Chemical Composition and Microstructural Morphology of Spines and Tests of Three Common Sea Urchins Species of the Sublittoral Zone of the Mediterranean Sea

In the Mediterranean Sea, the species Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis often coexist, occupying different subareas of the same habitat. The mechanical and chemical properties of their calcitic skeletons are affected both by their microstructural morphology and chemical composition. The present study describes the main morphologic features and the possible temporal differences in elemental composition of the test and spines of the three species, while also determining the molar ratio of each element of their crystalline phase. Scanning electron microscopy showed major differences in the ultrastructure of the spines, while minor differences in the test were also noticed. More specifically, the spines of all three sea urchins possess wedges, however A. lixula exhibits bridges connecting each wedge, while barbs are observed in the wedges of S. granularis. The spines of P. lividus are devoid of both microstructures. Secondary tubercles are absent in the test of A. lixula, while the tests and spines of all three species are characterized by different superficial stereom. Energy dispersive x-ray spectroscopy detected that Ca, Mg, S, Na and Cl were present in all specimen. Mg and Mg/Ca showed significant differences between species both in test and spines with S. granularis having the highest concentration. The spines of P. lividus exhibited lowest values between all species. Differences between spines and test were observed in all elements for P. lividus except S. A. lixula exhibited different concentrations between test and spines for Ca, Mg and Mg/Ca, whereas S. granularis for Mg, Cl and Mg/Ca. Finally, temporal differences for Ca were observed in the test of P. lividus and the spines of S. granularis, for Mg in test of S. granularis, for S in the spines of A. lixula and the test and spine of S. granularis, for Na in the test of P. lividus and A. lixula and for Cl and Mg/Ca in the test P. lividus. Powder X-ray diffractometry determined that, out of all three species, the spines of P. lividus contained the least Mg, while the test of the same species exhibited higher Mg concentration compared to A. lixula and S. granularis. The current study, although not labeling the specimens attempts to estimate potential time-related elemental differences among other results. These may occur due to changes in abiotic factors, probably water temperature, salinity and/or pH. Divergence in food preference and food availability may also play a key role in possible temporal differences the skeletons of these specie

High resolution geophysical imaging of buried relics in itanos archaeological site

Summarization: Non-invasive high-resolution geophysical techniques, such as ground penetrating radar (GPR), electrical tomography and seismics, have been applied in archaeological investigations during a geophysical survey, which took place in the archaeological site of Itanos in Greece. The main objective of survey was to delineate the remains of buried relics in selected areas by combining these high-resolution geophysical methods. Three sets of GPR antennas were employed to achieve optimal system performance. GPR time slices, presented in a series of maps and electrical tomography resistivity sections revealed features at different depths related to soil resistance and magnetic gradient anomalies, attributed to buried relics of building walls. In particular, in the ancient harbor compatible results were obtained from seismic refraction, surface waves, GPR, electrical tomography and other geophysical methods, indicating that the depth to the bedrock is varying from 2 to 10 m.Presented on

Mechanical defensive adaptations of three Mediterranean sea urchin species

Summarization: In the Mediterranean, Paracentrotus lividus and Sphaerechinus granularis are important drivers of benthic ecosystems, often coexisting in sublittoral communities. However, the introduction of the invasive diadematoid Diadema setosum, which utilizes venomous spines, may affect these communities. To describe the mechanical properties of the test and spines of these three species, specimens were collected in winter of 2019 from the sublittoral zone of the Dodecanese island complex, southeastern Aegean Sea. This region serves as a gateway for invasive species to the Mediterranean Sea. Crushing test was conducted on live individuals, while 3-point bending test was used to estimate spine stiffness. Porosity and mineralogy of the test and spine, thickness of the test, and breaking length of the spine were measured and compared, while the microstructural architecture was also determined. The test of S. granularis was the most robust (194.35 ± 59.59 N), while the spines of D. setosum (4.76 ± 2.13 GPa) exhibited highest flexibility. Increased porosity and thickness of the test were related to increased robustness, whereas increased flexibility of the spine was attributed to high porosity, indicating that porosity in the skeleton plays a key role in preventing fracture. The spines of S. granularis exhibited highest length after fracture % (71.54 ± 5.5%). D. setosum exhibited higher values of Mg concentration in the test (10%) compared with the spines (4%). For the first time, the mineralogy of an invasive species is compared with its native counterpart, while a comparison of the mechanical properties of different species of the same ecosystem also takes place. This study highlights different ways, in which sea urchins utilize their skeleton and showcases the ecological significance of these adaptations, one of which is the different ways of utilization of the skeleton for defensive purposes, while the other is the ability of D. setosum to decrease the Mg % of its skeleton degrading its mechanical properties, without compromising its defense, by depending on venomous bearing spines. This enables this species to occupy not only tropical habitats, where it is indigenous, but also temperate like the eastern Mediterranean, which it has recently invaded.Presented on: Ecology and Evolutio

