ALBERT

Description: Cross-system studies on the response of different ecosystems to global change will support our understanding of ecological changes. Synoptic views on the planet's two main realms, the marine and terrestrial, however, are rare, owing to the development of rather disparate research communities.We combined questionnaires and a literature review to investigate howthe importance of anthropogenic drivers of biodiversity change differs amongmarine and terrestrial systems and whether differences perceived by marine vs. terrestrial researchers are reflected by the scientific literature. This included asking marine and terrestrial researchers to rate the relevance of different drivers of global change for either marine or terrestrial biodiversity. Land use and the associated loss of natural habitatswere rated as most important in the terrestrial realm,while the exploitation of the sea by fishing was rated as most important in the marine realm. The relevance of chemicals, climate change and the increasing atmospheric concentration of CO2 were rated differently for marine and terrestrial biodiversity respectively. Yet, our literature review provided less evidence for such differences leading to the conclusion that while the history of the use of land and sea differs, impacts of global change are likely to become increasingly similar.

Description: Diese Broschüre und die gleichnamige Ausstellung befassen sich mit der Entwicklung des Echolots, für das der Kieler Physiker und Unternehmer Alexander Behm im Jahr 1913 das erste Patent erhielt. Erfahren Sie mehr über die Geschichte der Tiefenmessung im Ozean – von den ersten Handloten im alten Ägypten über die dampfgetriebenen Lotmaschinen des 19. Jahrhunderts, der Entwicklung der ozeanischen Tiefenkarten bis hin zur heutigen Vermessung des Meeresbodens mit modernen Fächerecholoten.

Description: Tillage is a central element in agricultural soil management and has direct and indirect effects onprocesses in the biosphere. Effects of agricultural soil management can be assessed by soil, crop, and ecosystemmodels, but global assessments are hampered by lack of information on the type of tillage and their spatialdistribution. This study describes the generation of a classification of tillage practices and presents the spatiallyexplicit mapping of these crop-specific tillage systems for around the year 2005.Tillage practices differ by the kind of equipment used, soil surface and depth affected, timing, and their pur-pose within the cropping systems. We classified the broad variety of globally relevant tillage practices intosix categories: no-tillage in the context of Conservation Agriculture, traditional annual, traditional rotational,rotational, reduced, and conventional annual tillage. The identified tillage systems were allocated to griddedcrop-specific cropland areas with a resolution of 5 arcmin. Allocation rules were based on literature findings andcombine area information on crop type, water management regime, field size, water erosion, income, and aridity.We scaled reported national Conservation Agriculture areas down to grid cells via a probability-based approachfor 54 countries. We provide area estimates of the six tillage systems aggregated to global and country scale. Wefound that 8.67 Mkm2of global cropland area was tilled intensively at least once a year, whereas the remaining2.65 Mkm2was tilled less intensely. Further, we identified 4.67 Mkm2of cropland as an area where ConservationAgriculture could be expanded to under current conditions.The tillage classification enables the parameterization of different soil management practices in various kindsof model simulations. The crop-specific tillage dataset indicates the spatial distribution of soil managementpractices, which is a prerequisite to assess erosion, carbon sequestration potential, as well as water, and nutrientdynamics of cropland soils. The dynamic definition of the allocation rules and accounting for national statistics,such as the share of Conservation Agriculture per country, also allow for derivation of datasets for historical andfuture global soil management scenarios. The resulting tillage system dataset and source code are accessible viaan open-data repository (DOIs: https://doi.org/10.5880/PIK.2019.009 and https://doi.org/10.5880/PIK.2019.010,Porwollik et al., 2019a, b).

Description: In our meeting Dynamic Earth – from Alfred Wegener to today and beyond we will review how Wegener‘s findings evolved into to modern Earth system science including its impact on climate and the Earth surface, and how this system affects our daily life: where humans live, what risks we are exposed to, where we find our resources. In the meeting we will hold sessions that cover the entire geoscience spectrum (from mineral physics over solid earth geodynamics to the climate sciences) and that explore the consequences of Wegeners findings on how humans use our planet today (from energy and mineral resources over georisks to utilisation of the subsurface and materials for modern society). We have invited keynote speakers that are eminent international scientists in these fields. In events open to the general public we will get an account of Wegeners final trip to Greenland on the history of science of his hypothesis.

