Posidonia oceanica (L.) Delile Is a Promising Marine Source Able to Alleviate Imiquimod-Induced Psoriatic Skin Inflammation.

Psoriasis is a chronic immune-mediated inflammatory cutaneous disease characterized by elevated levels of inflammatory cytokines and adipokine Lipocalin-2 (LCN-2). Recently, natural plant-based products have been studied as new antipsoriatic compounds. We investigate the ability of a leaf extract of the marine plant Posidonia oceanica (POE) to inhibit psoriatic dermatitis in C57BL/6 mice treated with Imiquimod (IMQ). One group of mice was topically treated with IMQ (IMQ mice) for 5 days, and a second group received POE orally before each topical IMQ treatment (IMQ-POE mice). Psoriasis Area Severity Index (PASI) score, thickness, and temperature of the skin area treated with IMQ were measured in both groups. Upon sacrifice, the organs were weighed, and skin biopsies and blood samples were collected. Plasma and lesional skin protein expression of IL-17, IL-23, IFN-γ, IL-2, and TNF-α and plasma LCN-2 concentration were evaluated by ELISA. PASI score, thickness, and temperature of lesional skin were reduced in IMQ-POE mice, as were histological features of psoriatic dermatitis and expression of inflammatory cytokines and LCN-2 levels. This preliminary study aims to propose P. oceanica as a promising naturopathic anti-inflammatory treatment that could be introduced in Complementary Medicine for psoriasis.

Antioxidant Activity, Inhibition of Intestinal Cancer Cell Growth and Polyphenolic Compounds of the Seagrass Posidonia oceanica's Extracts from Living Plants and Beach Casts.

The aim of the present study was to investigate the use of Posidonia oceanica for making products beneficial for human health. Firstly, we demonstrated that the antioxidant defense (i.e., SOD and APX activity) of P. oceanica's living leaves (LP) has low efficacy, as they partly neutralize the produced H2O2. However, high H2O2 levels led LP to produce, as a response to oxidative stress, high phenolic content, including chicoric acid, p-coumaric acid, caftaric acid, trans-cinnamic and rutin hydrate, as shown by UHPLC-DAD analysis. In addition, LP extracts inhibited intestinal cancer cell proliferation. Moreover, P. oceanica's beach casts consisting of either Wet 'Necromass' (WNP) or Dry 'Necromass' (DNP) were used for preparing extracts. Both DNP and WNP exhibited antioxidant and antiproliferative activities, although lower as compared to those of LP extracts. Although both P. oceanica's meadows and beach casts are considered priority habitats in the Mediterranean Sea due to their high ecological value, legislation framework for beach casts forbidding their removal is still missing. Our results suggested that both LP and DNP could be utilized for the production of high-added value products promoting human health, provided that a sustainability management strategy would be applied for P. oceanica's meadows and beach casts.

The resilience of transplanted seagrass traits encourages detection of restoration success.

Restoration of coastal ecosystems, particularly those dominated by seagrasses, has become a priority to recover the important ecosystem services they provide. However, assessing restoration outcomes as a success or failure remains still difficult, probably due to the unique features of seagrass species and the wide portfolio of practices used on transplanting actions. Here, several traits (maximum leaf length, number of leaves, leaf growth rate per shoot, and leaf elemental carbon and nitrogen contents) of transplanted seagrass Posidonia oceanica were compared to reference meadows in five sites of Western Mediterranean Sea in which restoration were completed in different times. Results have evidenced the resilience of transplanted P. oceanica shoots within a few years since restoration, as traits between treatments changed depending on the elapsed time since settlement. The highlighted stability of the restoration time effect suggests that the recovery of the plants is expected in four years after transplanting.

Impact assessment of multiple pressures on ecosystem services with a state and transition model: Application to Posidonia oceanica seagrass meadows.

