Variations in the Composition, Antioxidant and Antimicrobial Activities of Cystoseira compressa during Seasonal Growth

The underexplored biodiversity of seaweeds has recently drawn great attention from researchers to find the bioactive compounds that might contribute to the growth of the blue economy. In this study, we aimed to explore the effect of seasonal growth (from May to September) on the in vitro antioxidant (FRAP, DPPH, and ORAC) and antimicrobial effects (MIC and MBC) of Cystoseira compressa collected in the Central Adriatic Sea. Algal compounds were analyzed by UPLC-PDA-ESI-QTOF, and TPC and TTC were determined. Fatty acids, among which oleic acid, palmitoleic acid, and palmitic acid were the dominant compounds in samples. The highest TPC, TTC and FRAP were obtained for June extract, 83.4 ± 4.0 mg GAE/g, 8.8 ± 0.8 mg CE/g and 2.7 ± 0.1 mM TE, respectively. The highest ORAC value of 72.1 ± 1.2 µM TE was obtained for the August samples, and all samples showed extremely high free radical scavenging activity and DPPH inhibition (>80%). The MIC and MBC results showed the best antibacterial activity for the June, July and August samples, when sea temperature was the highest, against Listeria monocytogenes, Staphylococcus aureus, and Salmonella enteritidis. The results show C. compressa as a potential species for the industrial production of nutraceuticals or functional food ingredients.

Seasonal Changes in Essential Oil Constituents of Cystoseira compressa: First Report

Marine macroalgae are well known to release a wide spectrum of volatile organic components, the release of which is affected by environmental factors. This paper aimed to identify the essential oil (EO) compounds of the brown algae Cystoseira compressa collected in the Adriatic Sea monthly, from May until August. EOs were isolated by hydrodistillation using a Clavenger-type apparatus and analyzed by gas chromatography coupled with mass spectrometry (GC–MS). One hundred four compounds were identified in the volatile fraction of C. compressa, accounting for 84.37–89.43% of the total oil. Samples from May, June, and July were characterized by a high share of fatty acids (56, 69, and 34% respectively) with palmitic acid being the dominant one, while in the August sample, a high content of alcohols (mainly phytol and oleyl alcohol) was found. Changes in the other minor components, which could be important for the overall aroma and biological activities of the algal samples, have also been noted during the vegetation periods. The results of this paper contribute to studies of algal EOs and present the first report on C. compressa EOs.

Effects of Natural and Anthropogenic Stressors on Fucalean Brown Seaweeds Across Different Spatial Scales in the Mediterranean Sea

Algal habitat-forming forests composed of fucalean brown seaweeds (Cystoseira, Ericaria, and Gongolaria) have severely declined along the Mediterranean coasts, endangering the maintenance of essential ecosystem services. Numerous factors determine the loss of these assemblages and operate at different spatial scales, which must be identified to plan conservation and restoration actions. To explore the critical stressors (natural and anthropogenic) that may cause habitat degradation, we investigated (a) the patterns of variability of fucalean forests in percentage cover (abundance) at three spatial scales (location, forest, transect) by visual estimates and or photographic sampling to identify relevant spatial scales of variation, (b) the correlation between semi-quantitative anthropogenic stressors, individually or cumulatively (MA-LUSI index), including natural stressors (confinement, sea urchin grazing), and percentage cover of functional groups (perennial, semi-perennial) at forest spatial scale. The results showed that impacts from mariculture and urbanization seem to be the main stressors affecting habitat-forming species. In particular, while mariculture, urbanization, and cumulative anthropogenic stress negatively correlated with the percentage cover of perennial fucalean species, the same stressors were positively correlated with the percentage cover of the semi-perennial Cystoseira compressa and C. compressa subsp. pustulata. Our results indicate that human impacts can determine spatial patterns in these fragmented and heterogeneous marine habitats, thus stressing the need of carefully considering scale-dependent ecological processes to support conservation and restoration.

Antioxidant and Antisteatotic Activities of Fucoidan Fractions from Marine and Terrestrial Sources

Fucoidan is a fucose-rich sulfated polysaccharide typically found in the cell wall of marine algae but also recently isolated from terrestrial sources. Due to a variety of biological activities, including antioxidant properties, fucoidan exhibits an attractive therapeutic potential against a wide array of metabolic diseases associated with oxidative stress. We used FTIR, 1H NMR and 13C NMR spectroscopy to investigate the structural features of a fucoidan fraction extracted from the brown alga Cystoseira compressa (CYS). The antioxidant potential of CYS was measured by DPPH, ABTS and FRAP assays, which revealed a radical scavenging capacity that was confirmed in in vitro cellular models of hepatic and endothelial cells. The same antioxidant effects were observed for another fucoidan fraction previously identified in the terrestrial tree Eucalyptus globulus (EUC). Moreover, in hepatic cells, CYS and EUC exhibited a significant antisteatotic action, being able to reduce intracellular triglyceride content through the regulation of key genes of hepatic lipid metabolism. EUC exerted stronger antioxidant and antisteatotic effects as compared to CYS, suggesting that both marine and terrestrial sources should be considered for fucoidan extraction and therapeutic applications.

