Bachelor's degree programme in Environmental Sciences, 48 pages (first and second reviewer)

Worldwide and also in the Wadden Sea of the north-west German coast, a decrease in the extent of seagrass meadows can be observed. The dwarf seagrass grows within a bulb structure mainly within the growth areas at the edge and on the bulb. Why fewer plants establish in the depressions between the bulbs and to what extent the plants that do establish differ in their vitality from those within other growth areas will be analysed in this study. Data on the site conditions will be recorded. These include both the grain size composition and the organic content of the sediment as well as the temperature and brightness values within the respective growth area. In addition, the leaves on the rhizome per 10 cm², the average leaf length, the biomass of the above-ground and underground plant parts and the chlorophyll concentration are determined as vitality parameters.

The results show that the site conditions do not differ between the different growth areas with regard to the grain size composition and the organic content of the sediment. High temperature and brightness values were determined, particularly during low tide during the day, which differed depending on the growth areas and the two study sites. Dwarf seagrass is highly adaptable to changing environmental conditions. However, temperatures above the tolerance threshold were measured in the Seefeld mudflats in particular.

Statistically significant differences in the vital parameters between the growth areas are shown above all by the two variables leaves on the rhizome per 10 cm² and leaf length. At both locations, significantly more and longer leaves are counted on and at the edge of the bulb. In the Seefeld mudflats, longer but fewer leaves were counted on the rhizome. In the mudflats of the Lütetsburger Plate, the result is the opposite. Here, shorter but significantly more leaves are recorded on the rhizome. In addition, significantly longer rhizomes were measured in the bottom growth area at both sites. The biomass and chlorophyll concentration differed significantly only at the Lütetsburger Plate site, with the highest values being measured within the top growth area.

Bachelor's degree programme in Environmental Sciences, 58 pages (first and second reviewer)

The aim of this thesis is to determine the stability of seagrass meadows. To achieve this, one-metre-deep boreholes were drilled at three distinct sites (Seefeld, Lütetsburg, Sylt) to extract historical data on the occurrence of seagrass meadows. Analyses encompassing particle size determination, loss on ignition, and diatom identification were conducted to address this inquiry. Additionally, the seagrass-proxy Cocconeis placentula (diatom) was used to further confirm the presence of seagrass. The results indicate that the cover of seagrass meadows changed in the drilling locations over time.

Bachelor's degree programme in Environmental Sciences, 36 pages (first and second reviewer)

This thesis deals with the invasive neophyte Campylopus introflexus. The species has spread rapidly on the East Frisian Islands and is able to form dominant stands with a cover of up to 100 per cent. This has many negative effects on the flora and fauna.
The theoretical background to neophytes, invasiveness and mosses is discussed first, followed by a look at the dynamics of Campylopus introflexus on the East Frisian island of Spiekeroog. The following questions were answered:

Is the colonised area continuing to decrease or is the overgrown area expanding? And to what extent and in which areas of the island is the population changing? Or is the area remaining more or less stable and is it rather a spatial shift of the species?

The study area is located to the west of the island of Spiekeroog in the German Wadden Sea off the coast of Lower Saxony. It covers 328 hectares and extends around the centre of the island in the shape of a horn. This area consists mainly of Tertiary dunes up to 370 years old, on which Campylopus introflexus was already able to spread strongly at earlier mapping dates (2002, 2018), which are referred to in this work.

To answer the question, field mapping was carried out in March 2023. All occurrences of the species were documented in field maps. These were then digitised using ArcGIS Pro software and processed into maps, including the data sets from 2002 and 2018. A presence-absence study was created for the three points in time.

The populations of Campylopus introflexus have risen sharply compared to 2018, but have not (yet) reached the level of 2002. The spread is mainly towards the north and adjacent to existing areas. Only a small proportion of the populations remained constant at all three mapping dates. The number of areas located at new sites is therefore high. Complete declines of Campylopus areas were also shown.

The dynamics of the species are high and the hypothesis that this is a spatial shift of the species was confirmed. It was also possible to determine the further spread of the species, which currently occupies around eleven per cent of the study area. Even Campylopus populations that were already dead or at least very weakened are recovering. Effective control methods are not yet known, which is why further spread to the limits of the species' capabilities is to be expected.