A significant challenge in the integration of ecosystem services into decision-making processes lies in effectively capturing the dynamics of marine socio-ecological systems, including their evolutionary pathways, equilibrium states, and tipping points. This paper explores the evolutionary trajectories of a vital marine ecosystem endemic to the Mediterranean Sea: the Posidonia oceanica seagrass meadows, in response to various drivers of change. A state-and-transition model is employed to assess the ecosystem services provided by P. oceanica across different states defined by selected transitions, such as overfishing, fragmentation, pollution, and invasion by non-native species. To apply this model, scientific expertise is combined with field data generated using the Ecosystem-Based Quality Index to evaluate the conservation status of P. oceanica. This integrated approach allows for the representation of the ecosystem services offered by the meadows across different states, leveraging ecological data. The findings highlight the disproportionate impact on provisioning services, particularly sea urchins and commercial fish production, which suffer the most under various stressors. Notably, when these services decline to critical levels, the meadows cease to provide significant benefits. Finally, a synthesized representation is presented, merging ecological insights with monitoring data, offering a framework that is more accessible to stakeholders and decision-makers.

Analysis of Posidonia oceanica's Stress Factors in the Marine Environment of Tremiti Islands, Italy.

Posidonia oceanica significantly contributes to the health of oceans and coastal areas; however, its progressive decline is becoming an increasing source of concern. The present preliminary study aims to assess the chemical parameters that describe the state of preservation of the aforementioned plant meadows located in the Tremiti Islands archipelago. To better understand the plants' response to external factors, the emission of biogenic volatile organic compounds (BVOCs) was investigated using Posidonia oceanica as a biological indicator. Subsequently, the heavy metal concentrations (Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Sn, Ti, Tl, V, Zn) in sediments, leaves, and seawater were determined and pollution indicators were calculated to assess the deviation from the natural background levels of sediments. The dimethyl sulfoniopropionate (DMSP) to dimethyl sulfoxide (DMSO) ratio was calculated to evaluate the oxidative stress levels in the meadows because the DMSP naturally present in Posidonia oceanica is oxidized to DMSO and decreases the ratio of DMSP/DMSO. BVOC analysis revealed dimethyl sulphide (DMS) as the most abundant molecule. Morphological features led to variations in metal concentrations across sampling sites, with sheltered bays displaying a higher metal content. Degradation is indicated by a greater DMSO content in the outer leaves. In accordance with the metal content, the bioindicator ratio confirms greater degradation on the south side, which aligns with increased oxidative stress.

Marine heatwave and reduced light scenarios cause species-specific metabolomic changes in seagrasses under ocean warming.

Climate change and extreme climatic events, such as marine heatwaves (MHWs), are threatening seagrass ecosystems. Metabolomics can be used to gain insight into early stress responses in seagrasses and help to develop targeted management and conservation measures. We used metabolomics to understand the temporal and mechanistic response of leaf metabolism in seagrasses to climate change. Two species, temperate Posidonia australis and tropical Halodule uninervis, were exposed to a combination of future warming, simulated MHW with subsequent recovery period, and light deprivation in a mesocosm experiment. The leaf metabolome of P. australis was altered under MHW exposure at ambient light while H. uninervis was unaffected. Light deprivation impacted both seagrasses, with combined effects of heat and low light causing greater alterations in leaf metabolism. There was no MHW recovery in P. australis. Conversely, the heat-resistant leaf metabolome of H. uninervis showed recovery of sugars and intermediates of the tricarboxylic acid cycle under combined heat and low light exposure, suggesting adaptive strategies to long-term light deprivation. Overall, this research highlights how metabolomics can be used to study the metabolic pathways of seagrasses, identifies early indicators of environmental stress and analyses the effects of environmental factors on plant metabolism and health.

Sustainable Exploitation of Posidonia oceanica Sea Balls (Egagropili): A Review.

