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

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.

scholarly journals A new approach to the opening of the eastern Mediterranean Sea and the origin of the Hellenic subduction zone. Part 2: The Hellenic subduction zone

2019 ◽  
Vol 56 (11) ◽  
pp. 1144-1162 ◽  
Author(s):  
Xavier Le Pichon ◽  
A.M. Celâl Şengör ◽  
Caner İmren
Keyword(s):  
Mediterranean Sea ◽  
Subduction Zone ◽  
Eastern Mediterranean ◽  
Accretionary Wedge ◽  
Geophysical Research ◽  
Independent Evidence ◽  
Eastern Mediterranean Sea ◽  
Northern Margin ◽  
Hellenic Subduction Zone ◽  
The North

We discuss the structure of the present Hellenic subduction zone. We show that the present Hellenic subduction zone was formed at about 15 Ma when it started to consume the Mediterranean lithosphere and to form the large accretionary wedge that covers a large part of the eastern Mediterranean. We establish that there is independent evidence that the very large Hellenic Trough that it created was formed simultaneously. Shortly before, an 8–10 km thick backstop that extends 200 km southward, where it presently abuts the African margin, was put into place. We reconstruct the northern margin of the eastern Mediterranean Sea prior to the Hellenic subduction in a new and independent way. The faults recently identified by Sachpazi et al. (2016a . Geophysical Research Letters, 43: 651–658) and Sachpazi et al. (2016b . Geophysical Research Letters, 43: 9619–9626) within the Hellenic seismic slab are a key element of our reconstruction. This is because the slab, which is part of the Nubia plate, is rigid and the faults within it coincide with the lines of slip congruent with the relative motion of the Aegean block over it. These faults demonstrate that about 400 to 500 kilometers of eastern Mediterranean lithosphere have been subducted with essentially the same southwestward direction of motion during the last 15 Myr. Our reconstruction shows that before the onset of the Hellenic subduction, the northern margin of the eastern Mediterranean Sea coincided with a major Jurassic transform fault that limited the eastern Mediterranean to the north during its formation in the Jurassic and Early Cretaceous as proposed in part 1. We discuss the implications of this reconstruction on the Neogene evolution of the Anatolia–Aegea block and its geodynamics.

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

Desalination ◽  
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

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

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.

Spatio-temporal survey of the coastal carbonate system offshore Lebanon-Levantine Mediterranean Sea

2020 ◽  
Author(s):  
Abed El Rahman Hassoun ◽  
Milad Fakhri ◽  
Majd Habib ◽  
Anthony Ouba ◽  
Sharif Jemaa ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Dissolved Inorganic Carbon ◽  
Eastern Mediterranean ◽  
Mixed Layer Depth ◽  
Total Alkalinity ◽  
Critical Parameters ◽  
Carbonate System ◽  
Preliminary Results ◽  
Open Sea ◽  
Spatio Temporal

<p>The coastal carbonate system regulates the pH of the coastal waters and controls the circulation of CO<sub>2</sub> between land-sea interfaces and open sea system. In the context of the ELME (Evaluation of the Lebanese Marine Environment: A multidisciplinary study) project, a seasonal survey of the carbonate system has been started in 2019 through the sampling of 3 different transects starting from the coast towards the open sea, offshore two Lebanese cities (Beirut and Tyre) to evaluate the spatio-temporal variations of this system in coastal areas. The carbonate chemistry is being studied by measuring both total alkalinity (A<sub>T</sub>) and total dissolved inorganic carbon (C<sub>T</sub>), together with other critical parameters in coastal ecosystems such as temperature, salinity, pH, dissolved oxygen, nutrients (phosphates, nitrates, nitrites, silicates), and chlorophyll a. The preliminary results show that the highest carbonate system inventories (2546.4 and 2266 µmol kg<sup>-1</sup> for A<sub>T</sub> and C<sub>T</sub> respectively) were measured in transects influenced by discharges of dumpsite and port areas (offshore Beirut) where positive and significant correlations (p << 0.005) have been recorded with nutrients, particularly with nitrites (> 10 µmol kg<sup>-1</sup>). Furthermore, TrOCA approach was used to estimate the anthropogenic CO<sub>2</sub> concentrations (C<sub>ANT</sub>) below the mixed layer depth. The results demonstrate that all waters in both studied areas are contaminated by C<sub>ANT</sub>, even the deep ones (> 400 m) located in the furthest monitored station, with values greater than 70 µmol kg<sup>-1</sup>. This fact raises concerns about the effects of such relatively high C<sub>ANT</sub> concentrations on coastal organisms therein. This work presents the preliminary results of an ongoing study. The continuity of this project will help to assess the relationship between land-based anthropogenic pressures and the coastal biogeochemistry in a changing Eastern Mediterranean Sea.</p>

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