Master's programme Karlsruhe Institute of Technology, 61 pages (first reviewer)

Due to their numerous ecosystem functions, seagrass beds play a key role in climate and coastal protection and provide a habitat worthy of protection for numerous marine organisms. Nevertheless, there is a worldwide decline in seagrass beds. In the Wadden Sea of Lower Saxony, the populations of the seagrass species Zostera noltii have also declined drastically. The factors responsible for the decline in seagrass stocks in the Wadden Sea of Lower Saxony are not yet known.

The following study therefore investigates the extent to which heavy metal pollution is a factor in the decline of Zostera noltii in the Wadden Sea. For this purpose, surface sediment analyses were carried out in different cover areas of two eulittoral Zostera noltii stands and the heavy metal concentration, the grain size distribution and the proportion of organic matter before and during the vegetation period of Zostera noltii were investigated. In addition, the heavy metal concentration in the biomass of Zostera noltii was determined. The heavy metal concentration was found to be influenced by the grain size composition, the organic content and the iron concentration in the sediment. Heavy metals adsorb predominantly on clay minerals, organic material and iron oxides/hydroxides. There was a landing effect in the grain size composition due to the sedimentation of finer material with decreasing distance from the coastline, which was reflected in the heavy metal concentration. The cover seemed to have little influence on the heavy metal concentration in the sediment, but in the heavily vegetated area of a seagrass bed, higher concentrations of heavy metals adsorbed on clay minerals were found, suggesting increased clay mineral accumulation due to the vegetation. A strong accumulation of arsenic and copper was found in the sediment. A comparison of the study areas indicates a relatively similar accumulation of heavy metals in the sediments of the two study areas. The sediment concentrations of all heavy metals except for arsenic were below the OSPAR limit values. The accumulation of heavy metals in seagrass plants does not appear to be primarily species-specific, but rather element- and organ-specific. Mercury, arsenic and chromium were mainly accumulated in the root biomass and cobalt in the leaves of Zostera noltii . Zostera noltii appeared to take up approximately the same concentration of the respective heavy metal from the sediment in the two study areas.

Bachelor's degree programme in Environmental Sciences, 43 pages (first and second reviewer)

The findings obtained in this thesis are basic data. They are building blocks in a mosaic of investigations that still need to be carried out and answer some questions, the answers to which can only be a starting point for more in-depth questions.

This work shows that the composition of the winter vegetation communities in the salt marsh on the back mudflats of Spiekeroog is clearly influenced by local differences in altitude, the microrelief. This finding should sensitise us to the fact that modelling in which the salt marsh is, to exaggerate, an inclined plane whose height gradient rises constantly from the edge of the mudflats to the land is not accurate. For accurate modelling, it will be necessary to take into account the fact that salt marsh plants also occur in "atypical" areas. Also, the topography itself as a factor in wave attenuation will otherwise be misjudged.

This work also shows that there is no direct correlation between the grain size composition of the soil and the winter vegetation in the salt marsh. The grain size distribution was found to be very homogeneous, even across most zones. In contrast to the significance of the micro-relief, these results indicate that no special consideration needs to be given to the grain size composition for the physical properties of salt marshes in coastal protection and their modelling.

The question of the form and shape of the coastal defence of the future is one that we cannot avoid if the coasts are to remain habitable. Salt marshes can play a role in the coastal defence of the future. Their importance in dampening waves during floods and storm surges is well known and significant. However, the extent of their benefits is less well understood. The question of how important salt marshes are for coastal protection in the future must be asked today, as we must set the course today for dealing with the coming sea level rise. Projects such as the "Gute Küste Niedersachsen" project will be crucial to the discussion of the future, as they provide information and give us options on how we can shape coastal protection.

Bachelor's programme in Environmental Sciences, 37 pages (first reviewer)

Alien species are one of the biggest triggers of biodiversity loss. Most research on neo-phytes, especially invasive neophytes, addresses impact on arthropods and native plants. However, the impact of neophytes on bird populations is less well known. This thesis examines whether the neophytes Campylopus introflexus (Hedw.) and Senecio inaequidens (DC.) influence the behaviour and abundance of the Northern wheatear, oe-nantheoenanthe.