Posidonia oceanica (L.) Delile is the main seagrass plant in the Mediterranean basin that forms huge underwater meadows. Its leaves, when decomposed, are transported to the coasts, where they create huge banquettes that protect the beaches from sea erosion. Its roots and rhizome fragments, instead, aggregate into fibrous sea balls, called egagropili, that are shaped and accumulated by the waves along the shoreline. Their presence on the beach is generally disliked by tourists, and, thus, local communities commonly treat them as waste to remove and discard. Posidonia oceanica egagropili might represent a vegetable lignocellulose biomass to be valorized as a renewable substrate to produce added value molecules in biotechnological processes, as bio-absorbents in environmental decontamination, to prepare new bioplastics and biocomposites, or as insulating and reinforcement materials for construction and building. In this review, the structural characteristics, and the biological role of Posidonia oceanica egagropili are described, as well as their applications in different fields as reported in scientific papers published in recent years.

Ameliorative Effect of Posidonia oceanica on High Glucose-Related Stress in Human Hepatoma HepG2 Cells.

Metabolic disorders characterized by elevated blood glucose levels are a recognized risk factor for hepatocellular carcinoma (HCC). Lipid dysregulation is critically involved in the HCC progression, regulating energy storage, metabolism, and cell signaling. There is a clear link between de novo lipogenesis in the liver and activation of the NF-κB pathway, which is involved in cancer metastasis via regulation of metalloproteinases MMP-2/9. As conventional therapies for HCC reach their limits, new effective and safe drugs need to be found for the prevention and/or adjuvant therapy of HCC. The marine plant Posidonia oceanica (L.) Delile is endemic to the Mediterranean and has traditionally been used to treat diabetes and other health disorders. The phenol-rich leaf extract of Posidonia oceanica (POE) is known to have cell-safe bioactivities. Here, high glucose (HG) conditions were used to study lipid accumulation and fatty acid synthase (FASN) expression in human HepG2 hepatoma cells using Oil Red O and Western blot assays. Under HG conditions, the activation status of MAPKs/NF-κB axis and MMP-2/9 activity were determined by Western blot and gelatin zymography assays. The potential ameliorative role of POE against HG-related stress in HepG2 cells was then investigated. POE reduced lipid accumulation and FASN expression with an impact on de novo lipogenesis. Moreover, POE inhibited the MAPKs/NF-κB axis and, consequently, MMP-2/9 activity. Overall, these results suggest that P. oceanica may be a potential weapon in the HCC additional treatment.

Extensive polyploid clonality was a successful strategy for seagrass to expand into a newly submerged environment.

Polyploidy has the potential to allow organisms to outcompete their diploid progenitor(s) and occupy new environments. Shark Bay, Western Australia, is a World Heritage Area dominated by temperate seagrass meadows including Poseidon's ribbon weed, Posidonia australis. This seagrass is at the northern extent of its natural geographic range and experiences extremes in temperature and salinity. Our genomic and cytogenetic assessments of 10 meadows identified geographically restricted, diploid clones (2n = 20) in a single location, and a single widespread, high-heterozygosity, polyploid clone (2n = 40) in all other locations. The polyploid clone spanned at least 180 km, making it the largest known example of a clone in any environment on earth. Whole-genome duplication through polyploidy, combined with clonality, may have provided the mechanism for P. australis to expand into new habitats and adapt to new environments that became increasingly stressful for its diploid progenitor(s). The new polyploid clone probably formed in shallow waters after the inundation of Shark Bay less than 8500 years ago and subsequently expanded via vegetative growth into newly submerged habitats.

Resilience of seagrass populations to thermal stress does not reflect regional differences in ocean climate.