Master's programme Marine Environmental Sciences, 101 pages (first and second reviewer)

English version see below.

Salt marshes are a unique habitat that has been extremely affected by human utilisation over the last 2000 years. In most German salt marshes, close-meshed drainage systems have been constructed for utilisation. In recent decades, their ecological importance has come to the fore and, contrary to the trend of global decline, the area of salt marshes in Germany is growing. Due to their ecological importance and many protection statuses, attempts are being made to restore some of the salt marshes to as natural a state as possible. However, various studies on renaturalisation measures have shown that artificial drainage systems, once integrated, persist and only slowly give way to a natural tidal marsh system. The effects of drainage systems have only been partially researched and are currently still a component of many German salt marshes.

As part of this master's thesis, sedimentological and botanical influences of the drainages on the salt marshes were investigated. Eight transects next to the Grüppen (artificial channels) of the Langeoog summer polder and five transects next to the tideways of the natural salt marsh of the Ostplate on Spiekeroog were analysed using several methods. Elevation profiles were created, vegetation compositions recorded and sediment samples analysed for loss on ignition and grain size composition. The thickness of the marsh soil and the soil strength were also recorded and map material was analysed in terms of flux density (a ratio of drainage/priel distance to area). The results were statistically analysed using canonical correspondence analysis with regard to the distribution patterns for sites, plants and transects.

The investigations showed that the group and tidal flat systems have an influence on the sedimentation process and the spatial distribution patterns as well as the micro-relief and thus also on the vegetation. Group and tidal flat systems show different, sometimes opposing distribution patterns of grain size and loss on ignition. The neighbouring elevation profiles and the closely associated vegetation also show major differences between groups and tidal creeks.

***************************************************************

Salt marshes are a unique habitat that have been heavily influenced by human activities over the past 2000 years. In order to facilitate land use, dense artifical drainage systems have been installed in most German salt marshes. However, in recent decades, their ecological significance has gained prominence, and contrary to the global loss, the area of salt marshes in Germany is expanding. Efforts are being made to restore salt marshes to their natural state, considering their protected status. However, various studies have shown that installed drainage systems, once integrated, persist stubbornly and only gradually give way to a natural channel system during restoration measures. The impacts of these artificial drainage systems have just been partially investigated.

This master's thesis examines the sedimentological and botanical influences of artifical and natural drainage systems on salt marshes. Eight transects located next to the artificial channels of Langeoog's "Sommerpolder" and eight transects located next to the natural channels of Spiekeroog's "Ostplate" salt marsh were studied using different methods. Elevation profiles were created, vegetation compositions were recorded, and sediment samples were analysed for loss on ignition and grain size distribution. Additionally, the thickness of the entire marsh soil as well as the soil density were measured, and cartographic material was evaluated for flux-dense (a quotient of the drainage-/ irrigation system to the area). The results were statistically analysed using Canonical Correspondence. Analysis to determine distribution patterns for sites, species, and transects. The investigations revealed that artifical and natural drenage systems have an impact on sedimentation processes, spatial distribution patterns, microtopography and consequently, vegetation in the salt marshes. The artifical and natural drenage systems show different, partly opposite distribution patterns of grain size and loss on ignition. Also, the elevation profiles and the closely associated vegetation show significant differences between the two systems.

Master's programme Marine Environmental Sciences, 55 pages (first reviewer)

The incorporation of carbon in soil is highly influenced by soil structure and the spatial accessibility of organic matter in relation to the pore system. Structural indicators are induced by the applied management system and crop rotation, which then impact the microbial activity. It is yet difficult to analyse, but this thesis aims to connect soil structure with soil biology.

By measuring undisturbed, intact soil cores with an X-ray CT scanner and isothermal micro calorimetry, the structural indicators got combined with biological activity analysis. Soil cores were taken from different management systems in conventional and reduced tillage fields, each from maize and winter wheat. 3-dimensional X-ray CT pictures were taken to calculate structural parameters, which were then connected to the different management systems. They were moreover correlated to the results of heat dissipation in a calorimeter. For this experiment, the samples were applied with glucose solution and water.

