Terrestrial diatoms as tracers in catchment hydrology: a review

Abstract

Diatoms are remarkable organisms. They are present in almost all habitats containing water (e.g., lakes, streams, soils, bark) and rank among the most common algal groups in both freshwaters and marine ecosystems. The ubiquitous character of aquatic diatoms has triggered countless applications as environmental tracers for studies in water quality, paleoclimate reconstruction and sediment tracing. However, diatoms also occur in the terrestrial environment. It is this plethora of diatom life-forms that has recently triggered interest in their use as tracers of hydrological processes. The use of diatoms in catchment hydrology has been very limited. Part of the reason is that until recently, the taxonomy and ecology of terrestrial diatom assemblages were largely unknown. However, in the past decade, much work has been done to quantify terrestrial diatom reservoir size, dynamics, and potential depletion following precipitation events. Therefore, such terrestrial diatoms now hold promise for use in catchment hydrology-for tracing runoff flow sources and pathways across a wide range of spatial scales. Here we review the literature on terrestrial diatoms and describe the various sampling protocols that have been designed and tested for specific applications in hydrological processes research. We review and summarize the work on terrestrial diatom reservoir characterization, transport mechanisms and pathways to show how such diatom-based tracer work might be possible at the catchment scale for rainfall-runoff studies. Finally, we present a vision for future work that might take advantage of terrestrial diatoms in catchment hydrology and discuss the main challenges going forward. © 2017 The Authors. WIREs Water published by Wiley Periodicals, Inc. How to cite this article:WIREs Water 2017Water , 4:e1241. doi: 10.1002Water /wat2.1241 INTRODUCTION D iatoms (Bacillariophyta) are present in almost all habitats containing water (e.g., lakes, streams, soils, litter, bark). They count among the most common algal groups in both freshwaters and marine ecosystems. 1 Despite their microscopic size (10-200 microns), 2 diatoms generate an impressive amount of carbon through photosynthesis: almost as much as all rainforests combined. 3 Identification of diatoms date back to the early 1700s as noted by Round et al. 1 Decades later, Otto Friedrich Müller published the first description of a diatom in 1783 (Vibrio paxillifer ≡ Bacillaria paradoxa). Since then, This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. more than 64,000 diatom species have been described-and new species are added to that list almost daily with the number of extant species extrapolated to ca 100,000. 4,5 The identification of diatoms (from the Greek 'diatomos' or 'cut in half') commonly relies on the highly differentiated cell wall (or frustule) that is mostly co...

Using a multi-hypothesis framework to improve the understanding of flow dynamics during flash floods

“…While several ranges of value for the internal flow velocities have been simulated, a reasonable restriction based on the velocity likelihood could be foreseen. This further perspective should also shift experimental studies toward a better assessment of the water transit time along the different pathways at the hillslope scale, either using direct methods such water isotope tracing (Tetzlaff et al, 2018), developing imaginative indirect ones such as the diatom tracing (Pfister et al, 2017b), or taking advantage of suspended particles and water turbidity measurements.…”

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“…This shows that simulations of solute chemistry require an accurate estimation of the TTDs that goes beyond conservative tracer input–output relationships, and that accounts for the potential multiple modes of transport associated with different age fractions (Benettin et al, 2017). On the other hand, this also means that stream chemistry data (Neal et al, 2013) and new available tracers (Abbott et al, 2016; Hissler, Stille, Guignard, Iffly, & Pfister, 2014; Pfister et al, 2017; Visser et al, 2019) can be used to validate TTDs deduced from a conservative tracer input–output relationship (Guillet et al, 2019). Overall, these results highlight the need for new methods that do not calibrate TTDs using tracer input–output relationships but instead measure the TTDs directly, such as (Kim et al, 2016; Kirchner, 2019).…”

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“…An interesting outcome was that the percentage of terrestrial diatoms in the stream samples increased when a peak in the hydrograph occurred meaning that they are indeed responsive to changes in stream flow conditions (Klaus et al, 2015;Martínez-Carreras et al, 2015;Pfister et al, 2015). As a follow-up to this proof-of-concept work, Pfister et al (2017) have advocated to better characterize the spatial and temporal dynamics of the terrestrial diatom reservoir -paving the way for new diatom sampling protocols of higher spatial and temporal resolution (Klaus et al, 2015). This should eventually provide new insights into the initiation of hydrological connectivity across the catchment (as inferred from diatom flushing to the stream from various terrestrial reservoirs).…”