scholarly journals Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

2011 ◽  
Vol 8 (3) ◽  
pp. 827-840 ◽  
Author(s):  
M. Le Moal ◽  
H. Collin ◽  
I. C. Biegala
Keyword(s):  
Mediterranean Sea ◽  
16S Rdna ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Central Mediterranean ◽  
Surface Distribution ◽  
Western Mediterranean Sea ◽  
Diazotrophic Cyanobacteria ◽  
The Mediterranean ◽  
Marine Areas

Abstract. The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study, we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH genes phylogenies. These genetic analyses were possible owing to the development of a new PCR protocol adapted to scarce microorganisms that can detect as few as 1 cell ml−1 in cultures. Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized to the Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml−1 of Richelia were detected in the eastern basin, while small (0.7–1.5 μm) and large (2.5–3.2 μm) Nitro821-targeted cells were recovered at all stations with a mean concentration of 3.5 cell ml−1. The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. In the central and the eastern Mediterranean Sea no 16S rDNA and nifH sequence from UCYN was obtained as cells concentration were close to, or below PCR detection limit. Bradyrhizobium sequences dominated nifH clone libraries from picoplanktonic size fractions. A few sequences of γ-proteobacteria were also detected in the central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the development of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles, and/or photosynthetic activity, to acquire carbon for sustaining diazotrophy.

scholarly journals Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: from the origin of plastids to the dominance of rhizobia

2010 ◽  
Vol 7 (6) ◽  
pp. 8779-8816 ◽  
Author(s):  
M. Le Moal ◽  
H. Collin ◽  
I. C. Biegala
Keyword(s):  
Mediterranean Sea ◽  
Nifh Gene ◽  
Western Mediterranean ◽  
Central Mediterranean ