22 research outputs found

    Chapter Impact of cliff erosion on marine sediment composition - indication of local coastline evolution (Vrgada Island, Croatia)

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    Erosive coastal cliffs formed in soft-rocks sediments along the generally carbonaceous Eastern Adriatic are a rare feature. The one from the Vrgada Island gave rise to the idea that local seabed surface sediment may reflect the composition of the cliff sediment. First results of sedimentological analyses showed that sediment samples collected on both sides of the cliff contain material eroded mostly from the eastern side of the cliff. Subsequent longshore drift caused by dominant waves likely sort fallen material, transporting its finer fractions to the northern side and further into the sea

    Can multiple fish farms be integrated within a semi-enclosed bay without causing acute ecosystem degradation?

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    The current study explores the possibility that multiple fish farms (FFs) containing sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) can be successfuly integrated within a semi enclosed bay in the Croatian Adriatic. The research focuses on determining principal environmental factors (EFs) that control the integration and atempts to estimate their individual and synergic ability to influence deposition and removal of organic matter (OM) and trace elements (TE) from the system. The complexity of the designated tasks demanded a comprehensive number of various datasets and samples to be used in the analysis. The ADCP data revealed strong wind induced currents forming within the research domain resulting in high system flushing efficiency (3.5 – 6 days). The sediment samples from all stations contained relatively inert minerals which contributed to overall low OM and TE concentrations and very limited variability found across the entire bathymetric range. The thermal advection effect recorded at two stations was attributed to specific seabed topography and the hydrodynamic response formed during Maestral wind episodes. The results indicate that a successful integration of four FFs has taken place within the research site (semi enclosed bay), and that the key EFs responsible for its success are strong wind induced hydrodynamics, favorable seabed topography and sediment mineral composition. The synergy of the principal EFs that formed within the system was found to have an attenuating effect regarding FFs chemical influence (OM and TE) and an amplifying one regarding spatial footprint which extended to ≈ 2000 m distance

    Karakterizacija sitno-zrnaste frakcije površinskog sedimenta u kanalskom području istočne strane Jadranskog mora

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    This paper presents results of a study conducted to provide detailed characterization of fine-grained fraction in the selected surface sediment sampled along the eastern Adriatic Sea. The studied fraction was dominated by silt-sized material and composed of carbonate particles (both of biogenic and terrigenous origin), biogenic silica and terrigenous siliciclastic particles. Both components, biogenic and terrigenous were deposited in recent and sub recent conditions. The knowledge about mineral and granulometric composition and the origin of fine-grained particles is essential for understanding sedimentological processes. The obvious complex composition of the fine-grained fraction should be taken into account when environmental studies are to be carried out.Ovaj članak prikazuje rezultate istraživanja provedenih kako bi se detaljnije okarakterizirala sitno-zrnasta frakcija u odabranim uzorcima površinskog sedimenta uzorkovanih na području istočnog dijela Jadranskog mora. U sitno-zrnastoj frakciji generalno prevladava materijal veličine praha, a cjelokupna se frakcija sastoji od karbonatnih čestica biogenog i terigenog porijekla, biogenog opala i terigenih siliciklastičnih čestica. Obje komponente, biogena i terigena, taložene su u recentnim i subrecentnim uvjetima. Poznavanje granulometrijskog i mineralnog sastava sitno-zrnaste frakcije osnova je razumijevanja sedimentoloških procesa, a njegovu očitu kompleksnost bi svakako trebalo uzeti u obzir pri istraživanjima kakvoće morskih okoliša

    The Sedimentary record of Pleistocene aeolian – alluvial deposits on Vrgada Island (eastern Adriatic coast, Croatia)

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    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. This study focused on a coastal cliff trending N – S on the northern part of the island. Aeolian-alluvial deposits, which are 12.5 m thick were analysed and three different facies in this succession described. The lowermost facies A highlights a strong aeolian influence marked by an increased silt percentage and was deposited during colder climate conditions. Sand and gravel in facies B were deposited by streams of dense, cold water formed by melting snow and ice from the nearby Dinaric mountains. The bioturbated sandy facies C was probably formed during a warmer climate. An unusually high percentage of augite in the lowermost part of facies A can be explained by the input of volcanic dust, most likely from the Roman or Campanian volcanoes in Italy. This, combined with the surface textures on quartz grains detected from SEM photographs indicates a short distance transport for the sediment, no matter which mechanism was dominant. The sediments from 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

    Origin and distribution of surface sediments in the Grgur Channel, Adriatic Sea, Croatia

