scholarly journals Spatial distribution of Bacteria and Archaea and amoA gene copy numbers throughout the water column of the Eastern Mediterranean Sea

2008 ◽  
Vol 3 (2) ◽  
pp. 147-158 ◽  
Author(s):  
Daniele De Corte ◽  
Taichi Yokokawa ◽  
Marta M Varela ◽  
Hélène Agogué ◽  
Gerhard J Herndl
Keyword(s):  
Spatial Distribution ◽  
Mediterranean Sea ◽  
Water Column ◽  
Eastern Mediterranean ◽  
Amoa Gene ◽  
Gene Copy ◽  
Eastern Mediterranean Sea ◽  
Copy Numbers ◽  
Gene Copy Numbers

Predominance of ammonia-oxidizing archaea andnirK-gene-bearing denitrifiers among ammonia-oxidizing and denitrifying populations in sediments of a large urban eutrophic lake (Lake Donghu)

2013 ◽  
Vol 59 (7) ◽  
pp. 456-464 ◽  
Author(s):  
Jie Hou ◽  
Xiuyun Cao ◽  
Chunlei Song ◽  
Yiyong Zhou
Keyword(s):  
Amoa Gene ◽  
Eutrophic Lake ◽  
Gene Copy ◽  
Nirs Gene ◽  
Bacterial Amoa Gene ◽  
Archaeal Amoa Gene ◽  
Copy Numbers ◽  
Significant Difference ◽  
Nirk Gene ◽  
Gene Copy Numbers

The coupled nitrification–denitrification process plays a pivotal role in cycling and removal of nitrogen in aquatic ecosystems. In the present study, the communities of ammonia oxidizers and denitrifiers in the sediments of 2 basins (Guozhenghu Basin and Tuanhu Basin) of a large urban eutrophic lake (Lake Donghu) were determined using the ammonia monooxygenase subunit A (amoA) gene and the nitrite reductase gene. At all sites of this study, the archaeal amoA gene predominated over the bacterial amoA gene, whereas the functional gene for denitrification nirK gene far outnumbered the nirS gene. Spatially, compared with the Tuanhu Basin, the Guozhenghu Basin showed a significantly greater abundance of the archaeal amoA gene but less abundance of the nirK and nirS genes, while there was no significant difference of bacterial amoA gene copy numbers between the 2 basins. Unlike the archaeal amoA gene, the nirK gene showed a significant difference in community structure between the 2 basins. Archaeal amoA diversity was limited to the water–sediment cluster of Crenarchaeota, in sharp contrast with nirK for which 22 distinct operational taxonomic units were found. Accumulation of organic substances were found to be positively related to nirK and nirS gene copy numbers but negatively related to archaeal amoA gene copy numbers, whereas the abundance of the bacterial amoA gene was related to ammonia concentration.

scholarly journals Spatial distribution and abundance of the megabenthic fauna community in Gabes gulf (Tunisia, eastern Mediterranean Sea)

2012 ◽  
Vol 13 (1) ◽  
pp. 12 ◽  
Author(s):  
H. EL LAKHRACH ◽  
A. HATTOUR ◽  
O. JARBOUI ◽  
K. ELHASNI ◽  
A.A. RAMOS-ESPLA
Keyword(s):  
Spatial Distribution ◽  
Mediterranean Sea ◽  
Vegetation Cover ◽  
Eastern Mediterranean ◽  
Ecological Condition ◽  
Eastern Mediterranean Sea ◽  
Bottom Type ◽  
North East ◽  
Starting Point ◽  
Marine Diversity

The aim of this paper is to bring to light the knowledge of marine diversity of invertebrates in Gabes gulf. The spatial distribution of the megabenthic fauna community in Gabes gulf (Tunisia, Eastern Mediterranean Sea), together with the bottom type and vegetation cover, were studied. The abundance of the megabenthic fauna was represented by eight groups: Echinodermata (38%), Crustacea (21%), Tunicata (19%), Mollusca (13%), Porifera (4%), Cnidaria (3%), Bryozoa, and Annelida (2%). It was spatially more concentrated in the coast area of the gulf than in the offshore waters. This area, especially, in Southern Kerkennah, North-est of Gabes and North-east of Djerba appeared to be in a good ecological condition  hosting a variety of species like the paguridsPaguristes eremita and Pagurus cuanensis, the brachyura Medorippe lanata, Inachus doresttensis, the Gastropoda Hexaplex trunculus, Bolinus brandaris, Aporrhais pespelecani, andErosaria turdus, the Bivalvia Fulvia fragilis, the Echinoidea Psammechinus microtuberculatus, Holothuria polii,Ophiothrix fragilis and Antedon mediterranea, and the AscidiaceaAplidium cf. conicum, Didemnum spp, and Microcosmus exasperatus.The species’ compositions of the megabentic fauna community showed clearly that the spatial analysis represented the differences between the community of these two regions (inshore waters and offshore waters). These differences were closely related to peculiar characters of the fauna and biotopes (depth, bottom type and vegetation cover community). The results of the present study should be considered as a necessary starting point for a further analysis of priceless benthic fauna contribution to the marine environment and its organisms.

