The ecological assessment of European aquatic ecosystems is regulated under the framework directives on strategy for water and marine environments. Benthic macroinvertebrates are the most used biological quality element for ecological assessment of rivers, coastal-marines, and transitional waters. The morphological identification of benthic macroinvertebrates is the current tool for their assessment. Recently, DNA-based tools have been proposed as effective alternatives. The main current limits of DNA-based applications include the incompleteness of species recorded in the DNA barcode reference libraries and the primers bias. Here, we analysed the influence of the incompleteness of DNA barcode databases on species diversity indices, ecological indicators, and ecological assessment in transitional waters of the southeast Mediterranean, taking into account the availability of commonly sequenced and deposited genomic regions for listed species. The ecological quality status assigned through the potential application of both approaches to the analysed transitional water ecosystems was different in 27% of sites. We also analysed the inter-specific genetic distances to evaluate the potential application of the DNA metabarcoding method. Overall, this work highlights the importance to expand the barcode databases and to analyse, at the regional level, the gaps in the DNA barcodes.

The transition to low-carbon energy systems requires scalable and energy-efficient routes for producing liquid biofuels that are compatible with existing fuel infrastructures. This review focuses on bio-oil production from phototrophic microorganisms, highlighting their high biomass productivity, rapid growth, and inherent capacity for carbon dioxide fixation as key advantages over conventional biofuel feedstocks. Recent progress in thermochemical conversion technologies, particularly hydrothermal liquefaction (HTL) and fast pyrolysis, is critically assessed with respect to their suitability for wet and dry algal biomass, respectively. HTL enables direct processing of high-moisture biomass while avoiding energy-intensive drying, whereas fast pyrolysis offers high bio-oil yields from lipid-rich feedstocks. In parallel, catalytic upgrading strategies, including hydrodeoxygenation and related hydroprocessing routes, are discussed as essential steps for improving bio-oil stability, heating value, and fuel compatibility. Beyond conversion technologies, innovative biological and biotechnological strategies, such as strain optimization, stress induction, co-cultivation, and synthetic biology approaches, are examined for their role in tailoring biomass composition and enhancing bio-oil precursors. The integration of microalgal cultivation with wastewater utilization is briefly considered as a supporting strategy to reduce production costs and improve overall sustainability. Overall, this review emphasizes that the effective coupling of advanced thermochemical conversion with targeted biological optimization represents the most promising pathway for scalable bio-oil production from phototrophic microorganisms, positioning algal bio-oil as a viable contributor to future low-carbon energy systems.