Assessing the impact of an integrated educational program on Greek students' knowledge about coastal lagoons and attitudes towards marine environment conservation.

The primary objective of this study is to contribute to the conservation and sustainable use of seas by promoting Ocean Literacy. It investigates the impact of an educational program on Greek primary and secondary public school students' knowledge about coastal lagoons and attitudes towards marine environment conservation. An educational resource titled "Exploring the Coastal Lagoons" was developed to facilitate the non-formal educational intervention. The program involved classroom, fieldwork/outdoor and laboratory activities, focusing on enhancing understanding of coastal lagoons' abiotic and biotic characteristics and human interconnection. Results showed improved knowledge and slightly more positive attitudes after the didactic intervention. The study underlines the effectiveness of targeted educational interventions in marine sciences, suggesting that non-formal educational settings influence student outcomes more than family or informal sources. Younger students appeared more adaptable and responsive to educational stimuli. The study advocates for refined educational strategies integrating cognitive and emotional elements, emphasizing real nature experience.

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.

Transcriptome and proteome analysis reveals the anti-cancer properties of Hypnea musciformis marine macroalga extract in liver and intestinal cancer cells.

BACKGROUND: Marine seaweeds are considered as a rich source of health-promoting compounds by the food and pharmaceutical industry. Hypnea musciformis is a marine red macroalga (seaweed) that is widely distributed throughout the world, including the Mediterranean Sea. It is known to contain various bioactive compounds, including sulfated polysaccharides, flavonoids, and phlorotannins. Recent studies have investigated the potential anticancer effects of extracts from H. musciformis demonstrating their cytotoxic effects on various cancer cell lines. The anticancer effects of these extracts are thought to be due to the presence of bioactive compounds, particularly sulfated polysaccharides, which have been shown to have anticancer and immunomodulatory effects. However, further studies are needed to fully understand the molecular mechanisms that underlie their anticancer effects and to determine their potential as therapeutic agents for cancer treatment. METHODS: H. musciformis was collected from the Aegean Sea (Greece) and used for extract preparation. Transcriptome and proteome analysis was performed in liver and colon cancer human cell lines following treatment with H. musciformis seaweed extracts to characterize its anticancer effect in detail at the molecular level and to link transcriptome and proteome responses to the observed phenotypes in cancer cells. RESULTS: We have identified that treatment with the seaweed extract triggers a p53-mediated response at the transcriptional and protein level in liver cancer cells, in contrast to colon cancer cells in which the effects are more associated with metabolic changes. Furthermore, we show that in treated HepG2 liver cancer cells, p53 interacts with the chromatin of several target genes and facilitates their upregulation possibly through the recruitment of the p300 co-activator. CONCLUSIONS: Overall, the available evidence suggests that extracts from H. musciformis have the potential to serve as a source of anticancer agents in liver cancer cells mainly through activation of a p53-mediated anti-tumor response that is linked to inhibition of cellular proliferation and induction of cell death.

Antioxidant Activity and Inhibition of Liver Cancer Cells' Growth of Extracts from 14 Marine Macroalgae Species of the Mediterranean Sea.

Macroalgae exhibit beneficial bioactivities for human health. Thus, the aim of the present study was to examine the antioxidant and anticancer potential of 14 macroalgae species' extracts, namely, Gigartina pistillata, Gigartina teedei, Gracilaria gracilis, Gracilaria sp., Gracilaria bursa pastoris, Colpomenia sinuosa, Cystoseira amentacea, Cystoseira barbata, Cystoseira compressa, Sargassum vulgare, Padina pavonica, Codium fragile, Ulva intestinalis, and Ulva rigida, from the Aegean Sea, Greece. The antioxidant activity was assessed using DPPH, ABTS•+, •OH, and O2•- radicals' scavenging assays, reducing power (RP), and protection from ROO•-induced DNA plasmid damage assays. Moreover, macroalgae extracts' total polyphenol contents (TPCs) were assessed. Extracts' inhibition against liver HepG2 cancer cell growth was assessed using the XTT assay. The results showed that G. teedei extract's IC50 was the lowest in DPPH (0.31 ± 0.006 mg/mL), ABTS•+ (0.02 ± 0.001 mg/mL), •OH (0.10 ± 0.007 mg/mL), O2•- (0.05 ± 0.003 mg/mL), and DNA plasmid breakage (0.038 ± 0.002 mg/mL) and exhibited the highest RP (RP0.5AU 0.24 ± 0.019 mg/mL) and TPC (12.53 ± 0.88 mg GAE/g dw). There was also a significant correlation between antioxidant activity and TPC. P. pavonica (IC50 0.93 ± 0.006 mg/mL) exhibited the highest inhibition against HepG2 cell growth. Conclusively, some of the tested extracts exhibited significant chemopreventive properties, and so they may be used for food products.

