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Comprehensive spatial and temporal data on sediment quality in the Adriatic Sea are lacking. Therefore, prior to planned anthropogenic interventions in the local marine environment, such as deepening of the Rovinj harbour, the results of physicochemical and ecotoxicological analyses of five local coastal sediments were compared with regional averages and SQGs of neighbouring countries. Analyses of sediment grain size, content of metals and heavy metals, PAHs and PCBs were performed according to standard protocols. Sediment quality was classified according to French legislation (N1 and N2 level) and sediment guidelines. The phytotoxicity of the eluates was studied by flax seed germination tests. The logistic regression models Pmax and Pavg were used to estimate the probability of toxic effects. Except for the open sea (S5), all other sediments had concentrations slightly higher than the N1 for some metals (Cu, Ni, Hg, Cr) or ΣPAHs, while the Rovinj harbour (S1) reached the N2 value for mercury. The phytotoxicity assay with sediment eluates showed inhibition of germination, root length and root biomass production, with an average phytotoxicity index (PI) ranging from 6.06% to 42.00%. Significant correlations of Pavg and Pmax values with phytotoxicity and other specific parameters were found. In general, according to the applied SQGs, there are no potential ecological impacts on the marine environment at any of the investigated sites, with the exception of site S1.

The association and statistical correlation of anthropogenically important trace metals (TM) Cd, Cu, Pb, Zn and degraded marine microplastic (MP) extracted from the bulk debris samples at two locations from two marine systems, estuarine and coastal, in the Croatian Adriatic coastal area were assessed. The abundance of MP particles at both sites were primarily defined by local wave climate, with the open coastal site containing 9- fold more microplastic particles (>4 mm) as compared to the semi-closed estuarine, or twice as much considering bulk plastics. Generally, the higher abundance of adsorbed metal on MP were observed in the more anthropogenically influenced estuary than in the open coastal site and followed the order: polystyrene > polypropylene > low density polyethylene. The amounts of adsorbed zinc were the highest on all types of plastics at both sites, while the affinity of polystyrene for metals followed: Zn > Pb ≈ Cu > Cd.

The Cetina River Basin (CRB) belongs to a Dinaric karst area (Croatia). According to the obtained results on water and sediment quality, the Cetina River reaches the sixth goal of Sustainable Development (source of drinking water). Together with the CRB water quality assessment, it was confirmed that sediments undoubtedly contribute to the purification of watercourses from trace metals as well as organic matter. In 5 years, water samples were collected at 20 sampling sites and sediment samples were collected at 18 sampling sites. The fresh water of the Cetina River belongs to the hydrocarbonate type due to its lithology. The concentrations of the measured elements in the sediments, normalized to Al, are an indicator of possible pressures affecting the ecosystem of the river. According to the Principal Component Analysis (PCA) for elements in sediments, Principal Component 1 (PC1) describes the geogenic origin of the elements, while Principal Component 2 (PC2) describes positive values reflecting anthropogenic pressures (Total Nitrogen, TN; and Total Phosphorus, TP). Depending on element composition, the factor scores related to PC1 and PC2 resulted in four different groups of sites. The first three groups of sediments showed geological impact, while the fourth group was partially anthropogenic in origin. The hierarchical cluster analysis showed four clusters in relation to the content of the elements. Cluster analysis of all elements and the Total Organic Carbon (TOC) in the sediments showed grouping in only two clusters, the first cluster consisting of Ca, and the second of TOC with other elements.

Removal of Posidonia oceanica banquettes from Sakarun beach (Dugi otok Island, Croatia) was a common practice to increase recreational use during the summer tourist season. The sandy part of the beach showed gradual erosion and has partially disappeared. Geological and geomorphological investigations (including bedrock characterization, analysis of sediment grain size and carbonate content, beach profiling, and digital surface modelling) were conducted over nine-month period to investigate the relationship between the banquette removal and sediment loss. The results indicate that the continuous removal of sediment-laden posidonia banquette may cause a deficit in the beach sediment budget, the effects of which may not become apparent until several-year delay.