Chemical composition and microstructural morphology of spines and tests of three common sea urchins species of the sublittoral zone of the Mediterranean Sea

Summarization: In the Mediterranean Sea, the species Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis often coexist, occupying different subareas of the same habitat. The mechanical and chemical properties of their calcitic skeletons are affected both by their microstructural morphology and chemical composition. The present study describes the main morphologic features and the possible temporal differences in elemental composition of the test and spines of the three species, while also determining the molar ratio of each element of their crystalline phase. Scanning electron microscopy showed major differences in the ultrastructure of the spines, while minor differences in the test were also noticed. More specifically, the spines of all three sea urchins possess wedges, however A. lixula exhibits bridges connecting each wedge, while barbs are observed in the wedges of S. granularis. The spines of P. lividus are devoid of both microstructures. Secondary tubercles are absent in the test of A. lixula, while the tests and spines of all three species are characterized by different superficial stereom. Energy dispersive x-ray spectroscopy detected that Ca, Mg, S, Na and Cl were present in all specimen. Mg and Mg/Ca showed significant differences between species both in test and spines with S. granularis having the highest concentration. The spines of P. lividus exhibited lowest values between all species. Differences between spines and test were observed in all elements for P. lividus except S. A. lixula exhibited different concentrations between test and spines for Ca, Mg and Mg/Ca, whereas S. granularis for Mg, Cl and Mg/Ca. Finally, temporal differences for Ca were observed in the test of P. lividus and the spines of S. granularis, for Mg in test of S. granularis, for S in the spines of A. lixula and the test and spine of S. granularis, for Na in the test of P. lividus and A. lixula and for Cl and Mg/Ca in the test P. lividus. Powder X-ray diffractometry determined that, out of all three species, the spines of P. lividus contained the least Mg, while the test of the same species exhibited higher Mg concentration compared to A. lixula and S. granularis. The current study, although not labeling the specimens attempts to estimate potential time-related elemental differences among other results. These may occur due to changes in abiotic factors, probably water temperature, salinity and/or pH. Divergence in food preference and food availability may also play a key role in possible temporal differences the skeletons of these speciesΠαρουσιάστηκε στο: Animal

Χαρτογραφική απεικόνιση καταλληλότητας εδαφών στην περιοχή Βασιλείων του Ν. Ηρακλείου, στα πλαίσια του γενικού πολεοδομικού σχεδιασμού