scholarly journals On the Circulation and Thermohaline Properties of the Eastern Mediterranean Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Milena Menna ◽  
Riccardo Gerin ◽  
Giulio Notarstefano ◽  
Elena Mauri ◽  
Antonio Bussani ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Column ◽  
Mixed Layer ◽  
Eastern Mediterranean ◽  
Mixed Layer Depth ◽  
Eastern Mediterranean Sea ◽  
Salt Fingers ◽  
Main Circulation ◽  
Satellite Altimetry Data

The circulation of the Eastern Mediterranean Sea is characterized by numerous recurrent or permanent anticyclonic structures, which modulate the pathway of the main currents and the exchange of the water masses in the basin. This work aims to describe the main circulation structures and thermohaline properties of the Eastern Mediterranean with particular focus on two anticyclones, the Pelops and the Cyprus gyres, using in-situ (drifters and Argo floats) and satellite (altimetry) data. The Pelops gyre is involved in the circulation and exchange of Levantine origin surface and intermediate waters and in their flow toward the Ionian and the Adriatic Sea. The Cyprus Gyre presents a marked interannual variability related to the presence/absence of waters of Atlantic origin in its interior. These anticyclones are characterized by double diffusive instability and winter mixing phenomena driven by salty surface waters of Levantine origin. Conditions for the salt finger regime occur steadily and dominantly within the Eastern Mediterranean anticyclones. The winter mixing is usually observed in December–January, characterized by instability conditions in the water column, a gradual deepening of the mixed layer depth and the consequent downward doming of the isohalines. The mixing generally involves the first 200 m of the water column (but occasionally can affect also the intermediate layer) forming a water mass with well-defined thermohaline characteristics. Conditions for salt fingers also occur during mixing events in the layer below the mixed layer.

scholarly journals Thalassospira sp. Isolated from the Oligotrophic Eastern Mediterranean Sea Exhibits Chemotaxis toward Inorganic Phosphate during Starvation

2011 ◽  
Vol 77 (13) ◽  
pp. 4412-4421 ◽  
Author(s):  
Annemarie Hütz ◽  
Karin Schubert ◽  
Jörg Overmann
Keyword(s):  
Mediterranean Sea ◽  
Water Column ◽  
Inorganic Phosphate ◽  
Phosphate Uptake ◽  
Eastern Mediterranean ◽  
Phosphate Limitation ◽  
Soluble Phosphate ◽  
Free Living ◽  
Eastern Mediterranean Sea ◽  
Content Type

ABSTRACTThe eastern Mediterranean Sea represents an ultraoligotrophic environment where soluble phosphate limits the growth of bacterioplankton. Correspondingly, genes coding for high-affinity phosphate uptake systems and for organophosphonate utilization are highly prevalent in the plankton metagenome. Chemotaxis toward inorganic phosphate constitutes an alternative strategy to cope with phosphate limitation, but so far has only been demonstrated for two bacterial pathogens and an archaeon, and not in any free-living planktonic bacterium. In the present study, bacteria affiliated with the genusThalassospirawere found to constitute a regular, low-abundance member of the bacterioplankton that can be detected throughout the water column of the eastern Mediterranean Sea. A representative (strain EM) was isolated in pure culture and exhibited a strong positive chemotaxis toward inorganic phosphate that was induced exclusively in phosphate-starved cultures. Phosphate-depleted cells were 2-fold larger than in exponentially growing cultures, and 43% of the cells retained their motility even during prolonged starvation over 10 days. In addition,Thalassospirasp. strain EM was chemotactically attracted by complex substrates (yeast extract and peptone), amino acids, and 2-aminoethylphosphonate but not by sugar monomers. Similarly to the isolate from the eastern Mediterranean, chemotaxis toward phosphate was observed in starved cultures of the other two available isolates of the genus,T. lucentensisDSM 14000TandT. profundimarisWP0211T. AlthoughThalassospirasp. represents only up to 1.2% of the total bacterioplankton community in the water column of the eastern Mediterranean Sea, its chemotactic behavior potentially leads to an acceleration of nutrient cycling and may also explain the persistence of marine copiotrophs in this extremely nutrient-limited environment.

scholarly journals The effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultraoligotrophic sea

2020 ◽  
Author(s):  
Tamar Guy-Haim ◽  
Maxim Rubin-Blum ◽  
Eyal Rahav ◽  
Natalia Belkin ◽  
Jacob Silverman ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Column ◽  
Nutrient Dynamics ◽  
Eastern Mediterranean ◽  
Oxygen Demand ◽  
Bacterial Biomass ◽  
Ecosystem Functions ◽  
Water Interface ◽  
Overlying Water ◽  
Eastern Mediterranean Sea

