German Baltic Sea Coast Research Articles

Impact of a coastal protection measure on sandy-beach meiofauna at Ahrenshoop (Baltic Sea, Germany): results from metabarcoding and morphological approaches are similar

Sand nourishment is a common and often applied coastal protection measure along the beaches of the German Baltic Sea coast. At the tourist beach of Ahrenshoop, large-scale sand nourishments are completed every five years along a 4-km stretch. The nourishment in question was executed between the end of October 2021 and mid-February 2022. Meiofaunal communities at the beach-water interface were monitored at six stations before (September 2021) and for one year after the impact (March and September 2022, March 2023). To assess the effects of sand nourishment on meiofauna communities, two complementary approaches were employed: whole community metabarcoding and morphological determination and counting of the animals. Both methods produced consistent results regarding community response to disturbance and subsequent recovery. During the period from autumn 2021 to spring 2023, drastic changes in the composition of communities were observed. Directly after the impact, the taxa Acari and Annelida nearly disappeared, abundances of Copepoda decreased substantially, and Platyhelminthes increased notably. The fact that the studied beach held a low diversity may have facilitated that metabarcoding and morphological determination followed the same trend. After initial studies comprising both methods, efficient assessments using only metabarcoding may be considered for comparable sites and situations.

Ecological Impacts of Coastal Protection on the Vegetation of Sandy Coasts at the German Baltic Sea Coast

Sand nourishments and groynes as coastal protection measures (CPM) address similar challenges on sandy coasts but take different approaches: while groynes are intended to reduce alongshore sediment transport and erosion, nourishments add new sediment to the system to compensate for erosion. The aim of this study is to compare the ecological effects of such measures on the vegetation. To this end, nutrient analysis and botanical mappings were carried out on a site with installed groynes, a site where sand nourishments are regularly carried out, and a control site without any CPM. In addition to an increase in nutrient availability after the sand nourishment, significant changes in plant species diversity and composition were also measured. The number of higher plants, mosses, and lichen species was lower at the nourishment site. The opposite impacts were observed at the groyne site: an increase in sediment cover by higher plants and mosses and a distinct increase in lichen species. The results suggest that groynes lead to a stabilization of the coastal system and enable dense vegetation growth. In contrast, sand nourishments lead to nutrient input and unstable habitat conditions, attracting certain plant communities but preventing the establishment of ground-covering vegetation.

A Comprehensive Probabilistic Flood Assessment Accounting for Hydrograph Variability of ESL Events

AbstractFlood characteristics caused by extreme sea level (ESL) events depend largely on the magnitude of peak water levels (WLs) and their temporal evolution. However, coastal flood risk is generally assessed based on only a limited number of potential peak WLs and a selection of past events or a design hydrograph. We address this gap and systematically estimate (a) spatial annual and (b) event‐based flood probabilities by comprehensively accounting for both a wide range of peak ESLs and their temporal evolution, herein referred to as hydrograph intensity. We simulate flooding at the German Baltic Sea coast with the hydrodynamic model Delft3D. We produce probabilistic flood maps, which detail flood exposed areas together with annual probability of flooding. Additionally, we show how the flood extent changes, when accounting for upper, median, and lower quantiles of hydrograph intensities. Our results demonstrate that the relevance of the intensity is site and ESL dependent. While flood extents of some ESLs of the upper and lower intensity bounds indicate no differences, others differ by up to 45%. Further, we consider two ESLs (2.24 and 2.55 m) and simulate 100 intensities for each. Compared to intensity quantiles, this results in flood extents of up to 60% difference. Hence, we find that quantiles of intensity do not cover the full range when addressing uncertainty due to hydrograph variability. We, therefore, recommend accounting for a wide range of hydrograph intensities in addition to using a wide range of ESL in future flood risk assessments.

