Identifying key environmental variables structuring benthic fauna for establishing a biotic typology for Greek running waters

A central aspect of the Water Framework Directive 2000/60/EC addressed to Member Countries is to proceed to type-specific ecological assessment and classification by establishing typology systems. Sixty-four permanent stream sites distributed throughout mainland Greece and islands were assessed with macroinvertebrate indicators to evaluate their ecological quality. Local and catchment scale parameters were determined and recorded to obtain an integrated assessment of the main factors affecting stream integrity and macroinvertebrate communities. Twenty-three sites were classified as reference or good status in terms of biological, chemical and hydromorphological quality with the use of various metrics. Multivariate statistical techniques were performed (MDS, BIOENV, correlation analysis and PCA) to investigate the main environmental factors structuring benthic macroinvertebrate communities and to select candidate environmental variables for establishing a biotic typology for Hellenic rivers. The results revealed relatively distinct macroinvertebrate communities within defined abiotic zones of the country. Assemblages of macroinvertebrate fauna were most strongly associated to differences in geographical position, altitude, slope, catchment area, current velocity, conductivity and water temperature. In view of the lack of sufficient data at the country level on the three last variables and after considering cause-effect relationships between large scale variables and the latter, it has been demonstrated that a number of catchment scale variables could be used as robust surrogates.     

Improving Bayesian analysis for LISA Pathfinder using an efficient Markov Chain Monte Carlo method

We present a parameter estimation procedure based on a Bayesian framework by applying a Markov Chain Monte Carlo algorithm to the calibration of the dynamical parameters of the LISA Pathfinder satellite. The method is based on the Metropolis-Hastings algorithm and a two-stage annealing treatment in order to ensure an effective exploration of the parameter space at the beginning of the chain. We compare two versions of the algorithm with an application to a LISA Pathfinder data analysis problem. The two algorithms share the same heating strategy but with one moving in coordinate directions using proposals from a multivariate Gaussian distribution, while the other uses the natural logarithm of some parameters and proposes jumps in the eigen-space of the Fisher Information matrix. The algorithm proposing jumps in the eigen-space of the Fisher Information matrix demonstrates a higher acceptance rate and a slightly better convergence towards the equilibrium parameter distributions in the application to LISA Pathfinder data. For this experiment, we return parameter values that are all within ～1σ of the injected values. When we analyse the accuracy of our parameter estimation in terms of the effect they have on the force-per-unit of mass noise, we find that the induced errors are three orders of magnitude less than the expected experimental uncertainty in the power spectral density.     

Assessing water stress in Mediterranean lotic systems: insights from an artificially intermittent river in Greece

Water stress in Mediterranean countries is the result of both variable and changing climatic conditions and widespread anthropogenic pressures. Evrotas, an intermittent river located in Southern Greece, was used as a case study to assess the impacts of water stress on Mediterranean lotic ecosystems. Based on hydrological analyses, it was revealed that during prolonged drought years, such as the summers of 2007 and 2008, the vast majority of the Evrotas riverbed was completely desiccated, primarily as a result of substantial water abstraction for irrigation. The effects of desiccation on the riverine ecosystem were evaluated using fish and macroinvertebrate assemblages according to the demands of the Water Framework Directive 2000/60/EC (WFD). Faunal responses to water stress were assessed through comparisons of assemblages attributes in perennial and intermittent reaches and pre-drought versus post-drought communities. Effects of hydrological disturbance on fish species richness, density, percentage composition and size structure were more pronounced in intermittent than in perennial sites. The most obvious and immediate impact was the elimination of populations in the intermittent reaches. However, upon flow resumption, the recolonisation from upstream perennial reaches began, thereby permitting partial re-establishment of the depleted fish communities. Nevertheless, the structural integrity of fish communities remained severely impacted and recovery was markedly slow. On the contrary, post-drought macroinvertebrate assemblages were not affected by summer droughts, and the recruitment processes were rapid after flow resumption. Our findings point to the necessity of establishing a distinction between naturally and artificially driven intermittent rivers. We, therefore, propose the introduction of an “artificially intermittent Mediterranean river” condition within the context of the WFD assessment applications.     

Identification of hydrologic and geochemical pathways using high frequency sampling,REE aqueous sampling and soil characterization at Koiliaris Critical Zone Observatory,Crete

Koiliaris River watershed is a Critical Zone Observatory that represents severely degraded soils due to intensive agricultural activities and biophysical factors. It has typical Mediterranean soils under the imminent threat of desertification which is expected to intensify due to projected climate change. High frequency hydro-chemical monitoring with targeted sampling for Rare Earth Elements (REE) analysis of different water bodies and geochemical characterization of soils were used for the identification of hydrologic and geochemical pathways. The high frequency monitoring of water chemical data highlighted the chemical alterations of water in Koiliaris River during flash flood events. Soil physical and chemical characterization surveys were used to identify erodibility patterns within the watershed and the influence of soils on surface and ground water chemistry. The methodology presented can be used to identify the impacts of degraded soils to surface and ground water quality as well as in the design of methods to minimize the impacts of land use practices.     