The field study took place on the East Frisian Island Norderney from^15thofJune 2021 until^6th of July 2021. Data was collected through behavioral studies on the Northern wheatear in 20 plots. A subdivision was made into plots with the occurrence of each neophyte species, the occurrence of one of both neophyte species, and comparison plots. Within these areas, both neophytes were recorded. Statistical analyses were conducted with the Software R and indicated that the behaviour of the Northern wheatear varied significantly in plots with neophyte occurrence. In the C. introflexus plots Northern wheatears exhibited lower foraging activity and an increased rest/vigilance within plots. In the S. inaequidens plots, three behavioural types showed a significant difference. The birds had a decreased rest/vigilance, increased locomotion, and a decrease in calls. In plots with occurrences of both neophytes, there was a significant increase in calls. Furthermore, the results showed that the abundance in the comparison plots was higher than in plots with a neophyte cover of 10-60 %. The shift of behaviour and abundance suggests that the neophytes affect the Northern wheatear's foraging and communication as well as their food supply and protection from predators through their proven alteration of structure, composition, and species diversity in Vegetation, as well as arthropod species diversity.

Bachelor's degree programme in Environmental Sciences, 74 pages (first and second reviewer)

Biodiversity on the East Frisian Islands is threatened by the immigration of invasive neophytes. The potato rose (Rosa rugosa) dominates the appearance of the island of Wangerooge. However, cactus moss (Campylopus introflexus) and narrow-leaved ragwort (Senecio inaequidens) are also widespread on the island and pose a threat to the natural vegetation. As phytosociological studies of these species were last carried out by Hahn almost 20 years ago, there is a lack of current data in this respect. The aim of this study is to investigate the association and habitat conditions of the three neophytes mentioned and to compare them with neophyte-free sites and the vegetation records of Hahn (2006) or, with regard to S. inaequidens , with Schmidt (2019). The aim is to determine how the neophyte populations have developed.

Vegetation surveys were carried out, soil parameters analysed and the microclimate determined. To improve comparability between the surveys, the TMAP types were also determined in addition to the communities.

Campylopus introflexus was mainly found in the TMAP types X.5.1 Corynephorus canescens type and the provisionally added X.5.6 Campylopus introflexus type. Rosa rugosa was only found in X.7.4 Rosa rugosa type. Senecio inaequidens was recorded in X.4.1 Ammophila arenaria type, X.5.1 Corynephorus canescens type and X.5.0 Dune grassland, unspecific.

Rosa rugosa not only has a different association and species composition, but also a completely different habitat compared to the absence sites. The soil in these areas can be determined as brown dune soil, while the absence areas are grey dune sites. The comparison with Hahn's results shows a negative development of the populations, especially as these were significantly poorer in species in 2021.

The Campylopusintroflexus populations show different results in the X.5.6 and X.5.1 sites. The community of X.5.6 is characterised by dominant stands of moss and shows advanced soil development. The X.5.1 does not differ from the sump areas. Compared to Hahn, there is no change in the plant sociology.

The results of the investigation of the Senecio inaequidens stands are not as clear as those of the other two neophytes. For example, the association has remained largely unclear. The ecological conditions do not differ from those of the sown areas. Overall, no influence of this species could be determined. In comparison with Schmidt (2019), a similar association was found.

Master's programme Landscape Ecology, 56 pages (first reviewer)

The macro brown alga Fucus vesiculosus is an essential habitat former in the North Atlantic and is increasingly under pressure due to climate change. Plasticity in traits can enable species to respond to and continue thriving in a changing environment. Therefore, studying functional traits x fitness interactions in species contributes to understand how species are affected by climate change.

In this study, I aimed to assess trait x fitness interactions in F. vesiculosus in response to exposure, by measuring growth as a fitness-proxy, and the functional traits buoyancy, specific thallus area (STA), surface area to perimeter ratio (SAP), length, and thallus dry matter content (TDMC). I hypothesised that investment in functional traits that increase photosynthesis and competition is higher on sheltered shores, whereas investment in functional traits that increase structural integrity as higher on exposed shores. Furthermore, I hypothesised that fitness is higher on sheltered shores, and that the respective functional traits increase individual's fitness in the environment in which they are prevalent in F. vesiculosus. Finally, I hypothesised that increased buoyancy directly increases fitness in F. vesiculosus on sheltered shores, whereas having no or a negative effect on fitness on exposed shores. I carried out an observational study to explore the trait allocation in F. vesiculosus individuals in response to wave exposure, and how this affected the fitness-proxy growth. Further, I conducted a transplant experiment to test the direct effect of buoyancy on the fitness-proxy growth in F. vesiculosus.