Raising dikes and managed realignment may be insufficient for maintaining current flood risk along the German Baltic Sea coast

Without upgrading existing adaptation, Germany is projected to be among those European countries that will suffer severe flood damages in 2100. Here we use a validated modeling framework to explore the effectiveness of two hypothetical upgrades to existing dike lines in reducing flood extent and population exposure along the German Baltic Sea coast. We perform a number of model runs where we increase the heights of existing dikes by 1.5 m, implement managed realignment as a nature-based solution, where physically plausible, and run a 200-year surge under two sea-level rise scenarios (1 and 1.5 m). We show that managed realignment is more effective in reducing future population exposure to coastal flooding compared to increasing dike heights. However, the maximum reduction in population exposure compared to a do-nothing approach amounts to only 26%, suggesting that even managed realignment is insufficient to maintain flood risk at today´s levels. The greatest potential for protecting people and property from future flooding lies in developing adaptation strategies for currently unprotected coastal sections.

Regional assessment of extreme sea levels and associated coastal flooding along the German Baltic Sea coast

Abstract. Among the Baltic Sea littoral states, Germany is anticipated to endure considerable damage as a result of increased coastal flooding due to sea-level rise (SLR). Consequently, there is a growing demand for flood risk assessments, particularly at regional scales, which will improve the understanding of the impacts of SLR and assist adaptation planning. Existing studies on coastal flooding along the German Baltic Sea coast either use state-of-the-art hydrodynamic models but cover only a small fraction of the study region or assess potential flood extents for the entire region but rely on global topographic data sources and apply the simplified bathtub approach. In addition, the validation of produced flood extents is often not provided. Here we apply a fully validated hydrodynamic modelling framework covering the German Baltic Sea coast that includes the height of natural and anthropogenic coastal protection structures in the study region. Using this modelling framework, we extrapolate spatially explicit 200-year return water levels, which align with the design standard of state embankments in the region, and simulate associated coastal flooding. Specifically, we explore (1) how flood extents may change until 2100 if dike heights are not upgraded, by applying two high-end SLR scenarios (1 and 1.5 m); (2) hotspots of coastal flooding; and (3) the use of SAR imagery for validating the simulated flood extents. Our results confirm that the German Baltic coast is exposed to coastal flooding, with flood extent varying between 217 and 1016 km2 for the 200-year event and a 200-year event with 1.5 m SLR, respectively. Most of the flooding occurs in the federal state of Mecklenburg-Western Pomerania, while extreme water levels are generally higher in Schleswig-Holstein. Our results emphasise the importance of current plans to update coastal protection schemes along the German Baltic Sea coast over the 21st century in order to prevent large-scale damage in the future.

Comparison of high turbidity events: Sand nourishments and storm events on sandy beaches at the Baltic Sea, Germany

Coastal zones are permanently under stress by storms, cliff breaks, waves and currents. These events can cause the retreat of the coastline and are currently compensated by beach nourishments. The commonality of these sediment eroding and accumulating processes are turbidity plumes created in coastal waters, increasing the resuspension of particles and possibly nutrient concentrations. To compare sand nourishments and storm events, total suspended solids (TSS) and nutrient measurements were performed during winter season at the German Baltic Sea Coast. A pre-experiment showed that the TSS was homogenous through the water column. There were significant differences between both events, with sand nourishments exceeding the TSS of storms with the factor two. Due to the nourishment mechanism, the relative organic content was lower than during storm events. The nutrient uptake was unsteady. Therefore, sand nourishment can be considered to have more influence on the ecology of sand shores than storm events.

