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Marine litter is a growing threat to the marine environment. Mapping of marine litter is becoming increasingly important to detect its potential hotspots and prevent their spread. In this paper, the applicability of the multibeam echo sounder (MBES) WASSP S3 and remotely operated underwater vehicle (ROV) Chasing M2 was tested in the detection and mapping of marine litter on the seafloor within the wider area of the St. Ante Channel (Šibenik, Croatia). Also, the precision assessment of WASSP S3 was tested at different cruising speeds. Results have shown that Chasing M2 can be used effectively for the initial detection of marine debris in shallow waters. However, if the underwater navigation and positioning system and auxiliary measurement scales are not used, the ROV has limited capabilities in deriving morphometric parameters of marine litter on the seafloor. This was determined by comparing the 3D model of a tire which was derived using video photogrammetry captured with ROV and the 3D model of a tire which was produced using a hand-held 3D scanner. Furthermore, the results have shown the WASSP S3 is not suitable for identifying marine litter smaller than 1 m at depths up to 10 m. The MBES WASSP S3 can detect marine litter that has a minimum area of 100 * 100 cm and a height of around 40 cm at depths up to 10 m. The results pointed to the need for caution when choosing an adequate sensor to detect and map marine litter on the seafloor. In addition, MBES interval measurements have shown that WASSP S3 precision is in the centimeter range (

Fizikalno-kemijske komponente morskog ekosustava, kakvoća mora, sedimenta, priljev slatke vode i nutrijenata te drugi ne biološki parametri i procesi također su vrlo važni za ribolovne zone i kao takvi mogu biti ključni za konačnu kvalitetu proizvoda ribarstva. Mogućnost rješavanja problema u morskom ekosustavu varira ovisno o tome jesu li oni uzrokovani ljudskim djelovanjem ili su neovisni o njima, ali u oba slučaja moraju se prepoznati ograničenja koja su nametnuta održivom razvoju ribarstva. S tim u vezi Okvirna direktiva o pomorskoj strategiji (2008/56/EC) zahtjeva primjenu integriranog pristupa u procjeni morskog ekosustava u cilju očuvanju čistog i zdravog morskog okoliša pa i u pogledu održivog razvoja ribarstva i proizvodnje zdrave hrane iz mora. Dostupni rezultati procjene morskog ekosustava u G5/G6 zoni, te donjem dijelu rijeke Neretve dobiveni su na vrlo ograničenom broju lokacija monitoringa i nedovoljni su za pouzdanu procjenu stanja morskog okoliša na cijelom ribolovnom području G5/G6 zone.

Defined clines in anchialine ecosystems act as selection barriers that influence species distributions. Along with light resources and nutrient limitations, cline areas are recognized promoters of microbial evolution in these complex habitats. To reveal microbial diversity and its potential ecological role in biogeochemical cycles along a salinity gradient, we sampled different water masses and analyzed microbial diversity using 16S rRNA amplicon sequencing along with physicochemical parameters during two seasons (spring and summer). Our results showed that a well-defined halocline maintained the stratification of the water column in both seasons, with a slight shift in the position of the halocline. The stabile halocline promoted the accumulation of the sulfide in anoxic (euxinic) water layers situated between the oxic surface layer (characterized by lower salinity and impacted by precipitation) and the seawater layer (characterized by oxygen saturated seawater of high salinity entering the cave). The oxic and anoxic layers exhibited notable differences in microbial community composition at all depths. Interestingly, the oxygenic and brackish depths were predominantly inhabited by bacterial lineages, while the saline and anoxic depths were dominated by archeal lineages. In terms of average relative abundance, Nanoarchaeota were the most abundant archaeal lineage, accounting for more than 40% of ASVs in the anoxic depths and exhibiting high diversity in 16S rRNA gene sequences. During summer, bacterial lineages of Campylobacterota co-occurred with Nanoarchaeota, with the highest abundance of ~50% in the photic surface layer.

Anchialine caves have been the subject of increasing research in recent years due to their interesting aquatic environment, which combines the characteristics of a subterranean estuary (stratified water body) and a deep ocean (lack of light and oxygen, chemosynthesis, slow water exchange). In the Republic of Croatia, along the Adriatic coast and on the islands, almost one hundred and fifty anchialine speleological objects are known, of which only a few have been partially explored. Due to the freshwater surface layer, many of them served as a source of drinking water throughout history, which is why we find archaeological finds in or near them. In the last 15 years, preliminary exploration of 7 anchialine speleological objects ("Špilja pod Orljakom", "Špilja Čapljina" also known as a Sarcophagus cave, "Vodena jama na Srimi", "Izvor Litno", "Špilja u uvali Vidrovača", "Bićinska pećina", "Špilja Mandalina") have been carried out along the estuary of the Krka River. The physico- chemical characteristics of the water column were determined in all newly discovered caves and the caves have been mapped by standard topographical methods. The concentrations and trace metals (Hg, Cd, Pb, Cu, Zn, Ni and Co) were determined for the first time in the water column of these caves. The concentrations of organic matter and nutrients were also determined, and the aquatic fauna was studied. In some caves the Microeukaryotic and prokaryotic communities were studied. In order to assess the caves' connections with the estuary or the surrounding sea, the movement of the water level in the caves was studied. In the last 15 years, preliminary archaeological investigations of the caves and their surroundings were also carried out. The results obtained confirm the uniqueness and interest of anchialine caves and pits along the estuary of the Krka River and show the need for their further exploration.

Plastic pollution is widespread and well-studied problem, however bacterial colonization of marine plastic litter and its potential detrimental effect on the fish and human health is a relatively new issue. However, recent research suggests that microorganisms living on plastics, known as plastisphere, could be distinctive from the surrounding habitat. There is also a lack of research on marine plastic litter obtained by fishing trawlers in the Adriatic Sea. The aim of the present study was to evaluate the specificities of bacteria associated to plastic litter collected by commercial fishing trawlers in the southern Adriatic Sea (Croatia), with respect to seawater and sediment from the same habitat. Sampling took place in May 2021 along the G5 fishing zone (Neretva Channel) by commercial fishing trawlers. Bacteria from plastic, sediment and seawater samples were isolated on both Marine and TCBS agar plates incubated on 22°C and 35°C and were identified using MALDI TOF Mass Spectrometry, while antimicrobial resistance to 13 antibiotics was tested using disc diffusion method on Muller Hinton II agar plates. MALDI TOF MS analyses showed lower diversity of bacteria associated to plastic in comparison to sediment and seawater samples. The majority of bacteria from plastic litter belonged to the Vibrio genera with exceptional dominance of V. alginolyticus, a well known opportunistic pathogen in aquaculture that can also cause infections in humans. Conversely, the content of Vibrio spp was generally lower in sediment and water. Antibiotic resistance to ampicillin which is inherent to Vibrio spp, was prevalent among plastic- associated V. alginolyticus, while multiresistant strains occurred occasionally. The results of this study suggest that plastic litter may provide a suitable hotspot surface for the attachment of plastic-specific microbial colonizers. Our findings provide new insights about plastic litter as an important microbial niche in the marine environment.