Abstract. Over the past several decades, jellyfish blooms have intensified spatially and temporally, affecting functions and services of ecosystems worldwide. At the demise of a bloom, an enormous amount of jellyfish biomass sinks to the seabed and decomposes. This process entails reciprocal microbial and biogeochemical changes, typically enriching the water column and seabed with large amounts of organic and inorganic nutrients. Jellyfish decomposition was hypothesized to be particularly important in nutrient-impoverished ecosystems, such as the Eastern Mediterranean Sea – one of the most oligotrophic marine regions in the world. Since the 1970s, this region is experiencing the proliferation of a notorious invasive scyphozoan jellyfish, Rhopilema nomadica. In this study, we estimated the short-term decomposition effects of R. nomadica on nutrient dynamics at the sediment-water interface. Our results show that the degradation of R. nomadica has led to increased oxygen demand and acidification of overlying water as well as high rates of dissolved organic nitrogen and phosphate production. These conditions favored heterotrophic microbial activity, bacterial biomass accumulation, and triggered a shift towards heterotrophic bio-degrading bacterial communities, whereas autotrophic pico-phytoplankton abundance was moderately affected or reduced. This shift may further decrease primary production in the water column of the Eastern Mediterranean Sea. Deoxygenation, acidification, nutrient enrichment and microbial community shifts at the sediment-water interface may have a detrimental impact on macrobenthic communities. Based on these findings we suggest that jelly-falls and their decay may facilitate an additional decline in ecosystem functions and services.

Fe isotope and Fe speciation study of water column redox dynamics during Eastern Mediterranean sapropel events S5 and S7

2020 ◽  
Author(s):  
Alan Matthews ◽  
Ayelet Benkovitz ◽  
Nadya Teutsch ◽  
Simon Poulton ◽  
Miryam Bar-Matthews ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Column ◽  
Black Sea ◽  
Eastern Mediterranean ◽  
The Black Sea ◽  
Eastern Mediterranean Sea ◽  
Positive Balance ◽  
Fe Speciation ◽  
Bottom Waters ◽  
Oxide Minerals

<p>Sapropels S5 and S7 formed in the semi-enclosed Eastern Mediterranean Sea  during peak interglacial periods MIS5e and MIS7a, respectively. This study investigates the dynamics of  water column redox change during their formation, through Fe isotope and Fe speciation studies of cores taken at 2550 m depth at site ODP-967 south of Cyprus. Both sapropels show an inverse correlation between δ<sup>56</sup>Fe and Fe<sub>T</sub>/Al, with slopes mostly matching that found for the Black Sea, pointing to a benthic shelf to basin shuttle of Fe and subsequent precipitation of Fe sulphides in highly euxinic bottom waters. An exception to these Black Sea-type trends occurs during the later, peak stages of S7, where the negative δ<sup>56</sup>Fe - Fe<sub>T</sub>/Al slope shallows. Fe speciation studies reveal that the dominant highly reactive Fe phase (Fe<sub>HR</sub>) in the sapropels is pyrite, with Fe (oxyhydr)oxides forming the second major mineral component. Fe<sub>HR</sub>/Fe<sub>T</sub> plots show increased strengthening of anoxic water conditions during the transformation from pre-sapropel sediment into the sapropel. Nevertheless, despite the evidence for highly euxinic conditions from both Fe isotopes and high Mo concentrations in the sapropels, Fe<sub>py</sub>/Fe<sub>HR</sub> ratios remain below values commonly used to identify water column euxinia. This apparent contradiction is ascribed to the sedimentary preservation of a high flux of crystalline Fe (oxyhydr)oxide minerals to the basin, which resulted in a relatively low degree of sulphidation, despite the presence of euxinic bottom waters.  Thus, the operationally defined ferruginous/euxinic boundary for Eastern Mediterranean Sea sapropels is better placed at Fe<sub>py</sub>/Fe<sub>HR</sub> = 0.6, which is somewhat below the usually ascribed lower limit of 0.7. Consistent with the significant presence of crystalline Fe (oxyhydr)oxides, the change in the δ<sup>56</sup>Fe - Fe<sub>T</sub>/Al slope during peak S7 is ascribed to an enhanced monsoon-driven flux of detrital Fe(III) oxides from the River Nile into the Eastern Mediterranean basin. The euxinic water column conditions that developed in sapropels S5 and S7 are interpreted to reflect the positive balance between dissolved sulphide formation and rates of reductive dissolution of Fe (oxyhydr)oxide minerals. Both of these parameters in turn depend on the extent to which water overturn times are reduced during sapropel formation. Water overturn rate is therefore considered to define the strength of euxinic water column conditions during these periods of organic carbon-rich sedimentation.</p>

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