Bachelor's programme Environmental Sciences: 60 p. (First reviewer)

With the help of vegetation surveys and the measurement of various hydrological and hydrochemical parameters, it is possible to characterise the vegetation and hydrology along a transect. The aim of this work was to determine whether there is a correlation between vegetation, hydrology and altitude.

Based on the results obtained and presented, the correlation can be confirmed. The influence of hydrodynamics (tides) changes depending on the altitude above the mean high tide line. Lower-lying areas of the transects, in this case the areas of the salt marsh, are more frequently flooded by the prevailing tides of seawater than higher-lying areas of the dunes. Vegetation surveys were carried out at selected study sites along the transects and groundwater samples were taken. In addition, the elevation of the transects was measured and an elevation profile created.

The groundwater samples from study sites 1 to 7 (salt marsh) and 10 (beach) have electrical conductivities between 2,450 µS/cm and 43,600 µS/cm (March and August 2012) and are therefore typified as brackish water. At study site 8 (dune), the groundwater sample taken has electrical conductivities of 312 µS/crn (March) and 269 µS/cm (August) and is therefore categorised as freshwater. It can be assumed that there is a freshwater deposit under the dune (study site 8). Study sites 1 to 7 and 10 are flooded more frequently due to their location and altitude above MThw. The measured conductivities and ion concentrations indicate this assumption. The lower-lying study sites are similar in terms of equivalent concentrations and show a higher degree of mineralisation than the freshwater sample from study site 8. At 3.07 m above sea level, this site is the highest of all the sites used for groundwater sampling and is therefore the least frequently reached by seawater. The groundwater samples from the remaining sites show highly mineralised Na-CI water, whereas groundwater sample 8 shows only slightly mineralised Ca-Mg-HCO3-CI water. Thus, the degree of mineralisation and the electrical conductivities indicate differences in the frequency of flooding. The same applies to the existing plant communities. Salicornietum strictae occurs in the eulittoral (study site 1), which is flooded approx. 300 times per year. This is followed by the Andel grassland, in this case the Puccinellietum maritimae, the Halimionetum portulacoidis and the Plantagini-Limonietum. These occur at different altitudes above MThw, with the Plantagini-Limonietum occurring in slightly higher areas. These areas are still flooded around 200 times a year. The communities were identified at study sites 2 to 4 and 5 and are categorised as the "Lower salt marsh" biotope type. At site 4a, which is located in an area that could not be assigned to a single community, the Festuca rubra community was classified on an island-like elevation. The situation is similar at site 5 a), which is Agropyretum litoralis. Both communities belong to the "Upper salt marsh" biotope type, but occur within the "Lower salt marsh" due to the elevations. Agropyretum litoralis could also be classified in the transition to the dune area (sites 6 and 7). The typical plant community of white dunes, Elymo-Ammophiletum arenariae, occurs on the dune (sites 8 and 9). The occurrence of the different plant communities along the transects indicates a dependence on the altitude and thus on the frequency of flooding. The degree of mineralisation and the electrical conductivity are also factors that depend on the altitude. This can be explained by the higher altitude above MThw, which means that the probability of flooding is lower. The altitude above MThw also changes the corridor spacing. These changes also influence the occurrence of different plant communities.

With reference to the research question of the thesis, it can therefore be concluded that there is a clear correlation between vegetation, hydrology and altitude. Based on the vegetation surveys carried out and the analyses of the hydrological parameters, differences were found along the transects. These are due to the altitude above sea level and accordingly above MThw. The selected study sites were also able to demonstrate the influence of hydrodynamics as a function of altitude for the eastern plateau of Spiekeroog. The study sites are flooded by seawater at different frequencies depending on the altitude above MThw. This made it possible to determine the differentiated plant communities and the differences in hydrology and hydrochemistry, particularly in the mineralisation levels of the groundwater samples and the electrical conductivity.

Bachelor's programme in Environmental Sciences: 52 pp. (First reviewer)

From the results of sedimentological, diatomological and geoelectrical investigations, the palaeolandscape in the phases of marine influence can be reconstructed relatively comprehensively. With additional data from 14C dating and palynological analyses, a fairly good overall picture of the changes during the Holocene can be created. The following insights were gained.

• The Holocene landscape in the Black Brack was characterised by fluctuations in sea level.
  
  
• The first transgression phase was gradual. This can be seen in the transitions from peat to brackish-lagoon sediments.
  
  
• An increasing marine influence in the course of the transgression can be demonstrated by the diatom deposits.
  
  
• The second transgression begins with a high-energy natural event that erodes part of the peat.
  
  
• Along a west-east transect, the varying influence of the sea is recognisable, spreading from east to west.
• Local differences occur due to the different morphology of the palaeolandscape.
  
  
• The results of the sediment and diatom analyses confirm each other.

Bachelor programme Environmental Geosciences at the University of Trier: 48 p. (first reviewer)

Earlier investigations by WARTENBERG and FREUND (2012) revealed that there are probably two separate depositional areas in the Jade Bay, a western and an eastern one. Relatively little is known about the Holocene development of the eastern Jade Bay, as it is more difficult to access than the western one. In order to find out more about the eastern Jade Bay, a 15 metre deep borehole was drilled inland of the dyke near Stollhamm.

This drill core was analysed sedimentologically and plynologically and then interpreted with regard to its genesis. The Holocene base was not reached by the borehole, so that it is assumed that the Pleistocene sediments in the east of the Jade Bay are deeper than in the west. This was already described by STREIF 1990.