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    Granulometrical, mineralogical and morphological investigation of the sea-bottom sediments in the Grgur Channel revealed five sediment types; the most frequent of them are muds containing some amount of coarse sediment fractions (sand and gravel). The coarsest fractions are prevalently composed of recent shell fragments. Unexpected well rounded carbonate gravel was found SE of the Prvić Island at 83 m of water depth. This gravel was presumably transported, shaped and deposited during a lowstanding sea-level by stream and/or in beach environment. Fine-grained fractions have siliciclastic composition and show a prevalenty terrigenous origin. One part of the fine-grained fraction originates from recent subaerial weathering of flysch outcrops and the other from subaerial erosion of presently submerged flysch outcrops active during a lower sea-level. Due to the rapid Late Pleistocene-Holocene transgression, the investigated sediments are now below the present wave-base. Due to the presumed very low or even negligible recent sedimentation in the study area, older sediments in the Grgur Channel remain uncovered and mixed by burrowing organisms. Therefore, analyzed surface sediments from the Grgur Channel are considered as a mixture of recent and subrecent deposits. By this investigation, a new seabed sediments map of the Grgur Channel was produced, as an improvement of the existing sedimentological map of the Kvarner area

    Integration of Terrestrial Laser Scanning and UAS Photogrammetry in Geological Studies: Examples from Croatia

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    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

    Effects of low and high irradiation levels on growth and PSII efficiency in Lemna minor L.

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    Plant growth and reproduction depend on light energy that drives photosynthesis. In the present study we compared growth characteristics, photosynthetic pigments content and photosystem II (PSII) performance in Lemna minor L. grown in two different irradiation regimes: low light (LL) – 50 μmolPHOTONS m-2 s-1 and high light (HL) – 500 μmolPHOTONS m-2 s-1. The main goal was to investigate the photosynthetic regulatory mechanisms that ensure adjustment to different light conditions and integrate these observations with the data on plant multiplication and biomass production. For this purpose, we measured chlorophyll (Chls) and carotenoid (Cars) contents and analyzed the energy fluxes through the PSII by saturation pulse method as well as by Chl a transient induction and JIP test. In a comparison of the effect of LL and HL on plant multiplication and fresh biomass, it was shown that the effect on growth was primarily attributed to the biomass reduction in LL while the effect on number of plants was much smaller. Total Chl and Cars contents were decreased in plants exposed to HL which indicated long-term acclimation response to the increased irradiance. Furthermore, the HL plants revealed better capability for the utilization of absorbed light in photosynthesis accompanied by photoprotective adjustment of certain number of PSII reaction centers from active to dissipative mode of functioning. In conclusion, our study showed that duckweed plants had great adjustment potential to different irradiation conditions, which might be of great importance not only under variable light availability but also when simultaneously challenged by some other environmental disturbance (e.g. different pollutants)

    Implementing an efficient beach erosion monitoring system for coastal management in Croatia

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    This paper proposes a coastal erosion monitoring system for beach erosion management, which we demonstrate on natural and artificial pocket gravel beaches in Croatia. The approach uses low-cost Structure-from-Motion (SfM) photogrammetric imaging and multi-view stereo (MVS) to produce high-resolution 3D beach models for detecting morphological changes and erosion occurrence. Coastal state indicators, such as the shoreline position and subaerial beach volume, are derived from the 3D models and used to quantify changes between surveys. The method is illustrated through two case studies and, to our knowledge, these are the first repetitive measurements taken on the Croatian eastern Adriatic Coast (CEAC). In case of the natural Brseč beach, beach rotation was found to be a response to natural forcing from waves of various incident directions. For the artificial Dugi Rat beach, which loses sediment every winter and is subsequently re-nourished every spring, monitoring showed that beach nourishment is of limited durability. Both case studies showed that the SfM-MVS technique is suitable for the rapid and frequent acquisition of 3D survey data, from which quantitative coastal indicators can be derived to inform future coastal management interventions. Significantly, this low-cost data acquisition has a great potential for regular beach management survey. The introduction of beach monitoring in Croatia is timely because emerging Integrated Coastal Zone Management (ICZM) practices will require data-based approaches. Moreover, rare natural pocket beaches and the ever-increasing number of artificial beaches are extremely vulnerable to natural and man-made changes. Adaptive beach management, based on systematic monitoring data, should be included in the ICZM, and we detail how SfM-MVS-based monitoring can be used at different levels of the ICZM. Implementing robust ICZM monitoring will require broad considerations and consultation with all stakeholders, so we propose that SfM-MVS beach surveys should be initially integrated into the existing monitoring practices for CEAC sea water bathing quality. Extension of the existing database with rapidly-gathered low-cost 3D beach survey data, from a number of targeted beaches, could be used to provide a crucial baseline for the ICZM and strategic coastal monitoring of the CEAC
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