Abstract
Abstract. Lake sediment characterization, a prerequisite for the vulnerability assessment of lake ecosystems, demands reliable in situ methods for the characterization of the sediment layer composition. A unified characterization of lake sediments within lake ecotopes (open water, open water patches within the reed, and the reed) is still a challenge. Each ecotope is covered by different classical scientific disciplines (hydrography and terrestrial remote sensing to soil physics) with their specific characterization methods. Recently, a complementary tool that bridges the gap between land and hydrographic surveying methods was introduced. It is a non-acoustic device that combines two soil physical sensors (a capacitive sensor and a cone penetrometer) and GNSS-positioning in a measuring system (CSPS). The CSPS enables rapid in situ delineation of water–mud–consolidated lakebed interfaces. The system was successfully applied across ecotopes at the Neusiedler See, a well-mixed shallow lake rich in fine-grained sediments. The geo-referenced vertical CSPS profiles show ecotope-specific layer composition. The effects of wind-induced turbidity, particle size, and electrical conductivity were analysed. The water–mud interface was precisely delineated at the open water due to a persistent high water content gradient, equivalent to a lutocline. The penetration resistance (PR) for open water showed either a shallow and highly compacted consolidated lakebed or a consolidated lakebed with a partially compacted layer above, while in the reed the PR smoothly increased until reaching the deepest penetration depths.
Highlights
The Neusiedler See is the largest lake in Austria (315 km2), and comprises two different ecotopes – the open water and the reed belt (178 km2) (Dokulil and Herzig, 2009)
The CSPS was successfully applied in the shallow Neusiedler See
The characteristic layer compositions are presented for the different ecotopes at the shallow, endorheic Neusiedler See: (1) the open water area, (2) the open water patches within the reed – sparse reed patches and Braunwasser, and (3) the reed
Summary
The Neusiedler See is the largest lake in Austria (315 km2), and comprises two different ecotopes – the open water and the reed belt (178 km2) (Dokulil and Herzig, 2009). This endorheic lake is well mixed and rich in fine-grained sediments that form a distinct mud layer. Inorganic turbidity in the reed is completely missing for two reasons: first the extremely calm water due to less wind exposure, and secondly the chemophysical effects between the humic colloids and the finestgrained sediments. The turbidity within the reed belt is only secondarily impacted by the stormy conditions at the open water due to water drift from and into the open water (Tauber, 1959)
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