Copper uptake kinetics and toxicological effects of ionic Cu and CuO nanoparticles on the seaweed Ulva rigida.

Copper ion (Cu2+) and copper oxide (CuO) nanoparticle (NP) ecotoxicity are of increasing concern as they are considered to be a potential risk to marine systems. This study represents the first attempt to evaluate CuO NP impacts on the seaweeds and Cu2+ on the chlorophyte Ulva rigida. Effects on oxidative stress, antioxidant defence markers, photosystem II function, thalli growth, and cell viability in U. rigida exposed for 4 up 72 h to1 and 5 mg L-1 Cu2+ and CuO NPs were examined. Hydrogen peroxide (H2O2) generation, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and growth inhibition seemed to be reliable and early warning markers of toxicity. The most important variables of the principal component analysis (PCA): H2O2 generation, antioxidant stress markers, and growth-based toxicity index, were higher at 1 mg L-1 CuO NPs compared to CuSO4 and at 5 mg L-1 CuSO4 compared to CuO NPs. Intracellular uptake kinetics fit well to the Michaelis-Menten equation. The higher toxicity at 5 mg L-1 CuSO4 compared to 1 mg L-1 was due to the higher Cu uptake with increasing concentration, suggesting and higher accumulation ability. On the contrary, 1 mg L-1 CuO NPs induced more strongly toxicity effects than 5 mg L-1. The relatively stronger effect of CuO NPs at 1 mg L-1 than the respective CuSO4 concentration could be attributed to the higher rate of initial uptake (Vc) and the mean rate of Cu uptake [Cmax/(2 × Km)] at CuO NP treatment. The intracellular seaweed experimental threshold of Cu, which coincided with the onset of oxidative stress, was within the Cu concentration range recorded in Mediterranean Ulva spp., indicating that it may pose a substantial risk to marine environments.

The Enzymatic and Non-Enzymatic Antioxidant System Response of the Seagrass Cymodocea nodosa to Bisphenol-A Toxicity.

The effects of environmentally relevant bisphenol A (BPA) concentrations (0.3, 1 and 3 µg L-1) were tested at 2, 4, 6 and 8 days, on intermediate leaves, of the seagrass Cymodocea nodosa. Hydrogen peroxide (H2O2) production, lipid peroxidation, protein, phenolic content and antioxidant enzyme activities were investigated. Increased H2O2 formation was detected even at the lowest BPA treatments from the beginning of the experiment and both the enzymatic and non-enzymatic antioxidant defense mechanisms were activated upon application of BPA. Elevated H2O2 levels that were detected as a response to increasing BPA concentrations and incubation time, led to the decrease of protein content on the 4th day even at the two lower BPA concentrations, and to the increase of the lipid peroxidation at the highest concentration. However, on the 6th day of BPA exposure, protein content did not differ from the control, indicating the ability of both the enzymatic and non-enzymatic mechanisms (such as superoxide dismutase (SOD) and phenolics) to counteract the BPA-derived oxidative stress. The early response of the protein content determined that the Low Effect Concentration (LOEC) of BPA is 0.3 µg L-1 and that the protein content meets the requirements to be considered as a possible early warning "biomarker" for C. nodosa against BPA toxicity.

Principles and concepts about seagrasses: Towards a sustainable future for seagrass ecosystems.

