Defense Abstracts

PhD thesis: Life below the city - Environmental drivers, habitat suitability and biodiversity patterns in urban groundwater ecosystems

Date: 21.08.2026, 11:00, Hörsaal 1, UBB

Supervisor: Christian Griebler

Abstract

Groundwater ecosystems are home to a variety of fascinating organisms that play a crucial role in global aquatic invertebrate biodiversity, as well as in maintaining ecosystem functions and good water quality. Still, groundwater fauna biodiversity remains severely underexplored. Consequently, and despite their ecological importance, the environmental drivers of stygofauna biodiversity, particularly at local to regional scales, also remain ambiguous. This holds true especially for urban aquifers, where multiple stressors converge and interact. Therefore, this thesis investigates which environmental drivers and anthropogenic pressures shape groundwater fauna habitat suitability and biodiversity patterns with a focus on the shallow aquifers of the city of Vienna (Austria) as a model system for a multifactorial urban setting. Following an integrative approach, existing knowledge was compiled and used to develop a predictive habitat suitability framework, which was then applied and compared with the detailed characterization of the groundwater ecosystem in Vienna, including groundwater quality and biodiversity, based on a comprehensive dataset from over 150 observation wells.

The results underline that groundwater fauna distribution and community composition are impacted rather by the interaction of multiple environmental drivers than single factors. Oxygen availability, and particularly redox conditions, were identified as main drivers. Furthermore, the physical habitat characteristics (e.g. aquifer type, hydraulic conductivity, depth) and groundwater temperature were found to be key factors with respect to stygofauna habitat suitability. In urban aquifers, most of these drivers can be modified and accelerated by anthropogenic pressures such as surface sealing, subsurface infrastructure, altered groundwater recharge, groundwater warming and the formation of subsurface heat islands. The interplay of several of these factors can furthermore lead to geochemical processes that can promote pollution and contaminant mobilization. The combination of these multiple factors results in complex biodiversity patterns. The developed habitat suitability framework demonstrated that the meaningful combination of key environmental variables can result in feasible predictions of groundwater crustacean biodiversity patterns, despite the inherent complexity of urban groundwater ecosystems. Additionally, the observed groundwater crustacean biodiversity in Vienna was with 47 stygobiont and stygophile species unexpectedly high for a multi-pressure urban area and can be considered a subterranean biodiversity hotspot by international comparison.

Overall, this thesis underlines the significance of a multi-factorial and scale-specific approach for identifying groundwater biodiversity patterns. It links environmental drivers with habitat suitability and biodiversity patterns and highlights the importance of integrating ecological variables into groundwater assessment and management frameworks. The thesis provides transferable knowledge for applied groundwater ecology in urban aquifers and promotes holistic and sustainable management and conservation strategies.