It has been found that the soil structural parameters were influenced by both, tillage practises and crop rotation. Reduced tillage created more biopores and a better connected pore system, whereas conventional tilled fields contained more particulate organic matter from the ploughing. Maize roots moreover led to bigger pores and also entailed more organic matter by root exudates. A higher porosity and especially a higher surface density led to a larger heat dissipation for soil cores with glucose addition. Not only samples with glucose released energy in the calorimeter though, but also soil cores with water.

The labile and easily available organic matter that was mobilised in the used saturation and drainage method played an important role in this. The margin between pore surface and soil matrix therefore seems to be a reactive, important interface. The organic matter seems to adhere to the pore surface and can then easily be converted and produced energy in the form of heat.

These results were compared with disturbed soil structure in form of repacked soil cores, where it was clearly shown that the strong heterogeneity of undisturbed soil cores has an impact on the biological activity. The labile carbon was also important, which was compensated for by a longer incubation time before the calorimeter measurement.

More research is still needed in analysing the different microbial communities and their specific influences by various crops. More samples, also at comparable harvesting states would be valuable for verification of the found results.

Bachelor's degree programme in Environmental Sciences, 49 pages (first and second reviewer)

In the present study, it was shown that the late bird cherry is very abundant in the open dune habitats of Spiekeroog, with the focus of the occurrences both in 2018 and 2022 in coastal dunes with crowberry heath. The densest occurrences are currently in the area of the Hermann-Lietz-Schule and on forest edges east of the Kläranlange. The spread of the species in 2001, 2018 and 2022 confirms Hahn's (2006) prediction that the species would spread rapidly on Spiekeroog in the future and develop into a problem species.

As part of this study, the current spread of the species into previously uncolonised areas of the central dune area and south of the campsite was also shown. In principle, the highest risk potential exists in biotope types of high conservation value that are sensitive to nutrient inputs, groundwater lowering and/or shading. In the study area, this applies above all to grey dune grassland, wet coastal dune valleys, coastal dunes with crowberry heath or creeping willow scrub. This results in the highest risk potential in the area of the Hermann-Lietz-Schule, where the late bird cherry sometimes reaches high densities in the above-mentioned habitats and penetrates small-scale biotope types of the wood-free coastal dune valleys with individual specimens. The biotope types in the area of the campsite and the central dune area are potentially endangered by the colonisation or spread of Prunus serotina.

Early intervention and removal of initial occurrences, as prescribed by the national park administration's inspection scheme, is without doubt the most suitable method of reacting to an alien species. However, in the case of the late weeping cherry, this has not been done in the past, or not sufficiently. Complete eradication of the species no longer appears feasible due to the diaspore bank and the number of individuals. However, in view of the potential threat and the expansive dispersal behaviour of the species on Spiekeroog, management should be considered in order to continue to comply with the legal provisions of EU Regulation 1143/2014, the Federal Nature Conservation Act and the conservation purpose of the national park in the future. Control in the form of removal of the species is most urgently required in the areas north and south of the campsite and in the central dune area. At the same time, efforts should be made to push back the species in the area of the Hermann-Lietz-Schule. Finally, it is also advisable to reduce the spread of the neophyte in the northern dune bend and in the dunes west of the village and in the forest of the Wester Friederikenwald in order to improve or maintain the conservation status of sea buckthorn and creeping willow scrub, crowberry heaths and grey dune grassland and to prevent the spread of the neophyte. The occurrences in the coastal dune copses, which were not recorded as part of this study, should be checked for their specific threat potential if necessary. However, as high numbers of individuals were recorded at the edges of the forest in some cases, it is necessary to reduce the dispersal potential in favour of the open dune habitats, e.g. in the area of the village, the sewage treatment plant or in the forest of the Wester Friederikental.

Bachelor's degree programme in Environmental Sciences, 34 pages (first reviewer)

The climate in Switzerland has been changing at an unprecedented rate since 1980. Climatic changes such as the distribution of precipitation, the number of hot days, changes in snow cover and the shift of the zero degree line have an impact on the cryosphere in the Alps. Glaciers are retreating, the thawing depth of the surface layer of permafrost soils is increasing, the temperature below the ZAA is rising and the speed of movement of rock glaciers is increasing. (Fischer et al. 2022, Smith et al. 2022).