Seagrasses grow in shallow marine and estuarine environments worldwide, providing multiple ecosystem services. However, a global trend of seagrass loss has been documented. Thus, increasing awareness of seagrass value is crucial for the sustainability of these vital ecosystems. This study aims to contribute to the creation of a seagrass-literate society, by defining key principles and concepts in relation to seagrasses that a seagrass-literate person should know. Six principles about seagrasses were defined. Each one is underpinned by a set of concepts. These principles and concepts concern key issues of seagrass biology (Principles 1-4), value (Principles 3-5), loss and protection (Principle 5), and research (Principle 6). Seagrass principles and concepts can be primarily used for educational purposes and as a practical resource to policy- and decision- makers. Our attempt could stimulate a collaborative effort of scientists and educators, aiming to improve the recommended principles and concepts, and to contribute to seagrass conservation.

Nickel uptake kinetics and its structural and physiological impacts in the seagrass Halophila stipulacea.

The present work aims to provide insight into interactions between trace metals and higher plants, focusing on nickel uptake and its effects in seagrasses at environmentally relevant concentrations. Total and intracellular nickel accumulation kinetics, nickel effects on structural cell components, oxidative stress marker and cellular viability, and the accumulation kinetics-toxic effects relationship were investigated in leaves of Halophila stipulacea plants incubated in seawater under laboratory conditions containing nickel ions at 0.01-10 mg L-1 for 14 days. Nickel accumulation kinetics in H. stipulacea young and older apical leaves followed a Michaelis-Menten-type equation, allowing the calculation of uptake parameters; uptake rate (Vc) and equilibrium concentration (Ceq) tended to increase with the increase of nickel concentration in the medium. A dose- and uptake parameter-dependent actin filament (AF) and endoplasmic reticulum (ER) impairment was observed, whereas no effects occurred on microtubules and cell ultrastructure. AF disturbance and ER aggregation were firstly observed in differentiated cells at the lowest concentration on the 12th and 14th day, respectively, while AF disruption in meristematic cells firstly occurred at 0.05 mg L-1; the effects appeared earlier and were more acute at higher concentrations. Increased H2O2 levels were detected, while, at the highest exposures, a significant reduction in epidermal cell viability in older leaves occurred. The lowest total nickel concentrations in young leaves associated with AF disturbance onset at nickel exposure concentrations of 0.01-1 mg L-1 varied between 18.98 and 63.93 µg g-1 dry wt; importantly, they were comparable to nickel concentrations detected in seagrass leaves from various locations. The relationships between exposure concentration, uptake kinetic parameters and toxic effect onset were satisfactorily described by regression models. Our findings suggest that (a) nickel may pose a threat to seagrass meadows, (b) H. stipulacea can be regarded as an efficient biomonitor of nickel, (c) AF and ER impairment in seagrass leaves can be considered as early biomarkers of nickel-induced stress, and (d) the regression models obtained can be used as a tool to evaluate ambient nickel levels and to detect ecotoxicologically significant nickel contamination. The data presented can be utilized in the management and conservation of the coastal environment.

Evaluation of the spatiotemporal effects of bisphenol A on the leaves of the seagrass Cymodocea nodosa.

The organic pollutant bisphenol A (BPA) causes adverse effects on aquatic biota. The present study explored the toxicity mechanism of environmentally occurring BPA concentrations (0.03-3 µg L-1) on the seagrass Cymodocea nodosa intermediate leaf photosynthetic machinery. A "mosaic" type BPA effect pattern was observed, with "unaffected" and "affected"" leaf areas. In negatively affected leaf areas cells had a dark appearance and lost their chlorophyll auto-fluorescence, while hydrogen peroxide (H2O2) content increased time-dependently. In the "unaffected" leaf areas, cells exhibited increased phenolic compound production. At 1 µg L-1 of BPA exposure, there was no effect on the fraction of open reaction centers (qP) compared to control and also no significant effect on the quantum yield of non-regulated non-photochemical energy loss in PSII (ΦΝΟ). However, a 3 µg L-1 BPA application resulted in a significant ΦΝΟ increase, even from the first exposure day. Ultrastructural observations revealed electronically dense damaged thylakoids in the plastids, while effects on Golgi dictyosomes and the endoplasmic reticulum were also observed at 3 µg L-1 BPA. The up-regulated H2O2 BPA-derived production seems to be a key factor causing both oxidative damages but probably also triggering retrograde signalling, conferring tolerance to BPA in the "unaffected" leaf areas.

