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| Titel |
Hydrological connectivity inferred from diatom transport through the riparian-stream system |
| VerfasserIn |
N. Martínez-Carreras, C. E. Wetzel, J. Frentress, L. Ector, J. J. McDonnell, L. Hoffmann, L. Pfister |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 7 ; Nr. 19, no. 7 (2015-07-16), S.3133-3151 |
| Datensatznummer |
250120764
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| Publikation (Nr.) |
 copernicus.org/hess-19-3133-2015.pdf |
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| Zusammenfassung |
| Diatoms (Bacillariophyta) are one of the most common and diverse algal
groups (ca. 200 000 species, ≈ 10–200 μm, unicellular,
eukaryotic). Here we investigate the potential of aerial diatoms (i.e.
diatoms nearly exclusively occurring outside water bodies, in wet, moist or
temporarily dry places) to infer surface hydrological connectivity between
hillslope-riparian-stream (HRS) landscape units during storm runoff events.
We present data from the Weierbach catchment (0.45 km2, northwestern
Luxembourg) that quantify the relative abundance of aerial diatom species on
hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and
vegetation) and within streams (i.e. stream water, epilithon and epipelon).
We tested the hypothesis that different diatom species assemblages inhabit
specific moisture domains of the catchment (i.e. HRS units) and,
consequently, the presence of certain species assemblages in the stream
during runoff events offers the potential for recording whether there was
hydrological connectivity between these domains or not. We found that a higher percentage of aerial diatom
species was present in samples collected from the riparian and hillslope
zones than inside the stream. However, diatoms were absent on hillslopes
covered by dry litter and the quantities of diatoms (in absolute numbers)
were small in the rest of hillslope samples. This limits their use for
inferring hillslope-riparian zone connectivity. Our results also showed that
aerial diatom abundance in the stream increased systematically during all
sampled events (n = 11, 2011–2012) in response to incident
precipitation and increasing discharge. This transport of aerial diatoms
during events suggested a rapid connectivity between the soil surface and the
stream. Diatom transport data were compared to two-component hydrograph
separation, and end-member mixing analysis (EMMA) using stream water
chemistry and stable isotope data. Hillslope overland flow was insignificant
during most sampled events. This research suggests that diatoms were likely
sourced exclusively from the riparian zone, since it was not only the largest
aerial diatom reservoir, but also since soil water from the riparian zone was
a major streamflow source during rainfall events under both wet and dry
antecedent conditions. In comparison to other tracer methods, diatoms require
taxonomy knowledge and a rather large processing time. However, they can
provide unequivocal evidence of hydrological connectivity and potentially be
used at larger catchment scales. |
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