These changes result in an increased risk of natural hazards. Strategies and measures to minimise natural hazards are therefore particularly important. Agreements such as the Alpine Convention play an important role in prevention measures. They ensure that the member states share their experience in dealing with natural hazards, thus leading to international progress in risk management. Another important point of such agreements is that the member states are required to map areas with regard to natural hazards and then designate these as hazard zones. Switzerland has complied with this requirement in its Spatial Utilisation Act (see Article 6.2.c RPG).

Spatial planning is another preventive measure. By prohibiting construction in certain areas, or only under certain conditions, a possible danger is avoided. However, spatial planning can only influence future land use plans. It has little influence on existing land uses. This is where measures designed to minimise the residual risk of natural hazards come into play. Such measures are usually structural measures that are based not only on empirical knowledge but also on studies and research. Nevertheless, the residual risk can never be completely avoided, as natural hazards often have cascading effects that are difficult to model in advance.

Further research and observation of climatic changes in the Alps is therefore absolutely essential in order to further minimise the risk of natural hazards in the future. This is especially true with regard to further climate changes in the coming decades. As these changes are beyond historical experience, it is important to analyse the processes in the high mountains in detail in order to develop new strategies and methods that can keep up with the speed of change in nature.

Finally, it should be noted that climatic changes in the Alps do not only affect the inhabitants of the Alpine regions. The climatic processes also have an impact on regions outside the Alps. In particular, Europe's status as a "water reservoir" may pose major challenges for the population in the coming decades. The potential of glacial lakes as energy reservoirs is another interesting perspective that should not be ignored, especially in times of energy crises. This requires close co-operation between state institutions, NGOs, scientists and the population.

Bachelor's degree programme in Environmental Sciences, 55 pages (first reviewer)

English version see below.

Nature conservation interests and nature sports in ecologically sensitive areas repeatedly lead to land use conflicts and management challenges for the responsible authorities. For example, kitesurfing in the Wadden Sea UNESCO World Heritage Site is also in conflict with nature conservation interests. The parties to the conflict disagree on the extent of the spatial and temporal restrictions on kitesurfing. Ultimately, the discourse culminated in legal proceedings. Throughout the course of the conflict, there were difficulties in finding solutions and compromises. The aim of this work is therefore to identify these problem areas in order to gain insights for future conflicts over the use of space and, at best, to avoid them. Guided interviews were conducted to record the conflict and the views of the individual stakeholders. These were analysed using Mayring's qualitative content analysis method. Saretzki's conflict analysis served as the theoretical basis.

The analysis revealed that three fundamental causes made the conflict complex and protracted: Lack of communication, lack of information transfer and lack of trust. In addition, these three problem areas were mutually dependent. It also became clear that as soon as differences between interests arise, a culture of dialogue must be created at an early stage to prevent disagreements from turning into conflict. Mediation or moderation techniques are also helpful in resolving conflicts of interest. For the organising body, management is becoming increasingly complex due to the diverse user interests.

******************************************

Nature conservation interests and nature sports repeatedly lead to land use conflicts and management challenges for the responsible authority in ecologically sensitive areas. The sport of kitesurfing in the Wadden Sea UNESCO World Heritage Site is in conflict with nature conservation interests. The conflicting parties disagree on the extent of territorial and temporal restrictions of kitesurfing. Most recently, the discourse resulted in a court case. Throughout the course of the conflict, difficulties arose in finding solutions and compromises. Therefore, the goal of this thesis is to locate these trouble spots in order to gain insights for later land use conflicts and, at best, to be able to avoid them. To capture the conflict and the views of the individual actors, guided interviews were conducted. These were evaluated with the help of qualitative content analysis according to Mayring. Saretzki's conflict analysis served as the theoretical basis.
The evaluation revealed that three fundamental causes made the conflict complex and protracted: Lack of communication, lack of information transfer, and lack of trust. In addition, these three problem areas are mutually dependent. Furthermore, it became apparent that as soon as differences between interests arise, a dialogue culture must be created at an early stage in order to prevent conflict from arising from disagreements. Mediation or moderation techniques are also helpful in resolving conflicts of interest. For the organising authority, management is becoming increasingly complex due to the diverse interests of users.