Coastal water quality management is a public health concern, as poor coastal water quality can harbor pathogens that are dangerous to human health. Tourism-oriented countries need to actively monitor the condition of coastal water at tourist popular sites during the summer season. In this study, routine monitoring data of $Escherichia\ Coli$ and enterococci across 15 public beaches in the city of Rijeka, Croatia, were used to build machine learning models for predicting their levels based on environmental parameters as well as to investigate their relationships with environmental stressors. Gradient Boosting (Catboost, Xgboost), Random Forests, Support Vector Regression and Artificial Neural Networks were trained with measurements from all sampling sites and used to predict $E.\ Coli$ and enterococci values based on environmental features. The evaluation of stability and generalizability with 10-fold cross validation analysis of the machine learning models, showed that the Catboost algorithm performed best with R$^2$ values of 0.71 and 0.68 for predicting $E.\ Coli$ and enterococci, respectively, compared to other evaluated ML algorithms including Xgboost, Random Forests, Support Vector Regression and Artificial Neural Networks. We also use the SHapley Additive exPlanations technique to identify and interpret which features have the most predictive power. The results show that site salinity measured is the most important feature for forecasting both $E.\ Coli$ and enterococci levels. Finally, the spatial and temporal accuracy of both ML models were examined at sites with the lowest coastal water quality. The spatial $E. Coli$ and enterococci models achieved strong R$^2$ values of 0.85 and 0.83, while the temporal models achieved R$^2$ values of 0.74 and 0.67. The temporal model also achieved moderate R$^2$ values of 0.44 and 0.46 at a site with high coastal water quality.

The aim of the study was to determine the correlation of metals on floating marine litter and weathered microplastic samples from the pristine area. Sampled were collected from the accumulated material on the natural beach in Mala Stupica Cove (Žirje Island, Croatia) in June 2020. In addition to weathered microplastic, the concentrations of dissolved metals in the seawater, at the same location were determined. According to these measurements, the sampling site can be considered pristine, with Cd and Pb concentrations as background values and Zn and Cu as elements that have no toxic effect, based on the classification proposed by Bakke et al., (2010). The metals of interest due to their high toxicity were Zn, Cd, Pb, and Cu.After sampling, the collected material was sieved through a metal sieve with a 4 mesh size, resulting in 4 subsamples (>4 mm; 4-2 mm; 2-1 mm; 1-0.250 mm). The type of plastic particles from subsample >4 mm was determined by FTIR spectroscopy performed on Bruker Tensor 27 in the region from 400-4000 cm-1. On such defined particles and in the seawater sample, trace metal concentrations were determined by the electrochemical method differential pulse anodic stripping voltammetry (DPASV) with standard addition method by Metrohm Autolab modular potentiostat/galvanostat Autolab PGSTAT204. A static mercury drop electrode (SMDE) was used as the working electrode.Plastic particles were isolated from additional two fractions (2-1 mm and 1-0.250 mm) as bulk samples, but without polystyrene, and the metal concentration was also determined using the same method. Due to the particle size, the type of plastic was not determined. Additional analyzes of metal concentrations on a defined and isolated polystyrene particles (PS) from a subsample (4-2 mm) and (2-1 mm) were also performed.By analogy with sediment particles, one would expect smaller microplastic particles to have higher metal concentrations due to their larger specific surface area, but this was not observed in this study. The metal concentration varied with the type of plastic, and from the observed results, plastics could be ranked according to their affinity for the analyzed metals, as follows: polystyrene (PS)>Polypropylene (PP)>Low-density polyethylene (LDPE). According to an average concentration of all analyzed samples defined as LDPE, Zn could be single out as an element with around 7-time higher affinity for LDPE than other elements (Cd, Pb, and Cu). For samples defined as PP, the highest affinity is observed for Pb, even 30 times higher than in LDPE, followed by Zn and Cu, while Cd has similar values as in LDPE. For PS samples affinity of all elements is higher in comparison with the LDPE and PP, as follows: Pb>Cu> Zn>Cd, with a concentration of Pb 2.5 times higher than in PP and even 88 times higher than in LDPE. A general conclusion could be drawn, but the observed wide ranges indicate the need for additional research to determine the relationship between the degree and type of weathering with the associated metals.This work has been fully supported by Croatian Science Foundation under the project lP-2019-04-5832.

The history of metal pollution in the semi-enclosed and human-influenced marine system of the Boka Kotorska Bay (Southern Adriatic) was studied considering geological composition of the surrounding catchment, the sedimentation rate and the mineralogical and early diagenetic processes in the recent sediments. The determination of background concentrations of metals, undertaken for the first time in this environment, proved to be particularly important for Ni and Cr, which are naturally enriched in the sediments of the southern Adriatic. The results showed widespread moderate contamination with Pb and Sn since the 1970s, while the upper layers of sediments near shipyards, marinas and urban areas were more contaminated with Sn, Cu, Pb, Zn, Cd, As, Sb and Mo. The transport of material through the narrow straits separating different parts of Boka Kotorska Bay resulted in a different geochemical composition of the smaller bays and a limited distribution of contaminated sediments from local sources.

