Macroalgae Ulva lactuca, has been employed as a natural source for the production of extracts with potent bioactivity. The biochemical characterization showed that the macroalgae biomass contains a remarkable amount of the polysaccharide Ulvan (49.9 wt%) which is a valuable chemical compound well known for its benefits in human health. Four nontoxic solvents, water, ethyl acetate, ethanol, and an ethanol/water mixture (70:30 v/v) were examined for their recovery efficiency of total carotenoid and phenolic contents. Experimental results showed that the aqueous mixture of ethanol was the most efficient solvent in the recovery of bioactive compounds with extraction yield of 10–15% dw. The effect of extraction parameters, namely time, temperature, and the ratio of biomass to solvent, on the carotenoid and phenolic compounds’ content, antioxidant activity, and extraction yield, was investigated, using the ethanol/water mixture as a solvent. The extract obtained under 60 °C, 3 h of extraction time and 1:10 biomass to solvent mass ratio showed the highest antioxidant activity. This extract maintained its antioxidant capacity almost stable for five days of storage under cool and dark conditions. Finally, specific phenolic and carotenoid compounds in the U. lactuca extracts were identified using the High-Performance Liquid Chromatography (HPLC) technique.

C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio were used for that purpose. The extracts’ total carotenoid (TCC) and phenolic contents (TPC), as well as their antioxidant activity (IC50), were determined within the process of identification of the most efficient solvent. This screening procedure revealed ChCl:1,2 butanediol (1:4)/H₂O 70/30 w/w as the most compelling solvent; thus, it was employed thereafter for the extraction process optimization. Three extraction parameters, i.e., solvent-to-biomass ratio, temperature, and time were studied regarding their impact on the extract’s TCC, TPC, and IC50. For the experimental design and process optimization, the statistical tool Response Surface Methodology was used. The resulting models’ predictive capacity was confirmed experimentally by carrying out two additional extractions under conditions different from the experimental design.

The diet of the lionfish (Pterois miles), an invasive species in the Aegean Sea, was examined by collecting stomach content data from fish collected in three study sites in the Aegean Sea (southern Crete, Kastellorizo, and Nysiros islands). Prey composition in terms of numerical abundance and frequency of occurrence was used to compare lionfish’s diet between these sites. Lionfish largely preyed upon teleosts (4% to 83% numerical abundance and 16% to 58% frequency of occurrence, depending on the site) and decapods (12% to 95% numerical abundance and 11% to 81% frequency of occurrence). The most important teleost families in lionfish’s diet were Gobiidae, Labridae, and Scorpaenidae, while decapods and especially the family Scyllaridae and the genus Plesionika were the dominant decapod prey items. The lionfish was found to be an especially successful generalist across the study sites, an opportunistic, predatory species overall, and at the same time, at a local level, it seems to be an equally successful specialist that could increase the predation mortality of already stressed prey populations and can be a serious threat to endemic, critically endangered, and/or commercially important species.

Efforts are made to produce functional aquaculture diets capable of promoting fish growth and health while being sustainable at social, economic and environmental levels. One of the emerging threats in aquaculture has become the antibiotic resistance phenomena due to antimicrobial drugs. Therefore, functional feed additives of marine origin have been introduced globally as an alternative to fish antibiotics. Towards the selection of natural and sustainable resources of bioactive compounds, seaweed has been proven to be a source of valuable substances showing antibacterial activity. Aim of this study is to evaluate the inhibition of bacterial growth caused by an ethanolic extract of the macroalgae Ulva lactuca against important aquaculture bacterial strains. Vibrio anguillarum O1, Photobacterium damselae sub. piscicida and Tenacibaculum maritimum, were incubated for 48 hours in sterile Brain Heart Infusion Broth and tested for resistance to the extract using broth cultures. The algal extract successfully inhibited the growth of all strains. The optimum inhibition was achieved for VAO1 and PHDP by the undiluted and 1:1 diluted extract, while for TMAR, by the 1:3 dilution as well. The antibacterial activity that the extract provided is considered to be the result of the containing bioactive compounds of the algal strain, such as polysaccharides, carotenoids and phenolic compounds.

Ulva spp. has been investigated as a feed additive with promising results, while literature concerning the use of its ethanolic extracts on the European seabass diet is scarce. Such extracts have shown promising results towards the reduction of the use of antibiotics and the improvement of the final product quality in the aquaculture industry. The objective of this study was to investigate the effects of a Ulva lactuca extract of high antioxidant activity as a result of extraction process optimization on the growth performance and flesh biochemical composition of Dicentrarchus labrax. 450 fingerlings were separated into three experimental groups, and fed with supplemented diets at 1% and 3% w/w Ulva extract inclusion for 8 weeks. The specific growth rate of fish subjected to 3% inclusion increased at a rate of ~28% during the trial, while flesh mineral content was found to be ~15% higher than the control population (p<0.05). Total protein content was found to be lower for fish subjected to 1% inclusion of the extract (p0.05). Results of this study indicate that the targeted extraction of bioactive compounds from algae can potentially result in overcoming drawbacks regarding their digestibility and subsequently improve their use in the aquaculture industry.

European seabass (Dicentrarchus labrax) hematology is widely used in nutrition, welfare, stress and health studies, yet results from different laboratories are often difficult to compare. This critical narrative review examines how preanalytical handling, analytical procedure and biological context affect that comparability. It is written for researchers, diagnostic laboratories and aquaculture health teams that collect or use D. labrax blood data. Primary European seabass studies are discussed directly where they provide quantitative operating conditions, method comparisons or measurable biological changes. Manual microscopy, automated analyzers and flow cytometry are considered separately because nucleated erythrocytes and thrombocytes create different sources of error in each approach. The review distinguishes practical quality-control checks from the fuller reporting required for reproducibility and separates published operating conditions from numerical limits that have not been validated for the species. Seasonal studies show large coordinated shifts in red blood cell count (RBC), hemoglobin concentration (Hb) and hematocrit (Hct), whereas white blood cell count (WBC) and thrombocyte results remain particularly dependent on cell definition and analytical method. Published pooled estimates are useful for broad comparison but not as universal diagnostic limits. The most defensible use of European seabass hematology is therefore within a defined population, a stated sampling protocol and a method whose performance is known for the intended measurement.