Effects of titanium dioxide nanoparticles on leaf cell structure and viability, and leaf elongation in the seagrass Halophila stipulacea.

The ecotoxicity of titanium dioxide nanoparticles (TiO2 NPs) is of increasing concern due to their extensive use in a variety of applications. This study aims to achieve a better understanding of TiO2 NP ecotoxicity by assessing for the first time their effects on seagrasses. Changes in leaf cell structure and viability, and leaf elongation in Halophila stipulacea exposed under laboratory conditions to environmentally relevant TiO2 NP concentrations (0.0015-1.5 mg L-1) for 8 days were assessed. Actin filament (AF) disturbance firstly occurred in differentiating cells at 0.0015 mg L-1 on the 8th day, while in meristematic cells at 0.15 mg L-1 on the 6th day, both deteriorating concentration- and time-dependently. Endoplasmic reticulum (ER) appeared aggregated firstly at 0.015 mg L-1 on the 8th day and earlier at the highest concentrations, while microtubules and cell ultrastructure appeared unaffected. Dead cells mainly occurred in older leaves; dead tooth, margin and intercostal epidermal cells exceeded 5% at 0.15-1.5 mg L-1. A significant leaf elongation inhibition occurred at 0.015-1.5 mg L-1 in older leaves and at 1.5 mg L-1 in young apical leaves. AF, ER and leaf elongation impairment in H. stipulacea, being susceptible response parameters, could be used as early warning markers. A risk quotient >1 was calculated, indicating that TiO2 NPs may pose a significant risk to the environment. The data presented underline the need for additional TiO2 NP-seagrasses toxicity information, and could be utilized for the protection of the coastal environment.

Physiological, structural and ultrastructural impacts of silver nanoparticles on the seagrass Cymodocea nodosa.

Silver nanoparticles (AgNPs) are an emerging contaminant, currently considered to be a significant potential risk to the coastal environment. To further test potential risk, and to determine effect concentrations and sensitive response parameters, toxic effects of environmentally relevant AgNP concentrations on the seagrass Cymodocea nodosa were evaluated. Alterations of the cytoskeleton, endoplasmic reticulum, ultrastructure, photosystem II function, oxidative stress markers, cell viability, and leaf, rhizome and root elongation in C. nodosa exposed to AgNP concentrations (0.0002-0.2 mg L-1) under laboratory conditions for 8 days were examined. An increase in H2O2 level, indicating oxidative stress, occurred after the 4th day even at 0.0002 mg L-1. Increased antioxidant enzyme activity, potentially contributing to H2O2 level decline at the end of the experiment, and reduced protein content were also observed. Actin filaments started to diminish on the 6th day at 0.02 mg L-1; microtubule, endoplasmic reticulum, chloroplast and mitochondrion disturbance appeared after 8 days at 0.02 mg L-1, while toxic effects were generally more acute at 0.2 mg L-1. A dose-dependent leaf elongation inhibition was also observed; as for juvenile leaves, toxicity index increased from 2.8 to 40.7% with concentration. Hydrogen peroxide (H2O2) overproduction and actin filament disruption appeared to be the most sensitive response parameters, and thus could be utilized as early warning indicators of risk to seagrass meadows. A risk quotient of 1.33 was calculated, confirming previous findings, that AgNPs may pose a significant risk to the coastal environment.

Silver nanoparticle toxicity effect on the seagrass Halophila stipulacea.

