Topic 3: Intermittent flow – hydrological effects and impacts on benthic communities, ecological state and functioning of riverine systems

Introduction/background

Intermittent flow is widely seen as one characteristic of Mediterranean riverine systems, but have recently become spreading in South and Eastern Central Europe. Hydrology, as a main driver of aquatic processes decisively shapes ecological functions and the linked ecosystem services (ES) in human-modified landscapes. Drought and low flow may lead to further loss and fragmentation of aquatic ecosystems resulting in a degradation of functional connections culminating in a change of nutrient cycling and species turn-over. Little is known so far about these effects on ES like provisioning usable water, self-purification processes, primary production and biodiversity patterns in Central Europe and lessons learned from Southern Countries cannot be easily and uncritically transformed.

Main objective/research question/hypothesis

The PhD topic will therefore focus on macroinvertebrates as integrative indicators of functionality, integrity, and resilience of aquatic ecosystems under drought conditions. Several case-study areas will be established in which the following issues will be addressed  (I) the effects of drought and the interlinked connectivity and fragmentation patterns of aquatic systems on benthic communities regarding diversity and functional metrics including biological water quality indices; (II) seasonal patterns of organismic responses and linked metrics/traits to hydrological cycles to acquire a deeper understand of resilience/resistance strategies; (III) the connectivity of gene flows and interconnections within metapopulations of selected species typical for intermittent and permanent flow respectively; (IV) Additionally, as drying phenomena of smaller catchments are largely unknown indicative macroinvertebrate communities will be screened and tested as early warning indicators for drought-risk assessment.

Approach/methods and time frame

The study is focused on South-Eastern Austria. As this PhD topic is closely related to Topic 4, the same analyses will be performed. A1) Data collection and assessment of structural indicators, such as functional traits and groups of macroinvertebrates. A2) Statistical space-time modelling of hydrological conditions. A3) Statistical assessment of the link between hydrological characteristics and ecological indicators. Issues (I to IV) will additionally be analysed using e-DNA metabarcoding approaches.

Time frame: Four years, with monitoring (A1, year 1-2), space-time models (A2, year 2),  multivariate indicator assessment (A3, year 3), publications (year 4).