Rare earth elements (bio)leaching from zircon and eudialyte concentrates

Sands containing placers enriched with heavy minerals such as zircon, garnet, ilmenite, rutile, magnetite and monazite are recovered as construction material from the German Baltic Sea coast. The heavy minerals could be concentrated by gravity and magnetic separation. Rare earth elements (REE) were enriched in zircon concentrates as well as in concentrates of the zirconium-containing mineral eudialyte from a deposit in Greenland. In order to test bioleaching for REE extraction from these concentrates, experiments with cultures of mesophilic as well as moderately thermophilic, acidophilic, lithoautotrophic bacteria and gluconic acid-producing organoheterotrophic bacteria were run in shake flasks or pH-controlled 2 L bioreactors at 30 °C or 42 °C. Elemental sulfur and glucose served as substrate for the autotrophs and heterotrophs, respectively. Chemical leaching experiments as controls for bioleaching by the autotrophs were run without bacteria and adjusted over time to the same pH by sulfuric acid addition as previously measured in the inoculated bioreactors, in order to estimate bioleaching versus chemical leaching at the same pH. Chemical leaching experiments as controls for bioleaching by the heterotrophs were run with added gluconic acid as well as other organic acids. The results showed no significant differences in REE extraction between chemical and biological runs under same conditions (pH, temperature or gluconic acid concentration), indicating that bioleaching was in fact acid leaching based on the enzymatic oxidation of elemental sulfur to sulfuric acid in case of the autotrophs and gluconic acid production from glucose in case of the heterotrophs. The amount of extracted REEs increased with decreasing pH. Mesophiles versus moderate thermophiles did not show remarkable differences. The extraction efficiency for the single REEs was maximum 35% for zircon concentrates but up to about 70% for the eudialyte concentrate. This study allows for a comparison of chemical leaching vs. bioleaching and shows the limitation of bioleaching for processing heavy minerals for REE extraction.

Application of High-Resolution Near-Infrared Imaging Spectroscopy to Detect Microplastic Particles in Different Environmental Compartments

Microplastic particles (MPP) occur in various environmental compartments all over the world. They have been frequently investigated in oceans, freshwaters, and sediments, but studying their distribution in space and time is somewhat limited by the time-consuming nature of the available accurate detection strategies. Here, we present an enhanced application of lab-based near-infrared imaging (NIR) spectroscopy to identify the total number of MPP, classify polymer types, and determine particle sizes while maintaining short measuring times. By adding a microscopic lens to the hyperspectral camera and a cross slide table to the setup, the overall detectable particle size has been decreased to 100 µm in diameter. To verify and highlight the capabilities of this enhanced, semi-automated detection strategy, it was applied to key areas of microplastic research, such as a lowland river, the adjacent groundwater wells, and marine beach sediments. Results showed mean microplastic concentrations of 0.65 MPP/L in the Havel River close to Berlin and 0.004 MPP/L in the adjacent groundwater. The majority of MPP detected in the river were PP and PE. In 8 out of 15 groundwater samples, no MPP was found. Considering only the samples with quantifiable MPP, then on average 0.01 MPP/L was present in the groundwater (98.5% removal during bank filtration). The most abundant polymers in groundwater were PE, followed by PVC, PET, and PS. Mean MPP concentrations at two beaches on the German Baltic Sea coast were 5.5~MPP/kg at the natural reserve Heiligensee and Hüttelmoor and 47.5 MPP/kg at the highly frequented Warnemünde beach.

Coastal Adaptation to Climate Change and Sea Level Rise: Ecosystem Service Assessments in Spatial and Sectoral Planning

In this paper, we critically reflect on the ability of spatial and sectoral planning approaches to deal with regional climate change, especially sea level rise, and analyze the potential of ecosystem service assessments in regional coastal climate change adaptation planning. We present two concrete but contrasting case studies that focus on coastal realignment and wetland restoration as well as seaside tourism and resort development on the German Baltic Sea coast. The ecosystem service assessments compare past, present and potential future local development scenarios. Complementary, we apply the InVest and the Matrix ecosystem service assessment approaches. Despite some shortcomings, the proactive German hierarchical planning system seems suitable to deal with climate change and provide a framework for adaptation measures in coastal zones. It largely prevents a shift of climate change risks between municipalities and stakeholders. Comparative ecosystem service assessments seem well suited to play a role in the planning process by raising awareness about problems, possible solutions and consequences. On a local level, they can provide comprehensive insight into consequences of alternative measures. Our examples show that, in principle, potential future situations can be addressed with comparative ecosystem service approaches. We discuss whether the results of hypothetical future scenarios, with inherent uncertainties, might be misleading and counterproductive.

