Looking beyond stratification: a model-based analysis of the biological drivers of oxygen deficiency in the North Sea

Low oxygen conditions, often referred to as oxy- gen deficiency, occur regularly in the North Sea, a temperate European shelf sea. Stratification represents a major process regulating the seasonal dynamics of bottom oxygen, yet, low- est oxygen conditions in the North Sea do not occur in the regions of strongest stratification. This suggests that stratifi- cation is an important prerequisite for oxygen deficiency, but that the complex interaction between hydrodynamics and the biological processes drives its evolution. In this study we use the ecosystem model HAMSOM- ECOHAM to provide a general characterisation of the dif- ferent zones of the North Sea with respect to oxygen, and to quantify the impact of the different physical and biological factors driving the oxygen dynamics inside the entire sub- thermocline volume and directly above the bottom. With respect to oxygen dynamics, the North Sea can be subdivided into three different zones: (1) a highly produc- tive, non-stratified coastal zone, (2) a productive, season- ally stratified zone with a small sub-thermocline volume, and (3) a productive, seasonally stratified zone with a large sub- thermocline volume. Type 2 reveals the highest susceptibility to oxygen deficiency due to sufficiently long stratification pe- riods (textgreater60 days) accompanied by high surface productivity resulting in high biological consumption, and a small sub- thermocline volume implying both a small initial oxygen in- ventory and a strong influence of the biological consumption on the oxygen concentration. Year-to-year variations in the oxygen conditions are caused by variations in primary production, while spatial dif- ferences can be attributed to differences in stratification and water depth. The large sub-thermocline volume dominates the oxygen dynamics in the northern central and northern North Sea and makes this region insusceptible to oxygen de- ficiency. In the southern North Sea the strong tidal mixing inhibits the development of seasonal stratification which pro- tects this area from the evolution of low oxygen conditions. In contrast, the southern central North Sea is highly suscep- tible to low oxygen conditions (type 2). We furthermore show that benthic diagenetic processes represent the main oxygen consumers in the bottom layer, consistently accounting for more than 50% of the overall consumption. Thus, primary production followed by rem- ineralisation of organic matter under stratified conditions constitutes the main driver for the evolution of oxygen defi- ciency in the southern central North Sea. By providing these valuable insights, we show that ecosystem models can be a useful tool for the interpretation of observations and the es- timation of the impact of anthropogenic drivers on the North Sea oxygen conditions

Adolescent leisure reading and its longitudinal association with prosocial behavior and social adjustment

Reading is a popular leisure activity for children, teenagers, and adults. Several theories agree that reading might improve social cognition, but the empirical evidence remains tentative, with research on adolescents especially lacking. We employed a very large, and nationally representative, longitudinal dataset from the National Educational Panel Study (NEPS) in Germany to examine this hypothesis. Specifically, we tested whether reading prospectively predicted future self-reported prosocial behavior and social adjustment in adolescents, controlling for a number of covariates. Two-way cross-lagged panel analyses probed the longitudinal relationship between leisure reading and these social outcomes from Grade 6 to Grade 9. In addition, we examined the effect of cumulative reading experience across Grades 5–8 on future social outcomes, using structural equation modeling. We also explored the unique contributions of cumulative reading experience in different literary genres (classic literature, popular literature, nonfiction, comic books). Cumulative reading in general did not predict future prosocial behavior and social adjustment. However, cumulative reading of modern classic literature was positively associated with later prosocial behavior and social adjustment

Drohnen als Partner im Luftraum

In unserem Beitrag fassen wir drei Themen einer jüngst veröffentlichten Studie zur Technikfolgenabschätzung ziviler Drohnen zusammen. Erstens legen wir dar, dass der Rechtsbegriff der Drohne unklar geregelt ist und dass eine technische Definition des Begriffs „Drohne“ der falsche Weg ist. Wir präsentieren eine alternative Einbindung des Drohnenbegriffs in das europäische Luftfahrtrecht. Zweitens beschreiben wir die Komplexität der technisch zu regelnden Aspekte, um eine Einbindung von Drohnen in das Luftraumsystem ohne direkten Sichtkontakt zu ermöglichen. Wir beschreiben das Problem der technischen Sicherheit und die Komponenten eines Verkehrsmanagementsystems für Drohnen. Drittens verdeutlichen wir, dass bei der Bewältigung der ethischen, rechtlichen und sozialen Herausforderungen von Drohnen eine Vollzugslücke besteht, insbesondere im Datenschutz