Description: Microorganisms are important drivers of the carbon, nitrogen, and sulfur cycles on earth. They can adapt to various substrates and, thus, inhabit ecological niches too extreme for higher lifeforms, such as sub- and anoxic or even sulfidic waters. They follow a wide range of ecological strategies with variable levels of specialization to their environment. In the highly stratified water column of the Baltic Sea, respiration of organic matter in combination with sluggish ventilation causes the formation of anoxic zones. Here, organic material is decomposed anaerobically, which leads to the increased production of hydrogen sulfide – a highly toxic compound for higher lifeforms (e.g. multicellular organisms). The transition zone between sulfidic and suboxic conditions, the redox zone, is inhabited by two chemolithoautotrophic key organisms, both with the same ability to detoxify hydrogen sulfide via oxidation with nitrate. Interestingly, both organisms show an overlapping abundance. While the gammaproteobacterial SUP05 clade is most abundant in the suboxic zone, the epsilonproteobacterial Sulfurimonas GD17 subgroup dominates the sulfidic zone. This led to the question of how these two organisms can survive within the same habitat although they exhibit the same substrate requirements. In Paper I, I coupled phylogenetic identification with single-cell uptake measurements of SUP05 and Sulfurimonas GD17 in environmental samples from the Gotland Deep redox zone. I was able to identify niche separation due to different substrate utilization strategies: SUP05 is streamlined, non-motile, and slowly utilizing; essentially a K-strategist, adapted to low substrate conditions and omnipresent in most of the oxygen minimum zones worldwide. In contrast, Sulfurimonas GD17 is a fast utilizing r-strategist, specialized for high and fluctuating substrate conditions, which uses chemotactic behavior to move into regions of favorable substrate conditions. Together they drive a highly efficient detoxification machinery in the Baltic Sea redox zone. Remarkable microbial strategies which influence matter cycling can be found in other pelagic environments as well. Sinking particles are considered an important potential habitat for pelagic microorganisms due to their substrate richness and structural heterogeneity, as well as their omnipresence in the world oceans. Within individual porous particles, it is theorized that innumerable redox gradients should exist at the microscale, whose attributes in aggregate would drive and control significant elemental fluxes globally. However, marine particles still represent a major black box in microbial ecology due to their fragile nature, which makes them inaccessible for detailed micro-scale observations. Therefore, I present in Paper II a cryogel-based embedding and slicing approach, which enables detailed microscopic investigations of the microbial community within the intact particle structure. The approach is compatible with most structural and phylogenetic staining protocols, such as for different extracellular exopolymers and microbial identification using various fluorescent in situhybridization (FISH) protocols. It also allows the three-dimensional reconstruction of whole aggregates as well as precise porosity calculations and is, moreover, applicable to sediment traps for undisturbed in situ samplings. As Paper I clearly illustrates, cellular abundance and species distribution must be accompanied by cellular activity measurements to fully describe an organism’s ecological role. In Paper III, I therefore present an optimized embedding and slicing method based on soft and hard plastic resins, which enables single-cell uptake measurements using modern nano-scale secondary ion mass spectrometer (NanoSIMS) measurements across the complex microzone structures of marine particles. Embedded specimens were characterized by low outgassing and ablation properties within the ultra-high vacuum chamber (i.e. good conditions for NanoSIMS), but high secondary ion yields. Moreover, critical aspects of cellular biogeochemistry, such as the potential use of alternative electron acceptors by microorganisms, could be identified within particles for the first time, visible as 34S and 15N enrichments from stable isotope labelled sulfate and nitrate in single cells. Staining properties for structural compounds similar to those in Paper II, enabled three-dimensional reconstruction and porosity calculations as well. The combination of both methods presented in Paper II and Paper III opens up new ways to investigate the microbial ecology and their interaction with the particle structure in terms of phylogeny and activity. The influence of the particle-associated microbial community on matter cycling at larger scales depends both on particle structure (above) and on particle abundance and distribution in the water column. To scale up results measured by the methods developed above, we need to identify and measure the distributions of fragile particles at high vertical resolution, without physical distortion. In Paper IV, I present a coupled study of optical particle quantification, physical particle characterization, as well as molecular sequencing in the region of Fram Strait. Calculated particle sinking trajectories and microbial genetic source tracking revealed a strong vertical connectivity between the observed microbial communities. This connectivity was most pronounced in areas with sea ice coverage, where almost half of the particle-associated communities in the deep sea were linked to surface-derived microbes. In turn, it could be concluded that further sea ice decline in the Arctic Ocean may reduce vertical microbial connectivity, which possibly alters current biogeochemical cycling. This study exemplifies the huge potential of optical quantification coupled to microbiological and molecular methods for multiscale particle investigations. The abundance and sinking behavior of particles are highly influenced by biological processes, including microbial degradation and remineralization, as well as grazing and repackaging by zooplankton. However, physical forcing, particularly on the sub-meso and mesoscale, critically shape particle distributions in the water column. In Paper V, I present a combined investigation of optical particle counting and classification as well as Acoustic Doppler Current Profiler (ADCP) based current velocity measurements in a cyclonic eddy of the South Atlantic. I observed vertical propagation of presumably wind-driven inertial wave energy following the vorticity field at the eddy perimeter, a process known as ‘inertial chimney’ effect. The resulting zone of increased horizontal shear in the upper 1500 m caused increased upward vertical nutrient flux, supporting enhanced primary production and intensified particle formation in surface eddy. I could show that particles 〉 0.5 mm in diameter generally followed the relative vorticity field, leading to a sub-surface V-shape of the particle distribution that has not previously been observed. Repackaging and fragmentation by copepods in combination with low carbon-specific degradation led to a threefold increased carbon flux to the deep sea in the center of the eddy. I concluded that cyclonic eddies must regularly cause increased deep carbon export events, in the oligotrophic South Atlantic gyre, and globally. Global matter cycles, including entire pelagic food webs, are affected by the microbial dynamics of sinking particles. These, in turn, are shaped by a wide variety of physical and biological processes ranging from the microscale to mesoscale. Sinking particles and their complex communities thus represent a biogeochemical link between small- and large-scale processes. My work highlights how the global impacts of particle-associated microbial communities can only be understood through investigations using interdisciplinary approaches at multiple scales. In my thesis, I used cutting-edge methodologies to investigate microbial processes at the micro-scale, and built strategies to integrate these processes into a broader understanding of microbial dynamics at oceanographic scales of relevance to the global ocean.