Information on silver nanoparticle (AgNP) phytotoxicity on seagrasses is provided for the first time. Toxic effects of environmentally relevant AgNP concentrations on Halophila stipulacea were assessed to identify sensitive biomarkers, to determine threshold effect concentrations and to evaluate potential risks. Potential alterations in the cytoskeleton, endoplasmic reticulum, cell ultrastructure and viability, oxidative stress parameters and elongation in H. stipulacea leaves exposed to AgNP concentrations ranging from 0.0002 to 0.2 mg L-1 for 8 days were examined. The first signs of actin filament (AF) response in differentiating cells, exhibiting disorientation and slight bundling, were observed on the 4th day at 0.0002 mg L-1, while at the end of the experiment and at the higher concentrations, AFs were extremely bundled. Endoplasmic reticulum was affected in meristematic and differentiating cells; massive aggregations and loss of the "grainy" structure were observed, initially on the 6th day at 0.002 mg L-1. Effects on microtubules were detected on the last day at 0.2 mg L-1. An increase in H2O2 levels on the 4th and/or 6th day even at 0.0002 mg L-1 was followed by a decrease on, or up to the last day. On the 6th day at the lowest concentration, elevated malondialdehyde content, and superoxide dismutase and peroxidase activity were detected, indicating oxidative damage and antioxidant defense mechanism activation. Dead epidermal cells mainly occurred at 0.02 and 0.2 mg L-1, while no dead vein cells were detected. A significant inhibition in leaf elongation was observed only at 0.2 mg L-1. Therefore, AF disturbance in differentiating leaf cells, being a susceptible response parameter, could be regarded as an early warning indicator of risk posed by AgNPs to H. stipulacea meadows, while most of the remaining parameters examined also constitute useful biomarkers. The lowest observed effect concentration (0.0002 mg L-1), being within the range of environmentally relevant AgNPs concentrations, suggests the possibility of negative impacts of AgNPs on seagrass health. A risk quotient of 1.33 was calculated, indicating that AgNPs may pose a significant potential risk to the coastal environment. The data presented highlight the importance of future research to further investigate the seagrass-AgNP interactions, stress the need for a refinement of the environmental risk assessment of AgNPs and could be utilized for the design of biomonitoring programs for rational management of the coastal environment.

Environmentally relevant bisphenol A concentrations effects on the seagrass Cymodocea nodosa different parts elongation: perceptive assessors of toxicity.

Toxicity data on bisphenol A (BPA) effects on aquatic macrophytes remain scarce. Therefore, environmentally relevant BPA concentrations (0.03, 0.1, 0.3, 0.5, 1, and 3 µg L-1) were tested on the seagrass Cymodocea nodosa different parts length increase. All plant parts, at low BPA concentrations (0.03-0.3 µg L-1), elongated equally to the control, while their lengthening and elongation rates gradually decreased by increasing BPA concentrations. A gradual increase of "Toxicity index" with increasing BPA concentrations was observed but was lower for juvenile blades and higher for plagiotropic rhizomes and adult leaves. In all parts, the LOECs were 0.3 and the NOECs 0.1 µg L-1 at 10th day. Juvenile blades displayed, under acute stress, lengthening inhibition at lower concentrations than the rhizomes and adult blades, but at a lower extent. The EC50 values were lower for the rhizome internodes, followed by the adult blades and higher for the juvenile blades. Using as a biological "endpoint" the elongation, all C. nodosa parts and specifically the rhizomes and adult blades, followed by intermediate blades, adult sheaths, and juvenile blades, seemed to be sensitive BPA toxicity assessors. The evaluation of the relative sensitivity of the different parts to BPA toxicity could help identify the most suitable seagrass part for early diagnosis of the risk posed by BPA to seagrass meadows and could constitute a valuable tool to derive the seawater quality criteria and to be used in BPA monitoring programs for rational management of the coastal environment.

Zinc Uptake, Photosynthetic Efficiency and Oxidative Stress in the Seagrass Cymodocea nodosa Exposed to ZnO Nanoparticles.

