking water production. IBF is therefore widespread and expected to increase in the future. Existing research has focussed on the purification efficiency and abstraction capacity of IBF, while no studies investigated the ecological effects of IBF on surface water bodies. The aim of this thesis was to analyse the potential effects of IBF on surface water bodies, primarily lakes, by (1) developing a concept based on an extensive literature review, (2) a modelling study testing different scenarios of IBF effects on shallow lake ecosystems and (3) a field and laboratory study of the sediment quality in an urban lake affected by IBF and its effects on benthic primary producers. The model study was performed using the shallow lake ecosystem model PCLake and investigated the effects of IBF by focussing on five mechanisms: 1) Loss of CO2 inflow via groundwater, 2) Loss of nutrient inflow via groundwater, 3) Increase in seasonal temperature variation, 4) Increase in sedimentation rate and 5) Increase in sediment oxygen penetration depth. In addition, the impact of lake size and depth on the effect size was investigated. For the field and laboratory study sediment cores were collected from the urban Lake Müggelsee, at six locations with expected high impact of IBF and six locations with expected low impact of IBF. The sediments were analysed for grainsize distribution, organic matter content, phosphorus availability, total phosphorus and heavy metals. They were also used in a growth experiment to study if changes to the sediment characteristics by IBF would affect the growth of periphyton and submerged macrophytes. Numerous potential effects of IBF, categorized into physical, chemical and biological effects, were identified from available literature. Effects on very large rivers were iv thought to be small or negligible while effects on lakes and slow flowing lowland rivers were expected to be potentially adverse. By interrupting the groundwater seepage, IBF would at the same time interrupt CO2 and nutrient inflow via groundwater, increase seasonal temperature variation and the retention times in lakes. In extreme cases, extensive pumping could significantly lower lake water tables and streamflow. Many of the potential effects identified during the literature study could be tested in the modelling study. The results showed that the impact of IBF on shallow lake ecosystems was mainly caused by interrupting groundwater seepage. Increased summer water temperatures promoted cyanobacteria blooms and the loss of CO2 inflow via groundwater reduced macrophyte growth and promoted turbid states in lakes. This was true for most of the tested scenarios. In a few cases, when in the initial state groundwater CO2 concentrations were low and nutrient concentrations were high, IBF interrupted nutrient loading via groundwater, reduced phytoplankton growth and promoted a clear-water state. The net effect of IBF impact on sedimentation rate and oxygen penetration depth resulted in higher phosphorus binding in the sediment, but the effect was small. The field and laboratory study revealed that sediments from locations with a high impact of IBF had higher phosphorus availability and iron content.