René Sachse

Extending one-dimensional models for deep lakes to simulate the impact of submerged macrophytes on water quality

Submerged macrophytes can stabilise clear water conditions in shallow lakes. However, many existing models for deep lakes neglect their impact. Here, we tested the hypothesis that submerged macrophytes can affect the water clarity in deep lakes. A one-dimensional, vertically resolved macrophyte model was developed based on PCLake and coupled to SALMO-1D and GOTM hydrophysics and validated against field data. Validation showed good coherence in dynamic growth patterns and colonisation depths. In our simulations the presence of submerged macrophytes resulted in up to 50% less phytoplankton biomass in the shallowest simulated lake (11?m) and still 15% less phytoplankton was predicted in 100?m deep oligotrophic lakes. Nutrient loading, lake depth, and lake shape had a strong influence on macrophyte effects. Nutrient competition was found to be the strongest biological interaction. Despite a number of limitations, the derived dynamic lake model suggests significant effects of submerged macrophytes on deep lake water quality. Existing models were innovatively combined to study macrophyte effects in deep lakes.Submerged macrophytes can significantly affect the water clarity in deep lakes.This effect depends on lake geometry, depth, and nutrient loading.

Altered spatio-temporal dynamics of RNase H2 complex assembly at replication and repair sites in Aicardi–Goutières syndrome

Ribonuclease H2 plays an essential role for genome stability as it removes ribonucleotides misincorporated into genomic DNA by replicative polymerases and resolves RNA/DNA hybrids. Biallelic mutations in the genes encoding the three RNase H2 subunits cause Aicardi-Goutières syndrome (AGS), an early-onset inflammatory encephalopathy that phenotypically overlaps with the autoimmune disorder systemic lupus erythematosus. Here we studied the intracellular dynamics of RNase H2 in living cells during DNA replication and in response to DNA damage using confocal time-lapse imaging and fluorescence cross-correlation spectroscopy. We demonstrate that the RNase H2 complex is assembled in the cytosol and imported into the nucleus in an RNase H2B-dependent manner. RNase H2 is not only recruited to DNA replication foci, but also to sites of PCNA-dependent DNA repair. By fluorescence recovery after photobleaching, we demonstrate a high mobility and fast exchange of RNase H2 at sites of DNA repair and replication. We provide evidence that recruitment of RNase H2 is not only PCNA-dependent, mediated by an interaction of the B subunit with PCNA, but also PCNA-independent mediated via the catalytic domain of the A subunit. We found that AGS-associated mutations alter complex formation, recruitment efficiency and exchange kinetics at sites of DNA replication and repair suggesting that impaired ribonucleotide removal contributes to AGS pathogenesis.

Large-scale impact of climate change vs. land-use change on future biome shifts in Latin America

Climate change and land-use change are two major drivers of biome shifts causing habitat and biodiversity loss. What is missing is a continental-scale future projection of the estimated relative impacts of both drivers on biome shifts over the course of this century. Here, we provide such a projection for the biodiverse region of Latin America under four socio-economic development scenarios. We find that across all scenarios 5-6% of the total area will undergo biome shifts that can be attributed to climate change until 2099. The relative impact of climate change on biome shifts may overtake land-use change even under an optimistic climate scenario, if land-use expansion is halted by the mid-century. We suggest that constraining land-use change and preserving the remaining natural vegetation early during this century creates opportunities to mitigate climate-change impacts during the second half of this century. Our results may guide the evaluation of socio-economic scenarios in terms of their potential for biome conservation under global change.

Testing socio-cultural valuation methods of ecosystem services to explain land use preferences

Highlights • Land use preferences are assessed by novel, interactive visualisation tool LANDPREF.• Visitors were clustered into 5 groups according to land use preferences.• Socio-cultural values of ecosystem services could not explain land use preferences.• Socio-cultural values of ecosystem services could not replace land use preferences.

Wie zeigt sich der Klimawandel in den deutschen Talsperren

Langzeitdaten von deutschen Talsperren zeigen eine Erhöhung der Temperaturen der oberen Wasserschichten vor allem im Winter, Frühling und Frühsommer. Die Trends sind regional ähnlich. Da sich schon geringe Temperaturerhöhungen auf die biotische und abiotische Struktur und somit auf die Wasserbescha enheit auswirken, ergibt sich für Trink wassertalsperren die Notwendigkeit, die Bewirtschaftung an die Veränderungen anzupassen.