Mud volcanoes and pockmarks are sites which methane and other gases seep out towards the overlyin... more Mud volcanoes and pockmarks are sites which methane and other gases seep out towards the overlying water. This supply and the microbiologically-mediated processes of these cold seeps can be the basis of unique microbial habitats. Although mud volcanoes and pockmarks vary in the seepage rate and chemical composition of their outflows, the communities found in geographically adjacent systems seem to harbor comparable microbial communities. For the East Mediterranean Sea, only sporadic data exist on its major mud volcanoes and pockmarks collected through a few oceanographic cruises; however, further the knowledge of these systems should be gained by microbiological and sequence-based investigations.
2. The Norway lobster Nephrops norvegicus, also known as Dublin bay prawn is a Decapod Crustacean... more 2. The Norway lobster Nephrops norvegicus, also known as Dublin bay prawn is a Decapod Crustacean of the Family Nephropidae that is widely distributed in silty areas, of the continental shelf and the upper continental slope, of the Northeast Atlantic and the Mediterranean Sea. The Norway lobster is a highly commercial species in the areas where it is found. Efforts for the commercial rearing of the species have not succeeded yet due to lack of knowledge on the nutritional habits of the species on rearing conditions and on its exact nutritional demands. 3. This thesis studied for the first time the gut bacterial diversity of Nephrops norvegicus. Studies were performed in natural and reared populations, where different food sources were provided. The project targeted in finding the factors that shape gut bacterial diversity and in detecting symbiotic, non toxic and non pathogenic bacterial species that can influence the digestive functions of N. norvegicus and could potentially be use...
The idea that 'everything is everywhere, but the environment selects' has been seminal in... more The idea that 'everything is everywhere, but the environment selects' has been seminal in microbial biogeography, and marine phytoplankton is one of the prototypical groups used to illustrate this. The typical argument has been that phytoplankton is ubiquitous, but that distinct assemblages form under environmental selection. It is well established that phytoplankton assemblages vary considerably between coastal ecosystems. However, the relative roles of compartmentalization of regional seas and site-specific environmental conditions in shaping assemblage structures have not been specifically examined. We collected data from coastal embayments that fall within two different water compartments within the same regional sea and are characterized by highly localized environmental pressures. We used principal coordinates of neighbour matrices (PCNM) and asymmetric eigenvector maps (AEM) models to partition the effects that spatial structures, environmental conditions and their overlap had on the variation in assemblage composition. Our models explained a high percentage of variation in assemblage composition (59–65%) and showed that spatial structure consistent with marine compartmentalization played a more important role than local environmental conditions. At least during the study period, surface currents connecting sites within the two compartments failed to generate sufficient dispersal to offset the impact of differences due to compartmentalization. In other words, our findings suggest that, even for a prototypical cosmopolitan group, everything is not everywhere.
One of the most widely reared fish in the Mediterranean Sea is Sparus aurata. The succession of S... more One of the most widely reared fish in the Mediterranean Sea is Sparus aurata. The succession of S. aurata whole-body microbiota in fertilized eggs, five, 15, 21 and 71 days post hatch (dph) larvae and the contribution of the rearing water and the provided feed (rotifers, Artemia sp. and commercial diet) to the host’s microbiota was investigated by 454 pyrosequencing of the 16S rRNA gene diversity. In total, 1917 bacterial operational taxonomic units (OTUs) were found in all samples. On average, between 93 ± 2.1 and 366 ± 9.2 bacterial OTUs per sample were found, with most of them belonging to Proteobacteria and Bacteroidetes. Ten OTUs were shared between all S. aurata stages and were also detected in the rearing water or diet. The highest OTU richness occurred at the egg stage and the lowest at the yolk sac stage (5 dph). The rearing water and diet microbial communities contributed in S. aurata microbiota without overlaps in their microbial composition and structure. The commercial ...
Canadian Journal of Fisheries and Aquatic Sciences, 2012
Trichodesmium erythraeum is a species of marine cyanobacteria that forms extensive blooms in trop... more Trichodesmium erythraeum is a species of marine cyanobacteria that forms extensive blooms in tropical and subtropical areas, predominantly in the Indian and Pacific oceans. An extensive bloom of this species, identified by microscopic and molecular analysis, is recorded for the first time at latitude greater than 30°N in Lesvos Island, Aegean Sea, eastern Mediterranean. Analysis of climatological trends revealed that the September 2010 bloom followed an extended period of the highest sea surface temperature and lowest wind speed observed since 1955, leading to a shallow thermocline formation. These conditions are considered among the main prerequisites for T. erythraeum bloom development. Analysis of abiotic parameters showed that other important factors for Trichodesmium proliferations, such as iron availability, oligotrophic conditions, and salinity levels, typical for the eastern Mediterranean, were also favourable. These findings seem directly linked to climate change already re...
Mud volcanoes and pockmarks are sites which methane and other gases seep out towards the overlyin... more Mud volcanoes and pockmarks are sites which methane and other gases seep out towards the overlying water. This supply and the microbiologically-mediated processes of these cold seeps can be the basis of unique microbial habitats. Although mud volcanoes and pockmarks vary in the seepage rate and chemical composition of their outflows, the communities found in geographically adjacent systems seem to harbor comparable microbial communities. For the East Mediterranean Sea, only sporadic data exist on its major mud volcanoes and pockmarks collected through a few oceanographic cruises; however, further the knowledge of these systems should be gained by microbiological and sequence-based investigations.
