This dissertation advances the use of Unmanned Aerial Vehicles (UAVs) and satellite imagery in environmental monitoring, specifically targeting eutrophication indicators and bathing water quality within aquatic and coastal ecosystems. Through a cumulative series of studies, innovative approaches integrating UAV remote sensing, deep learning techniques, and the quasi-analytical algorithm for precise water quality assessments and vegetation mapping were developed and validated. This work addresses gaps in the current capabilities for ecological observation and management, with advancements in both methodology and application. The research establishes a comprehensive framework for UAV surveys, illustrating the effectiveness of combining diverse sensor technologies and analytical methods for detailed vegetation analysis. This framework supports efforts in biodiversity conservation, ecosystem structure analysis, and monitoring phenological and stress-related changes in vegetation, guiding environmental scientists and resource managers in the adoption of UAV technology across various ecosystems. In the assessment of changes in aquatic vegetation, particularly reed beds, the study highlights the utility of the normalized difference water index derived from Sentinel-2/MSI data and Yen binary thresholding, validated through UAV imagery. This approach is found reliable in detecting mowing-induced changes in reed beds, with enhanced accuracy for areas larger than 0.1 ha. Furthermore, the quasi-analytical algorithm for estimating Secchi depth from multispectral UAV imagery was tested, identifying Hedley's sun glint correction method as the most precise. The research emphasizes the algorithm's adaptability and the impact of environmental factors, such as CDOM concentration and solar zenith angle, on the accuracy of Secchi depth measurements, underscoring the potential of UAV technology in providing scalable and efficient water quality assessments across extensive areas. Lastly, the study explores the performance of the U-Net model in segmenting beach wrack from UAV imagery, indicating that "RGB" data combinations yield the most accurate beach wrack detections. Contrary to expectations, the addition of multispectral and elevation data did not significantly improve segmentation accuracy, suggesting the importance of selecting appropriate data combinations based on specific site characteristics to optimize model performance across varied coastal landscapes. Collectively, these studies represent a significant advancement in the application of UAV and satellite technologies for environmental monitoring, offering methodologies and insights for the comprehensive assessment of aquatic and coastal ecosystem health. This integrated approach not only enhances current monitoring practices but also establishes a new standard for precision and efficiency in environmental science research.

The cumulative doctoral dissertation based on four peer-reviewed scientific publications presents the development of a tailor-made indicator set and the computer-aided user-friendly Indicator-based Sustainability Assessment Tool (InSAT). This study explores how the appropriate use of sustainability indicators, incorporation of environmental, social and economic aspects, can help to assess whether the coastal and marine management initiatives lead to a more sustainable development, and also enables evaluate the quality of the management process. The application of core and optional indicators highlights the strengths and weaknesses of the coastal management measures in different implementation levels. Moreover, the study analyses to what extent, how and when InSAT can be applied within a step-wise System Approach Framework (SAF) to support coastal management. Further, it is explored how other integrated approaches like ICZM, MSP, and Land/Urban planning can benefit from the tool which facilitates the dialogue between stakeholders, society and decision-makers.

This study, for the first time, presents comprehensive analysis of ice cover phenology, thickness distribution, as well as impact on the aquatic environment of the largest lagoon in Europe – the Curonian Lagoon. Combination of advanced remote sensing imaging techniques, conventional in situ observations, and numerical modelling techniques enabled the exploration of new approaches in the monitoring and forecasting of the ice cover. Using satellite data in the numerical modeling framework SHYFEM revealed the importance of high resolution ice observations for describing the physical processes during the ice cover season, such as circulation, water exchange capabilities, saltwater intrusions, water residence time, and suspended sediment dynamics. The incorporation of an advanced sea ice thermodynamic model in the modelling framework SHYFEM, together with remote sensing and ground observations, serve as an important tool for the analysis and representation of ice thickness over the whole lagoon surface, testing the impact of different climate change scenarios on the ice cover, and further improve the numerical description of this freshwater lagoon.

In this study the sediment transport mechanisms in the biggest lagoon in Europe, the Curonian Lagoon, with high river discharge and sediment loadings, were evaluated using numerical modelling. An already developed hydrodynamic model and sediment transport model were applied to the domain that represents the Curonian Lagoon. A new formula for particle settling velocity was developed and introduced into the model that allowed achieving good agreement between the modelled and measured values (40-72%). The formula is based on the findings that the organic material plays a crucial role in the system especially in the presence of cyanobacteria in high water temperatures. The model was applied for different scenarios and purposes, i.e., to calculate the sediment budget, show deposition patterns, and evaluate extreme events caused by strong winds. The analysis of all these results provided the first detailed overview of the status of the Curonian Lagoon environment, showing the important role of the Nemunas River and the influence of ice cover for the sedimentation processes in the lagoon. Moreover, the impact of the sediment resuspension in the Curonian Lagoon was evaluated and climate change scenarios were applied. Climate change projections revealed that the lagoon will accumulate more sediments in the future, forming three main accumulation zones: in the Nemunas Delta front, in the southern part of the lagoon and south of Klaipėda Strait. The developed model is a valuable tool for further analysis of the south-eastern coasts of the Baltic Sea, the Curonian Lagoon and other transitional environments as well.