We characterized zinc oxide nanoparticles (ZnO NPs) by dynamic light scattering (DLS) measurements, and transmission electron microscopy (TEM), while we evaluated photosystem II (PSII) responses, Zn uptake kinetics, and hydrogen peroxide (H2O2) accumulation, in C. nodosa exposed to 5 mg L-1 and 10 mg L-1 ZnO NPs for 4 h, 12 h, 24 h, 48 h and 72 h. Four h after exposure to 10 mg L-1 ZnO NPs, we noticed a disturbance of PSII functioning that became more severe after 12 h. However, after a 24 h exposure to 10 mg L-1 ZnO NPs, we observed a hormetic response, with both time and dose as the basal stress levels needed for induction of the adaptive response. This was achieved through the reduced plastoquinone (PQ) pool, at a 12 h exposure, which mediated the generation of chloroplastic H2O2; acting as a fast acclimation signaling molecule. Nevertheless, longer treatment (48 h and 72 h) resulted in decreasing the photoprotective mechanism to dissipate excess energy as heat (NPQ) and increasing the quantum yield of non-regulated energy loss (ΦNO). This increased the formation of singlet oxygen (1O2), and decreased the fraction of open reaction centers, mostly after a 72-h exposure at 10 mg L-1 ZnO NPs due to increased Zn uptake compared to 5 mg L-1.

Trace elements in the seagrass Posidonia oceanica: Compartmentation and relationships with seawater and sediment concentrations.

Seagrasses are employed to assess trace element levels in seawater and sediments; however, their capacity as bioindicators of trace elements in seawater has been recently questioned, due to the scarcity of a significant seagrass-seawater relationship. In the aim to provide an insight into trace element accumulation in the seagrass Posidonia oceanica, Cd, Co, Cr, Cu, Ni and Pb concentrations in seawater, sediments, and several seagrass compartments (adult leaf blades, intermediate leaf blades, adult leaf sheaths, juvenile leaves, orthotropic rhizomes, plagiotropic rhizomes, and roots of plagiotropic rhizomes) from the coasts of Thrace, Greece were determined. Uni- and multivariate data analyses were applied. A comparison with reported element concentrations revealed that this coastal area can be generally classified as an area of no marked Cd, Co, Cr, Cu, Ni and Pb anthropogenic enrichment. Trace elements showed a non-uniform distribution among seagrass compartments; adult leaf blades displayed the highest mean Cd and Ni concentrations, adult leaf blades, plagiotropic rhizomes and roots the highest mean Co concentrations, juvenile leaves the highest mean Cu concentration, and plagiotropic rhizomes the highest mean Cr and Pb concentrations, indicating that the accumulation varies with element, compartment and compartment age. Cd, Cr and Ni in adult leaf blades reached mean tissue-seawater accumulation factors of 103, while Co of 104, implying that this seagrass is a strong accumulator of these elements from solution. Cd, Co, Cr, and Ni concentrations in leaf compartments, particularly adult leaf blades, positively correlated with their concentrations in seawater, and Pb concentrations in plagiotropic rhizomes and roots with sediment Pb concentration. Thereby, P. oceanica could be regarded as a biondicator for Cd, Co, Cr and Ni in seawater, and for Pb in sediments. The results presented provide an insight on trace element accumulation in P. oceanica, and can be utilized for the design of biomonitoring programs.

The effects of Bisphenol A on the seagrass Cymodocea nodosa: Leaf elongation impairment and cytoskeleton disturbance.

Bisphenol A (BPA) is an emerging pollutant of environmental concern, classified as "moderately toxic" and "toxic", causing adverse effects on aquatic biota. Although information about BPA toxicity on aquatic fauna is available, the data about BPA effects on aquatic flora remain scarce, missing for marine macrophytes. The effects of environmentally relevant BPA concentrations (ranging from 0.03 to 3 µg L-1) on juvenile leaf elongation and the cytoskeleton (microtubules, MTs and actin filaments, AFs) were studied in the seagrass Cymodocea nodosa for 1-10 days. The suitability of cytoskeleton disturbance and leaf elongation impairment as "biomarkers" for BPA stress were tested. The highest BPA concentrations (0.3, 0.5, 1 and 3 µg L-1) affected significantly leaf elongation from the onset of the experiment, while defects of the cytoskeleton were observed even at lower concentrations. In particular, MTs were initially disrupted (i.e. "lowest observed effect concentrations", LOECs) at 0.1 µg L-1, while AFs were damaged even at 0.03 µg L-1. AFs appeared thus to be more sensitive to lower BPA concentrations, while there was a correlation between leaf elongation impairment and MT defects. Thus, AF damages, MT disruption and leaf elongation impairment in C. nodosa, in this particular order, appear to be sensitive "biomarkers" of BPA stress, at the above environmentally relevant BPA concentrations.

