Decadal oscillations in the Mediterranean Sea: a result of the overturning circulation variability in the eastern basin?

2006 ◽  
Vol 31 ◽  
pp. 257-271 ◽  
Author(s):  
G Pisacane ◽  
V Artale ◽  
S Calmanti ◽  
V Rupolo
Keyword(s):  
Mediterranean Sea ◽  
Overturning Circulation ◽  
Eastern Basin ◽  
The Mediterranean

scholarly journals Ecology of aerobic anoxygenic phototrophic bacteria along an oligotrophic gradient in the Mediterranean Sea

2011 ◽  
Vol 8 (4) ◽  
pp. 973-985 ◽  
Author(s):  
D. Lamy ◽  
C. Jeanthon ◽  
M. T. Cottrell ◽  
D. L. Kirchman ◽  
F. Van Wambeke ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Bacterial Growth ◽  
Growth Response ◽  
Anoxygenic Phototrophic Bacteria ◽  
Carbon Limitation ◽  
Organic Substrates ◽  
Western Basin ◽  
Eastern Basin ◽  
Nutrient Additions ◽  
The Mediterranean

Abstract. Aerobic anoxygenic phototrophic (AAP) bacteria are photoheterotrophic prokaryotes able to use both light and organic substrates for energy production. They are widely distributed in coastal and oceanic environments and may contribute significantly to the carbon cycle in the upper ocean. To better understand questions regarding links between the ecology of these photoheterotrophic bacteria and the trophic status of water masses, we examined their horizontal and vertical distribution and the effects of nutrient additions on their growth along an oligotrophic gradient in the Mediterranean Sea. Concentrations of bacteriochlorophyll-a (BChl-a) and AAP bacterial abundance decreased from the western to the eastern basin of the Mediterranean Sea and were linked with concentrations of chlorophyll-a, nutrient and dissolved organic carbon. Inorganic nutrient and glucose additions to surface seawater samples along the oligotrophic gradient revealed that AAP bacteria were nitrogen- and carbon-limited in the ultraoligotrophic eastern basin. The intensity of the AAP bacterial growth response generally differed from that of the total bacterial growth response. BChl-a quota of AAP bacterial communities was significantly higher in the eastern basin than in the western basin, suggesting that reliance on phototrophy varied along the oligotrophic gradient and that nutrient and/or carbon limitation favors BChl-a synthesis.

scholarly journals Sertularia marginata (Cnidaria: Hydrozoa) in the Mediterranean: an alien species in expansion?

2013 ◽  
Vol 14 (2) ◽  
pp. 384 ◽  
Author(s):  
M. M. GONZÁLEZ-DUARTE ◽  
C. MEGINA ◽  
M. BETHENCOURT
Keyword(s):  
Alien Species ◽  
Mediterranean Sea ◽  
Atlantic Coast ◽  
Western Mediterranean ◽  
Strait Of Gibraltar ◽  
Eastern Basin ◽  
Natural Zones ◽  
History Of ◽  
The Mediterranean ◽  
Natural Means

Mature and dense populations of the tropical hydroid species Sertulariamarginata were detected in the Alboran Sea (Western Mediterranean) and in the Atlantic coast of the Strait of Gibraltar. Until now, it had only been recorded in the eastern basin within the Mediterranean Sea.This species has previously been recorded in estuaries and anthropogenichabitats but, in the area studied here, we only found it in natural zones. These observations could indicate an early expansion and naturalization in the Mediterranean Sea. Due to its limited dispersion capacity by its own natural means and the history of its records, the observations provided here support the hypothesis of an arrival and a spread by anthropogenic vectors.A pathway of arrival and dispersion of alien species into the Mediterranean Sea is proposed for future monitoring: from Macaronesia (particularly Canary Islands) to the Atlantic coast of the Strait of Gibraltar and from here into the Mediterranean.