Chironomus plumosus lervos yra dažnai randamas makrozoobentoso organizmas įvairaus tipo vandenyse, įskaitant ir Kuršių marias. Šios lervos, kaip ir kiti vandens bei sausumos organizmai, sudaro su mikroorganizmais gyvybiškai svarbias sąveikas, vadinamas simbioze. Ši sąveika padeda apsirūpinti maistinėmis medžiagomis, atlieka apsaugines funkcijas, be to, manoma, kad gali prisidėti ir prie vykstančių biogeocheminių procesų – azoto ciklo (Stief, 2013). Azoto ciklo procesas susideda iš kelių pagrindinių etapų - azoto fiksacijos, nitritų redukcijos bei amonio oksidacijos už kuriuos yra atsakingi įvairūs funkciniai genai. Todėl, norint įvertinti chironomidų lervose esančių bakterijų potencialą vykdyti azoto ciklo virsmus, buvo atliekama realaus laiko polimerazės grandininė reakcija, kurios metu, naudojant skirtingus funkcinius DNR žymenis, kiekybiškai įvertintas bakterijų potencialas vykdyti atskirus azoto ciklo proceso etapus. Vykdant polimerazės grandininę reakciją atliktas reakcijos protokolo optimizavimas kiekvienam funkciniam genui. Optimizavus protokolą ir norint kiekybiškai įvertinti bakterijų potencialą vykdyti azoto ciklo proceso etapus, buvo naudojama DNR, kuri nurodo tiriamo geno gausumą, bei kDNR, kurios metu apskaičiuojamas tiriamo geno aktyvumas. Taip pat, norint įvertint Chironomus plumosus lervos mikrobiomą, atlikta 16S rRNR V3 regiono amplifikacija ir sekvenavimas. Šiame darbe tirti 3 mėginiai, kurių kiekvieną sudarė 4 Chironomus plumosus lervos, surinktos Kuršių mariose. Naudoti 4 funkcinių genų žymenys – nifH, kuris atsakingas už azoto fiksaciją, nirS bei nrfA, kurie atsakingi už nitritų redukciją, bei amoA, kuris naudojamas amonio oksidacijoje. Atliktos kiekybinės analizės metu ir naudojant DNR, buvo nustatyta, kad Chironomus plumosus lervoje gali vykti azoto fiksacija bei nitritų redukcija, bet amonio oksidacija – ne. Apskaičiuotas skirtingų funkcinių genų gausumas 1 grame lervos naudojant nirS geną yra 321,65 × 106 ± 24,8 × 106, nifH geną 16,88 × 106 ± 0,45 × 106, o mažiausiai nrfA geną - 0,25 × 106 ± 0,09 × 106. Atlikus realaus laiko polimerazės grandininę reakciją naudojant kDNR, pastebėta, kad genų aktyvumas buvo ženkliai mažesnis nei gausumas - vidutinis nirS geno kopijų skaičius 1 grame lervos 38,82 × 106 ± 11,66 × 106, nifH geno 0,09 × 106 ± 0,03 × 106, o mažiausiai nrfA geno 0,05 × 106 ± 0,02 × 106. Atlikus lervoje esančio mikrobiomo 16s rRNR V3 regiono sekvenavimą buvo identifikuoti pagrindiniai bakterijų tipai - Firmicutes (38,02%), Bacteroidetes (23,93%), Proteobacteria (23,08%) bei Actinobacteria (12,31%). Nors ir nedideliais kiekiais, tačiau buvo identifikuotos bakterijų šeimos, kurios gali vykdyti ne tik azoto fiksaciją bei nitritų redukciją, tačiau ir amonio oksidaciją. Apibendrinant tyrimo metu gautus rezultatus, galima teigti, kad atliekant kiekybinę funkcinių genų analizę realaus laiko polimerazės grandininės reakcijos metodu, svarbu optimizuoti reakcijos protokolą, atkreipiant dėmėsį į reakcijos specifiškumą ir efektyvumą, bei parinkti tinkamus mėginių skiedimus. Įvertinus Chironomus plumosus lervoje esantį mikrobiomą, buvo nustatyta, kad simbiontinės bakterijos turi potencialą vykdyti azoto ciklo procesus, tokius kaip azoto fiksaciją bei nitritų redukcija.

