In order to prevent the spread of COVID-19, contingency measures in the form of lockdowns were implemented all over the world, including in Croatia. The aim of this study was to detect if those severe, imposed restrictions of social interactions reflected on the water quality of rivers receiving wastewaters from urban areas. A total of 18 different pharmaceuticals (PhACs) and illicit drugs (IDrgs), as well as their metabolites, were measured for 16 months (January 2020–April 2021) in 12 different locations at in the Sava and Drava Rivers, Croatia, using UHPLC coupled to LCMS. This period encompassed two major Covid lockdowns (March–May 2020 and October 2020–March 2021). Several PhACs more than halved in river water mass flow during the lockdowns. The results of this study confirm that Covid lockdowns caused lower cumulative concentrations and mass flow of measured PhACs/IDrgs in the Sava and Drava Rivers. This was not influenced by the increased use of drugs for the treatment of the COVID-19, like antibiotics and steroidal anti-inflammatory drugs. The decreases in measured PhACs/IDrgs concentrations and mass flows were more pronounced during the first lockdown, which was stricter than the second.

Anguilla anguilla, the European eel, is an important species for aquaculture and fisheries. Its population has dropped dramatically in recent decades, reaching an all-time low. As a result, it has been listed as critically endangered on the IUCN Red List of Endangered Species since 2007. Therefore, constant population monitoring is essential to ensure the survival of this iconic species. Glass eel recruitment is declining worldwide, including the populations in the Mediterranean region. Despite the negative impact of man-made activities in Mediterranean coastal waters over the past few decades, data on spawning biomass escaping from the Mediterranean highlights the region’s importance for the global eel supply. Eel research and monitoring is done using conventional techniques, which have certain drawbacks. Therefore, the use of molecular-based detection as a credible choice for monitoring species in aquatic ecosystems was recently shown to be an effective management plan alternative. We present the first use of environmental DNA for monitoring eel populations in the Adriatic Sea and in the complex Dinaric karst freshwater ecosystem. The method has been demonstrated to be accurate and useful for detecting the presence of A. anguilla eDNA and identifying conservation areas. This is also the first study investigating the range and presence of the European eel in the Adriatic and in the Mediterranean Sea, as well as in underground karst systems, springs, and in the karst poljes of the Eastern Adriatic coast.

Legionella-like isolates, HB10 and PATHC038^T, were isolated from a cold water distribution system on a cruise ship in 2017. The strains have been characterized by employing discriminatory genome typing, matrix-assisted laser desorption/ionization time-of-flight MS technique, fatty acid profiling and biochemical tests, thus identifying a new species in the genus Legionella. Colonies displayed phenotypic characteristics typical of the family Legionellaceae, including a requirement for l-cysteine and testing catalase positive. Fatty acid methyl ester analysis showed that the predominant fatty acids detected in the studied strains are C16:0 iso, C16:1 ω7c, C16:0 and C15:0 anteiso. The obtained MIC values showed antimicrobial susceptibility to the antimicrobial drugs ciprofloxacin and erythromycin (0.8 and 2 µg ml⁻¹, respectively). The bacteria were also Gram-negative, rod-shaped, grew aerobically on buffered charcoal yeast extract agar and weakly grew on glycine-vancomycin-polymyxin-cycloheximide media at 36 °C with the ability to autofluoresce a blue-white colour when placed under a long-wavelength UV light (365 nm). The whole-genome sequencing performed displayed a G+C content of 38.2 mol%. The digital DNA–DNA hybridization analysis demonstrated a separation from the phylogenetically most related Legionella cherrii, with 54.7% DNA–DNA relatedness. The identity percentage measured by average nucleotide identity between the PATHC038^T strain and its respective closest species, L. cherrii, was 93.9%, also confirming the distinctiveness of the novel species. The 16S rRNA gene, mip and rpoB sequences showed a similarity of 98.7, 98.4 and 96.2%, respectively, with L. cherrii NCTC 11976^T. Additionally, average amino acid identity and percentage of conserved proteins analyses further supported their classification as a novel species. The results obtained in this study confirm the status of an independent species. The name proposed for this species is Legionella sheltonii sp. nov. with PATHC038^T (CCUG 76918T, ATCC TSD-370) as the type strain.