Temporal evolution of physical and chemical characteristics of the water column in the Easternmost Levantine basin (Eastern Mediterranean Sea) from 2002 to 2010

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.

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Modeling the effects of brine outflow from desalination plants on coastal food-webs of the Levantine basin (eastern Mediterranean Sea)

Desalination ◽

10.1016/j.desal.2020.114757 ◽

2020 ◽

Vol 496 ◽

pp. 114757

Author(s):

Michal Grossowicz ◽

Eyal Ofir ◽

Ateret Shabtay ◽

Julie Wood ◽

Eli Biton ◽

...

Keyword(s):

Food Webs ◽

Mediterranean Sea ◽

Eastern Mediterranean ◽

Eastern Mediterranean Sea ◽

Levantine Basin ◽

Desalination Plants

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Composition and distribution patterns of eukaryotic microbial plankton in the ultra-oligotrophic Eastern Mediterranean Sea

Aquatic Microbial Ecology ◽

10.3354/ame01933 ◽

2020 ◽

Vol 84 ◽

pp. 155-173

Author(s):

I Santi ◽

P Kasapidis ◽

S Psarra ◽

G Assimakopoulou ◽

A Pavlidou ◽

...

Keyword(s):

Mediterranean Sea ◽

Deep Sea ◽

Environmental Variables ◽

Eastern Mediterranean ◽

Distribution Patterns ◽

Eastern Mediterranean Sea ◽

Operational Taxonomic Units ◽

Microbial Eukaryotes ◽

Levantine Basin ◽

Microbial Plankton

Marine microbial eukaryotes play crucial roles in water-column ecosystems; however, there are regional gaps in the investigation of natural microbial eukaryote communities, and uncertainties concerning their distribution persevere. This study combined 18S rRNA metabarcoding, biomass measurements and statistical analyses of multiple environmental variables to examine the distribution of planktonic microbial eukaryotes at different sites and water layers in the ultra-oligotrophic Eastern Mediterranean Sea (Western Levantine Basin). Our results showed that microbial eukaryotic communities were structured by depth. In surface waters, different sites shared high percentages of molecular operational taxonomic units (MOTUs), but this was not the case for deep-sea communities (≥1000 m). Plankton biomass was significantly different among sites, implying that communities of a similar composition may not support the same activity or population size. The deep-sea communities showed high percentages of unassigned MOTUs, highlighting the sparsity of the existing information on deep-sea plankton eukaryotes. Water temperature and dissolved organic matter significantly affected community distribution. Micro-eukaryotic distribution was additionally affected by the nitrogen to phosphorus ratio and viral abundance, while nano- and pico-communities were affected by zooplankton. The present study explores microbial plankton eukaryotes in their natural oligotrophic environment and highlights that, even within restricted oceanic areas, marine plankton may follow distribution patterns that are largely controlled by environmental variables.

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

Applied and Environmental Microbiology ◽

10.1128/aem.00490-11 ◽

2011 ◽

Vol 77 (13) ◽

pp. 4412-4421 ◽

Cited By ~ 33

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.

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Spatial and seasonal evolution of dissolved oxygen and nutrients in the Southern Levantine Basin (Eastern Mediterranean Sea): chemical characterization of the water masses and inferences on the N:P ratios

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/s0967-0637(01)00022-x ◽

2001 ◽

Vol 48 (11) ◽

pp. 2347-2372 ◽

Cited By ~ 120

Author(s):

Nurit Kress ◽

Barak Herut

Keyword(s):

Dissolved Oxygen ◽

Mediterranean Sea ◽

Eastern Mediterranean ◽

Chemical Characterization ◽

Water Masses ◽

Eastern Mediterranean Sea ◽

Seasonal Evolution ◽

N:P Ratios ◽

Levantine Basin

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

10.5194/bg-2020-226 ◽

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.