Fatal aspergillosis and evidence of unrelated hearing loss in a harbor porpoise (Phocoena phocoena) from the German Baltic Sea

Detailed post-mortem investigations including the auditory pathway are needed to advance our understanding of how underwater noise and other stressors affect hearing in cetaceans. A 12-year-old female porpoise (Phocoena phocoena) stranded alive in June 2021 at the German Baltic Sea coast and died some hours later. The most significant pathological findings were lesions caused by a severe aspergillosis that spread from the lung and pulmonary lymph node to the cerebellum. Based on molecular sequencing, the fungus was identified as Aspergillus fumigatus. Severe pyogranulomatous and necrotizing inflammation was diagnosed in the lung and the associated lymph node. In the left part of the cerebellum, focal, severe purulent and necrotizing meningoencephalitis with intralesional fungal structures was confirmed histologically. In addition, multifocal, severe, chronic, granulomatous, and eosinophilic gastritis with intralesional parasite structures was found in the stomach. Parallel stripes (linear skin markings) were detected along the caudal part of both body sides, which have not been previously described for harbor porpoises. Inner ear analysis revealed evidence of focal loss of outer hair cells in several regions from 120 to 580 µm from the apex of the right cochlea using immunofluorescence. The evidence of low-frequency hearing impairment was compatible with noise-induced hearing loss. This is the first case of concurrent presumptive noise-induced hearing loss and unrelated aspergillosis in a free-ranging harbor porpoise.

Glass eels and viruses - a lesson learnt from stocking the eastern German Baltic Sea coast.

Concerns about Anguillid herpesvirus 1 (AngHV-1) in European eels, especially due to stocking measures, is increasingly coming into focus and raises questions regarding disease monitoring and prevention. In the past, stocking of AngHV-1-positive eels into waters assumed AngHV-1-free has led to a rapid increase of infected eels in the wild. For this study, a glass eel stocking experiment was conducted in the eastern German Baltic coast from 2014 - 2016. Retrospective analysis of stocked glass eels shows, that virus prevalence varied from 5.3 - 37.4 % during stocking years and appeared to be influenced by a prolonged holding period in the catching region. On average, 16 % glass eels were AngHV-1 positive. Given that stocked eels were alizarin red s marked, it was possible to monitor the local eel stock between 2018 and 2019 for AngHV-1 infection and additionally two commonly coinfections, namely European Virus Eel (EVE) and Europe eel virus X (EVEX), of marked and not marked eels. In recaptured eels, mortality was significantly higher in the glass eel cohort which was found to be heavily AngHV-1 infected (stocked in 2014) compared to the less infected cohorts. Furthermore, virus-positive stocked eels turned out to be disadvantaged compared to non-infected conspecifics in terms of total length and fat content. However, co-infections with EVE and EVEX could not be detected in this study. In conclusion, eel conservation and maintaining an economically successful eel fishery is probably best achieved by stocking eels that have been shown to be free of AngHV-1. This article is protected by copyright. All rights reserved.

Dune Erosion at the German Baltic Coast—Investigation and Analysis of a Large-Scale Field Experiment Compared to Life Dunes

