Abstract. The Curonian Lagoon is the largest coastal lagoon of the Baltic Sea. The Curonian Lagoon is a hypereutrophic water body beset with two major problems: eutrophication and algal blooms. Biological and chemical data for the study of water eutrophication and algal blooms were collected from 4 sampling points in the coastal and off-shore areas at distances of 1 km and 4–5 km from the Curonian Spit during the period from April 2007 to November 2016. The ratio of mineral nitrogen/phosphorus forms created conditions for regular Cyanobacteria hyperblooms during the summer and early autumn. Such blooms are followed by an increase in the concentration of ammonia nitrogen, pH and BOD5, their values exceeding the threshold limits for fishery water reservoirs. A distinct peak of chlorophyll a concentration was observed in the period of freshwater Cyanobacteria hyperbloom from July to September or October. During the “hyperbloom” of Cyanobacteria, their accumulation and decomposition, which was caused by a constant wind direction, also led to the local oxygen deficit and fish mortality in the coastal zone. Chlorophyll a concentration was always at the level of intensive bloom (10–100 μg/l) and over the period of 6 years (2008, 2010, 2011, 2012, 2014, 2016) it reached the hyperbloom state (above 100 μg/l). Water temperature appeared to be one of the key factors determining seasonal and long-term variability in phytoplankton abundance and, therefore, the level of eutrophication in the Curonian Lagoon.
Keywords • the Curonian Lagoon • pollution • nutrients • chlorophyll a • primary production • phytoplankton • eutrophication
Abstract. Three dumping sites located at the south-eastern part of the Baltic Sea at shallow depths near the shore of the Sambian Peninsula are considered. The first and second ones are located south and north of the Vistula Lagoon inlet, and are used now for disposing dredged material extracted from the Kaliningrad Seaway Canal. The third dumping site is located near the northern shore of the Sambian Peninsula, east of Cape Gvardeyskiy and assigned for disposing the dredged material extracted from the fairway to the Pionerskiy Port located nearby. All three dumping sites are located either in front of or not far from the eroded segments of the shore. The question behind the study is: Is it possible that disposed material is naturally transported from the damping site to the shore and accumulates there to protect it from erosion? A numerical hydrodynamic transport 3D model (MIKE) was used to model sediment transport under different wind actions. The winds with the speed stronger than 15 m/s wash out disposed material completely from the dumping site and spread it over a wide area with a negligible layer thickness. Winds of about 7–10 m/s transport material along the shore at a distance of a few kilometres; that may be useful for shore protection. Winds with a speed of about 5 m/sec or less do not lead to resuspension of sediments. The first location of the dumping site looks very ineffective for potential protection of the shore nearby. On the other hand, the second and especially the third locations are favourable for the transport of disposed material to the shore; the most favourable conditions are at onshore or alongshore currents.
Keywords • dumping • sediment transport • numerical simulation • wind waves • near shore currents
Abstract Detailed analysis of a core taken within the framework of the Marker Wadden project reveals the sedimentary history of the central part of the Netherlands following the Holocene sea level rise. Grain size and thermogravimetric analyses coupled with micropalaeontological and stable oxygen isotope data provide a solid framework for a detailed reconstruction of the landscape during this time interval. The Pleistocene landscape of fluviatile and aeolian deposits was succeeded by periods of marsh growth, brackish semi-enclosed lakes and tidal flats until a permanent connection with the North Sea was established. Palynological data suggest human activities in the immediate surroundings of the research area.
Abstract For a long time, the north-western part of the East European Craton, specifically the East Baltic region (EBR), was considered an aseismic territory. Historical earthquakes did take place in the EBR, but they occurred rarely and could not always be associated with tectonic conditions. The attitude towards seismicity of the region began to change after the Osmussaar earthquake on 25 October 1976 (M = 4.7) and especially after the Kaliningrad earthquakes on 21 September 2004 (Mw = 5.0; Mw = 5.2). In this study, the seismicity of the EBR was generalized over 13 years after the Kaliningrad region earthquakes on the basis of Scandinavian and our own data. In several cases focal mechanisms were solved for weak earthquakes. The study showed a tendency of seismic activity to decrease from northwest to southeast, a predominant concentration of earthquakes sources in the East Baltic coastal zone, and the activation of Ladoga-Bothnia, Vyborg, Olaine-Inčukalns, Võrtsjärv zones. The main problems are associated with a rare seismic network, high level of ambient seismic noise, and a large number of man-made sources.
