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At present, the problem of coastal erosion is increasingly coming to the fore. Rising sea level and intensification of extreme storms are often cited as the main causes of this disturbance. On the other hand, human activity is increasing in coastal areas through the construction and expansion of ports and the development of recreational infrastructure. The purpose of this article is to determine, on the basis of studies on the coast of the Baltic Sea off Lithuania, the impact on shore dynamics of natural (sea level fluctuations and extreme storms) and anthropogenic (construction of hydro-technical structures) factors. The work used sea level and extreme storm data from the Lithuanian Hydrometeorological Service. Data on shoreline position and change in sediments volume from 2002 to 2020 were also used based on direct measurements. The 20th century changes in the position of the shoreline were assessed in 1910 and 2005 maps. Analysis of the results of the studies showed that during the 20th century and the 21st century the beginning of the largest shoreline erosion took place not because of sea level rise and not even because of the effects of extreme storms, but because of human activity in the construction and renovation of Klaipėda and Šventoji ports jetties and Palanga pier.

Ocean fronts are sharp boundaries between different water masses and different types of vertical structure (stratification) that are usually accompanied by enhanced horizontal gradients of temperature, salinity, density, nutrients and other properties [1]. Fronts and the associated currents play important roles in heat and salt transport, oceanatmosphere interaction and ecosystem functioning. They are well known as contributors for elevated primary production areas, which are known as “hot spots” of marine life, from phytoplankton to apex predators. Moreover, the surface convergence can also lead to higher concentration of pollutants [2]. The main aim of this research is to analyze the distribution and alternation of hydrological fronts in the Baltic Sea. As fronts are high-gradient zones; therefore most objective computer-approaches to front identification are based on gradient computations. The approach used in this study is based on histogram analysis and Single Image Edge Detection (SIED) algorithm. Since a front is a boundary between two relatively uniform water masses, histograms of any oceanographic characteristic (e.g. SST) in the vicinity of the front should have two well-defined modes that correspond to the water masses divided by the front, while the latter corresponds to the frequency minimum between the modes (Fig. 1a). The front detection and tracking is conducted at three levels: window, image and pixel. The optimum window size found by Cayula and Cornillon [3] is 32 by 32 pixels. The front detection algorithm uses all pixel-based SST values within each window to compute a SST histogram for the given window. For each window that contains a front (a relatively narrow zone of enhanced SST gradient), the corresponding SST histogram would have a frequency minimum identified with the front [4]. To get a representative front distribution over the whole Baltic Sea area, it was made a composition of a few days. Numbers o f images composited show us the s tability and temporality of fronts. It is apparent that fronts occur much more frequently in certain areas compared to other. The large-scale distribution of fronts is aligned to the coast and follows the local bottom topography – along the Eastern Gotland basin extending north to the Western Estonian archipelago, Western Gotland basin, eastern coast of the Bothnian Sea, and in the Gulf of Finland along its northwestern coast extending southwest through Northern Baltic Proper to the coast of Sweden (Fig. 1b). Most of these fronts are distinct year-round. While others (beside Gulf of Riga, Pomeranian Bay, and Gulf of Gdansk) are frequent under the influence of a very strong stream of freshwater of rivers. Moreover, other small-scale fronts are found in the Arkona basin and Irbe Strait due to connection of two different basin with low or high salinity water.

During the reconstruction of 2001–2002, the Klaipėda port jetties were lengthened (the northern jetty by 205 m and the southern by 278 m). These works produced an impact on dynamic coastal processes in the neighbourhood of the port. The evaluation of the impact of jetties reconstruction was based on the data obtained in 1995–2010 during the monitoring of coastal dynamics in the port of Klaipėda. Study area includes 10 km coastal strip of mainland and 12 km coastal strip of Curonian Spit. The analysis of the data concerning the changes in the annual amount of coastal sediment served as a basis to evaluate the impact of Klaipėda port jetties on the trends in coastal dynamics prevailing before the reconstruction and their changes after it. It was found that in the mainland coastal stretch closest to the jetties, where in the last decade before jetties extension the seashore was relatively stable, the coastal erosion trends were dominant. Meanwhile, the closest to the jetties coastal stretch of the Curonion Spit, where erosion processes dominated in the last decade before jetties extension, stabilized right after the reconstruction and with a passage of time sediment accumulation trends have become prevailing. Article in English. Rekonstruotųjų Klaipėdos uosto molų įtaka gretimų jūros krantų dinamikai Santrauka.2001–2002 m. vykdant Klaipėdos jūrų uosto rekonstrukcijos darbus buvo prailginti molai (šiaurinis 205 m, pietinis – 278 m). Vertinant molų rekonstrukcijos įtaką jūros krantų greta uosto dinamikai remtasi nuo 1995 m. atliekamos jos stebėsenos duomenimis. Tyrimų rajonas apėmė 10 km ilgio žemyno kranto juostą ir 12 km ilgio Kuršių nerijos kranto juostą. Matavimai buvo atliekami 18 profilių žemyno krante ir 12 profilių Kuršių nerijos krante. Analizuojant kasmetinės kranto sąnašų kiekio kaitos duomenis įvertinta Klaipėdos uosto molų įtaka gretimų krantų dinamikos tendencijoms, vyravusioms iki molų rekonstrukcijos, ir jų pokyčiams po molų rekonstrukcijos. Nustatyta, kad žemyne, arčiausiai molų esančioje kranto atkarpoje, kurioje pastarąjį dešimtmetį iki uosto molų prailginimo krantas buvo santykinai stabilus, po rekonstrukcijos įsivyravo kranto ardos tendencijos. Kuršių nerijos krante, kur pastarąjį dešimtmetį iki molų prailginimo arčiausioje nuo molo kranto atkarpoje vyravo intensyviõs ardos procesai, po molų rekonstrukcijos krantas iš pradžių stabilizavosi, o vėliau čia pradėjo vyrauti sąnašų akumuliacijos tendencijos. Reikšminiai žodžiai:aplinkos stebėsena,Klaipėdos uostas,molai,kranto sąnašos,įplaukos kanalo pagilinimas