Cliffs formed in soft rocks are rare coastal forms along the Croatian eastern Adriatic and most exposed to natural erosional processes. The rare example of such cliff affected by anthropogenic activities was developed in marl-dominated flysch in the Split urban zone. Due to the panoramic view cliff-top area is being massively occupied since the 1980ies mostly for the tourism industry and urban development. In spite of increased pressure, little attention has been given to the cliff stability. Ongoing cliff erosion seriously endangers both, coastal infrastructure on the cliff-top, as well as at the narrow shore platform used as a recreational beach area, demanding the urgent development of erosion management plan. In order to do so, fundamental knowledge is needed to understand the cliff erosion driving mechanisms.The non-vegetated cliff face was scanned 11 times by terrestrial laser scanner during the 6-year period (2012-2018). Four representative profiles along the study area were compared on precisely georeferenced point clouds. Additionally, a close examination of the cliff-top, cliff face and shore platform was carried out over 15 times during various seasons and weather conditions in order to recognize erosional processes involved. Cliff retreat rates obtained from our monitoring ranged between 3 and 18 cm/y. Extreme erosion rates of 25-34 cm/y occurred during the 2014/2015 and 2017/2018 monitoring period. Both extremes occurred after autumn and spring high precipitation periods. A causal link between intensive rain periods and erosion was further observed after two landslides during spring 2018. Furthermore, many gullies caused by surface runoff were carved after heavy rains. At the same time, increased amount of groundwater caused seepage along structural discontinuities, inducing surface erosion below the seeping line. All observed erosional processes occasionally lead to the occasional formation of marly talus cones at the cliff toe. Their duration depends on wave climate, and are being gradually removed by waves.Obtained results showed that monitored coastal cliff is predominantly subjected to various processes of surface erosion related with high precipitation, while wave abrasion is of subordinate role. Predominant marl lithology is likely to cause further surface mechanical erosion, highlighting the need for erosion management to be developed.

Terrestrial laser scanning (TLS) in combination with Unmanned Aircraft System (UAS) and modern computer based photogrammetry is currently the best approach for the acquisition of high-resolution 3D spatial information. Highly realistic 3D spatial data sets are becoming the basis for detailed geological studies, providing a multidisciplinary approach in the study and research of both underground and above ground sites. To emphasize the variety of possible implementations of these state-of-the-art methodologies, four characteristic and yet quite different case studies are presented where such geodetic techniques are successfully employed. The presented case studies demonstrate that TLS and UAS photogrammetry, as non-contact surveying methods, are able to reduce survey time and total project costs. As added value, they provide high-resolution data that can be analyzed in a virtual environment from a sedimentological or structural aspect. Stored digital documentation also allows future multi-temporal spatial data comparison at any timeframe and scale, thus enhancing any target geological data gathering and analyses at the studied sites.

Vrgada Island is situated in the central part of the eastern Adriatic coast. Upper Cretaceous limestones crop out on the surface and Pleistocene sediments cover them in some parts of the island. In this study we focus on a coastal cliff elongated in the N – S direction, situated in the northern part of the island. Aeolian-alluvial deposits, which are 12.5 m thick have been analysed. Three different facies in this succession are described. Lowermost facies A has a strong aeolian influence marked by increased silt and clay percentage and was deposited during colder climate conditions. Structureless sand in facies B was deposited from dense, cold water formed by melting snow and ice from the nearby Dinaric mountains. Bioturbated sandy facies C was probably formed during warmer climate. Unusually high percentage of augite in the lowermost part of facies A can be explained by volcanic dust input, most likely from the Roman or Campanian volcanoes in Italy. Combination of surface textures on quartz grains detected from SEM photographs indicate a short transport of sediment, no matter which mechanism) was dominant. Age correlation of possible tephra horizon from Vrgada island with confirmed tephra from Susak Island and dated ice/snow melting period from nearby mountains points to Upper Pleistocene age of sediments, most likely MIS 3 and MIS 2. The sediments from the Vrgada Island represent a transitional zone between the north Adriatic islands, where aeolian sediments dominate and the South - Eastern Adriatic archipelago, where mixed alluvial and aeolian sediments were observed.