Surface sediments are interesting spots to analyze the paradigm of biodiversity and ecosystem functioning due to the multiple physic and chemical gradients that shape the interactions among microbial communities, macrofauna and primary producers. Sediments receive large inputs of organic matter and are sites of intense biogeochemical processes, mediated by microbial communities and facilitated by macrofauna, ultimately resulting in nutrients uptake by benthic primary producers or their recycling to the water column. The relationship between diversity and ecosystem functioning was analyzed at different spatial scales in the benthic compartment of two shallow eutrophic lagoons, the Curonian Lagoon (Lithuania) and the Sacca di Goro (Italy). Special attention was given to the benthic nitrogen (N) cycle, due to the critical role of this element in aquatic ecosystem functioning and to the complex regulation of its various oxic and anoxic reactions, carried out by diverse microbes and strongly influenced by macrofauna and primary producers. Investigations were carried out at different spatial scales included whole lagoon (macro-scale) as well as single macrofauna individuals and holobionts’ microbiomes (micro-scale). At the two lagoons the benthic functioning was evaluated by quantifying rates of whole system respiration and production via gas exchange, nutrient cycling and exchange at the sediment-water interface. Multivariate statistical analyses were used to reveal the interactions between the dominant macrofauna species and net solute fluxes and speculate about underlying processes. Such approach allowed to reconstruct how different macrofauna functional groups shape benthic N cycling in different macro areas of the Sacca di Goro, and determine net loss, net recycling or different level of coupling between processes (e.g., ammonification and nitrification, or nitrification and denitrification). In the Curonian Lagoon the whole scale approach was used to verify whether macrofauna act as a natural buffer against redox-dependent phosphorus recycling during short-term events of oxygen shortage. Manipulative experimental approaches addressed specific processes at the microscale, in sediments colonized by different macrofauna functional groups, and along gradients of density. Such approaches included intact or reconstructed sediment incubation, metabolic measurements of single macrofauna individuals, and the use of 15N-labeled inorganic N forms to measure specific microbial transformations (denitrification, anammox, nitrate ammonification, N-fixation) in sediments or in macrofauna microbiota. Moreover, molecular tools were used to analyze microbial diversity (16S rRNA metabarcoding) and activity (marker genes and transcripts) in holobionts. Three organisms that are abundant in the Curonian lagoon were considered: the burrowing larvae of Chironomus plumosus, the filter feeder bivalve Dreissena polymorpha and the phytophagous gammarid Pontogammarus robustoides. Results suggest that in the Sacca di Goro lagoon macrofauna play an important role, in regulating N transformations. However, its importance also depends on the prevailing environmental factors (i.e., salinity, hydrodynamics and background nutrient concentrations). Whereas in the Curonian Lagoon bioturbation did not significantly affect the nutrient metabolism and the stability of reductive-oxidative reactions during anoxia events. Molecular studies revealed that Chironomid larvae burrows are hot-spots of microbial communities involved in N cycling and that these organisms, via bioirrigation, significantly enhance both the recycling of ammonium and N removal via denitrification. Mussels primarily enhance the recycling of N to the water column, both via direct excretion and by stimulating dissimilatory nitrate reduction to ammonium. The latter is likely an effect of mussel’s biodeposits. For these two organisms the quantification of functional genes showed a significantly higher potential for microbial denitrification, nitrate ammonification and N2-fixation in macrofauna as compared to the surrounding environment. As chironomid and dreissenid densities in eutrophic lagoons are large, animals-associated microbes may account for a substantial (and so far, overlooked) N import and recycling. P. robustoides was finally demonstrated to have an important role in the survival of Chara contraria in the eutrophic Curonian Lagoon. The gammarid facilitates C. contraria via active grazing on the macroalgaeassociated epiphytes combined with ammonium excretion, thus supporting the growth of the characeans.

Vandens organizmų biologinių apaugų pasiskirstymas, palyginti su jų buveine, yra labai svarbus ekologijai ir suteikiantis pradinę įžvalgą apie vietos savybes, reguliuojančias populiacijas ir sankaupas. Šio tyrimo tikslas yra nustatyti biologinių apaugų gausumą, įvairovę ir pasiskirstymą ant dirbtinio ir natūralaus substrato penkiuose Varėnos rajono ežeruose. Tyrimo objektas gėlavandeniuose ežeruose įsikūrusios makrozoobentoso rūšys. Įgyvendinti darbo tikslą, buvo paruošti du skirtingi substrato tipai (natūralus iš medžio bei dirbtinis iš betono trinkelės) ir patalpinti ežerų dugne keturiems mėnesiams, o ištirti, kokios rūšys apauga substratus, pasirinktose vietose sutrinkti mėginiai laboratoriniam tyrimui. Tirtų ežerų vietose nustatyti 23 makrozoobentoso taksonai, kurių turtingumas ir individų gausumas skyrėsi tarp dirbtinių ir natūralių substratų tiek laiko tiek ežero atžvilgiu. Pagal sutinkamumo dažnio bendras vertes dažniausios makrozoobentoso rūšys buvo Dreissena polymorpha, Theodoxus sp., Psephenus sp., Bithynia tentaculata, Cyrnus flavidus, Caenis ungulata ir Limnephilus intricatus, o 8 rūšys randamos tik dirbtinuose ir 3 tik natūraliuose substratuose. Naudojant statistinę duomenų analizę nustatyta, kad didžiausias makrozoobentoso gausumas buvo dirbtiniame (1505 ind.m-2), o mažesnis natūraliame substrate (1008 ind.m-2). Daugiausia biologinių apaugų rasta Glūko ežero substratuose, o mažiausios vertės – Mergežerio ežero substratuose. Analizuojamų substratų tipų atveju laikas paveikė rūšių turtingumą bei gausumą ir buvo nustatytas bendras makrozoobentoso rūšių reprodukcijos laikas, kurio trukmė buvo nuo eksperimento pradžios (pirma mėginių ėmimo savaitė, birželio mėn. pradžia) iki 8 mėginių ėmimo savaitės (liepos pabaigos). Įvertinus aplinkos veiksnių įtaką makrozoobentoso rūšių paplitimui ir gausumui Varėnos rajono ežeruose nustatyta, kad ne tik substrato specifika, bet ir supantys aplinkos veiksniai, tokie kaip didelis ežero plotas, gylis ir miškingumas daro įtaką bendram makrozoobentoso taksonų skaičiui ir individų gausumui. Tyrimo rezultatai parodė, jog dirbtinių substratų struktūrų veikimas gali būti siejamas su bendru biologinių apaugų procesų poveikiu, įskaitant ir skirtingus abiotinius veiksnius.

