Publications
Following publications have been announced by our department Aquatic Nutrient Cycles. For further information please contact the marked co-authors of the publications:
Tobias-Hünefeldt, S.P., van Beusekom, J.E.E., Russnak, V., Dähnke, K., Streit, W.R., & Grossart, H.-P. (2024): Seasonality, rather than estuarine gradient or particle suspension/sinking dynamics, determines estuarine carbon distributions. Science of The Total Environment, Volume 926, 171962, doi:10.1016/j.scitotenv.2024.171962
Abstract:
Estuaries are important components of the global carbon cycle; exchanging carbon between aquatic, atmospheric, and terrestrial environments, representing important loci for blue carbon storage and greenhouse gas emissions. However, how estuarine gradients affect sinking/suspended particles, and dissolved organic matter dynamic interactions remains unexplored. We fractionated suspended/sinking particles to assess and characterise carbon fate differences. We investigated bacterial colonisation (SYBR Green I) and exopolymer concentrations (TEP/CSP) with microscopy staining techniques. C/H/N and dry weight analysis identified particle composition differences. Meanwhile, nutrient and carbon analysis, and excitation and emission matrix evaluations with a subsequent parallel factor (PARAFAC) analysis characterised dissolved organic matter.
The lack of clear salinity driven patterns in our study are presumably due to strong mixing forces and high particle heterogeneity along the estuary, with only density differences between suspended and sinking particles. Elbe estuary particles‘ organic portion is made up of marine-like (sinking) and terrestrial-like (suspended) signatures. Salinity did not have a significant role in microbial degradation and carbon composition, although brackish estuary portions were more biologically active. Indicative of increased degradation rates, leading to decreased greenhouse gas emissions, which are especially relevant for estuaries, with their disproportionate greenhouse gas emissions. Bacterial colonisation decreased seawards, indicative of decreased degradation, and shifts in microbial community composition and functions.
Our findings span diverse strands of research, concerning steady carbon contributions from both marine and terrestrial sources, carbon aromaticity, humification index, and bioavailability. Their integration highlights the importance of the Elbe estuary as a model system, providing robust information for future policy decisions affecting dissolved and particulate matter dynamics within the Elbe Estuary.
Strauss, J., Marushchak, M.E., van Delden, L., Sanders, T., Biasi, C., Voigt, C., Jongejans, L.L., & Treat, C. (2024): Potential nitrogen mobilisation from the Yedoma permafrost domain. Environ. Res. Lett. 19 043002, doi:10.1088/1748-9326/ad3167
Abstract:
Permafrost regions, characterised by extensive belowground excess ice, are highly vulnerable to rapid thaw, particularly in areas such as the Yedoma domain. This region is known to freeze-lock a globally significant stock of soil nitrogen (N). However, the fate of this N upon permafrost thaw remains largely unknown. In this study, we assess the impact of climate warming on the size and dynamics of the soil N pool in (sub-)Arctic ecosystems, drawing upon recently published data and literature. Our findings suggest that climate warming and increased thaw depths will result in an expansion of the reactive soil N pool due to the larger volume of (seasonally) thawed soil. Dissolved organic N emerges as the predominant N form for rapid cycling within (sub-)Arctic ecosystems. The fate of newly thawed N from permafrost is primarily influenced by plant uptake, microbial immobilisation, changes in decomposition rates due to improved N availability, as well as lateral flow. The Yedoma domain contains substantial N pools, and the partial but increasing thaw of this previously frozen N has the potential to amplify climate feedbacks through additional nitrous oxide (N2O) emissions. Our ballpark estimate indicates that the Yedoma domain may contribute approximately 6% of the global annual rate of N2O emissions from soils under natural vegetation. However, the released soil N could also mitigate climate feedbacks by promoting enhanced vegetation carbon uptake. The likelihood and rate of N2O production are highest in permafrost thaw sites with intermediate moisture content and disturbed vegetation, but accurately predicting future landscape and hydrology changes in the Yedoma domain remains challenging. Nevertheless, it is evident that the permafrost-climate feedback will be significantly influenced by the quantity and mobilisation state of this unconsidered N pool.