Drones as partners in the airspace: Framework conditions for regulation of civilian drones

In unserem Beitrag fassen wir drei Themen einer jüngst veröffentlichten Studie zur Technikfolgenabschätzung ziviler Drohnen zusammen. Erstens legen wir dar, dass der Rechtsbegriff der Drohne unklar geregelt ist und dass eine technische Definition des Begriffs „Drohne“ der falsche Weg ist. Wir präsentieren eine alternative Einbindung des Drohnenbegriffs in das europäische Luftfahrtrecht. Zweitens beschreiben wir die Komplexität der technisch zu regelnden Aspekte, um eine Einbindung von Drohnen in das Luftraumsystem ohne direkten Sichtkontakt zu ermöglichen. Wir beschreiben das Problem der technischen Sicherheit und die Komponenten eines Verkehrsmanagementsystems für Drohnen. Drittens verdeutlichen wir, dass bei der Bewältigung der ethischen, rechtlichen und sozialen Herausforderungen von Drohnen eine Vollzugslücke besteht, insbesondere im Datenschutz.In our article, we summarize three topics of a recently published study on technology assessment of civilian drones. First, we explain that the legal concept of drones is unclear and that a technical definition of the term "drone" would be the wrong way to go. We present an alternative approach to integrate the concept of drones into European aviation law. Second, we describe the complexity of the technical aspects to be regulated in order to enable the integration of drones into the airspace system beyond visual line of sight. We describe the problem of technical safety and the components of a drone traffic management system. Third, we point to an enforcement gap in coping with the ethical, legal, and social challenges of drones, particularly in data protection

A novel modeling approach to quantify the influence of nitrogen inputs on the oxygen dynamics of the North Sea

Oxygen (O2) deficiency, i.e., dissolved O2 concentrations below 6 mg O2 L-1, is a common feature in the southern North Sea. Its evolution is governed mainly by the presence of seasonal stratification and production of organic matter, which is subsequently degraded under O2 consumption. The latter is strongly influenced by riverine nutrient loads, i.e., nitrogen (N) and phosphorus (P). As riverine P loads have been reduced significantly over the past decades, this study aims for the quantification of the influence of riverine and non-riverine N inputs on the O2 dynamics in the southern North Sea. For this purpose, we present an approach to expand a nutrient-tagging technique for physical-biogeochemical models - often referred to as 'trans-boundary nutrient transports' (TBNT) - by introducing a direct link to the O2 dynamics. We apply the expanded TBNT to the physical-biogeochemical model system HAMSOM-ECOHAM and focus our analysis on N-related O2 consumption in the southern North Sea during 2000-2014. The analysis reveals that near-bottom O2 consumption in the southern North Sea is strongly influenced by the N supply from the North Atlantic across the northern shelf edge. However, riverine N sources - especially the Dutch, German and British rivers - as well as the atmosphere also play an important role. In the region with lowest simulated O2 concentrations (around 56 °N, 6.5 °E), riverine N on average contributes 39% to overall near-bottom O2 consumption during seasonal stratification. Here, the German and the large Dutch rivers constitute the highest riverine contributions (11% and 10%, respectively). At a site in the Oyster Grounds (around 54.5 °N, 4 °E), the average riverine contribution adds up to 41%, even exceeding that of the North Atlantic. Here, highest riverine contributions can be attributed to the Dutch and British rivers adding up to almost 28% on average. The atmospheric contribution results in 13%. Our results emphasize the importance of anthropogenic N inputs and seasonal stratification for the O2 conditions in the southern North Sea. They further suggest that reductions in the riverine and atmospheric N inputs may have a relevant positive effect on the O2 levels in this region