A multisource approach for coastal mapping purposes: Limeni bay,Mani and surrounding area,southern Greece

A multipurpose engineering geological map of a natural heritage site including inland and offshore areas has been compiled to provide information on many aspects for land use optimization, sustainable development and environmental protection. The mapping approach was based on data provided by conventional onland field works, marine remote sensing survey and aerial photo interpretation. These data sources were integrated into a GIS platform allowing reliable mapping solutions. The geological formations encountered were grouped into individual geotechnical units according to uniformity in lithological character, while the seabed sub-bottom structure was also obtained through several seafloor thematic map compilation. Shoreline variability and evolution for a long time period (1945–2008) were also investigated and mapped. The synergistic use of the results deducted from those disciplinary surveys is finally presented in a single engineering geological map covering the onshore and offshore area.     

Neotectonic evolution of northwestern-continental Greece

The post-Miocene sedimentary and structural evolution of NW-continental Greece changes from west to east.In the west, along the Ionian coast, the tectonic activity of the Mio-Pliocene marine sedimentation is reflected in olisthostromes and intrafoliated folds. During the emergence of the area at the Pliocene/Pleistocene boundary, low angle thrusting, dissolution cleavage and open NNW to NNE trending folds, were developed. This horizontal shortening is the result of active plate convergence between the Apulian plate and the Aegean plate. Subsequent vertical movements continuing till the precent, produces mainly NNW and ENE directed faults.In the east, between the Ionian coast and Pindus thrust, nonmarine sedimentation began, in the middle Pliocene, on a folded and partially eroded substratum. Long fault bounded intramountaneous basins formed during general uplift and extension in three directions: NNW, ENE and WNW. Extension in both areas, resulting from NNW and ENE faults, is interpreted in terms of the action of upwelling convective currents induced by the Hellenic subduction. As the Aegean back arc extension migrated slowly westwards, the whole study area was gradually affected by WNW trending grabens.

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Zusammenfassung Spätmiozäne Sedimentationsprozesse sowie strukturelle Entwicklung ändern sich in NW kontinental-Griechenland in E-W Richtung.An der Ionischen Küste wurden während der spätmiozänen Absenkung des Sedimentationsraumes mächtige Olisthostrome und intrafoliale Falten gebildet. An der Grenze des Plio/Pleistozäns wurden flache überschiebungen, Lösungsschieferung und NNW bis NNE streichende, geöffnete Falten entwickelt. Diese tektonische Strukturen sind das Ergebnis aktiver Plattenkonvergenz zwischen der apulischen lithosphären-Platte und der ägäischen Platte. Während der postorogenen Aufhebung sind NNW und ENE streichende Verwerfungen entstanden.Im mittleren Pliozän wurden im Raum zwischen Ionischem Meer und der Pindos überschiebung auf dem gefalteten und teilweise erodierten Untergrund vorwiegend limnisch-terrestrische Sedimente abgelagert. Während der postorogenen Ausweitung sind Absenkungsräume in NNW- und ENE Richtung entstanden. Sie sind vermutlich das Ergebnis von Konvektionsströmungen innerhalb der Asthenosphäre, die durch die Hellenische Subduktion hervorgerufen wurden.Die Krustenausdehnung im ägäischen »back-arc basin« hat sich kontinuierlich gegen Westen verlagert, so da\ West-Griechenland zusätzlich von WNW streichenden Grabenstrukturen weitgehend deformiert ist.

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Résumé La partie nord-occidentale de la Grèce continentale montre, d'est en ouest, une modification des processus sédimentaires et structuraux.A l'ouest, le long de la cÔte ionienne, la sédimentation marine subsidente tardi-miocène s'est accompagnée de puissants olisthostromes et de plis intrafoliaux. La limite Pliocène-Pleistocène a vu se développer des charriages peu inclinés et des plis ouverts NNE à NNW accompagnés d'une schistosité de dissolution. Ce raccourcissement horizontal est le résultat de la convergence des plaques apulienne et égéenne. Il a été suivi de mouvements subséquents verticaux, encore actifs aujourd'hui, responsables de failles de directions NNW et ENE.Plus à l'est, entre la cÔte ionienne et le charriage du Pinde, une sédimentation continentale s'est installée, au Pliocène moyen, sur le substratum plissé et partiellement érodé. Au cours du soulèvement post-orogénique, des bassins intramontagneux de grabens se sont formés selon trois directions: NNW, ENE et WNW. Les deux premières sont interprétées comme le résultat de courants de convection induits dans l'asthénosphère par la subduction hellénique. Les grabens WNW seraient en relation avec le déplacement progressif vers l'ouest de la zone d'extension crustale du bassin d'arrière-arc égéen.

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