scholarly journals New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

2015 ◽  
Vol 12 (23) ◽  
pp. 7025-7046 ◽  
Author(s):  
A. Guyennon ◽  
M. Baklouti ◽  
F. Diaz ◽  
J. Palmieri ◽  
J. Beuvier ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Mediterranean Sea ◽  
Coupled Model ◽  
Phosphate Limitation ◽  
Biogeochemical Model ◽  
Carbon Export ◽  
Western Basin ◽  
Eastern Basin ◽  
Basin Scale ◽  
The Mediterranean

Abstract. The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities, resulting in a potential major role of dissolved organic carbon (DOC) export in the biological pump. Strong DOC accumulation in surface waters is already well documented, though measurements of DOC stocks and export flux are still sparse and associated with major uncertainties. This study provides the first basin-scale overview and analysis of organic carbon stocks and export fluxes in the Mediterranean Sea through a modeling approach based on a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). The model is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are also of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are mutually consistent. Strong differences between the western and eastern basins are evidenced by the model for organic carbon export. Though less oligotrophic than the eastern basin, the western basin only supports 39 % of organic carbon (particulate and dissolved) export. Another major result is that except for the Alboran Sea, the DOC contribution to organic carbon export is higher than that of particulate organic carbon (POC) throughout the Mediterranean Sea, especially in the eastern basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports in light of intracellular quotas. Finally, according to the model, strong phosphate limitation of both bacteria and phytoplankton growth is one of the main drivers of DOC accumulation and therefore of export.

scholarly journals Long-term spatiotemporal dynamics of cephalopod assemblages in the Mediterranean Sea

2020 ◽  
Vol 83 (S1) ◽  
pp. 33
Author(s):  
Antoni Quetglas ◽  
Maria Valls ◽  
Francesca Capezzuto ◽  
Loredana Casciaro ◽  
Danila Cuccu ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Biodiversity Loss ◽  
Longitudinal Gradient ◽  
Eastern Basin ◽  
Mediterranean Countries ◽  
Spatial Differences ◽  
The Mediterranean ◽  
Increasing Temperature ◽  
Trawl Surveys

The Mediterranean Sea shows a trend of increasing temperature and decreasing productivity from the western to the eastern basin. In this work we investigate whether this trend is reflected in the cephalopod assemblages found throughout the Mediterranean. Data obtained with bottom trawl surveys carried out during the last 22 years by EU Mediterranean countries were used. In addition to analysing spatial differences in cephalopod assemblages, we also analysed putative temporal changes during the last two decades. For this purpose, the basin was spatially divided into bioregions, the trawling grounds were subdivided into depth strata, and the dataset was split into two time series of 11 years each. All analyses were done using PRIMER software. The species richness did not vary with the longitudinal gradient, though in most bioregions it showed a mild decrease with depth before plummeting in the deepest waters. Cluster analysis revealed four different bathymetric assemblages in all bioregions. Despite the contrasting conditions between basins and the claims of biodiversity loss, our study revealed that spatial and temporal differences during the last two decades were restricted to changes in the relative abundance of species from a common pool of species inhabiting the whole Mediterranean.

scholarly journals Thermodynamic Forecasts of the Mediterranean Sea Acidification

2016 ◽  
Vol 17 (2) ◽  
pp. 508 ◽  
Author(s):  
C. GOYET ◽  
A. HASSOUN ◽  
E. GEMAYEL ◽  
F. TOURATIER ◽  
M. ABBOUD-ABI SAAB ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Initial Conditions ◽  
Mixed Layer Depth ◽  
Total Alkalinity ◽  
Western Basin ◽  
Eastern Basin ◽  
Emissions Scenarios ◽  
The Mediterranean ◽  
Ph Decrease ◽  
Thermodynamic Equations

