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.

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.

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.

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.

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.

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.

Trace element patterns in marine macroalgae.

Novel information on interspecific variation in trace element accumulation in seaweeds is provided. Concentrations and concentration factors (CFs) of a wide set of elements (As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, U, V and Zn) in 26 dominant macroalgae from the Gulf of Thessaloniki, Aegean Sea were determined and compared. Uni-and multivariate data analyses were applied. Phaeophyceae showed higher concentrations and CFs of As and Sr than Rhodophyta and Chlorophyta, indicating that the accumulation of these elements is closely related to species biochemical composition. Filamentous macroalgae displayed higher concentrations and CFs of several elements, particularly Cd, Co, Cr, Cu, Mn and V than sheet-like, coarsely-branched and/or thick-leathery macroalgae, irrespective of phylogenetic relationships, indicating that the accumulation of several elements is largely related to thallus morphology and growth strategy. On a species basis, Cystoseira spp. showed both the highest concentrations and CFs of As, Padina pavonica of Sr and U, Ceramium spp. of Mn, Ceramium and Cladophora species of Co and Cu, Cladophora prolifera of Cr and Polysiphonia deusta and Ulva clathrata of Cd. Se concentration in Ulva rigida correlated positively with seawater Se concentration, and As concentration in this species with sediment As concentration. Thereby, these seaweeds could be regarded as potential biomonitors for the respective elements. A literature review was performed and global element concentrations and CFs were presented for seaweeds from genera collected during this survey. The data presented can contribute to the interpretation of biomonitoring data and the design of biomonitoring programs for the protection and management of coastal environments.

Effects of lead uptake on microtubule cytoskeleton organization and cell viability in the seagrass Cymodocea nodosa.

The effects of lead uptake on microtubule integrity and cell viability in intermediate-juvenile leaf blades of the seagrass Cymodocea nodosa were investigated under laboratory conditions in increasing exposure concentrations (0.1, 0.25, 0.5, 5, 10, 20 and 40mg/L). Uptake kinetics was generally fitted well to the Michaelis-Menten equation. The equilibrium concentration and the velocity of lead uptake tended to increase as the exposure concentration increased up to 5-10mg/L; equilibrium concentration values at most of the treatments were comparable to reported lead concentrations in seagrass leaves. Lead caused a drastic change in the microtubule organization; microtubule depolymerization was observed after 3-7 days of exposure, depending on metal dosage. This observation indicates that microtubule integrity could be utilized as an early biomarker of emerging lead contamination. Cell death starting to occur at later time than microtubule disturbance was also observed at all of the treatments. Microtubule depolymerization expressed as percentage of fluorescence intensity reduction and cell mortality expressed as percentage of dead cells (blue stained) increased with time. Toxic effects were first detected during or at the beginning of the steady state-phase of lead uptake. The lowest experimental tissue lead concentrations associated with the onset of toxic effects (18.33-20.24µg/g dry wt, 0.1-0.25mg/L treatments, 7th day) were comparable to or lower than lead concentrations measured in leaves of C. nodosa and other seagrass species from various geographical areas, probably implying that lead may play a important role in the worldwide decline of seagrass meadows. These lowest tissue concentrations were exceeded up to the 3rd day of incubation at higher exposure concentrations, but microtubule depolymerization at 0.5mg/L and cell death at 0.5-20mg/L were first detected at later time. The time period required for the onset of microtubule depolymerization tended to decrease as lead uptake velocity increased; in particular, a significant negative correlation was found between these variables. These results suggest that the onset of toxicity appears to be related to lead uptake rate rather than to the total tissue lead concentration. Thereby, tissue residues should be interpreted in relation to the time frame of the exposure, while the estimation of metal uptake rate could be utilized for predicting toxic effects. The data presented provide insight on metal uptake kinetics, toxicological effects and their linkage in seagrasses, contribute to a better understanding of metal toxicity on aquatic organisms and could be utilized in biomonitoring programmes for the identification of ecotoxicologically significant metal accumulation in coastal environments.

Kinetics of cadmium accumulation and its effects on microtubule integrity and cell viability in the seagrass Cymodocea nodosa.

