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| Titel |
Spatial and temporal variability of greenhouse gas emissions from a small and shallow temperate lake |
| VerfasserIn |
Leandra Praetzel, Marcel Schmiedeskamp, Tanja Broder, Caroline Hüttemann, Laura Jansen, Ulrike Metzelder, Ronya Wallis, Klaus-Holger Knorr, Christian Blodau |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150411
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| Publikation (Nr.) |
 EGU/EGU2017-14870.pdf |
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| Zusammenfassung |
| Small inland waters (< 1 km2) have recently been discovered as significant sources and sinks
in the global carbon cycle because they cover larger areas than previously assumed and
exhibit a higher metabolic activity than larger lakes. They are further expected to be
susceptible to changing climate conditions.
So far, little is known about the spatial and temporal variability of carbon dioxide (CO2)
and methane (CH4) emissions and in-lake dynamics of CH4 production and oxidation in
small, epilimnetic lakes in the temperate zone. Of particular interest is the potential
occurrence of “hot spots” and “hot moments” that could contribute significantly to total
emissions.
To address this knowledge gap, we determined CO2 and CH4 emissions and dynamics to
identify their controlling environmental factors in a polymictic small (1.4 ha) and shallow
(max. depth approx. 1.5 m) crater lake (“Windsborn”) in the Eifel uplands in south-west
Germany. As Lake Windsborn has a small catchment area (8 ha) and no surficial inflows, it
serves well as a model system for the identification of factors and processes controlling
emissions.
In 2015, 2016 and 2017 we measured CO2 and CH4 gas fluxes with different techniques
across the sediment/water and water/atmosphere interface. Atmospheric exchange was
measured using mini-chambers equipped with CO2 sensors and with an infra-red greenhouse
gas analyzer for high temporal resolution flux measurements. Ebullition of CH4 was
quantified with funnel traps. Sediment properties were examined using pore-water peepers.
All measurements were carried out along a transect covering both littoral and central parts of
the lake. Moreover, a weather station on a floating platform in the center of the lake recorded
meteorological data as well as CO2 concentration in different depths of the water
column.
So far, Lake Windsborn seems to be a source for both CO2 and CH4 on an annual scale.
CO2 emissions generally increased from spring to summer. Even though CO2 uptake could
be observed during some periods in spring and fall, CO2 emissions in the summer exceeded
the uptake. CO2 and CH4 emissions also appeared to be spatially variable between
littoral areas and the inner lake. Shallow areas turned out to be “hot spots” of CO2
emissions whereas CH4 emissions were - against our expectations - highest in the
center of the lake. Moreover, CH4 ebullition contributed substantially to total CH4
emissions.
Our results show the importance of spatially and temporally highly resolved long-term
measurements of greenhouse gas emissions and of potential controlling factors to address
diurnal, seasonal and inter-annual variability as well as possible feedbacks to climate change. |
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