Mussel farming, represents an environmentally friendly alternative for a high quality protein source and can at the same time be a measure to remove excess nutrients and improve the water transparency in eutrophic coastal waters. As such, it is considered a promising “blue growth” potential and a supportive internal mitigation measure within the EU Water Framework Directive (WFD). This study provides a comprehensive analysis of the different potentials of Mytilus spp. cultivation along the salinity gradient (7-17 PSU) of the German Baltic Sea coast. A combination of field experiments and model approaches revealed the economic feasibility and the mitigation potential of mussel farming regarding different biotic and abiotic environmental factors. A special focus was set on mesohaline coastal waters with low salinity levels (7-10 PSU), which place special demands on mussel farming practice. Here, two small scale pilot mussel farms were established to evaluate their effectiveness as a mitigation measure and to estimate potential environmental risks. Further stakeholder based tools were tested to support the implementation of coastal mussel cultivation within the WFD. Therefore, different stakeholder workshops were conducted to visualize the perception of sea-based mitigation measures in general and different mussel farming scenarios in detail. Our results showed that commercial blue mussel cultivation can only be economically profitable at salinities > 10 PSU and if mussels are sold for human consumption and marketed organically and locally. The mitigation and depletion potential of mussel cultivation depends on mussel growth and the amount of biomass that is cultivated in combination with the prevailing environmental factors. However, since mussel growth is closely coupled to the salinity level, mussel cultivation in low saline environments leads to lower improvement efficiencies. Our results also showed that participatory tools for expert and non-expert stakeholders are valuable tools to communicate and prevent misinformation during the discussion and implementation of new supportive internal mitigation measures.