A large part of the Baltic Sea coastline in the north-eastern provinces of Germany (Mecklenburg-Vorpommern and Schleswig-Holstein) is protected by coastal protection dunes, which are constructed and maintained to preserve a quasi-natural beach environment. The latest IPCC report predicts a significant sea level rise even in the Baltic, together with an increase in storm surges within the next decades. Sand dune constructions are particularly affected by these developments, in close connection to the increasing problems of sediment mining for beach nourishment and dune maintenance. In the BMBF research project PADO (Processes and Implications of Dune Breaching at the German Baltic Sea Coast), scientists from Rostock University and RWTH Aachen University investigated together with various partners how constructed sand dunes would fail during a storm surge, focusing on the erosion and the initiation and development of a breach. Therefore, a large-scale field experiment was installed at the beach of Rostock-Warnemünde, which was instrumented and surveyed in high resolution during the storm surge in November 2018, leading to the collapse of the dune, using innovative measurement systems, including terrestrial laser scanning and photogrammetry. The measurements were used to run a numerical model (XBeach) to simulate dune breaching for three different sections of existing sand dunes at the coast of Mecklenburg-Vorpommern. Additional investigations were made to analyse the filling and emptying of the polder areas behind the coastal protection dunes and the consequences of the floods with respect to saltwater intrusion. In this paper, the field experiment and the results from measurements and simulations are compared to one of the real reference dunes, and the transfer of results to a dune breach incident near Rostock in 2019 is discussed.

Spatial and temporal dynamics of water isotopes in the riverine‐marine mixing zone along the German Baltic Sea coast

AbstractRiver estuaries are characterized by mixing processes between freshwater discharge and marine water masses. Since the first are depleted in heavier stable isotopes compared with the marine realm, estuaries often show a linear correlation between salinity and water stable isotopes (δ18O and δ2H values). In this study, we evaluated spatial and seasonal isotope dynamics along three estuarine lagoon transects, located at the northern German Baltic Sea coast. The data show strong seasonality of isotope values, even at locations located furthest from the river mouths. They further reveal a positive and linear salinity‐isotope correlation in spring, but ‐in two of the three studied transects‐ hyperbolic and partially reverse correlations in summers. We conclude that additional hydrological processes partially overprint the two‐phase mixing correlation during summers: aside from the isotope seasonality of the riverine inflows, the shallow inner lagoons in the studied estuaries are influenced by evaporation processes. In contrast the estuarine outflow regions are under impact of significant salinity and isotope fluctuations of the Baltic Sea. Deciphering those processes is crucial for the understanding of water isotope and salinity dynamics. This is also of relevance in context of ecological studies, for example, when interpreting oxygen and hydrogen isotope data in aquatic organisms that depend on ambient estuarine waters.

Vegetation of the supralittoral and upper sublittoral zones of the Western German Baltic Sea coast: a phytosociological study

Abstract Supralittoral and shallow water seaweed communities are particularly exposed to impacts such as climate change and disturbance by humans. Therefore, their classification, the study of composition, and the monitoring of their structural changes are particularly important. A phytosociological survey of the supralittoral and upper sublittoral vegetation of the South West Baltic Sea revealed eight phytobenthos communities with two variants comprising 35 taxa of macrophytes (18 taxa of Chlorophyta, 13 taxa of Rhodophyta and four taxa of Phaeophyceae, Ochrophyta). Five of the eight communities were dominated by Ulvales (Ulva intestinalis, Kornmannia leptoderma, and three Blidingia species), the other three by Fucus vesiculosus. Most Fucus vesiculosus-dominated communities contained U. intestinalis and U. linza as subdominants. Only one of the communities had until now been described as an association ( Ulvetum intestinalis Feldman 1937). The syntaxonomic composition of the investigated vegetation includes both phytocenoses with the domination of green algae ( Ulvetum intestinalis Feldman 1937 and communities of Blidingia marginata, unidentified Blidingia spp. and Kornmannia leptoderma), as well as a number of communities dominated by Fucus vesiculosus. Mainly boreal Atlantic species and cosmopolitans make up the bulk of the species in these associations.

