Examination of aerial diatom flushing across watersheds in Luxembourg, Oregon and Slovakia for tracing episodic hydrological connectivity

Abstract

Hydrologicalrocesses research remains a field that is severely measurement limited. While conventional tracers (geochemicals, isotopes) have brought extremely valuable insights into water source and flowpaths, they nonetheless have limitations that clearly constrain their range of application. Integrating hydrology and ecology in catchment science has been repeatedly advocated as offeringotential for interdisciplinary studies that are eventually torovide a holistic view of catchment functioning. In this context, aerial diatoms have been shown to have theotential for detecting of the onset/cessation of rapid water flowpaths within the hillslope-riparian zone-stream continuum. However, many open questionsrevail as to aerial diatom reservoir size, depletion and recovery, as well as to their mobilisation and transportrocesses. Moreover, aerial diatoms remainoorly known compared to freshwater species and new species are still being discovered. Here, we ask whether aerial diatom flushing can be observed in three catchments with contrastinghysiographic characteristics in Luxembourg, Oregon (USA) and Slovakia. This is arerequisite for qualifying aerial diatoms as a robust indicator of the onset/cessation of rapid water flowpaths across a wider range ofhysiographical contexts. One species inarticular, (Hantzschia amphioxys (Ehr.) Grunow), was found to be common to the three investigated catchments. Aerial diatom species were flushed, in different relativeroportions, to the river network during rainfall-runoff events in all three catchments. Our take-away message from thisreliminary examination is that aerial diatoms appear to have aotential for tracing episodic hydrological connectivity through a wider range ofhysiographic contexts and therefore serve as a complementary tool to conventional hydrological tracers.