Blyškiosios baltakojės krevetės Litopenaeus vannamei sudaro 53% visos pasaulio vėžiagyvių akvakultūros rinkos. Uždarose akvakultūros sistemose (UAS) galima gaminti šviežias, neužšaldytas, kokybiškas krevetes, neatsižvelgiant į sezoną, klimatą ir priklausomybę nuo jūros vandens šaltinio. Tačiau, uždaros jūrinės akvakultūros sistemos reikalauja didelio kiekio aprūpinimo druskomis ir mineralinėmis medžiagomis, o tai gali sudaryti reikšmingas išlaidas. Stipriai mineralizuoto geoterminio vandens (geoterminio sūrimo) panaudojimas dirbtinio jūros vandens ruošimui galėtų padėti išspręsti šią problemą, tačiau kol kas dar nėra žinomas šio resurso poveikis blyškiosioms baltakojėms krevetėms. Todėl šio tyrimo tikslas – įvertinti skiesto geoterminio sūrimo poveikį auginamų blyškiųjų baltakojų krevečių fiziologijai ir UAS technologijai.įvertinti skiesto geoterminio vandens poveikį uždaroje akvakultūros sistemoje auginamų blyškiųjų baltakojų krevečių augimui, streso žymenims, mirtingumui ir mėsos kokybei. Įgyvendinant darbo tikslą, 2023.05-2024.05 laikotarpiu, Klaipėdos mokslo ir technologijų parko Verslo inkubatoriuje esančioje UAS, buvo atliekami du eksperimentiniai krevečių auginimai nuo jauniklio stadijos iki rinkos dydžio krevetės (15-25 g) dirbtiniame jūriniame vandenyje. Vieno auginimo metu 15 psu druskingumo dirbtinio jūrinio vandens ruošimui buvo naudojamas pagrindinių katijonų ir anijonų mineralų mišinys (kontrolinė grupė – K), antro auginimo metu – 110 g l-1 mineralizacijos geoterminis sūrimas iš Klaipėdos Geotermos gręžinio (geoterminė grupė – G). Auginimas buvo vykdytas 3 standartiniuose UAS atviruose 2,8 m2 ploto baseinuose. Tyrimo metu, buvo apskaičiuoti ilgio ir svorio prieaugio, specifinio augimo greičio (SAG), išgyvenamumo, derliaus biomasės, pašaro konversijos koeficientai (FCR) ir kiti augimo ir produkcijos rodikliai. Eksperimento pabaigoje buvo atliekamas krevečių mėsos tyrimas atskirų cheminių elementų bioakumuliacijos nustatymui, taip pat vertinamas streso lygis pagal gliukozės koncentraciją hemolimfoje, kuris yra vienas iš pagrindinių vėžiagyvių streso biocheminių žymenų. Kontrolinio auginimo efektyvumas buvo panašus ir net ties kai kuriais rodikliais prastesnis lyginant su skiesto geoterminio vandens eksperimentu. Lyginant išgyvenamumo vidurkius, G grupės išgyvenamumas buvo 28,5 procento didesnis už K grupės (p < 0,05). Vidutinis pašaro konversijos koeficientas G grupėje buvo statistiškai reikšmingai mažesnis už kontrolinės grupės (p < 0,05) – 1,16 ir 1,71, atitinkamai. Krevečių svorio ir ilgio augimo tempas abiejose tiriamosiose grupėse buvo panašus, tačiau dėl deguonies prisotinimo vandenyje trūkumo G grupės eksperimentas buvo 19 dienų trumpesnis. K grupės krevetės per 95 eksperimento dienas vidutiniškai pasiekė 23,57 ± 4,96 g svorį, o G grupės krevetės per 76 dienas pasiekė 15,76 ± 2,07 g svorį. Procedūrinis mirtingumas tendencingai mažėjo abiejose grupėse augant krevečių svoriui bei ilgiui ir statistiškai reikšmingo skirtumo tarpusavyje neturėjo (p > 0,05). Vertinant krevečių hemolimfos gliukozės koncentraciją, kaip reakcijos į stresą žymenį, statistiškai reikšmingas skirtumas nebuvo nustatytas, iš ko galima spręsti, kad krevetės auginamos skiestame geoterminiame vandenyje nepatiria papildomo diskomforto. Iš pasirinktinai tirtų cheminių elementų, krevečių mėsoje statistiškai reikšmingai skyrėsi tik kalcio (Paired t-test p = 0,004) ir cinko (Paired t-test p = 0,046) koncentracija, kuomet kalcio koncentracija buvo net keturis kartus didesnė geoterminės grupės krevečių mėsoje. Sunkiųjų metalų vertės buvo žemiau aptikimo ribos arba labai mažos ir saugios žmogaus vartojimui.

Vis dažniau susiduriama su sunkiųjų metalų ir kitų elementų tarša ne tik aplinkoje, bet ir gyvuosiuose organizmuose. Kadangi paukščių plunksnos gali būti kaip bioindikatoriai taršai tirti, šiame tyrime pasirinktos trys paukščių rūšys, kurių plunksnose buvo tiriamos sukauptos sunkiųjų metalų ir kitų elementų koncentracijos, taip įvertinant ir elementų bioakumuliaciją skirtingose buveinėse ir regionuose. Tyrimui pasirinktų vandens paukščių rūšių – ledinės anties, rudakaklio naro ir didžiojo kormorano – maitinimosi ir gyvenamosios teritorijos yra skirtingose geografiniuose regionuose. Ledinių ančių ir rudakaklių narų jaunikliai maitinasi Arkties regione, o didžiųjų kormoranų jaunikliai – Baltijos regione. Šio tyrimo tikslas buvo nustatyti ir palyginti skirtinguose regionuose besimaitinusių jūros paukščių plunksnų sunkiųjų metalų koncentracijas, taip įvertinant ir regionų užterštumą. Tyrimui surinkti plunksnų mėginiai iš 81 individo. Plunksnų mėginiai buvo apdoroti azoto rūgštimi ir vandenilio peroksidu, ir išmatuoti su indukuotai sužadintos plazmos spektrometru (ICP-MS). Rezultatai parodė, jog Baltijos regiono jūroje ir Kuršių mariose besimaitinančių didžiųjų kormoranų jauniklių plunksnos statistiškai reikšmingai skirėsi pagal Ar, Se ir Mn koncentracijas. Baltijos jūros kolonijos kormoranų plunksnose nustatyta didesnė elementų įvairovė. Analizuojant Arkties regiono paukščius, rudakaklių narų plunksnose buvo nustatytos aukštesnės Pb, Zn, Ni ir Hg koncentracijos negu ledinių ančių jauniklių plunksnose; taip pat aukštesnės δ 15N vertės rudakaklių narų plunksnose reprezentavo aukštesnį mitybinį lygmenį lyginant su ledinėmis antimis. Analizuojant sukauptas elementų koncentracijas pagal amžių ir lytį, ledinių ančių plunksnos nustatytas didžiausias skirtumas tarp patinų ir jauniklių. Lyginant taršą sunkiaisiais metalais pagal regioną, nustatyta jog didžiausia elementų įvairovė ir aukštesnės koncentracijos nustatytos Arkties regione, tai galėjo lemti skirtingos šių paukščių maitinimosi buveinės.