Stable Carbon Isotope Signature of Methane Released From Phytoplankton

Unidad de excelencia María de Maeztu CEX2019-000940-MAquatic ecosystems play an important role in global methane cycling and many field studies have reported methane supersaturation in the oxic surface mixed layer (SML) of the ocean and in the epilimnion of lakes. The origin of methane formed under oxic condition is hotly debated and several pathways have recently been offered to explain the "methane paradox." In this context, stable isotope measurements have been applied to constrain methane sources in supersaturated oxygenated waters. Here we present stable carbon isotope signatures for six widespread marine phytoplankton species, three haptophyte algae and three cyanobacteria, incubated under laboratory conditions. The observed isotopic patterns implicate that methane formed by phytoplankton might be clearly distinguished from methane produced by methanogenic archaea. Comparing results from phytoplankton experiments with isotopic data from field measurements, suggests that algal and cyanobacterial populations may contribute substantially to methane formationobserved in the SML of oceans and lakes

A model-based projection of historical state of a coastal ecosystem : relevance of phytoplankton stoichiometry

We employed a coupled physical-biogeochemical modelling framework for the reconstruction of the historic (H), pre-industrial state of a coastal system, the German Bight (southeastern North Sea), and we investigated its differences with the recent, control (C) state of the system. According to our findings: i) average winter concentrations of dissolved inorganic nitrogen and phosphorus (DIN and DIP) concentrations at the surface are ∼70–90% and ∼50–70% lower in the H state than in the C state within the nearshore waters, and differences gradually diminish towards off-shore waters; ii) differences in average growing season chlorophyll a (Chl) concentrations at the surface between the two states are mostly less than 50%; iii) in the off-shore areas, Chl concentrations in the deeper layers are affected less than in the surface layers; iv) reductions in phytoplankton carbon (C) biomass under the H state are weaker than those in Chl, due to the generally lower Chl:C ratios; v) in some areas the differences in growth rates between the two states are negligible, due to the compensation by lower light limitation under the H state, which in turn explains the lower Chl:C ratios; vi) zooplankton biomass, and hence the grazing pressure on phytoplankton is lower under the H state. This trophic decoupling is caused by the low nutritional quality (i.e., low N:C and P:C) of phytoplankton. These results call for increased attention to the relevance of the acclimation capacity and stoichiometric flexibility of phytoplankton for the prediction of their response to environmental change

Highly porous novel chondro-instructive bioactive glass scaffolds tailored for cartilage tissue engineering.

Abstract Cartilage injuries remain challenging since the regenerative capacity of cartilage is extremely low. The aim was to design a novel type of bioactive glass (BG) scaffold with suitable topology that allows the formation of cartilage-specific extracellular matrix (ECM) after colonization with chondrogenic cells for cartilage repair. Highly porous scaffolds with interconnecting pores consisting of 100 % BG were manufactured using a melting, milling, sintering and leaching technique. Scaffolds were colonized with porcine articular chondrocytes (pAC) and undifferentiated human mesenchymal stromal cells (hMSC) for up to 35 days. Scaffolds displayed high cytocompatibility with no major pH shift. Scanning electron microscopy revealed the intimate pAC-scaffold interaction with typical cell morphology. After 14 days MSCs formed cell clusters but still expressed cartilage markers. Both cell types showed aggrecan, SOX9 gene and protein expression, cartilage proteoglycan and sulfated glycosaminoglycan synthesis for the whole culture time. Despite type II collagen gene expression could not anymore be detected at day 35, protein synthesis was visualized for both cell types during the whole culturing period, increasing in pAC and declining after day 14 in hMSC cultures. The novel BG scaffold was stable, cytocompatible and cartilage-specific protein synthesis indicated maintenance of pAC's differentiated phenotype and chondro-instructive effects on hMSCs

The LabTogo-Project

A joint project between West African Science Service Center on Climate Change and Adapted Land Use (WASCAL), the University of Lomé and the German Biomass Research Center (Deutsches Biomasseforschungszentrum; DBFZ) was initiated in 2020. The project aims at evaluating alternative and regenerative energy sources for rural areas and creating the basis for successful implementation. In three different work packages, therefore, biomass potentials should be quantified, technologies should be examined with regard to their suitability and - in the case of biogas application - a research structure, pilot biogas laboratory, should be created that is necessary to enable the sustainable implementation of technologies