This paper is conceived as a contribution to understanding the tectonic setting in the Jabuka region in the Central Adriatic Sea, one of the seismically active regions within the Mediterranean. This seismicity is the result of the compressional tectonics within the Adria microplate, accompanied by halokinetic activity. The Jabuka Islet and the Jabuka Shoal appear to be Triassic igneous bodies extruded by diapir tectonics. Sedimentological, mineralogical and micropaleontological analyses of the surface sediments were done to provide insights into the depositional environment around these igneous outcrops. Coarse-grained gravelly sands surrounding the Jabuka Islet and the Jabuka Shoal are composed predominantly of biogenous detritus, containing small amounts of particles derived from igneous rocks. This highly carbonate sediment cover has been formed in the low-energy environment, below wave base and without terrigenous supply from remote areas. A peculiar finding of reworked Lower Miocene foraminiferal assemblage in the recent surface sediment accompanied with re-interpreted seismic profile was used to propose a conceptual geodynamic model for the Jabuka diapir protrusion. It suggested Miocene age for the earliest protrusion of the Jabuka diapir, followed by further Plio-Quaternary growth and shaping. Together with mostly Paleogene fossil calcareous nannoplankton, fossil foraminifera were presumed to have been weathered from the pierced and extruded overburden rocks and admixed to recent, slowly forming carbonate skeletal association, typical for cool-temperate depositional environments.

The adsorption properties in terms of cation exchange capacity and their relation to the soil and sediment constituents (clay minerals, Fe-, Mn-, and Al-oxyhydroxides, organic matter) were investigated in loess, soil-loess transition zone, and soil at four loess-soil sections in North-Western Croatia. Cation exchange capacity of the bulk samples, the samples after oxalate extraction of Fe, Mn and Al, and after removal of organic matter, as well as of the separated clay fraction, was determined using copper ethylenediamine. Cation exchange capacity (pH∼7) of the bulk samples ranges from 5 to 12 cmolc/kg in soil, from 7 to 15 cmolc/kg in the soil-loess transition zone, and from 12 to 20 cmolc/kg in loess. Generally, CEC values increase with depth. Oxalate extraction of Fe, Mn, and Al, and removal of organic matter cause a CEC decrease of 3–38% and 8–55%, respectively, proving a considerable influence of these constituents to the bulk CEC values. In the separated clay fraction (

Coastal zones are one of the most rapidly changing environments on the global scale, mainly caused by anthropogenic activities (industry, urbanization, tourism and food production). Coastal erosion is primarily a natural process, although human-induced coastal changes are becoming more and more present and are significant factors associated with the loss of beach capacity. The Eastern Adriatic coast (EAC) is one of the most rapidly growing touristic markets within the Mediterranean, along which beaches still represent a leading component of the tourism resource. The objective of this paper is to provide an overview of natural geomorphologic features of the EAC as a starting point for further investigation and sustainable management of the coastal zone. The EAC is generally steep and rocky, mostly built up of karstified carbonates, and characterized, thus, by variety of drowned karstic forms. Beaches in carbonates are mostly small, narrow and scattered pocket gravel beaches. Coasts developed in the flysch and associated rocks are characterized by longer sandy and gravel beaches. The total beach length along the EAC presumably does not exceed 5 % and a small proportion of the beach length in relation to the rest of the EAC emphasizes their value in the touristic valorization, indicating the need for protection and sustainable management. Due to their geomorphologic diversities, fragmentation, different orientation, length, sediment composition and budget, each beach should be studied separately and on a small scale. Detailed information on a beach profiles, the nearshore geomorphology, and the beach processes needed to plan a sustainable coastal development are still mostly missing.

Aeolian-alluvial deposits on the northern part of Vrgada Island were investigated in order to interpret deposition mechanisms and environmental conditions. Preliminary results of basic sedimentological analyses of 49 samples allowed distinguishing 3 facies along the cliff.