All over the world, coastal lagoons can differ in size, geomorphology, hydrodynamics, climatic conditions, etc. while being productive ecosystems in common. Therefore, studying the behavior of these ecosystems by assessing the ecosystem services (ES) they provide is a key to coastal lagoon management and decision-making. This research represents a comparative study of two different coastal lagoons, located respectively in the Atlantic Ocean and in the Baltic Sea. The saline water body, the Oualidia lagoon, despite its small size of only 4 km², provides life and sources of income to the surrounding communities, which makes it an attractive study site for the present research. While the nearly freshwater Curonian lagoon, the largest one in Europe, covers an area of up to 1584 km² is also rich in terms of ES. This comparative research is divided into three main parts, starting with (1) investigating the hydrodynamics of the study sites. (2) An expert-based scoring method was applied to assess the scores of ES in the coastal parts of the study sites for each of the CORINE land-cover classes (CLC). Then, (3) assessing and mapping the ES flow of 13 selected ES in the aquatic areas of both study sites.

This work presents a comprehensive study on the diversity and occurrence of cyanobacteria and their secondary metabolites in the Curonian Lagoon and coastal Baltic Sea. In the study, the ecological and socioecological significance of toxic cyanobacteria blooms as well as the biotechnological potential of cyanometabolites were explored. Phytoplankton analyses of samples collected in the Curonian Lagoon showed frequent occurrence of Aphanizomenon, Dolichospermum/Anabaena, Microcystis, Planktothrix and Woronichinia genera. Of these, Dolichospermum/Anabaena, Microcystis, and Planktothrix agardhii were confirmed by genetic methods as potential MCs producers. The assessment of water quality based on cyanobacteria parameters in the recreational areas of the Lithuanian Baltic Sea coast and Curonian Lagoon indicated a low probability of adverse health effects, with a higher risk in the southernmost part of the Curonian Lagoon. As these two systems are interconnected, the dynamics and structure of cyanobacteria in the Curonian Lagoon have significant impact on diversity and concentrations of cyanotoxins in the coastal areas of the sea. During the comprehensive studies of field samples collected in the Curonian Lagoon, 119 cyanometabolites representing eight different classes of the compounds were detected. Cyanopeptolins and microcystins were found to be most structurally diverse class of cyanopeptides. The observed diversity and considerable variation in rare and potentially new microcystin variants may indicate the presence of different cyanobacteria chemotypes in the lagoon. Bioactivity screening of phytoplankton samples from the Curonian Lagoon confirmed pharmaceutical potential of aquatic microorganisms. The samples were active against antibiotic resistant clinical and environmental bacteria strains, they inhibited serine proteases and reduced the viability of the T47D human breast adenocarcinoma cells.

The alarming increase of emerging pollutants like pharmaceuticals, personal care products, nanoplastics, and microplastics in aquatic ecosystems is a rising threat to water quality and marine organisms. This study examines the occurrence, distribution, bioaccumulation, and ecotoxicological impact of pharmaceutical, personal care product, nanoplastic, and microplastic pollutants across diverse aquatic ecosystems. A range of techniques were used for analysis, including high-performance liquid chromatography-tandem mass spectrometry, thermogravimetric analysis, micro-Raman spectroscopy, asymmetrical flow field-flow fractionation, optical microscopy, and acute toxicity test. Particles of nanoplastics and microplastics were detected in Urmia Lake, one of the largest salt lakes worldwide, located in Iran. Moreover, a total of 15 human pharmaceuticals and personal care products were discovered in fish and shrimp samples from four distinct markets, and in wastewater from locations in Latvia and Lithuania. Besides, a high concentration of microplastic particles was found in mussels (Mytilus spp.) from Svalbard, Norway. Laboratory tests were conducted using Daphnia magna as a model organism to evaluate the ecotoxicological implications of triclosan, caffeine, nanoplastic, and microplastic pollutants. Acute toxicity tests demonstrated a high mortality level in Daphnia magna exposed to a mixture of triclosan, caffeine, nanoplastic, and microplastic contaminants, highlighting the intricate challenges of assessing ecotoxicological risks. Compelling evidence was provided by the findings, showing the pervasive presence, distribution, and bioaccumulation of these emerging pollutants, as well as their harmful effects on aquatic ecosystems. They underscore the urgent need for comprehensive strategies to mitigate the release of pharmaceutical, personal care product, nanoplastic, and microplastic pollutants into aquatic ecosystems and safeguard the health of water bodies and marine organisms. This study also underscores the complexities of ecotoxicological risk assessment, indicating the necessity for more investigation that can account for interactions among triclosan, caffeine, nanoplastic, and microplastic pollutants.