Cadmium uptake kinetics in parts of the seagrass Cymodocea nodosa at high exposure concentrations.

BACKGROUND: Seagrass species have been recommended as biomonitors of environmental condition and as tools for phytoremediation, due to their ability to concentrate anthropogenic chemicals. This study aims to provide novel information on metal accumulation in seagrasses under laboratory conditions to support their use as a tool in the evaluation and abatement of contamination in the field. We investigated the kinetics of cadmium uptake into adult leaf blades, leaf sheaths, rhizomes and roots of Cymodocea nodosa in exposure concentrations within the range of cadmium levels in industrial wastewater (0.5-40 mg L-1). RESULTS: A Michaelis-Menten-type equation satisfactorily described cadmium accumulation kinetics in seagrass parts, particularly at 0.5-5 or 10 mg L-1. However, an S equation best described the uptake kinetics in rhizomes at 5 mg L-1 and roots at 10 and 20 mg L-1. Equilibrium concentration and uptake rate tended to increase with the exposure concentration, indicating that seagrass displays a remarkable accumulation capacity of cadmium and reflect high cadmium levels in the surrounding medium. Concerning leaf blades and rhizomes, the bioconcentration factor at equilibrium (range 73.3-404.3 and 14.3-86.3, respectively) was generally lower at higher exposure concentrations, indicating a gradual reduction of available binding sites. Leaf blades and roots accumulated more cadmium with higher rate than sheaths and rhizomes. Uptake kinetics in leaf blades displayed a better fit to the Michaelis-Menten-type equation than those in the remaining plant parts, particularly at 0.5-10 mg L-1. A marked variation in tissue concentrations mainly after the steady state was observed at 20 and 40 mg L-1, indicative of the stress induced on seagrass cells. The maximum concentrations observed in seagrass parts at 5 and 10 mg L-1 were comparatively higher than those previously reported for other seagrasses incubated to similar exposure concentrations. CONCLUSIONS: Cymodocea nodosa displays a remarkable cadmium accumulation capacity and reflects high cadmium levels in the surrounding medium. Kinetic models satisfactorily describe cadmium uptake in seagrass parts, primarily in adult leaf blades, at high exposure concentrations, permitting to predict cadmium accumulation in field situations. Cymodocea nodosa appeared to be a valuable tool in the evaluation and abatement of cadmium contamination in coastal areas.

Copper bioaccumulation, photosystem II functioning, and oxidative stress in the seagrass Cymodocea nodosa exposed to copper oxide nanoparticles.

Photosynthetic activity, oxidative stress, and Cu bioaccumulation in the seagrass Cymodocea nodosa were assessed 4, 12, 24, 48, and 72 h after exposure to two copper oxide nanoparticle (CuO NP) concentrations (5 and 10 mg L-1). CuO NPs were characterized by scanning electron microscopy (SEM) and dynamic light scattering measurements (DLS). Chlorophyll fluorescence analysis was applied to detect photosystem II (PSII) functionality, while the Cu accumulation kinetics into the leaf blades was fitted to the Michaelis-Menten equation. The uptake kinetics was rapid during the first 4 h of exposure and reached an equilibrium state after 10 h exposure to 10 mg L-1 and after 27 h to 5 mg L-1 CuO NPs. As a result, 4-h treatment with 5 mg L-1 CuO NPs, decreased the quantum yield of PS II photochemistry (Φ PSΙΙ ) with a parallel increase in the regulated non-photochemical energy loss in PSII (Φ NPQ ). However, the photoprotective dissipation of excess absorbed light energy as heat, through the process of non-photochemical quenching (NPQ), did not maintain the same fraction of open reaction centers (q p ) as in control plants. This reduced number of open reaction centers resulted in a significant increase of H2O2 production in the leaf veins serving possibly as an antioxidant defense signal. Twenty-four-hour treatment had no significant effect on Φ PSΙΙ and q p compared to controls. However, 24 h exposure to 5 mg L-1 CuO NPs increased the quantum yield of non-regulated energy loss in PSII (Φ NO ), and thus the formation of singlet oxygen (1O2) via the triplet state of chlorophyll, possible because the uptake kinetics had not yet reached the equilibrium state as did 10 mg L-1. Longer-duration treatment (48 and 72 h) had less effect on the allocation of absorbed light energy at PSII and the fraction of open reaction centers, compared to 4-h treatment, suggesting the function of a stress defense mechanism. The response of C. nodosa leaves to CuO NPs fits the "Threshold for Tolerance Model" with a threshold time (more than 4 h) required for induction of a stress defense mechanism, through H2O2 production.