The kinetics of cadmium accumulation and its effects on microtubule cytoskeleton and cell viability in leaf blades of the seagrass Cymodocea nodosa were investigated under laboratory conditions in exposure concentrations ranging from 0.5 to 40 mg L(-1). An initial rapid accumulation of cadmium was followed by a steady state. The Michaelis-Menten model adequately described metal accumulation; equilibrium concentration and uptake velocity tended to increase, whereas bioconcentration factor at equilibrium to decrease, as the exposure concentration increased. Cadmium depolymerized microtubules after 3-9 d of exposure, depending on trace metal concentration, indicating that microtubules could be used as an early biomarker of cadmium stress; cell death, occurring at later time than microtubule disturbance, was also observed. Microtubule depolymerization expressed as percentage of reduction of fluorescence intensity and cell mortality expressed as percentage of live cells increased with time. The lowest experimental tissue concentration associated with the onset of microtubule depolymerization and cell death (98.5-128.9µgg(-1)drywt, 0.5 mg L(-1) treatment, 7th and 9th d) was within the wide range of reported cadmium concentrations in leaves of seagrass species from various geographical areas. This lowest tissue concentration was exceeded up to the 3rd d at higher exposure concentrations, but toxic effects were generally detected at later time. The time periods required for the onset of depolymerization and for 10 and 50% of cells to die tended to decrease as the uptake velocity increased; in particular, significant negative correlations were found between these variables. These results suggest that toxicity appears to be a function of cadmium uptake rate rather than of the total tissue metal concentration. Hence, tissue residues should be interpreted in relation to the time frame of the exposure, while the estimation of metal uptake velocity could be utilized for predicting toxic effects. The data presented provide insight on the relationship between metal bioaccumulation and toxic effects in seagrasses and, overall, contribute to a better understanding of the impact of metals on aquatic organisms.

Trace element (Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V) distribution and seasonality in compartments of the seagrass Cymodocea nodosa.

Novel information on the biological fate of trace elements in seagrass ecosystems is provided. Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V concentrations in five compartments (blades, sheaths, vertical rhizomes, main axis plus additional branches, roots) of the seagrass Cymodocea nodosa, as well as in seawater and sediments from the Thessaloniki Gulf, Greece were determined monthly. Uni- and multivariate data analyses were applied. Leaf compartments and roots displayed higher Al, Mo, Ni and Se annual mean concentrations than rhizomes, B was highly accumulated in blades and Cr in sheaths; As, Ba, Sr and Tl contents did not significantly vary among plant compartments. A review summarizing reported element concentrations in seagrasses has revealed that C. nodosa sheaths display a high Cr accumulation capacity. Most element concentrations in blades increased in early mid-summer and early autumn with blade size and age, while those in sheaths peaked in late spring-early summer and autumn when sheath size was the lowest; elevated element concentrations in seawater in late spring and early-mid autumn, possibly as a result of elevated rainfall and associated run-off from the land, may have also contributed to the observed variability. Element concentrations in rhizomes and roots generally displayed a temporary increase in late autumn, which was concurrent with high rainfall, low wind speed associated with reduced hydrodynamism, and elevated sediment element levels. The bioaccumulation factor based on element concentrations in seagrass compartments and sediments was lower than 1 except for B, Ba, Mo, Se and Sr in all compartments, Cr in sheaths and U in roots. Blade V concentration positively correlated with sediment V concentration, suggesting that C. nodosa could be regarded as a bioindicator for V. Our findings can contribute to the design of biomonitoring programs and the development of predictive models for rational management of seagrass meadows.

Microtubule integrity and cell viability under metal (Cu, Ni and Cr) stress in the seagrass Cymodocea nodosa.

The effects of increasing Cu, Ni and Cr concentrations (0.5, 5, 10, 20 and 40 mg L(-1)) on microtubule organization and the viability of leaf cells of the seagrass Cymodocea nodosa for 13 consecutive days were investigated under laboratory conditions. Increased oblique microtubule orientation, microtubule depolymerization at the 5-40 mg L(-1) Ni treatments after 3 d of exposure, and a complete microtubule depolymerization at all Ni treatments after 5 d were observed. Cu depolymerised microtubules after three to 7 d of exposure, while Cr caused an extensive microtubule bundling after 9 or 11 d of exposure, depending on metal dosage. Fluorescence intensity measurements further consolidated the above phenomena. Cell death, occurring at later time than microtubule disturbance, was also observed at all Cu and Ni treatments and at the 10-40 mg L(-1) Cr treatments and adding to the above quantification of the number of dead cells clearly showed that only a portion of the cell population studied died. The data presented, being the first assessment of microtubule disturbance in seagrasses, indicate that microtubules in seagrass leaf cells could be used as a valuable and early marker of metal-induced stress in biomonitoring programmes.