Keywords · East Baltic region · Fennoscandian region · GEOFON · Baltic Virtual Seismic Network · earthquake focal mechanism · crystalline basement · man-made earthquake · seismotectonics
Abstract The easternmost part of the Gulf of Finland is characterized by intense coastal processes dominated by wave erosion. Reliable prediction of the coastal zone development, as well as effective strategy for coastal protection, demands a quantitative assessment of beach transformation and volume of sediment loss as a result of extreme storms. The main goal of this study based on results of terrestrial laser scanning was to establish volumes of eroded, transported, and redeposited sand during storm surge events that occurred between 2012 and 2017, and to verify a mathematical model of beach profile changes within key areas located in the Kurortny District of St. Petersburg (Gulf of Finland, Baltic Sea), where the longest set of levelling and terrestrial laser scanning was conducted. The resulting detailed 3D GIS models of coastal relief, based on high-resolution geodesic surveys, produced a highly reliable database of beachface transformation under the extreme storm impact and quantitative assessment of erosion volumes and sediment loss.
Abstract The article presents results of a pioneering research on the main geological features of the Hel Peninsula based on the analysis of seismic profiles and their comparison with geological cross-sections made on the basis of drillings. The following three parts of the tip structure have been identified: barrier basement (1), barrier core (2) and barrier upper part (3). Seismic facies distinguished therein were subsequently geologically interpreted as follows: Cretaceous marl and limestone (1.1), glacial till and diamicton (1.2), silt and clay of limnoglacial/limnic/marine origin (1.3), barrier sand of the core (2), and sand and peat of the barrier upper part (3). Geological cross-sections covering the geological structure of the tip of the Hel Peninsula underwater slope and the surrounding seabed. The slope base and the distal sand colluvium extent on the seafloor were determined. This paper is the first to present a crosswise section in this part of the Hel Peninsula.
Abstract The meteorological forcing on the occurrence of upwelling along the south-eastern Baltic Sea coast (Lithuanian-Latvian sector) is analysed in this study. The sea level pressure patterns and the locations of pressure centres inducing and inhibiting upwelling were identified. The research was performed for the years 1982–2017, for the months of May–September, when the sea waters are thermally stratified and the phenomenon is detectable. The frequency of upwelling is the highest in June (approximately 15%), July and August (11–13%) and the lowest in September (7%). The central and northern part of the Lithuanian–Latvian coast is most favourable for upwelling occurrence (frequency up to 20% in summer months). The main features of the sea level pressure patterns that induce upwelling in the research area are positive pressure anomalies spreading over Northern Europe and the Norwegian Sea, while negative anomalies encompass Southern Europe. Airflow around the anticyclonic centres gives a north-eastern component to the wind direction over the Lithuanian-Latvian shore. Two circulation types were recognized as inducing the occurrence of upwelling along the Lithuanian–Latvian coast. Both of them are characterized by the anticyclonic centres located west or northwest of the study area and intensify the northerly or north-easterly airflow over the research area. Different pressure patterns with the negative anomalies of sea level pressure spreading over the North Sea and the positive anomalies underlying Central Europe inhibit upwelling along the Lithuanian–Latvian coast. Such pressure conditions, bring about the western airflow component. More constant western winds restrain the upwelling process and bring about normal thermal stratification of coastal waters. A detailed analysis allowed the recognition of two circulation types inhibiting coastal upwelling in the study area. They reveal dipole patterns of sea level pressure anomalies, but the two inhibiting patterns differ substantially in the intensities and locations of the pressure centres and in wind conditions.
Abstract A short information on the renewed geological-geophysical mapping of the Lithuanian waters area of the Baltic Sea at a scale of 1:50 000 is presented. The survey was made by R/V MINTIS of the Klaipėda University built in 2014.