Description: The Wadden Sea has an important role for marine mammals in terms of resting, nursing and foraging. Harbor seal is the most abundant marine mammal species in this area. The use of the food resources of the Wadden Sea by seals is not clear, and previous studies showed that this species can travel kilometers away from their haul-outs to forage in the North Sea. In this study, we analyzed the stable isotopes of vibrissae from 23 dead harbor seals found on the island of Sylt to investigate their diet. The predator´s carbon and nitrogen isotope compositions were compared to the compositions of different potential prey items from the Sylt-Rømø Bight and from the North Sea in order to study seasonal pattern in the diet and in the foraging location. In parallel, seasonal variation of abundance and biomass of the potential prey items from the Sylt-Rømø Bight were studied and compare to their contribution to the seal´s diet. The results revealed a change in the seal´s diet from pelagic sources in spring to a benthic based diet in summer, and an increasing use of the North Sea resources in fall and winter in accordance with the seasonal variation of the availability of prey in the Sylt-Rømø Bight.

Description: Recent mobilisation of soil organic matter (SOM) in permafrost of the northern high latitudes is thought to have a significant impact on the carbon balance in the atmosphere. However, the environmental processes which influence SOM accumulation and remobilisation still need to be investigated more accurately. This study investigates the quantity and quality of SOM on Herschel Island in the western Canadian Arctic in relation to various landscape characteristics. To reach this goal, soil moisture, total organic carbon (TOC) and total nitrogen (TN) contents, stable carbon isotopes (∂¹³C) and TOC/TN ratios (C/N) were determined on 128 samples from twelve sediment cores reaching up to 250 cm depth. Drilling locations were chosen based on morphology, vegetation and soil properties and supported by satellite imagery and air photos. Seasonal thaw depths (active layer depths) correlate with ground disturbance and vegetation cover and lie between 20 and 100 cm. Well-preserved SOM is accumulated in the active layer and subjacent ice-rich permafrost of wet polygonal tundra. Uplands, hummocky tussock tundra and alluvial fans cover more than 50 % of the island and show heterogeneous SOM storage characteristics with considerable TOC contents being limited to the active layer. Disturbed areas with slope gradients greater than 6° show strong SOM degradation with low TOC contents throughout the active layer and permafrost strata. Linear regression and principal component analysis (PCA) shows that a decreasing SOM content is driven by increasing ground disturbance and reduced vegetation cover. Improved drainage decreases the preservation of SOM in the active layer. Future deepening of the active layer because of increasing temperatures and ground disturbance will remobilise SOM stored in ice-rich permafrost. This might increase carbon dioxide and methane emissions from permafrost landscapes.