Šio darbo tikslas buvo nustatyti tirpstančio ledyno poveikyje esančių sublitoralės makrozoobentoso bendrijų struktūros dėsningumus vakarų Svalbardo įlankose. Darbo metu, iš vakarų Svalbardo įlankose surinktos 3h trukmės vaizdo medžiagos buvo sukurtos 148 vaizdo įrašų mozaikos iš kurių, pasitelkus Arkties floros ir faunos taksonomijos ekspertų pagalbą, buvo identifikuoti 33 biologiniai ir biofiziniai požymiai. Pagal identifikuotus biologinius ir biofizinius požymius, kurie darbe taip pat įvardijami kaip morforūšys, buvo lyginamos Isjordeno ir Hornsundo fjordų įlankos esančios ledyno tirpsmo zonoje (Borebukta, Burgerbukta) su įlankomis esančiomis laisvoje nuo ledynų zonoje (Gipsvika, Adriabukta). Gauti rezultatai parodė, jog Adriabuktos, Burgerbuktos, ir Gipsvikos įlankose dominuoja iš dalies judrūs filtratoriai, o Borebuktoje dominuoja judrūs organizmai bei maitėdos. Didžiausius skirtumus tarp įlankų nulemia 8 tyrimų rajone dominuojančios morforūšys: Ceriantharia, dvigeldžiai, Sabellidae, ofiūros, bioturbuojančios kirmelės, krevetės, samangyviai Alcyonidium sp. ir Bryozoa undet individai. Burgerbuktos (54 ± 84 ind. trans-1), Adriabuktos (49 ± 68 ind. trans -1) ir Gipsvikos (25 ± 34 ind. trans-1) įlankose dominuoja daugiašerės Sabellidae, įlankose sudarydamos > 50 % bendro santykinio individų gausumo įlankoje, o Borebuktoje – ofiūros (76 ± 169 ind. trans-1), sudarydamos 78,4 % bendro santykinio individų gausumo įlankoje. Nustatyta, jog įlankos pagal bendrijas skiriasi tarpusavyje (Global ANOSIM R: 0,758; p = 0,001), o tirpstančio ledyno zona lemia didesnius skirtumus (Global ANOSIM R: 0,501; p = 0,001), nei Isjordeno ir Hornsundo fjordų geografinė padėtis (Global ANOSIM R: 0,398; p = 0,001). Pagal morforūšių dominavimą įlankų transektose buvo išskirtos 4 bendrijos: Sabellidae, bioturbuojančios kirmelės, samangyvių ir dvigeldžių bendrija, bei ofiūrų bendrija.

Coastal ecosystems, crucially supporting biodiversity and human well-being, are increasingly threatened by anthropogenic pressures. This thesis applies the concept of ecosystem service assessments in coastal management, offering novel methodologies and insights to address these challenges. The study explores the ecological functions and socio-economic values of diverse coastal habitats in the Baltic Sea, focusing on estuaries, sandy beaches, coastal lagoons, and macrophyte beds. The main aim is to enhance assessment methods for coastal ecosystem services, supporting management and policy implementation. For this, the main management issues were addressed within four assessment methods that were applied in this thesis (i.e. MESAT) and further developed (i.e. future scenarios, management scenarios and spatial habitat assessments). The results validate the assessment methods, showing their effectiveness in evaluating coastal ecosystem services and guiding management decisions. The developed ES assessment approaches and methods offer a useful toolkit for coastal management, applied in urban planning, beach management, coastal protection, and habitat restoration. The applicability and transferability of the developed assessment approaches are tested internationally, demonstrating their potential for addressing coastal management challenges beyond the Baltic Sea region. Furthermore, a SWOT analysis identifies the strengths (interdisciplinary, holistic), weaknesses (limited reliability, oversimplification), opportunities (policy integration, international harmonization), and threats (loss of scientific interest, competing approaches) when applying the ES concept in coastal management, guiding future research directions and applications. By enhancing our understanding of coastal ecosystems and their services, this study aims to support sustainable management practices and promote the conservation of coastal biodiversity.

One of the measures assumed to potentially help controlling cyanobacterial blooms is the use of aquatic plants and their allelochemicals. We studied effects of one of the most allelopathically active aquatic plants Myriophyllym spicatum on the potentially toxic cyanobacterium Microcystis aeruginosa. Cyanobacteria chlorophyll a concentrations were consistently lower in macrophyte treatments throughout the mesocosm experiment. The percentage of microcystin- and non-microcystin-producing M. aeruginosa genotypes in macrophyte treatments with respect to control treatments at the end of the experiment was not significantly different. For the laboratory single strain bioassay tests, both chlorophyll a concentrations and maximum quantum yields of the photosystem II were significantly diminished in non-microcystin producing relative to microcystin-producing M. aeruginosa strains. Our results indicate that although the use of M. spicatum could potentially lower cyanobacteria biomass, however, due to the allelopathic effect, it would potentially increase toxin producing M. aeruginosa genotype ratio, that would increase M. aeruginosa bloom toxicity.