Alien amphipods (Arthopoda; Crustacea) in the Tista Estuary, Halden, southeastern Norway

Two new amphipods for Norway Melita nitida and Corophium multisetosum (Crustacea; Amphipoda) were registered in brackish waters in the Tista Estuary in Halden, southeastern Norway. Both species were found in the samples from Tista’s outlet into the Idde Fjord, C. multisetosum in the beach zone and M. nitida at about 4 m depth. Melita nitida is a North American species first found in Europe in the Netherlands in 1998, and since then dispersed into the Baltic Sea via the Kiel Canal and now also found several places on the German Baltic Sea coast and in the Black Sea. Corophium multisetosum was collected even before the 1920s in Western Europe, and is considered native for Europe, whereas its relationship to North America is more ambiguous. From the British Isles and the Netherlands, it seems to have spread to Germany, Poland, Denmark and Sweden, and at present Norway. Until now the two species were found in small numbers at the Norwegian sites and their influence on the total benthic community is probably negligible in this initial phase. The Tista Estuary in Halden apparently appears to be a hotspot for alien brackish water species in Norway. Generally estuaries, with their combination of brackish water jointly with their unsaturated ecological niches and intensive international ship traffic, seem to possess the highest potential infection rate for aquatic systems with alien acrozoobenthic species.

Co-production of climate services: A story map for future coastal flooding for the city of Flensburg

Story maps offer the possibility to visualise scientific information and climate data in an accessible format and, as web-based tools, reach a large audience. However, the use of story maps in the context of climate services has not yet been widely explored or implemented. In this study we present a story map for communicating the potential impacts of flooding due to sea-level rise for the city of Flensburg, situated at the German Baltic Sea coast. The map is developed in the form of a web-based tool and includes background information on sea-level rise and coastal flooding as well as on coastal adaptation measures; interactive maps with information on city landmarks; and maps of future flooding scenarios based on numerical modelling. To increase the usability of the climate service we have applied a co-production approach and collaborated with the general public to identify user needs in an iterative process. Our study highlights the user needs for detailed visualisation of potential flooding due to sea-level rise as well as for further information on adaptation measures. As a climate service, our story map serves as a starting point for raising awareness among the general public and for initiating action for adaptation to reduce vulnerability to coastal flooding in Flensburg.

Future Changes in Wave Conditions at the German Baltic Sea Coast Based on a Hybrid Approach Using an Ensemble of Regional Climate Change Projections

In this study, the projected future long-term changes of the local wave conditions at the German Baltic Sea coast over the course of the 21st century are analyzed and assessed with special focus on model agreement, statistical significance and ranges/spread of the results. An ensemble of new regional climate model (RCM) simulations with the RCM REMO for three RCP forcing scenarios was used as input data. The outstanding feature of the simulations is that the data are available with a high horizontal resolution and at hourly timesteps which is a high temporal resolution and beneficial for the wind–wave modelling. A new data interface between RCM output data and wind–wave modelling has been developed. Suitable spatial aggregation methods of the RCM wind data have been tested and used to generate input for the calculation of waves at quasi deep-water conditions and at a mean water level with a hybrid approach that enables the fast compilation of future long-term time series of significant wave height, mean wave period and direction for an ensemble of RCM data. Changes of the average wind and wave conditions have been found, with a majority of the changes occurring for the RCP8.5 forcing scenario and at the end of the 21st century. At westerly wind-exposed locations mainly increasing values of the wind speed, significant wave height and mean wave period have been noted. In contrast, at easterly wind-exposed locations, decreasing values are predominant. Regarding the changes of the mean wind and wave directions, westerly directions becoming more frequent. Additional research is needed regarding the long-term changes of extreme wave events, e.g., the choice of a best-fit extreme value distribution function and the spatial aggregation method of the wind data.