The prevalence of local adaptation and phenotypic plasticity among populations is critical to accurately predicting when and where climate change impacts will occur. Currently, comparisons of thermal performance between populations are untested for most marine species or overlooked by models predicting the thermal sensitivity of species to extirpation. Here we compared the ecological response and recovery of seagrass populations (Posidonia oceanica) to thermal stress throughout a year-long translocation experiment across a 2800-km gradient in ocean climate. Transplants in central and warm-edge locations experienced temperatures > 29°C, representing thermal anomalies > 5°C above long-term maxima for cool-edge populations, 1.5°C for central and < 1°C for warm-edge populations. Cool-edge, central and warm-edge populations differed in thermal performance when grown under common conditions, but patterns contrasted with expectations based on thermal geography. Cool-edge populations did not differ from warm-edge populations under common conditions and performed significantly better than central populations in growth and survival. Our findings reveal that thermal performance does not necessarily reflect the thermal geography of a species. We demonstrate that warm-edge populations can be less sensitive to thermal stress than cooler, central populations suggesting that Mediterranean seagrasses have greater resilience to warming than current paradigms suggest.

Multidrug-resistant epi-endophytic bacterial community in Posidonia oceanica of Mahdia coast as biomonitoring factor for antibiotic contamination.

Faced with the significant disturbances, mainly of anthropogenic origin, which affect the Mediterranean coastal ecosystem, Posidonia oceanica (L.) Delile has often been used to assess the state of health of this environment. The present study aims to determine the multidrug resistance patterns among isolated and identified epi-endophytic bacterial strains in P. oceanica seagrass collected from Mahdia coastal seawater (Tunisia). To investigate the bacterial community structure and diversity from coastal seawater samples from Mahdia, total DNA extraction and 16S rRNA gene amplification were performed and analyzed by denaturing gradient gel electrophoresis (DGGE). The DGGE profiles showed that some bands were specific to a given site, while other bands were found to be common to more than one sample. In the other hand, bacterial strains were isolated from 1 mL of leaves and epiphytes suspension of P. oceanica seagrass in marine agar. Forty-three isolates were obtained, seven of them were selected and identified on the basis of 16S rRNA gene sequence analysis. These isolates belonged to the genus Bacillus, exhibiting 98-100% of identity with known sequences. Susceptibility patterns of these strains were studied toward commonly used antibiotics in Tunisia. All identified isolates were resistant to Aztreonam (72.1%), Ceftazidime (60.5%), Amoxicillin (56%) and Rifampicin (51.2%). S5-L13 strain had presented the highest multidrug resistance with a MAR index of 0.67.

Everything Is Everywhere: Physiological Responses of the Mediterranean Sea and Eastern Pacific Ocean Epiphyte Cobetia Sp. to Varying Nutrient Concentration.

Bacteria are essential in the maintenance and sustainment of marine environments (e.g., benthic systems), playing a key role in marine food webs and nutrient cycling. These microorganisms can live associated as epiphytic or endophytic populations with superior organisms with valuable ecological functions, e.g., seagrasses. Here, we isolated, identified, sequenced, and exposed two strains of the same species (i.e., identified as Cobetia sp.) from two different marine environments to different nutrient regimes using batch cultures: (1) Cobetia sp. UIB 001 from the endemic Mediterranean seagrass Posidonia oceanica and (2) Cobetia sp. 4B UA from the endemic Humboldt Current System (HCS) seagrass Heterozostera chilensis. From our physiological studies, both strains behaved as bacteria capable to cope with different nutrient and pH regimes, i.e., N, P, and Fe combined with different pH levels, both in long-term (12 days (d)) and short-term studies (4 d/96 h (h)). We showed that the isolated strains were sensitive to the N source (inorganic and organic) at low and high concentrations and low pH levels. Low availability of phosphorus (P) and Fe had a negative independent effect on growth, especially in the long-term studies. The strain UIB 001 showed a better adaptation to low nutrient concentrations, being a potential N2-fixer, reaching higher growth rates (µ) than the HCS strain. P-acquisition mechanisms were deeply investigated at the enzymatic (i.e., alkaline phosphatase activity, APA) and structural level (e.g., alkaline phosphatase D, PhoD). Finally, these results were complemented with the study of biochemical markers, i.e., reactive oxygen species (ROS). In short, we present how ecological niches (i.e., MS and HCS) might determine, select, and modify the genomic and phenotypic features of the same bacterial species (i.e., Cobetia spp.) found in different marine environments, pointing to a direct correlation between adaptability and oligotrophy of seawater.