Master's programme Marine Environmental Sciences, 109 pages (first reviewer)

English version see below.

In parallel to the global downward trend, seagrass stocks in the Wadden Sea of the southern North Sea are dwindling, and with them the numerous ecosystem functions and services. Triggers for the decline, especially eutrophication, have been known for years, but the role of macrozoobenthos is largely unexplored and knowledge of potential interactions is limited to individual species. In order to obtain an overview of the macrozoobenthos in seagrass meadows, sites with different degrees of exposure and seagrass densities were sampled and correlations and trends in the abundance of the organisms found with seagrass were determined. In the more exposed, more homogeneous mixed mudflats of the Lütetsburger Plate, not only were the maximum abundances of all organisms determined, but also a disproportionately high proportion of Polychaeta, while the muddy, more heterogeneous Seefelder Buchtenwatt is dominated by Polychaeta and Malacostraca with significantly lower accumulated abundances. Correlations with seagrass also proved to be species-specific within the classes. Furthermore, it was not possible to generalise whether the respective correlation was triggered by seagrass itself or the abiotic factors influencing seagrass growth (sediment composition, organic matter content) at the site. Since the temporal sequence of the occurrence of a species and the change in seagrass stocks (or vice versa) is unknown, the potential effect of or on seagrass was discussed for each species individually and compared with the abundances of this and other studies. In addition to direct herbivory on the plant itself, the mobilisation of nutrients from the sediment and thus induced phytoplankton blooms as well as destabilisation of the sediment by species such as Hediste diversicolor, Arenlcola marina or Cerastoderma edule can also damage seagrass populations. Species such as Macoma balthica, Peringia ulvae and Heteromastus filiformis can have positive effects, for example by making missing nutrients available or reducing nutrients in the event of eutrophication, grazing on epiphytes, detritus feeding or mutual anchoring in the sediment, and thus make an important contribution to seagrass protection and renaturation measures by favouring environmental conditions. However, local environmental factors must always be taken into account, as these can make a decisive contribution to the positive or negative influence of individual species of macrozoobenthos.

********************************************************

Following the global decline in seagrass stocks, populations drop in the southem Wadden Sea as well. Correspondingly, the seagrass's ecosystem functions and services are declining. Triggers like eutrophication are well known for a long time, whereas the role of macrozoobenthos is largely unexplored and knowledge about potential interactions are limited to single species only. To get an overview of all macrozoobenthos in local seagrass meadows, samples were taken from sites of different levels of exposure and seagrass density, and trends and correlations were determined. Maximum abundances were found in the more exposed and more homogeneous mixed sediment mudflat of the Lütetsburger Plate, with a particularly high percentage of Polychaeta. Abundances in the Jade Bay's more heterogeneous mudflats of the Seefelder Plate were domtnated by Polychaeta and additionally Malacostraca, though in lower total abundances. Correlating seagrass density and macrozoobenthos abundances proved to be highly dependent of both the species itself and ecological context. Furthermore, discriminating between the effect of seagrass itself and the effect of abiotic factors affecting seagrass growth and survival (sediment composition, organic material) on macrozoobenthos could not be generalised. Lacking information on chronological order of one species' presence in a seagrass meadow and a potential consequent change in seagrass density (or vice versa), the effects on or by seagrass were discussed for each macrozoobenthic species individually and com-pared to abundances found in this thesis and other publications. Aside from direct seagrass herbivory, mobilisation of nutrients from the sediment (followed by thereby induced phytoplankton blooms) and destabilisation of sediments by species like Hediste diversicolor, Arenicola marina, and Cerastoderma edule, can cause potential damage to seagrass meadows. Macoma balthica, Peringia ulvae, and Heteromastus filiformis on the other hand can have positive effects on seagrass meadows, among them the mobilisation of lacking nutrients from the sediment, reduction of nutrients during eutrophication, grazing of epiphytes, consuming detritus, and mutual anchorage in soft sediments. Hence, certain species may help facilitating environmental conditions for seagrasses and thereby make an important contribution to future conservation and restoration efforts. Yet, local environmental conditions are to be considered, as they may determine whether a species will facilitate or impede seagrass survival.