Anthropogenic CO2 is a major driver of the present ocean acidification. This latter is threatening the marine ecosystems and has been identified as a major environmental and economic menace. This study aims to forecast from the thermodynamic equations, the acidification variation (ΔpH) of the Mediterranean waters over the next few decades and beyond this century. In order to do so, we calculated and fitted the theoretical values based upon the initial conditions from data of the 2013 MedSeA cruise. These estimates have been performed both for the Western and for the Eastern basins based upon their respective physical (temperature and salinity) and chemical (total alkalinity and total inorganic carbon) properties. The results allow us to point out four tipping points, including one when the Mediterranean Sea waters would become acid (pH<7). In order to provide an associated time scale to the theoretical results, we used two of the IPCC (2007) atmospheric CO2 scenarios. Under the most optimistic scenario of the “Special Report: Emissions Scenarios” (SRES) of the IPCC (2007), the results indicate that in 2100, pH may decrease down to 0.245 in the Western basin and down to 0.242 in the Eastern basin (compared to the pre-industrial pH). Whereas for the most pessimistic SRES scenario of the IPCC (2007), the results for the year 2100, forecast a pH decrease down to 0.462 and 0.457, for the Western and for the Eastern basins, respectively. Acidification, which increased unprecedentedly in recent years, will rise almost similarly in both Mediterranean basins only well after the end of this century. These results further confirm that both basins may become undersaturated (< 1) with respect to calcite and aragonite (at the base of the mixed layer depth), only in the far future (in a few centuries).

scholarly journals Springtime contribution of dinitrogen fixation to primary production across the Mediterranean Sea

Ocean Science ◽  
2013 ◽  
Vol 9 (3) ◽  
pp. 489-498 ◽  
Author(s):  
E. Rahav ◽  
B. Herut ◽  
A. Levi ◽  
M. R. Mulholland ◽  
I. Berman-Frank
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
N2 Fixation ◽  
Eastern Mediterranean ◽  
Dominant Role ◽  
Early Spring ◽  
Western Basin ◽  
Eastern Basin ◽  
The Mediterranean ◽  
Planktonic Communities

Abstract. Dinitrogen (N2) fixation rates were measured during early spring across the different provinces of Mediterranean Sea surface waters. N2 fixation rates, measured using 15N2 enriched seawater, were lowest in the eastern basin and increased westward with a maximum at the Strait of Gibraltar (0.10 to 2.35 nmol N L−1 d−1, respectively). These rates were 3–7 fold higher than N2 fixation rates measured previously in the Mediterranean Sea during summertime and we estimated that methodological differences alone did not account for the seasonal changes we observed. Higher contribution of N2 fixation to primary production (4–8%) was measured in the western basin compared to the eastern basin (∼2%). Our data indicates that these differences between basins may be attributed to changes in N2-fixing planktonic communities and that heterotrophic diazotrophy may play a significant role in the eastern Mediterranean while autotrophic diazotrophy has a more dominant role in the western basin.

A new hypothesis about the surface circulation in the eastern basin of the mediterranean sea

2005 ◽  
Vol 66 (2-4) ◽  
pp. 287-298 ◽  
Author(s):  
Najwa Hamad ◽  
Claude Millot ◽  
Isabelle Taupier-Letage
Keyword(s):  
Mediterranean Sea ◽  
Eastern Basin ◽  
Surface Circulation ◽  
The Mediterranean ◽  
New Hypothesis

Pelagic Tar in the Mediterranean Sea, 1974–75

1975 ◽  
Vol 2 (4) ◽  
pp. 275-281 ◽  
Author(s):  
Byron F. Morris ◽  
James N. Butler ◽  
Adam Zsolnay
Keyword(s):  
Mediterranean Sea ◽  
Geometric Mean ◽  
Standing Stock ◽  
Relative Increase ◽  
Tyrrhenian Sea ◽  
Eastern Basin ◽  
Control Effectiveness ◽  
Moroccan Coast ◽  
Similar Survey ◽  
The Mediterranean