Enhanced Streptomyces roseochromogenes melanin production by using the marine renewable source Posidonia oceanica egagropili.

Since the possibility to biotechnologically produce melanin by Streptomycetes using plant biomass has been so far poorly investigated, Posidonia oceanica egagropili, a marine waste accumulating along the Mediterranean Sea coasts, was explored as a renewable source to enhance extracellular melanin production by Streptomyces roseochromogenes ATCC 13400. Therefore, different amounts of egagropili powder were added to a culture medium containing glucose, malt extract, and yeast extract, and their effect on the melanin biosynthesis was evaluated. A 2.5 g·L-1 supplementation in 120-h shake flask growths at 26 °C, at pH 6.0 and 250 rpm, was found to enhance the melanin production up to 3.94 ± 0.12 g·L-1, a value 7.4-fold higher than the control. Moreover, 2-L batches allowed to reach a concentration of 9.20 ± 0.12 g·L-1 in 96 h with a productivity of 0.098 g·L-1·h-1. Further studies also demonstrated that the melanin production enhancement was due to the synergistic effect of both the lignin carbohydrate complex and the holocellulose components of the egagropili. Finally, the pigment was purified from the broth supernatant by acidic precipitation and reversed-phase chromatography, characterized by UV absorbance and one- and two-dimensional NMR, and also tested for its chemical, antioxidant, and photo-protective properties. KEY POINTS: • S. roseochromogenes ATCC 13400 produces extracellular soluble melanin. • Egagropili added to the growth medium enhances melanin production and productivity. • Both the lignin carbohydrate complex and the holocellulose egagropili components influence the melanin biosynthesis.

Glucose Uptake and Oxidative Stress in Caco-2 Cells: Health Benefits from Posidonia oceanica (L.) Delile.

Posidonia oceanica (L.) Delile is an endemic Mediterranean marine plant of extreme ecological importance. Previous in vitro and in vivo studies have demonstrated the potential antidiabetic properties of P. oceanica leaf extract. Intestinal glucose transporters play a key role in glucose homeostasis and represent novel targets for the management of diabetes. In this study, the ability of a hydroalcoholic P. oceanica leaf extract (POE) to modulate intestinal glucose transporters was investigated using Caco-2 cells as a model of an intestinal barrier. The incubation of cells with POE significantly decreased glucose uptake by decreasing the GLUT2 glucose transporter levels. Moreover, POE had a positive effect on the barrier integrity by increasing the Zonulin-1 levels. A protective effect exerted by POE against oxidative stress induced by chronic exposure to high glucose concentrations or tert-butyl hydroperoxide was also demonstrated. This study highlights for the first time the effect of POE on glucose transport, intestinal barrier integrity, and its protective antioxidant effect in Caco-2 cells. These findings suggest that the P. oceanica phytocomplex may have a positive impact by preventing the intestinal cell dysfunction involved in the development of inflammation-related disease associated with oxidative stress.

Seagrass restoration monitoring and shallow-water benthic habitat mapping through a photogrammetry-based protocol.

Seagrasses rank among the most productive yet highly threatened ecosystems on Earth. Loss of seagrass habitat because of anthropogenic disturbances and evidence of their limited resilience have provided the impetus for investigating and monitoring habitat restoration through transplantation programmes. Although Structure from Motion (SfM) photogrammetry is becoming a more and more relevant technique for mapping underwater environments, no standardised methods currently exist to provide 3-dimensional high spatial resolution and accuracy cartographic products for monitoring seagrass transplantation areas. By synthesizing various remote sensing applications, we provide an underwater SfM-based protocol for monitoring large seagrass restoration areas. The data obtained from consumer-grade red-green-blue (RGB) imagery allowed the fine characterization of the seabed by using 3D dense point clouds and raster layers, including orthophoto mosaics and Digital Surface Models (DSM). The integration of high spatial resolution underwater imagery with object-based image classification (OBIA) technique provided a new tool to count transplanted Posidonia oceanica fragments and estimate the bottom coverage expressed as a percentage of seabed covered by such fragments. Finally, the resulting digital maps were integrated into Geographic Information Systems (GIS) to run topographic change detection analysis and evaluate the mean height of transplanted fragments and detect fine-scale changes in seabed vector ruggedness measure (VRM). Our study provides a guide for creating large-scale, replicable and ready-to-use products for a broad range of applications aimed at standardizing monitoring protocols in future seagrass restoration actions.

Antioxidant Bioactivity of Extracts from Beach Cast Leaves of Posidonia oceanica (L.) Delile.

The marine environment is a generous source of biologically active compounds useful for human health. In 50 years, about 25,000 bioactive marine compounds have been identified, with an increase of 5% per year. Peculiar feature of algae and plants is the production of secondary metabolites, such as polyphenols, synthesized as a form of adaptation to environmental stress. Posidonia oceanica is a Mediterranean endemic and dominant seagrass and represents a biologically, ecologically and geologically important marine ecosystem. Within this study, methanolic and ethanolic extracts were generated from fresh and dried Posidonia oceanica leaves, with the aim to employ and valorize the beach cast leaves. The best yield and antioxidant activity (polyphenols content equal to 19.712 ± 0.496 mg GAE/g and DPPH IC50 of 0.090 µg/µL.) were recorded in 70% ethanol extracts (Gd-E4) obtained from leaves dried for two days at 60 °C and ground four times. HPLC analyses revealed the presence of polyphenols compounds (the most abundant of which was chicoric acid) with antioxidant and beneficial properties. Bioactive properties of the Gd-E4 extracts were evaluated in vitro using fibroblast cells line (HS-68), subjected to UV induced oxidative stress. Pre-treatment of cells with Gd-E4 extracts led to significant protection against oxidative stress and mortality associated with UV exposure, thus highlighting the beneficial properties of antioxidants compounds produced by these marine plants against photo damage, free radicals and associated negative cellular effects. Beach cast leaves selection, processing and extraction procedures, and the in vitro assay results suggested the potentiality of a sustainable approach for the biotechnological exploitation of this resource and could serve a model for other marine resources.

Posidonia oceanica (L.) Delile Dampens Cell Migration of Human Neuroblastoma Cells.

Neuroblastoma (NB) is a common cancer in childhood, and lethal in its high-risk form, primarily because of its high metastatic potential. Targeting cancer cell migration, and thus preventing metastasis formation, is the rationale for more effective cancer therapy against NB. Previous studies have described the leaf extract from Posidonia oceanica marine plant (POE) as an antioxidant, anti-inflammatory agent and inhibitor of cancer cell migration. This study aims to examine the POE anti-migratory role in human SH-SY5Y neuroblastoma cells and the underlying mechanisms of action. Wound healing and gelatin zymography assays showed that POE at early times inhibits cell migration and reduces pro-MMP-2 release into culture medium. By monitoring expression level of key autophagy markers by Western blot assay, a correlation between POE-induced cell migration inhibition and autophagy activation was demonstrated. Cell morphology and immunofluorescence analyses showed that POE induces neurite formation and neuronal differentiation at later times. These results suggest POE might act against cell migration by triggering early nontoxic autophagy. The POE-induced cellular morphological change toward cell differentiation might contribute to prolonging the phytocomplex anti-migratory effect to later times. Overall, these results encourage future in vivo studies to test POE applicability in neuroblastoma treatment.

Lignin/Carbohydrate Complex Isolated from Posidonia oceanica Sea Balls (Egagropili): Characterization and Antioxidant Reinforcement of Protein-Based Films.