Photochemical changes and oxidative damage in the aquatic macrophyte Cymodocea nodosa exposed to paraquat-induced oxidative stress.

The non-selective herbicide paraquat (Pq) is being extensively used for broad-spectrum weed control. Through water runoff and due to its high water solubility it contaminates aquatic environments. Thus, the present study was carried out to investigate the photochemical changes and oxidative damage in the aquatic macrophyte Cymodocea nodosa to short- (2h) and long-term (24h) exposure to 2, 20, 200 and 1000µM paraquat (Pq) toxicity by using chlorophyll fluorescence imaging and H2O2 real-time imaging. The effective quantum yield of PSII (ΦPSII) show a tendency to increase at 2µM Pq after 2h exposure, and increased significantly at 20 and 200µM Pq. Τhe maximum oxidative effect on C. nodosa leaves was observed 2h after exposure to 200µM Pq concentration when the highest increases of ΦPSII due to high electron transport rate (ETR) resulted in a significant increase of H2O2 production due to the lowest non-photochemical quenching (NPQ) that was not efficient to serve as a protective mechanism, resulting in photooxidation. Prolonged exposure (24h) to 200µM Pq resulted in a decreased ΦPSII not due to an increase of the photoprotective mechanism NPQ, but due to high quantum yield of non-regulated energy loss in PSII (ΦNO), resulting to the lowest fraction of open PSII reaction centers (qp). This decreased ΦPSII has resulted to less Pq radicals to be formed, with a consequence of a small increase of H2O2 production compared to control C. nodosa leaves, but substantial lower than that of 2h exposure to 200µM Pq. Exposure of C. nodosa leaves to 1000µM Pq toxicity had lower effects on the efficiency of photochemical reactions of photosynthesis under both short- (2h) and long-term (24h) exposure than 200µM Pq. This was evident by an almost unchanged ΦPSII and qp, that remained unchanged even at a longer exposure time (48h), compared to control C. nodosa leaves. Thus, the response of C. nodosa leaves to Pq toxicity fits the "Threshold for Tolerance Model", with a threshold concentration of 200µM Pq required for initiation of a tolerance mechanism, by increasing H2O2 production for the induction of genes encoding protective processes in response to Pq-induced oxidative stress. Overall, it is concluded that chlorophyll fluorescence imaging constitutes a promising basis for investigating herbicide mode of action in aquatic plants and for detecting their protective mechanisms.

Trace element seasonality in marine macroalgae of different functional-form groups.

Novel information on the seasonality of element accumulation in seaweeds is provided. Seasonal patterns of As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, U, V and Zn concentrations in macroalgae belonging to different functional-form groups (Ulva intestinalis, Ulva rigida, Codium fragile, Gracilaria gracilis) from the Thessaloniki Gulf, Aegean Sea were determined and compared. Uni- and multivariate data analyses were applied. Element concentrations generally decreased during spring and/or summer, probably due to the growth effect, but a reverse trend, particularly in Ulva species, was also observed. Most elements (Cd, Co, Cr, Cu, Mo, Ni, Pb, Sr) in Ulva species displayed a comparatively low monthly variability, indicating that the extent of seasonal variation is closely related to thallus morphology and growth strategy. In particular, these data suggest that Cd, Co, Cr, Cu, Mo, Ni, Pb and Sr contents in fast-growing, sheet-like macroalgae are less influenced by the season, compared to their contents in coarsely-branched and thick-leathery macroalgae; therefore, sheet-like macroalgae may be more appropriate to be used in biomonitoring of coastal waters. The data presented could be utilized in the development of biomonitoring programmes for the protection of coastal environments.