Exotic Halophila stipulacea is an introduced carbon sink for the Eastern Mediterranean Sea

Carbon and nitrogen storage in exotic Halophila stipulacea were compared to that in native Posidonia oceanica and Cymodocea nodosa meadows and adjacent unvegetated sediments of the Eastern Mediterranean Sea and to that in native H. stipulacea of the Red Sea at sites with different biogeochemical conditions and level of human pressure. Exotic H. stipulacea possessed considerable storing capacity, with 2-fold higher Corg stock (0.71 ± 0.05 kg m−2 in the top 20 cm of sediment) and burial (14.78 gCorg m−2 y−1) than unvegetated areas and C. nodosa meadows and, surprisingly, comparable to P. oceanica. N (0.07 ± 0.01 kg m−2) and Cinorg (14.06 ± 8.02 kg m−2) stocks were similar between H. stipulacea and C. nodosa or unvegetated sediments, but different to P. oceanica. Corg and N stocks were higher in exotic than native H. stipulacea populations. Based on isotopic mixing model, organic material trapped in H. stipulacea sediments was mostly allochthonous (seagrass detritus 17% vs seston 67%). Corg stock was similar between monospecific and invaded C. nodosa meadows by H. stipulacea. Higher stocks were measured in the higher human pressure site. H. stipulacea introduction may contribute in the increase of carbon sequestration in the Eastern Mediterranean

Seeking the factors to stimulate the users in coastal zones planning. Case study: Open discussions with mussel farmers in the Axios river (GR)

In the framework of an integrated coastal zone management, the involvement of users is required and “open discussions” is one of the techniques used for their participation. The authors used this technique during a project for the sustainable development of mussel-culture in the coastal zone of the Axios Delta. Open discussion contributed to the acceptance of the scientific results by the users of the aquatic environment (mussel-farmers) who addressed trade-offs in their own way. The majority of their arguments were incorporated in the formation of the management rules, presented in the final report of this project. The present paper summarizes this experience as well as the existing ways for the involvement of users in a decision planning process and demonstrates how open discussion is a prerequisite factor for the success of sustainable development planning in Greece

Distribution of dissolved inorganic carbon and related parameters in the Thermaikos Gulf (Eastern Mediterranean)

Data on the distribution of dissolved inorganic carbon (measured as TCO2) and related parameters in the Thermaikos Gulf were obtained during May 1997. High TCO2 concentrations were recorded close to the bottom, especially in the northern part of the gulf, as a result of organic matter remineralisation. The positive relatively good correlation between TCO2 and both apparent oxygen utilisation (AOU) and phosphate at the last sampling depth confi rmed the regenerative origin of a large proportion of TCO2. The comparatively conservative behaviour of alkalinity, together with the relatively low value of the homogenous buffer factor β (β = ∂lnfCO2/∂lnTCO2) revealed that calcifi cation or carbonate dissolution takes place on a very small scale, simultaneously with the organic carbon production. The correlations between fCO2 and chlorophyll α, as well as AOU and the surface temperature, revealed that the carbon dioxide fi xation through the biological activity is the principal factor that modulates the variability of fCO2. A rough first estimate of the magnitude of the air-sea CO2 exchange and the potential role of the Thermaikos Gulf in the transfer of atmospheric CO2 was also obtained. The results showed that during May 1997, the Thermaikos Gulf acted as a weak sink for atmospheric CO2 at a rate of -0.60 - -1.43 mmol m-2 d-1, depending on which formula for the gas transfer velocity was used, and in accordance to recent reports regarding other temperate continental shelves. Extensive study of the dissolved inorganic carbon and related parameters, and continuous shipboard measurements of fCO2 a and fCO2 w during all seasons are necessary to safely quantify the role of the Thermaikos Gulf in the context of the coastal margins CO2 dynamics

The presence of (NRPS) and (PKS) genes at the deepsea hydrothermal field in the Aegean Sea

Deep-sea hydrothermal vents are characterized by extremely high concentrations of microorganisms in stark contrast to the surrounding sea bottom. Nevertheless, deepsea consumers do not rapidly remove the high biomass of prey from these communities maybe due to vent microbes’ chemical defenses which still remain largely unknown. Meanwhile, the detection of genes responsible for antimicrobial and cytotoxic activity such as non-ribosomal peptide synthases (NRPS) and polyketide (PKS) of deep-sea vent bacteria has not so far been attempted

Signs of low frequency dispersions in disordered binary dielectric mixtures (50-50)

Dielectric relaxation in disordered dielectric mixtures are presented by emphasizing the interfacial polarization. The obtained results coincide with and cause confusion with those of the low frequency dispersion behavior. The considered systems are composed of two phases on two-dimensional square and triangular topological networks. We use the finite element method to calculate the effective dielectric permittivities of randomly generated structures. The dielectric relaxation phenomena together with the dielectric permittivity values at constant frequencies are investigated, and significant differences of the square and triangular topologies are observed. The frequency dependent properties of some of the generated structures are examined. We conclude that the topological disorder may lead to the normal or anomalous low frequency dispersion if the electrical properties of the phases are chosen properly, such that for ``slightly'' {\em reciprocal mixture}--when $\sigma_1\gg\sigma_2$, and $\epsilon_1<\epsilon_2$--normal, and while for ``extreme'' {\em reciprocal mixture}--when $\sigma_1\gg\sigma_2$, and $\epsilon_1\ll\epsilon_2$--anomalous low frequency dispersions are obtained. Finally, comparison with experimental data indicates that one can obtain valuable information from simulations when the material properties of the constituents are not available and of importance.Comment: 13 pages, 7 figure

Measurements of biochemical markers of pollution in mussels Mytilus galloprovincialis from coastal areas of the Saronikos Gulf (Greece)

Alterations in a number of biochemical parameters in marine organisms represent specific markers of exposure to particular classes of contaminants. They are used as tools for the detection and monitoring of pollution. In this study, two biochemical markers of pollution, metallothionein (MT) content and acetylcholinesterase (AChE) activity were measured in indigenous and transplanted mussels Mytilus galloprovincialis from coastal areas within the Saronikos Gulf subject to high anthropogenic activities. Biannual measurements of the two biomarkers in indigenous mussel populations for two years revealed no significant differences among stations representing a pollution gradient. Limited differences in MT levels were only found between mussel populations transplanted at lesser and more impacted stations. Both biomarkers showed a variation with respect to the season of sampling, whilst during the second year of measurements a concomitant increase in metallothionein content with a decrease in acetylcholinesterase activity was noted. Our results indicate that the applied biochemical markers in indigenous mussel populations do not reflect the type of pollution in the Saronikos Gulf to a degree that can be used for pollution monitoring in the area