A lignin fraction (LF) was extracted from the sea balls of Posidonia oceanica (egagropili) and extensively dialyzed and characterized by FT-IR and NMR analyses. LF resulted water soluble and exhibited a brownish-to-black color with the highest absorbance in the range of 250-400 nm, attributed to the chromophore functional groups present in the phenylpropane-based polymer. LF high-performance size exclusion chromatography analysis showed a highly represented (98.77%) species of 34.75 kDa molecular weight with a polydispersity index of 1.10 and an intrinsic viscosity of 0.15. Quantitative analysis of carbohydrates indicated that they represented 28.3% of the dry weight of the untreated egagropili fibers and 72.5% of that of LF. In particular, eight different monosaccharides were detected (fucose, arabinose, rhamnose, galactose, glucose, xylose, glucosamine and glucuronic acid), glucuronic acid (46.6%) and rhamnose (29.6%) being the most present monosaccharides in the LF. Almost all the phenol content of LF (113.85 ± 5.87 mg gallic acid eq/g of extract) was water soluble, whereas around 22% of it consisted of flavonoids and only 10% of the flavonoids consisted of anthocyanins. Therefore, LF isolated from egagropili lignocellulosic material could be defined as a water-soluble lignin/carbohydrate complex (LCC) formed by a phenol polymeric chain covalently bound to hemicellulose fragments. LCC exhibited a remarkable antioxidant activity that remained quite stable during 6 months and could be easily incorporated into a protein-based film and released from the latter overtime. These findings suggest egagropili LCC as a suitable candidate as an antioxidant additive for the reinforcement of packaging of foods with high susceptibility to be deteriorated in aerobic conditions.

Structure and mechanics of aegagropilae fiber network.

Fiber networks encompass a wide range of natural and manmade materials. The threads or filaments from which they are formed span a wide range of length scales: from nanometers, as in biological tissues and bundles of carbon nanotubes, to millimeters, as in paper and insulation materials. The mechanical and thermal behavior of these complex structures depends on both the individual response of the constituent fibers and the density and degree of entanglement of the network. A question of paramount importance is how to control the formation of a given fiber network to optimize a desired function. The study of fiber clustering of natural flocs could be useful for improving fabrication processes, such as in the paper and textile industries. Here, we use the example of aegagropilae that are the remains of a seagrass (Posidonia oceanica) found on Mediterranean beaches. First, we characterize different aspects of their structure and mechanical response, and second, we draw conclusions on their formation process. We show that these natural aggregates are formed in open sea by random aggregation and compaction of fibers held together by friction forces. Although formed in a natural environment, thus under relatively unconstrained conditions, the geometrical and mechanical properties of the resulting fiber aggregates are quite robust. This study opens perspectives for manufacturing complex fiber network materials.

Cytotoxicity screening of supercritical fluid extracted seaweeds and phenylpropanoids.

Detached leaves of Posidonia oceanica and Zostera marina creating nuisance at the shores were extracted by means of supercritical CO2 enriched with a co-solvent, compared with that of soxhlet extraction. The extracts and their active compounds which are phenylpropanoids (chicoric, p-coumaric, rosmarinic, benzoic, ferulic and caffeic acids) were screened for cytotoxicity in cancer cell lines including human breast adenocarcinoma (MCF-7, MDA-MB-231, SK-BR-3), human colon adenocarcinoma (HT-29), human cervix adenocarcinoma (HeLa), human prostate adenocarcinoma (PC-3), Mus musculus neuroblastoma (Neuro 2A) cell lines and African green monkey kidney (VERO) as healthy cell line. Supercritical CO2 extracts proved to be more active than soxhlet counterparts. Particularly, Zostera marina extract obtained by supercritical CO2 at 250 bar, 80 °C, 20% co-solvent and a total flow rate of 15 g/min revealed the best IC50 values of 25, 20, 8 µg/ml in neuroblastoma, colon and cervix cancer cell lines. Among the major compounds tested, p-coumaric acid exhibited the highest cytotoxic against colon and cervix cell lines by with IC50 values of 25, 11 µg/ml. As for the effects on healthy cells, the extract was not cytotoxic indicating a selective cytotoxicity. Obtained supercritical CO2 extracts can be utilized as a supplement for preventive purposes.