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Planktonic foraminiferal ecozones: response of the pelagic environment to palaeoclimatic changes in the eastern Mediterranean Sea

Mediterranean Marine Science ◽

10.12681/mms.226 ◽

2003 ◽

Vol 4 (2) ◽

pp. 21 ◽

Cited By ~ 2

Author(s):

H. DRINIA ◽

A. ANTONARAKOU ◽

M. DERMITZAKIS

Keyword(s):

Mediterranean Sea ◽

Eastern Mediterranean ◽

Planktonic Foraminifera ◽

Chemical Properties ◽

Common Species ◽

Eastern Mediterranean Sea ◽

History Of ◽

Climatic History ◽

Cooling Trend ◽

Physical And Chemical

A detailed study of the planktonic environment of the eastern Mediterranean Sea has permitted the reconstruction of the climatic history of this part of the basin during the time span from 9.7 to 6.6 Ma. The eastern Mediterranean Sea is confirmed as having a strong sensitivity to the climatic changes that occurred during that timespan. One of the very few complete hemipelagic successions of the Upper Miocene in Mediterranean is found in Gavdos island (SW Crete). Quantitative and qualitative modifications of the planktonic foraminiferal communities observed in Metochia section exhibit a sequence of biological events summarized in 11 successive main time intervals. The bioevents are defined by frequency peaks and/or local (re)-occurrences or (temporary) disappearances of some of the taxa, in association with more or less important fluctuations of the more common species. The planktonic foraminifera show a strong correlation with sea surface temperature variations and with changes in the physical and chemical properties of the upper water column caused by the climatic instability. Two prominent shifts in faunal parameters divide the period recorded in Metochia section into three major time slices that are discussed in chronological order: a cooling trend from 9,7 to 7,6 Ma, a warmer period from 7,6 to 7,2 Ma and then a cooling trend which finishes at the Messinian.

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Seasonal and Interannual Variability of the CO2 System in the Eastern Mediterranean Sea: A Case Study in the North Western Levantine Basin

Frontiers in Marine Science ◽

10.3389/fmars.2021.649246 ◽

2021 ◽

Vol 8 ◽

Author(s):

Cathy Wimart-Rousseau ◽

Thibaut Wagener ◽

Marta Álvarez ◽

Thierry Moutin ◽

Marine Fourrier ◽

...

Keyword(s):

Mediterranean Sea ◽

Annual Cycle ◽

Eastern Mediterranean ◽

Total Alkalinity ◽

Carbonate System ◽

Eastern Mediterranean Sea ◽

The North ◽

Levantine Basin ◽

The Future ◽

North Western

The seasonal variability of the carbonate system in the eastern Mediterranean Sea (EMed) was investigated based on discrete total alkalinity (AT), total dissolved inorganic carbon (CT), and pH measurements collected during three cruises around Crete between June 2018 and March 2019. This study presents a detailed description of this new carbonate chemistry dataset in the eastern Mediterranean Sea. We show that the North Western Levantine Basin (NWLB) is unique in terms of range of AT variation vs. CT variation in the upper water column over an annual cycle. The reasons for this singularity of the NWLB can be explained by the interplay between strong evaporation and the concomitant consumption of CT by autotrophic processes. The high range of AT variations, combined to temperature changes, has a strong impact on the variability of the seawater pCO2 (pCO2SW). Based on Argo float data, an entire annual cycle for pCO2SW in the NWLB has been reconstructed in order to estimate the temporal sequence of the potential “source” and “sink” of atmospheric CO2. By combining this dataset with previous observations in the NWLB, this study shows a significant ocean acidification and a decrease in the oceanic surface pHT25 of −0.0024 ± 0.0004 pHT25 units.a–1. The changes in the carbonate system are driven by the increase of atmospheric CO2 but also by unexplained temporal changes in the surface AT content. If we consider that the EMed will, in the future, encounter longer, more intense and warmer summer seasons, this study proposes some perspectives on the carbonate system functioning of the “future” EMed.

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

10.5194/egusphere-egu2020-1864 ◽

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

Sapropels S5 and S7 formed in the semi-enclosed Eastern Mediterranean Sea &#160;during peak interglacial periods MIS5e and MIS7a, respectively. This study investigates the dynamics of &#160;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 &#948;56Fe and FeT/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 &#948;56Fe - FeT/Al slope shallows. Fe speciation studies reveal that the dominant highly reactive Fe phase (FeHR) in the sapropels is pyrite, with Fe (oxyhydr)oxides forming the second major mineral component. FeHR/FeT 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, Fepy/FeHR 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.&#160; Thus, the operationally defined ferruginous/euxinic boundary for Eastern Mediterranean Sea sapropels is better placed at Fepy/FeHR = 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 &#948;56Fe - FeT/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.

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