The drilled sediments are mainly brackish deposits, but peat layers are also present. Based on 14C dating and palynological analysis, the peat was dated to the Atlantic and Subboreal. At this time, the vegetation in western Germany consisted of a mixed oak forest in various forms (FIBAS 1949).

The local vegetation in the peat bogs is a growing salt marsh. The pollen composition corresponds to the characteristic salt marsh vegetation described by FREUND (2003). It is also clearly recognisable that the peat could not grow undisturbed; it was repeatedly disturbed by marine conditions, so that usually only initial peat formation was possible. Between the periods in which the peat grew, brackish-lagoonal conditions prevailed for a long time, and these make up the majority of the core sediments. The Holocene palaeoenvironment in the eastern Jade Bay and its surroundings is characterised by changing marine influences.

Master's programme Landscape Ecology: 71 p. (first reviewer)

The aim of this study was to get a better knowledge of the metal pollution and the mining history of the Falun area. It adds new information on the geochemistry of the lakes and the beginning of mining in the Falun region, together with the influence of early land use. The main focus is on three lakes Hagtjärnen, Stugutjärnen and Nästjärnen, which were previously dated and analysed regarding acidification by Ek et al. Additional supporting information is provided from records from 10 other lakes, which are located at distances between 0- 27 km from the Falun Copper mine. Another specific focus is on the lake Tisken, which has been assumed over the past 50 years to represent faithful historical record of mining in the Falun area. In this study this lake record was dated and analysed, too. The analyses resulted in four significant phases of environmental change, indicating the start of agriculture and mining, the development of each sector, as well as the sharp increase in pollution in the modern time period. Phase I covers the time period A.D. 700 - 1000 and represents the time of the early beginning of land use and small scale mining activities. Phase II represents the time between A.D. 1200 to 1450, which is dominated by an ongoing development of mining and a sharp increase in metal concentrations and occurrence of cultivated plants and plants favoured by disturbance from A.D. 1450 onwards. The third phase, representing the year A.D. 1540, clearly displays another period of sharp increases among the metal concentrations, which coincides with a peak in Cu production volumes. Phase IV covers the time period A.D. 1750 - 1900, referred to as Modern time, and features a clear increase in Pb pollution, which is linked to the introduction of tetrahyl Pb in the 1970s. Other metals increase also, together with cultivated plants like cereals, indicating an ongoing expansion of mining and agriculture. The results also indicate that Cu was not emitted as far as other elements, like for example Pb, which let to great pollution only in the lakes close to the Falun mine. Another important finding is that the lake Tisken does not represent a continual historical record, because the sediment is not a chronological sequence and instead likely represents mostly a catastrophic input of debris of mixed age. The C-14 dating shows that the sediment is mixed and disturbed in Tisken. As a consequence, the long-standing interpretation of Tisken's sediment record as an archive for the historical start and late development of mining at the Falun copper mine is incorrect.

Diploma Programme Landscape Ecology: 103 p. (first reviewer)

In recent decades, neobiota have been cited worldwide as the second most important cause of species extinction; globally, the number of species is decreasing as neobiota spread and rare species are pushed back (KLINGENSTEIN et al. 2003). In Europe and also in the Wadden Sea, the situation is seen as less catastrophic, as positive factors are now also being recognised and the issue is beginning to be viewed from several angles (cf. e.g. KOWARIK 2010).

The subject of this study was the description of neobiota and the investigation of how they are dealt with in the trilateral Wadden Sea. To this end, Crassostrea gigas, which has been declared as invasive and is spreading rapidly, and Ensis americanus, which occurs rather inconspicuously, were analysed. Experts from the Netherlands, Germany and Denmark were also consulted on the subject. Looking at the investigations in the context of this work, the next step could be to expand the expert survey and include people from the trilateral Wadden Sea co-operation, for example, as well as interviewing more experts from ministries in order to examine not only the scientific side, but also to shed light on the issue at a political level. It would be beneficial if all surveys were conducted as interviews, as the flow of information is much greater in a personal interview, but the logistical realisation of the interviews and the processing of the data are very time-consuming.

The results of the study show that an invasive species such as Crassostrea gigas also has a number of positive effects. Although the alien species competes with the native Mytilus edulis, it is described as a habitat engineer that also creates valuable habitat for species native to the Wadden Sea. It is clear that combating an established, widespread alien species is not a possible option for nature conservation planning, and not just for economic reasons. Other measures must be taken to deal with neobiota, as an increase in exotic species in the Wadden Sea is also to be expected in the near future, especially in the wake of global warming (cf. Quality Status Report 2009, DANKERS 2011 Exb.) The main focus should be on prevention in order to prevent the introduction and introduction of neobiota into the Wadden Sea, especially through the two main vectors in the marine sector, aquaculture and shipping traffic. It would make sense for all three countries to ratify the Ballast Water Convention quickly, as the implementation of the directives will take several years. However, in order to work preventively, it would be necessary to implement rapid detection programmes for alien species not only in the Wadden Sea, but also at an international level. Sporadically occurring neobiota should be recorded quickly in order to have the opportunity to prevent their spread and establishment in the Wadden Sea and other areas (see BUSCHBAUM 2011 Exb.).

A rapid development and transnational implementation of prevention programmes is desirable to ensure that the addition of alien species to the native diversity can be accepted, but that the Wadden Sea is not flooded by a large number of alien species.