Regional economic analysis of flood defence heights at the German Baltic Sea coast: A multi-method cost-benefit approach for flood prevention

Mean and extreme sea-level uncertainties, as well as uncertainty about future flood exposure, hinder the risk-based optimisation of flood protection investments. To deal with these uncertainties, cost-benefit analysis (CBA) and methods for robust decision-making can be combined. This paper sequentially applies CBA, robust optimisation methods and info-gap analysis to find efficient and robust coastal flood protection strategies for the German Baltic Sea coast. The CBA results suggest that – under flood risk assumptions – a share of the coast of Schleswig-Holstein (9.3–10.1%; 60–65 km) and Mecklenburg-Vorpommern (4.1–10.0%; 78–189 km) with relatively high flood exposure, might currently be under-protected from a social welfare perspective. Present Value estimates of regional investment costs of five regret or loss minimising strategies range from 1.7 to 4.8 billion Euro across robustness metrics at 3% discounting. The info-gap analysis suggests that some of these strategies will fail to prevent large-scale damages under high-end scenarios. We conclude that a multi-method cost-benefit approach can be used to narrow down the number of solutions that are both potentially efficient and sufficiently robust by investigating strategy performance within, across and beyond predefined scenarios.

Vibrio vulnificus, an increasing threat of sepsis in Germany?

The prevalence of Vibrio vulnificus heavily depends on the temperature and salinity of the sea water. In the course of climate change an increase in cases of fatal sepsis caused by V.vulnificus at the German Baltic Sea coast could be detected. To generate awareness for alife-threatening infection with increasing incidence in Germany. This article presents an overview of the current state of the literature followed by an exemplary description of cases with Vvulnificus sepsis caused by contact with water in the Baltic Sea, which were treated at the Medical University in Greifswald in summer 2018. In the presence of risk factors, such as liver and kidney diseases, immunosuppression and male sex, there is adanger of severe sepsis if damaged skin comes into contact with contaminated sea water. Apronounced organ dysfunction can frequently be found on admission. In these cases the diagnosis must be made promptly and timely surgical cleansing and antibiotic treatment should be initiated (e.g. acombination of tetracyclines and third generation cephalosporins). Sepsis due to V. vulnificus will probably increase over the coming years. Because there is alatency in some cases between infection and onset of sepsis, physicians beyond the coastal region must also be informed about this disease.

Long-term Changes of Waves at the German Baltic Sea Coast: Are There Trends from the Past?

Dreier, N.; Mannikus, R., and Frohle, P., 2020. Long-term changes of waves at the German Baltic Sea Coast: Are there trends from the past? In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020.JournalofCoastalResearch,SpecialIssueNo.95,pp.1416–1421.CoconutCreek(Florida),ISSN0749-0208.For the development of future coastal and flood protection strategies and methods as well as the adaptation of today's existing protection structures, possible impacts of climate change on the long-term changes of the local wave conditions in the future and the past need to be analysed and assessed. In this study, two main research questions are raised: (i) Are there any long-term changes of the waves derived from numerical model data?, (ii) How well can the COSMO model reproduce the wave climate for the past? To answer those questions, two reanalysis wind data sets (COSMO-REA6 and coastDat2) for the past based on the COSMO model are used for the calculation of long-term time series of hourly wave parameters (SWAN) at the German Baltic Sea Coast. The long-term changes of the average wave conditions in the past are analysed and assessed for the coastDat2 data set for both average values and the frequency of occurrence of significant wave height and mean wave direction over time periods of 30 years. Moreover, the statistical significance of the changes of the frequency is assessed based on statistical hypothesis tests. In agreement with previous analysis of the future long-term changes of the wave climate, a large multi-(decadal), spatial and seasonal variability of the changes exist and the changes depend on the exposition of the coast towards the prevailing westerly winds. At westerly wind exposed locations, trends towards an increase of the 30 year annual averages of significant wave height up to 5 % were found, with possible larger changes of the 30 year seasonal averages, and trends towards more waves coming from westerly directions. The long-term changes of extreme wave conditions in the past are analysed based on extreme value statistics and over time periods of 30 years. Slightly increasing respectively decreasing trends between -5 % and +9 % (-0.16 m/+0.27 m) of significant wave heights with a return period of 200 years have been found at westerly respectively easterly wind exposed locations.