The Baltic Sea is one of the most important wintering sites for sea ducks. However, these species are facing significant population declines. The remaining populations are increasingly vulnerable to anthropogenic disturbances and challenges, i.e. climate and environmental changes, bycatch, diseases, etc. The wintering season in the Baltic Sea is a crucial time for sea ducks to forage and building up body reserves to survive until the next breeding season. Prioritising their foraging areas is essential for their survival and conservation of the species. Therefore, the aim of this work was to identify important feeding areas for wintering sea ducks, the velvet scoter (Melanitta fusca) and long-tailed duck (Clangula hyemalis), based on the energetic value of the seabed and their energy requirements. Special emphasis was placed on: (I) dietary analysis and identification of priority prey species, (II) investigation and description of feeding behaviour using literature data, visual observations and transmitter data, and (III) definition of the seabed energy available and the energy requirements of sea ducks. The results demonstrated that long-tailed ducks and velvet scoters were feeding predominantly on four sessile prey species in soft-bottom areas: the bivalves Macoma balthica, Cerastoderma glaucum, Mya arenaria and the polychaete Hediste diversicolor. The prey species in the environment showed similar biomass along the study area, which corresponded to the coastal waters down to 30 m depth along the Lithuanian Curonian Spit. However, the prey indicated distinct biomass distribution at depths from 3 to 25 m, going from 0 g m-2 at 3 m to a maximum of 122.8 g m-2 at 25 m. The analysis of the behaviour through visual observation indicated that the principal activity during the day was diving (61%), while resting, comfort and locomotion were similar (11.1-14.0%). The transmitter data analysis showed similar results, indicating that the diving behaviour was the principal activity during the day, but negligible at night, especially in March when daylight was longer than in December. The diving depth distribution indicated that velvet scoters preferred depths below 12 m, but they can reach 3 times deeper waters down to 36 m. Converting the dietary and behavioural information into daily energy expenditure (DEE) allowed to obtain daily energy values for the long-tailed duck 1854 kJ d-1 and the velvet scoter 2751 kJ d-1, while in the environment, the modelled prey biomass distribution converted into energy indicated values ranging from 58 kJ to 632 kJ m-2. The areas of high prey energy availability were recorded in the southern part of the Lithuanian Curonian Spit in waters deeper than 15 m. The energy balance, derived from the ratio between prey energy available on the seabed and sea duck energetic costs indicated a relative importance of a seabed to support DEE of a single sea duck individual. The results showed that the areas where benthic prey contributes relatively more to DEE are sufficient to sustain the wintering populations of the long-tailed duck and velvet scoter during the whole winter. These areas of high contribution of benthic prey to the DEE are recommended to consider for inclusion in the 10% of strictly protected areas planned by 2030 under the EU Biodiversity Strategy (EC, 2022). Moreover, in light of the knowledge that anthropogenic disturbance displace these endangered species; boat traffic, fishing activities, and other disturbing activities are recommended for management in the shallow areas (down to 15 m depth) in order to effectively protect sea ducks.

This study provides the analysis of the macrozoobenthos species sensitivity values and application of Benthic Quality Index (BQI) for the assessment of the south-eastern part of the Baltic Sea. The numerical sensitivity concept and its use in BQI were tested for different depths, macrozoobenthos communities and types of anthropogenic disturbance. The BQI was validated against total nitrogen, total phosphorus and chlorophyll concentrations, and the dynamics of macrozoobenthos sensitivity groups was used to characterise water quality class boundaries for the coastal waters. The specificity and sensitivity of the BQI was assessed using the non-parametric Signal detection theory method and its performance in relation to eutrophication parameters was tested for the open coastal waters and plume of the Curonian Lagoon. Additionally, the detailed recommendations for the coastal water status assessment in the southeastern part of the Baltic Sea were provided.

One of the unique places in Europe in both environmental and cultural terms is the Curonian Spit – a massive sandy barrier separating the Curonian Lagoon from the Baltic Sea. Straddling both the Lithuanian and the Russian parts, the Spit is included into the UNESCO list of cultural heritage monuments. From the geological point of view, it is still an “alive” environment dominated by aeolian deposits. Detailed investigations of the Dead (Grey) Dunes massif along the Lithuanian part of the Spit using ground-penetrating radar (GPR) and magnetic susceptibility (MS) surveys, supported by radiocarbon ( 14 C) chronological framework of paleosols and infrared optically stimulated luminescence (IR-OSL) ages of sand horizons, have advanced understanding of aeolian landscape evolution. The detailed analysis of the received data did not allow distinguishing separate soil-forming generations and supported the idea of only one long continuous period of permanent formation of palaeosols. According to the data of palaeodynamic reconstructions carried out in the Dead (Grey) Dunes massif, mid-Holocene phase of dune activity was of a local character and likely did not exceed several centuries. GPR surveys enabled a series of paleogeographic reconstructions of the massif for different time intervals of its evolutionary history.