In order to contribute to the debate on the role of fluvial erosion in the shaping of karst, two nearby areas with different karstic landscapes were compared. Areas A and B are located relatively close to each other on the southern side of the Krk Island (Adriatic Sea, Croatia). Both areas are composed of similar limestone with a very high CaCO 3 content. Area A is a typical doline or polygonal type (“classical”) of karst with numerous dolines (up to 57/km 2 ) covered with terra rossa (red soil) and Mediterranean maquis shrubland. Dolines are located in zones which correspond to the strike of the main geological structures. Dry karstic valleys are visible only on gently inclined coastal slopes bordering the karstic plateau. In contrast, area B is typical of a bare karst landscape with a strong (palaeo)fluvial imprint. The dolines are absent, and the bedrock is only sporadically covered with terra rossa. Palaeogene marls have been observed in a few elongated depressions and in the coastal zone of area B. Along steep coastal slopes, valleys (up to 460 m/km 2 ) are cut into the carbonates. The traces of episodic surface flows are visible in some of these valleys, in contrast to the valleys in area A. Remnants of a disrupted ancient fluvial network are clearly visible on the elevated karstic plateau in area B. Differences in the recent morphology are attributed mainly to varying thicknesses of the Palaeogene impermeable marly cover, and the intensity of tectonics in the two areas.

The aim of this research was to explore the possibility of a successful and balanced integration of fish farming installations into an ecosystem dominated by Posidonia oceanica (L.) Delile species. We selected light, temperature, seabed topography, sediment characteristics, meadow density, bottom coverage, maximum leaf length and lower depth limit as principle components in assessing the influence of the fish farm. All P. oceanica descriptors showed significant correlation with light deprivation effect while sediment organic matter content revealed slightly higher values than normal, increasing with distance from the cages. The results point to a conclusion that in such lightly nutrient enriched ecosystems, the seagrass growth and distribution are principally controlled by the shadow that cages cast on the seabed below, and that when carefully planned, fish farms do not necessarily degrade the health status of the surrounding area, but in fact facilitate a transition into a secondary stable state.

The choice of analytical method and sample pretreatment has significant consequences for the shape of particle-size distribution (PSD) frequency curves, and therefore for the evaluation of soil textural parameters. Here, the comparison of several granulometric methods based on different physical principles is presented: wet sieving (WS), based on gravity and the mechanical force of water, was combined with pipette (PP) sedimentation/settling velocity, Micromeritics SediGraph (MS) sedimentation/x-ray attenuation and Coulter Counter (CC) electroresistance particle counting. The Malvern Mastersizer (MM), an instrument based on laser diffraction, was used without WS. Twelve typical temperate-region soil types were chosen for this study on the basis of their mineral composition, organic matter content, conductivity and magnetic susceptibility. The modalities of PSD frequency curves obtained by different methods were compared. The results showed considerably larger clay-fraction contents determined with the sedimentation techniques, PP and MS, than that obtained by CC or MM. Statistical correlation and regression models were used to compare the fractions of clay, silt and sand obtained with different methods. Linear correlations were found in almost all cases, except those comparing clay fractions obtained by CC with those obtained by MM, PP and MS methods. These correlations were non-linear. The observed difference was attributed to the presence of aggregates and/or magnetic properties of soil particles. However, more data are needed to verify this hypothesis. The implications of sample pre-treatment with dispersant and hydrogen peroxide (H 2 O 2 ) were evaluated by the MS and CC techniques and observed by the scanning electron microscope. H 2 O 2 was found to be an efficient disaggregating agent. The use of dispersant resulted in the increased amount of the clay fraction measured by the MS method.

The recent shape of the coast in the Kvarner area is primarily a consequence of the drowning of karst relief due to sea-level rise during the Holocene. Further sea-level rise and increased storminess in this coastal area is expected in the future. In order to assess coastal vulnerability, two stretches of the mainland coast and the coast of four main islands in Kvarner have been examined. Most of the coast in the Kvarner area has a low risk of wave-induced marine erosion and has low vulnerability to predicted sea-level changes due to its rocky origin. Carbonate rocky coasts make up most of the coasts, whereas coasts formed in siliciclastic (flysch) rocks are less common. The largest proportion of fine grained beaches (over 20%) is found on Rab Island, due to a higher presence of less resistant flysch rocks. In order to develop mitigation and adaptation plans for future coastal changes, an integrated coastal zone management is proposed.

Glavica (natural) and Dugi Rat (artificial) gravel beaches in Croatia were monitored using ground-based photography and structure-from-motion (SfM) photogrammetry, in order to assess morphological changes after storm events. In contrast to stormy waves caused by Bora winds (NE), Sirocco winds (SE) induced waves which initiated morphological changes on both beaches. Beach orientation with respect to the prevailing wind directions is the governing factor determining direction and quantity of sediment transport. We demonstrate that the SfM approach using Agisoft PhotoScan Pro and high accuracy dGPS measurement can give DEMs with error on control points generally