2. The Norway lobster Nephrops norvegicus, also known as Dublin bay prawn is a Decapod Crustacean... more 2. The Norway lobster Nephrops norvegicus, also known as Dublin bay prawn is a Decapod Crustacean of the Family Nephropidae that is widely distributed in silty areas, of the continental shelf and the upper continental slope, of the Northeast Atlantic and the Mediterranean Sea. The Norway lobster is a highly commercial species in the areas where it is found. Efforts for the commercial rearing of the species have not succeeded yet due to lack of knowledge on the nutritional habits of the species on rearing conditions and on its exact nutritional demands. 3. This thesis studied for the first time the gut bacterial diversity of Nephrops norvegicus. Studies were performed in natural and reared populations, where different food sources were provided. The project targeted in finding the factors that shape gut bacterial diversity and in detecting symbiotic, non toxic and non pathogenic bacterial species that can influence the digestive functions of N. norvegicus and could potentially be use...
The idea that 'everything is everywhere, but the environment selects' has been seminal in... more The idea that 'everything is everywhere, but the environment selects' has been seminal in microbial biogeography, and marine phytoplankton is one of the prototypical groups used to illustrate this. The typical argument has been that phytoplankton is ubiquitous, but that distinct assemblages form under environmental selection. It is well established that phytoplankton assemblages vary considerably between coastal ecosystems. However, the relative roles of compartmentalization of regional seas and site-specific environmental conditions in shaping assemblage structures have not been specifically examined. We collected data from coastal embayments that fall within two different water compartments within the same regional sea and are characterized by highly localized environmental pressures. We used principal coordinates of neighbour matrices (PCNM) and asymmetric eigenvector maps (AEM) models to partition the effects that spatial structures, environmental conditions and their overlap had on the variation in assemblage composition. Our models explained a high percentage of variation in assemblage composition (59–65%) and showed that spatial structure consistent with marine compartmentalization played a more important role than local environmental conditions. At least during the study period, surface currents connecting sites within the two compartments failed to generate sufficient dispersal to offset the impact of differences due to compartmentalization. In other words, our findings suggest that, even for a prototypical cosmopolitan group, everything is not everywhere.
One of the most widely reared fish in the Mediterranean Sea is Sparus aurata. The succession of S... more One of the most widely reared fish in the Mediterranean Sea is Sparus aurata. The succession of S. aurata whole-body microbiota in fertilized eggs, five, 15, 21 and 71 days post hatch (dph) larvae and the contribution of the rearing water and the provided feed (rotifers, Artemia sp. and commercial diet) to the host’s microbiota was investigated by 454 pyrosequencing of the 16S rRNA gene diversity. In total, 1917 bacterial operational taxonomic units (OTUs) were found in all samples. On average, between 93 ± 2.1 and 366 ± 9.2 bacterial OTUs per sample were found, with most of them belonging to Proteobacteria and Bacteroidetes. Ten OTUs were shared between all S. aurata stages and were also detected in the rearing water or diet. The highest OTU richness occurred at the egg stage and the lowest at the yolk sac stage (5 dph). The rearing water and diet microbial communities contributed in S. aurata microbiota without overlaps in their microbial composition and structure. The commercial ...
Canadian Journal of Fisheries and Aquatic Sciences, 2012
Trichodesmium erythraeum is a species of marine cyanobacteria that forms extensive blooms in trop... more Trichodesmium erythraeum is a species of marine cyanobacteria that forms extensive blooms in tropical and subtropical areas, predominantly in the Indian and Pacific oceans. An extensive bloom of this species, identified by microscopic and molecular analysis, is recorded for the first time at latitude greater than 30°N in Lesvos Island, Aegean Sea, eastern Mediterranean. Analysis of climatological trends revealed that the September 2010 bloom followed an extended period of the highest sea surface temperature and lowest wind speed observed since 1955, leading to a shallow thermocline formation. These conditions are considered among the main prerequisites for T. erythraeum bloom development. Analysis of abiotic parameters showed that other important factors for Trichodesmium proliferations, such as iron availability, oligotrophic conditions, and salinity levels, typical for the eastern Mediterranean, were also favourable. These findings seem directly linked to climate change already re...
We analyzed the bacterial and archaeal community structure of two adjacent
irrigation well waters... more We analyzed the bacterial and archaeal community structure of two adjacent irrigation well waters of the Lake Karla Basin, Central Greece, in order to elucidate their connectivity or confinement by using 454 tag pyrosequencing of the 16S rRNA genes. Although considerable overlap was found at the phylum/high taxonomic level, and also at the operational taxonomic units (OTU) level, the dominant, and most likely active, prokaryotes represented by these OTUs were very different between the two wells. As expected, we found higher bacterial species richness compared to that of archaeal, and this renders Bacteria better for the study of connectivity or confinement of water wells. Some of the taxonomic groups found are amongst those found typically in the terrestrial subsurface and also those that have been recently described, enhancing the importance of the subsurface for expanding our knowledge on microbial diversity. The majority of the archaeal and several of the bacterial OTUs, including the most dominant ones in each well, were related to marine or saline environments, indicating the previously suggested persistence of fertilizer residuals in the basin’s soils.
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Papers by Alexandra Meziti
irrigation well waters of the Lake Karla Basin, Central Greece, in order to elucidate their
connectivity or confinement by using 454 tag pyrosequencing of the 16S rRNA genes.
Although considerable overlap was found at the phylum/high taxonomic level, and also at
the operational taxonomic units (OTU) level, the dominant, and most likely active,
prokaryotes represented by these OTUs were very different between the two wells. As
expected, we found higher bacterial species richness compared to that of archaeal, and this
renders Bacteria better for the study of connectivity or confinement of water wells. Some
of the taxonomic groups found are amongst those found typically in the terrestrial
subsurface and also those that have been recently described, enhancing the importance of
the subsurface for expanding our knowledge on microbial diversity. The majority of the
archaeal and several of the bacterial OTUs, including the most dominant ones in each well,
were related to marine or saline environments, indicating the previously suggested
persistence of fertilizer residuals in the basin’s soils.