Water quality monitoring in coastal areas and estuaries poses significant challenges due to the intricate interplay of hydrodynamic, chemical, and biological processes, regardless of the chosen monitoring methods. In this study, we analyzed the applicability of different monitoring sources using in situ data, uncrewed-aerial-vehicle (UAV)-mounted hyperspectral sensing, and Sentinel-2-based multispectral imagery. In the first part of the study, we evaluated the applicability of existing empirical algorithms for water quality (WQ) parameter retrieval using hyperspectral, simulated multispectral, and satellite multispectral datasets and in situ measurements. In particular, we focused on three optically active WQ parameters: chlorophyll a ($Chl,a$), turbidity (TUR), and colored dissolved organic matter (CDOM) in oligotrophic coastal waters. We observed that most existing algorithms performed poorly when applied to different reflectance datasets, similar to previous findings in small and optically complex water bodies. Hence, we proposed a novel set of locally based empirical algorithms tailored for determining water quality parameters, which constituted the second part of our study. The newly developed regression-based algorithms utilized all possible combinations of spectral bands derived from UAV-generated hyperspectral data and exhibited coefficients of determination exceeding 0.9 for the three considered WQ parameters. The presented two-part approach was demonstrated in the semi-enclosed area of Kaštela Bay and the Jadro River estuary in the Central Eastern Adriatic Sea. This study introduces a promising and efficient screening method for UAV-based water quality monitoring in coastal areas worldwide. Such an approach may support decision-making processes related to coastal management and ultimately contribute to the conservation of coastal water ecosystems.

The vertical distribution of chlorophyll in coastal waters is influenced by a combination of the hydrodynamic environment and different biotic and abiotic processes. The spatial and temporal occurrences of chlorophyll profiles provide a good representation of the changes in the marine environment. The majority of studies in the Adriatic Sea have so far been conducted in areas unaffected by anthropogenic pressure. Our study site is located near two marine outfalls, which are part of the public sewage system. This study aims to characterize the chlorophyll vertical distribution and describe its variability based on the stratification conditions and the presence of a wastewater effluent plume. Based on these conditions, we identified three characteristic scenarios/types of chlorophyll profiles. The first one occurs when the vertical mixing of the water column creates the upwelling of chlorophyll and nutrients to the upper part of the water column. The second and third scenarios occur during stratified conditions and differ by the extent of the effluent plume intrusion. Using modern fluorescence techniques, we identified and described three different vertical chlorophyll profiles, characterizing them according to their physical and biological parameters and processes. For cases with a visible effluent intrusion, we confirmed the importance of the pycnocline formation in keeping the effluent below and maintaining the higher water quality status at the top of the water column.

Background/Objectives: Pseudomonas aeruginosa is one of the leading causes of ventilator-associated pneumonia (VAP) and ventilator-associated tracheobronchitis (VAT), with a worldwide spread of difficult-to-treat high-risk clones. This study aimed to investigate the virulence potential and to characterize phenotypic and genotypic antimicrobial resistance (AMR) in P. aeruginosa causing VAP/VAT in the Intensive Care Unit (ICU), University Hospital of Split, Croatia. Methods: The study included P. aeruginosa isolates obtained from ICU patients who met the criteria for VAP or VAT, between January 2023 and January 2024. Isolates were identified using MALDI-TOF MS and tested for antimicrobial susceptibility (AST). A subset of phenotypically multidrug-resistant (MDR) isolates was further analyzed using whole-genome sequencing (WGS) and multilocus sequence typing. Results: A high rate of resistance was detected to ceftazidime (23.4%), imipenem (39.6%), and meropenem (43.8%). WGS confirmed the presence of multiple AMR genes, including the bla_VIM-2 gene, whose genetic environment highlights a complex MDR locus integrating multiple AMR determinants and mobile genetic elements. All tested isolates possessed genes for class C (bla_PDC34, bla_PDC374 or bla_PDC16) and class D (bla_OXA-2, bla_OXA-10 or bla_OXA-50) β-lactamases, fosA, aph(3′)-IIb and crpP genes. Additionally, WGS analysis revealed the presence of numerous virulence genes including those for adherence (Type IV pili and Fap protein production), motility (such as flgF), biofilm formation (e.g., algE and mucE), quorum sensing (lasI, lasR, rhlI and rhlR), exotoxin (toxA and plcH) and exoenzyme activity (exoU, exoT, exoS, exoY, pcrV, hcp1 and lasA). The isolates belonged to four different sequence types: ST235, ST446, the high-risk ST253 and the widely distributed ST395. Phylogenomic comparison demonstrated that the isolates from this study do not originate from a single clonal source, but instead represent multiple globally distributed high-risk P. aeruginosa lineages introduced into the clinical setting. Conclusions: Due to the emergence of high-risk clones with broad AMR and strong virulence potential, ineffectiveness of standard empirical therapy may be anticipated, highlighting the urgent need for new therapeutic approaches (including those targeting major virulence factors).

In this study, we report the first record of the brown alga Stypopodium schimperi in the Adriatic Sea, which also represents the northernmost occurrence of this Lessepsian species within the Mediterranean. Species identification was confirmed through morphological examination and molecular analyses based on genotyping of the chloroplast genes rbcL, psbA, and psaA. During a 3-year observation period, S. schimperi demonstrated a vigorous increase in both coverage and spatial distribution. Starting from a few observed thalli in autumn 2020, coverage reached 100% over a large area. Consequently, this resulted in a drastic reduction of native macroalgae on rocky bottoms, mostly at depths of 5-20 m, which we quantified via photo-quadrat analyses along a gradient of its coverage. In conclusion, this non-indigenous species has the potential to become one of the most invasive in the Adriatic Sea, with a high likelihood of spreading further into the northwestern Mediterranean.

Background/Objectives: Acinetobacter baumannii is a major cause of infections in Intensive Care Units (ICUs), driving mortality through high-level antimicrobial resistance. This study utilized whole-genome sequencing (WGS) to evaluate the phenotypic, genotypic and virulence features of carbapenem-resistant A. baumannii (CRAB), which has caused ventilator-associated pneumonia/tracheobronchitis (VAP/VAT) in the ICU of the University Hospital of Split, Croatia. Methods: Over 1 year, lower respiratory tract specimens from 79 VAP/VAT patients were analyzed. CRAB isolates were identified via MALDI-TOF MS and evaluated for antimicrobial susceptibility, and a representative subset underwent WGS and multilocus sequence typing (MLST). Results: Out of 106 specimens, 18 non-duplicate CRAB strains were isolated. Five isolates underwent genomic analysis, identifying two globally distributed, high-risk Pasteur lineages: ST2 and ST492. These lineages displayed distinct resistomes: ST2 carried bla_OXA-23 and bla_ADC-73, while ST492 harbored plasmid-borne bla_OXA-72 (Rep3-T1/AB082 cluster) and bla_ADC-30. All isolates shared aminoglycoside/macrolide-resistance genes, conserved efflux pumps, and virulence determinants (bau, bas, ent, bar) crucial for acinetobactin synthesis and respiratory colonization. Phylogenetic analysis confirmed regional circulation and genetic links to neighboring countries. Conclusions: This study highlights the evolutionary dynamics of endemic CRAB lineages in a Croatian ICU and their global dissemination, which poses a critical threat, demanding strict infection control and novel therapeutics.