During the period 6 December 1974 to 20 January 1975, the R/V Westward circumnavigated the Mediterranean Sea and took quantitative samples of pelagic tar at 48 stations. These have been compared with a similar survey made in 1969 by the R/V Atlantis II and with some data published in the USSR. In the ‘Ionian Sea’ (between Crete and the Strait of Sicily) the geometric mean of tar concentration has decreased significantly—from 60 mg/m2 in 1969 to 5 mg/m2 in 1974–75. In other regions of the Mediterranean, no significant changes were found. However, in both the ‘Tyrrhenian Sea’ west of Italy and the ‘Alboran Sea’ along the Algerian-Moroccan coast, tar concentrations have increased by about a factor of two, roughly corresponding to the relative increase in tanker traffic in the Mediterranean as a whole. In the ‘Balearic Sea’, 1975 levels were lower than those of 1969, but the data may not be comparable because of the different geographic regions covered.At present, the total standing stock of pelagic tar in the Mediterranean is lower than in 1969, due to the decrease in pollution of the eastern basin. With the reopening of the Suez Canal, changes in the amounts of tar should be carefully monitored as a measure of pollution control effectiveness.

scholarly journals Sertulariamarginata (Cnidaria: Hydrozoa) in the Mediterranean: an alien species in expansion?

2014 ◽  
Author(s):  
M.M. GONZÁLEZ-DUARTE ◽  
C. MEGINA ◽  
M. BETHENCOURT
Keyword(s):  
Alien Species ◽  
Mediterranean Sea ◽  
Atlantic Coast ◽  
Western Mediterranean ◽  
Strait Of Gibraltar ◽  
Eastern Basin ◽  
Natural Zones ◽  
History Of ◽  
The Mediterranean ◽  
Natural Means

Mature and dense populations of the tropical hydroid species Sertulariamarginata were detected in the Alboran Sea (Western Mediterranean) and in the Atlantic coast of the Strait of Gibraltar. Until now, it had only been recorded in the eastern basin within the Mediterranean Sea.This species has previously been recorded in estuaries and anthropogenichabitats but, in the area studied here, we only found it in natural zones. These observations could indicate an early expansion and naturalization in the Mediterranean Sea. Due to its limited dispersion capacity by its own natural means and the history of its records, the observations provided here support the hypothesis of an arrival and a spread by anthropogenic vectors.A pathway of arrival and dispersion of alien species into the Mediterranean Sea is proposed for future monitoring: from Macaronesia (particularly Canary Islands) to the Atlantic coast of the Strait of Gibraltar and from here into the Mediterranean.

scholarly journals Springtime contribution of dinitrogen fixation to primary production across the Mediterranean Sea

2013 ◽  
Vol 10 (1) ◽  
pp. 1-26 ◽  
Author(s):  
E. Rahav ◽  
B. Herut ◽  
A. Levi ◽  
M. R. Mulholland ◽  
I. Berman-Frank
Keyword(s):  
Mediterranean Sea ◽  
Surface Waters ◽  
N2 Fixation ◽  
Eastern Mediterranean ◽  
Dominant Role ◽  
Early Spring ◽  
Strait Of Gibraltar ◽  
Western Basin ◽  
Eastern Basin ◽  
The Mediterranean

Abstract. Dinitrogen (N2) fixation rates were measured during early spring across the different provinces of Mediterranean Sea surface waters. N2 fixation rates, measured using 15N2 enriched seawater, were lowest in the eastern basin and increased westward with a maximum at the Strait of Gibraltar (0.10 to 2.35 nmol N L−1 d−1, respectively). These rates were 3–7 fold higher than N2 fixation rates measured previously in the Mediterranean Sea during summertime. Moreover, comparisons between N2 fixation rates measured during dark versus natural light incubations (48 h) show higher rates during dark incubations at the eastern Mediterranean stations but lower rates at the western stations. This suggests that heterotrophic diazotrophy has a significant role in the Eastern Mediterranean while autotrophic diazotrophy has a more dominant role in the Western basin.

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