Wir untersuchen sowohl einzelne Prozesse in aquatischen Systemen als auch ganze Systeme natürlicher Gewässer. Neben der Grundlagenforschung und der interdisziplinären Systemanalyse stehen anwendungsnahe Projekte besonders im Fokus.
Das chaotische Verhalten von Wirbeln macht unter anderem die Wetterprognosen so schwierig. Forschende von ETH Zürich, Eawag und WSL haben jetzt zusammen mit internationalen Partnern eine neuartige experimentelle Methode...
Das chaotische Verhalten von Wirbeln macht unter anderem die Wetterprognosen so schwierig. Forschende von ETH Zürich, Eawag und WSL haben jetzt zusammen mit internationalen Partnern eine neuartige experimentelle Methode entwickelt, die mit viel weniger Aufwand genauere Analysen der Bewegungen und Energien von Turbulenzen in Flüssigkeiten ermöglicht.
Saboret, G., Dermond, P., & Brodersen, J. (2021). Using PIT-tags and portable antennas for quantification of fish movement and survival in streams under different environmental conditions. Journal of Fish Biology, 99(2), 581-595. doi:10.1111/jfb.14747, Institutional Repository
While PIT-tag tracking using mobile antennas is being increasingly used to study fish movement and survival in streams, little is known about the limitations of the method, especially over longer periods of time and under different environmental settings. We used 6 years of data combining tagging, mobile antenna tracking and recaptures of Salmo trutta in multiple small streams in the Lake Lucerne drainage area in Switzerland to evaluate the relative importance of different environmental and intrinsic factors affecting the efficiency of the method. Our study system and experimental design allowed us to accurately verify the continuous presence and survival of recaptured fish in the stream after tracking, which meant that we could estimate detection probability with high confidence. The mean detection probability of tagged trout was 43%, but we found that fish length had a strong negative effect on detection probability, especially in males. Multivariate axes of stream environmental features did not predict efficiency but stream width alone was significantly positively correlated with efficiency. Additionally, stream temperature when tracking had a positive effect on fish detectability. Tag loss at recapture was globally rare (<8%) but common in large postspawn females (>30%). Based on the escape response of fish after detection, we could estimate the proportion of ghost tags, which reached a plateau of around 80% 2 years after tagging. We finally showed that our models of tag loss, fish detection and escape response are needed to interpret detection events. Our results highlight that individual variation in detection probability and tag loss is high and has to be considered for analysis.
Hofmann, A. M., Kuefner, W., Mayr, C., Dubois, N., Geist, J., & Raeder, U. (2021). Unravelling climate change impacts from other anthropogenic influences in a subalpine lake: a multi-proxy sediment study from Oberer Soiernsee (Northern Alps, Germany). Journal of Aquatic Ecosystem Stress and Recovery, 848(18), 4285-4309. doi:10.1007/s10750-021-04640-8, Institutional Repository
Mountain lakes are increasingly impacted by a series of both local and global disturbances. The present study reveals the eutrophication history of a remote subalpine lake (Oberer Soiernsee, Northern Alps, Germany), triggered by deforestation, alpine pasturing, hut construction, tourism and atmospheric deposition, and identifies the intertwined consequences of on-going global warming on the lake’s ecosystem. The primary objective was to disentangle the various direct and indirect impacts of these multiple stressors via down-core analyses. Our multi-proxy approach included subfossil diatom assemblages, carbon and nitrogen stable isotope ratios and subfossil pigments from dated sediments. Shifts within the diatom assemblages were related to variations in trophic state, lake transparency, water temperature and thermal stratification. The organic carbon isotope (δ13Corg) records, the diatom valve density and the pigment concentrations documented the development of primary production and composition. Total nitrogen isotope values (δ15N) are more likely to reflect the history of atmospheric nitrogen pollution than lake-internal processes, also mirrored by the decoupling of δ15N and δ13Corg trends. The composition of sedimentary pigments allowed a differentiation between planktonic and benthic primary production. Concordant trends of all indicators suggested that the lake ecosystem passed a climatic threshold promoted by local and long-distance atmospheric nutrient loadings.