Increased ammonium levels occurring during benthic algal blooms are potentially toxic to fucalean algae

During the spring of 2016, benthic blooms of Acinetospora crinita (Ectocarpales, Phaeophyceae) producing voluminous mucilaginous aggregates frequently occurred at surveyed locations of the west Istrian Coast (northern Adriatic Sea, Croatia). In mucilage-affected macroalgal assemblages, the concentration of ammonium ranged from 50 to 300 μM. To investigate whether ammonium has the potential to harm fucalean species, a selected taxon, Cystoseira compressa was exposed to increased ammonium concentrations in laboratory conditions. Experiments revealed that exposure to 50 μM ammonium severely damaged the thalli while exposure to 300 μM caused complete necrosis of thalli in 2 days. These findings suggest that benthic algal blooms, enhanced by climate change and eutrophication, can negatively affect the populations of fucalean species due to production of ammonium during the decay of mucilaginous aggregates, causing thallus necrosis.

Thermal Performance Reflects Evolutionary Legacies of Seaweeds and Seagrasses Across a Regional Climate Gradient

Comparative patterns in thermal performance between populations have fundamental implications for a species thermal sensitivity to warming and extreme events. Despite this, within-species variation in thermal performance is seldom measured. Here we compare within-species variation in thermal performance across the Mediterranean Sea, with between-species variation within communities, for two species of seagrass (Posidonia oceanica and Cymodocea nodosa) and two species of seaweed (Padina pavonica and Cystoseira compressa). Experimental populations from four locations representing approximately 75% of each species global distribution and a 6ºC gradient in summer temperatures were exposed to 10 temperature treatments (15ºC to 36ºC), reflecting median, maximum and future temperatures. Thermal performance displayed the greatest variability between species, with optimal temperatures differing by over 10ºC within the same location. Within-species differences in thermal performance were also important for P. oceanica which displayed large thermal safety margins within cool and warm-edge populations and small safety margins within central populations. Overall, experimental upper thermal limits reflected genus-level realised thermal limits, more than realised species-limits or maximum local temperatures. Our findings suggest patterns of thermal performance in Mediterranean seagrasses and seaweeds retain deep ‘pre-Mediterranean’ evolutionary legacies, resulting in unexpected patterns of vulnerability to warming within benthic marine communities.

Diversity of Epiphytic Bacterial Communities Associated with Adriatic Fucacean Species Phycosphere

The aim of the study was to explore the relationship between membrane-regulating functional lipids of three fucacean species and their associated epiphytic bacterial communities. The analyzed algae Treptacantha barbata, Carpodesmia crinita and Cystoseira compressa, formerly classified under the Cystoseira genus, are indigenous to the Adriatic Sea. The thalli of sampled Fucales species were divided into perennial and annual parts. T. barbata and C. crinita show high contents of mono- and polyunsaturated fatty acids but, however, show a clear distinction between branches, cauloids and apical parts. Along with the highest unsaturation degree (4.32), the C. crinita branches and apical parts demonstrated high proportion of both C18 and C20 polyunsaturated fatty acids, with eicosapentaenoic (C20:5 n-3) and arachidonic (C20:4 n-6) fatty acids up to 5.46% and 13.82%, respectively. The highest proportion of saturated fatty acids was found in thalli of C. compressa, particularly on cauloids and old branches (≥90%). The similarity profile routine analysis of fatty acids and microbial community structure has shown clear separation of the cauloids and apical parts from the branches of C. crinita and T. barbata. Based on the nonmetric multidimensional scaling analysis several representatives of the Gammaproteobacteria class, identified as Vibrionales (Vibrio), Cellvibrionales and Xanthomonadales, which contributed strongly to the separation of T. barbata apical parts and branches, C. compressa receptacles and C. crinita branches from the T. barbata cauloids and C. crinita apical parts and cauloids. The highest richness in polyunsaturated fatty acids, in particular C18:3(n-3), C20:4(n-6) and C20:5(n-3), was observed on branches, accompanied by a distinctive epiphytic microbial structure dominated by numerous representatives with potentially beneficial biological activity. The results showed a strong relationship between fatty acid profiles of the analyzed species and phycosphere community structure, underlining the host physiological condition in shaping the biological interactions and maintaining a healthy microbiome, as well as compiling the ecophysiological and molecular research in order to better assess the resilience of the ecosystem.

Quality Characteristics and Functional and Antioxidant Capacities of Algae-Fortified Fish Burgers Prepared from Common Barbel (Barbus barbus)

Introduction. Algae have been used as natural ingredients to produce new canned fish burgers prepared from minced flesh of common barbel. In this research, the impact of the addition of Cystoseira compressa and Jania adhaerens at concentrations of 0.5, 1, and 1.5% w/v on the texture and sensory characteristics of fish burgers were investigated. Results. Compared to controls, fish burgers containing 1% algae had better texture and sensory properties (P < 0.05). Also, these burger formulations had higher water and oil holding capacities as well as swelling ability, due to the important polysaccharides and dietary fibers contents of algae. In addition, algae-supplemented burgers were characterized as having low L⁎, a⁎, and b⁎ values, which made the color appear to be paler. Thanks to their high richness in pigments (chlorophylls and carotenoids) and polysaccharides, algae considerably enhance the antioxidant activities of the new ready-to-eat fish burgers. So, Cystoseira compressa and Jania adhaerens could be used as nutritious additives to produce new fish-based products.