My studies showed that on sheltered shores buoyancy and STA were prevalent and mainly affected fitness in F. vesiculosus. However, F. vesiculosus' investment in TDMC was primarily affected by desiccation time and decreased the fitness-proxy growth independent of wave exposure. Finally, F. vesiculosus' investment in length, and SAP was driven by neighbouring algae and the relation to fitness was not clear.

Bachelor's degree programme in Environmental Sciences, 22 pages (first reviewer)

Worldwide, species are introduced into various new habitats in which they then become established. These species include the Pacific crabs Hemigrapsus takanoi and Hemigrapsus sanguineus . They arrived on the European coast in the 1990s and have spread from there to the Wadden Sea in the North Sea. They now share this habitat with the native crab Carcinus maenas . The populations of the introduced species on the island of Sylt have a high population density. The question therefore arises as to how these large numbers can be fed. Carrion is therefore one of the possible food resources.

On the one hand, experiments were carried out in which the amount of carrion consumed was analysed. The species C. maenas ate the most carrion (females with 4.10g ± 1.19g and males with 3.82g ± 1.27g for the mussel) followed by the species H. takanoi (females with 2.35g ± 0.92g and males with 3.61g ± 1.02g for the mussel). It was also shown that there is a slight preference for mussels over oysters. Furthermore, experiments were carried out on the perception of carrion from different distances. It was found that C. maenas was usually the quickest to find and eat the carrion. The two introduced species were significantly slower than C. maenas in eating the carrion at greater distances. This suggests that the native species is likely to be more dominant in the competition for carrion as it is faster at finding and eating the carrion. This indicates that carrion plays an important role in supplementing the diet and may play an important part in sustaining the high population densities of crabs on the reef.

Master's programme Marine Environmental Sciences, 48 pages (first reviewer)

English version see below.

The amphibian and reptile populations in the southern part of the nature reserve "Garlstedter Moor und Heidelandschaft mit Heidhofer Teichen" were analysed. Nine bodies of water were mapped during the amphibian spawning season and the surrounding area was searched for reptiles. With moor frog (Rana arvalis), grass frog (Rana temporaria). Common toad (Bufo bufo), pond frog (Pelophylax esculent'as), pond newt (Lissotriton vulgaris). Five amphibian species and three reptile species were recorded in the area, along with the grass snake (Natrix natrix), the common lizard (Zootoca vimpara) and the slow worm (Anguis fragilis) . The data was compared with the results of the 2013 survey. Since then, three spawning waters in the area have disappeared due to drying out and another body of water dried up in the spring. The populations of moor frogs and grass frogs have plummeted compared to 2013, while common toads are still abundant in the area. It is proposed to remove the fish stocking, remove shading shrubs on the banks of the water bodies and manage the water level of the adjustable former fish ponds in order to improve the spawning water situation for the amphibians.

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The populations of amphibians and reptiles in the southern part of the nature reserve "Garlstedter Moor und Heidelandschaft mit Heidhofer Teichen", Lower Saxony, were investigated. Nine water bodies were mapped during the amphibian spawning time. Reptiles were observed in the surrounding area. Five species of amphibians and three species of reptiles have been recorded in the area: Moor Frog (Rana arvalis), Common Frog (Rana temporaria), Common Toad (Bufo Bu/o), Edible Frog (Pelophylax esculentus). Smooth Newt (Lissotriton vulgaris), Grass Snake (Natrix natrix), Viviparous Lizard (Zootoca vivipara) and Slow Worm (Anguis fragüis). The data were compared with the results of the 2013 survey. Since then, three spawning waters in the area have disappeared due to desiccation and another dried up in spring 2021. The Stocks of Moor Frog and Grass frog sharply decreased since 2013. Common Toads continue to be abundant in the area. It is proposed to remove the fish population, shading shrubs along the banks of water bodies and to manage the water level of the regulatable former fish ponds to improve the spawning water situation for amphibians.