Master's programme Marine Environmental Sciences, 55 pages (first reviewer)

- An analysis based on the back dyke of the Langeoog summer polder. -

The Wadden Sea habitat is of international importance as a breeding habitat for various wading birds, such as the oystercatcher(Haematopus ostralegus) and the redshank(Tringa totanus), due to the characteristics of special biotope types, e.g. salt marshes. At the same time, many breeding birds are endangered by the consequences of anthropogenic climate change such as sea level rise and the increase in flood events during the breeding season. A lack of research in this area shows a need to consider the relationship between flooding during the breeding season and changes in breeding populations in salt marshes.

To answer the question of how flooding during the breeding season affects breeding populations, the frequency of summer storm surges {levels > 1.5 m during the breeding period), as well as the breeding pair density of H. ostralegus and T. totanus, were each analysed for trends in the period from 1997 to 2021. These data sets were then analysed for a possible correlation. The proportion of potentially flooded nests was determined using probability classes by intersecting the mapped nest/ territory locations with elevation models and water levels.

Former summer polder areas on the East Frisian island of Langeoog and, in order to exclude local effects, comparable salt marsh areas on the neighbouring island of Spiekeroog were selected as the study area. In the course of a renaturalisation measure, a dyke was built back on Langeoog in 2004; this project was suitable as a model for possible effects of sea level rise on breeding bird populations. The question of whether dyke restoration measures are beneficial for breeding avifauna and how breeding populations in salt marshes could develop in the course of climate change was also addressed.

The study showed that there was an increase in summer storm surges in the period from 1997 to 2021 and that the proportion of potentially flooded nests increased in almost all study areas within the study period. The same applies when a summer polder was diked back, which also increased the number of nests that were flooded. However, the effects of increased flooding on the breeding population were species-specific. While H. ostralegus tended to react negatively to flooding, no negative effects of summer storm surges on T. totanus breeding populations were recognisable, suggesting that breeding populations are influenced multifactorially. In the period from 1997 to 2021, a negative trend in the breeding pair density of H. ostralegus was observed in all study areas; this development can be observed throughout the Wadden Sea area and is likely to continue in the long term. The breeding pair density of T. totanus in the study areas, on the other hand, shows a positive to constant development in the period analysed, but the trend is still negative throughout the Wadden Sea.

Bachelor programme Environmental Sciences, 31 pages (first reviewer)

This bachelor thesis aimed to develop a workflow for laser ablation with inductively coupled plasma mass spectrometry (LA-ICP-MS) in line scan mode for a case study in forensic dendrochemistry. Two tree cores of Alnus glutinosa and one tree core of Betula pendula which were likely exposed to contamination with zinc, lead and arsenic, that originated from a glass factory in southwestern Sweden were analysed to test the method. The sampled trees did not predate the pollution event but documented the stop of glass production in 1979, the remediation of a contaminated landfill in 1986 and the demolition of the industrial building in 2008. The focus of the work was to adapt the LA-ICP-MS analysis technique to the application area of dendrochemistry and thus to be able to evaluate its potential for this research discipline. The results show that the reconstruction of annually resolved isotopic patterns in tree rings is possible via LA-ICP-MS in line scan mode. Although the trees documented the overall decreased concentration of ⁶⁶Zn, ²⁰⁸Pb and⁷⁵As in the environment most likely due to the remedial activities the results do not suggest that ²⁰⁸Pb and ⁷⁵As are reliable dendrochemical markers. The study found that ⁶⁶Zn is a marker isotope for the exact reconstruction of remediation work in 1986. Hence, Betula pendula and Alnus glutinosa can be regarded as suitable species for dendroforensic research. For two trees where the ⁶⁶Zn and ⁷⁵As levels correlated negatively with temperature, it was found that the isotopes decline coincided with remediation activities and not with negative temperature-growth relationships.