Περίληψη: Σκοπός της έρευνας αυτής αποτέλεσε η οριοθέτηση και χαρτογραφική απεικόνιση δι- αβαθμισμένων εδαφών ως προς την καταλληλότητα τους για ασφαλή δόμηση στην περι- οχή Βασιλειών, στο πλαίσιο της εκπόνησης Μελέτης Γενικού Πολεοδομικού Σχεδιασμού του Πολεοδομικού συγκροτήματος Ηρακλείου. Γεωμετρικού τύπου δεδομένα, (κλίσεις και παρατάξεις στρωμάτων και επιφανειών ασυνέχειας), δεδομένα που προέκυψαν από την στατιστική επεξεργασία μεσοσκοπικών τεκτονικών στοιχείων (ροδογράμματα), δε- δομένα από παρατηρήσεις πεδίου καθώς και από την επεξεργασία αεροφωτογραφιών (τα όρια των γεωλογικών σχηματισμών), καθώς επίσης και τα ερμηνευμένα στοιχεία των γε- ωφυσικών διασκοπήσεων απεικονίστηκαν σε χάρτες, με χρήση του υπάρχοντος τοπογρα- φικού υποβάθρου της περιοχής σε κλίμακα 1:5.000. Από την συνδυασμένη ερμηνεία των στοιχείων των χαρτών αυτών προέκυψε μια τελική χαρτογραφική απεικόνιση, που περιέ- χει τις οριοθετιμένες περιοχές διαβαθμισμένων εδαφών ως προς την καταλληλότητα τους για ασφαλή δόμηση.Παρουσιάστηκε στο: 8ο Εθνικό Συνέδριο Χαρτογραφίας - Η χαρτογραφία του ευ ζη

Definition of inferred faults using 3d geological modeling techniques: a case study in Tympaki basin in Crete, Greece

Summarization: The purpose of this paper is to recognize inferred faults in Tympaki basin (Crete is-land) which cannot be observed on the surface, as the area is covered by recent de-posits. The identification of the faults is crucial for the study of the sea-water intrusion in Tympaki basin that has been observed during the last years. 3D geological modelling techniques were used for reaching the aforementioned goal. The data used include the digital elevation model (DEM) of the area, the boundary surface between geologic formations and the litho - stratigraphic logs of thirty nine (39) wells. Initially a 3D stratigraphic model was set-up depicting the spatial extension of Plio-Quaternary and Neogene deposits. Next, with emphasis on the litho - stratigraphic logs of the wells, the boundary between the geological formations was defined in a 3D space. The regional unconformity between the Plio-Quaternary and Neogene formations is possibly the result of tectonic activity of inferred faults. The traces of the inferred faults were drawn and they were compared with the faults suggested by previous studies.Παρουσιάστηκε στο: 13th International Congres

Estimating Soil Clay Content Using an Agrogeophysical and Agrogeological Approach: A Case Study in Chania Plain, Greece

Thorough knowledge of soil lithology and its properties are of considerable importance to agriculture. These parameters have a direct impact on water permeability and the content of the water in soil, which represent significant factors in crop yield, decisively determining the design of irrigation systems and farming processes. In the framework of this study, and considering the inevitable impacts of climate change, the rational management of water resources and the optimization of irrigation through innovative technologies become of significant importance. Thus, we propose an interdisciplinary approach based on robust techniques from the allied fields of earth (geological mapping, geophysical methods) and soil sciences (sampling, mechanical analysis) assisted by statistics and GIS techniques. Clay or the sum of clay and silt soil content is successfully determined from the normalized chargeability using induced polarization and electrical resistivity techniques. Finally, we distinguished three classes (S1, S2 and S3) considering the clay or the sum of clay and silt soil content in the study area (a) based on the dry period geophysical data and (b) using as classification criterion the spatial distribution of the geological formations

Imaging sand dunes at Kedrodasos coastal area, Crete, Greece

Μη διαθέσιμη περίληψηNot available summarizationPresented on

Contribution of the electrical tomography in the protection of tradiotional wells at Mirabello , eastern Crete

Summarization: This paper focuses on the use of geological and geophysical tools in order to contribute in creating a cultural route from the town of Neapoli to the coastal areas, through the cisterns of Epano Mirabello, Eastern Crete. The first stage of this study involves the restoration and use of the threatened traditional wells and cisterns. In order to achieve this, a detailed geological mapping of the area and a geoelectrical survey were conducted to estimate the thickness of the soil layer (impermeable substrates). The methodology used in this paper provided valuable information regarding the subsoil condition and the sources of the cisterns' water supply system, helping in the proper planning of the cultural route.Παρουσιάστηκε στο: Protection and restoration of the environment X