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Polymenakou P.N.,Hellenic Center for Marine Research

The atmosphere has been described as one of the last frontiers of biological exploration on Earth. The composition of microbial communities in the atmosphere is still not well-defined, and taxonomic studies of bacterial diversity in the outdoor air have just started to emerge, whereas our knowledge about the functional potential of air microbiota is scant. When in the air, microorganisms can be attached to ambient particles and/or incorporated into water droplets of clouds, fog, and precipitation (i.e., rain, snow, hail). Further, they can be deposited back to earth's surfaces via dry and wet deposition processes and they can possibly induce an effect on the diversity and function of aquatic and terrestrial ecosystems or impose impacts to human health through microbial pathogens dispersion. In addition to their impact on ecosystem and public health, there are strong indications that air microbes are metabolically active and well adapted to the harsh atmospheric conditions. Furthermore they can affect atmospheric chemistry and physics, with important implications in meteorology and global climate. This review summarizes current knowledge about the ubiquitous presence of microbes in the atmosphere and discusses their ability to survive in the atmospheric environment. The purpose is to evaluate the atmospheric environment as a source of pathogenic or beneficial microbes and to assess the biotechnological opportunities that may offer. © 2012 by the authors. Source

The number of marine alien species reported in Galil (Biol Invasions, 2009) is incomplete. Recent literature suggests that the number of aliens is nearly 1,000 and that the introduction rate is way off the 10 species per year suggested by Galil (Biol Invasions, 2009). © 2010 Springer Science+Business Media B.V. Source

Kontoyiannis H.,Hellenic Center for Marine Research
Journal of Geophysical Research: Oceans

The Saronikos Gulf three-dimensional flow structure is mapped by objective analysis in 12 acoustic Doppler current profiler surveys (4 seasonal surveys per period for the periods May 1998-May 1999, May 2000-May 2001, May 2003-May 2004) under various winds. Robust seasonal flows throughout the Gulf are basically induced by thermohaline effects (winter water subduction, different responses to atmospheric heating of shallow and deeper areas of the Gulf) and density contrasts with inflowing Aegean waters. Inner Gulf observations show that the seasonal flows are modified by the wind, while recurrent structures (cyclonic and anticyclonic) appear between the seasonal flows and the coast of Attica. In summer an anticyclonic and a cyclonic flow exists throughout the Gulf above and below the pycnocline, respectively, with a jet observed to meander within the Inner Gulf. In winter and early spring an anticyclonic flow prevails in the upper ∼100 m. In late spring-early summer cyclonic and anticyclonic flow occurs in the upper (∼0-40 m) and deeper (∼60-100 m) layers, respectively. The predominant northerly winds in summer and winter push the Inner Gulf eastward seasonal jet to the south and favor the formation of a recurrent cyclonic upwelling structure between this jet and Attica. Northwesterly, westerly, and southerly winds favor the northward meandering of the seasonal jet in the Inner Gulf and no recurrent structures appear in the limited space between this jet and Attica. In the southeast area of the Inner Gulf, the wind-driven flow fluctuations at 30 m have time scales of 3.5-4 days. Observed meandering period is ∼13 days; meandering characteristics are close to instability predictions. Time scales of flows due to recurrent structures are ∼8 days. Copyright 2010 by the American Geophysical Union. Source

Chronis T.G.,Hellenic Center for Marine Research
Journal of Geophysical Research: Atmospheres

The first Precision Lightning Network, monitoring the Cloud-to-Ground (CG) lightning stroke activity over Greece and surrounding waters is operated and maintained by the Hellenic National Meteorological Service. This paper studies the regional (land/water interface), seasonal and diurnal variability of the CG strokes as a function of density, polarity and peak current. Additional investigation uniquely links the CG stroke current to sea surface salinity and cloud electrical capacitance. In brief, this study's major findings area as follows: (1) The seasonal maps of thunder days agree well with the regional climatic convective characteristics of the study area, (2) the CG diurnal variability is consistent with the global lightning activity observations over land and ocean, (3) the maxima of monthly averaged CG counts are located over land and water during typical summer and fall months respectively for both polarities, (4) CG peak currents show a distinct seasonality with larger currents during relatively colder months and smaller currents during summer months, and (5) strong linear trends between -CGs and sea surface salinity; (6) this trend is absent for +CGs data analysis of the employed database relate to the thunderstorm's RC constant and agrees with previous numerical modeling studies. Copyright 2012 by the American Geophysical Union. Source

Simboura N.,Hellenic Center for Marine Research
Environmental monitoring and assessment

An analysis of the results of the 12-year regular monitoring (2000-2012) of benthic communities in Saronikos Gulf and Elefsis Bay (Eastern Mediterranean, Greece) in relation to the functioning of the Psittalia Wastewater Treatment Plant (WWTP) and advances in treatment is presented. Benthic community indicators applied include the Bentix index adopted for the implementation of the Water Framework Directive (WFD); the diversity and species richness proposed in combination with the Bentix index for the evaluation of certain attributes of the Sea-floor Integrity descriptor for the marine waters of Greece, under the Marine Strategy Framework Directive (MSFD), and the evenness index. The benthic and environmental data were treated according to the distance from the outfall, largely accounting for the variance of the indicators, to investigate trends along the monitoring. Results showed an upgrade of the condition of the benthic communities of Saronikos Gulf throughout the monitoring period mostly demonstrated by the Bentix and diversity indices. A change in the trends of most indices was especially evident after 2004, especially in the areas more adjacent to the outfall zones, when the advanced secondary biological treatment plant was completed and commissioned. Sediment parameters' trend patterns indicate a delayed reaction to recovery processes in relation to benthic indices. An evaluation of the current status of the benthic communities based on the indices applied showed a gradient from a moderate ecological status at stations up to a distance of 8,000 m from the outfalls to good environmental and ecological status at more remote stations. At shallower stations located at a distance of more than 4,000 m from the outfall, benthic communities also present good environmental status. In Elefsis Bay, the enclosed physiography, shallower depth and local pressures result in more adverse environmental conditions for benthic communities and a more complex influence from WWTP advances. Source

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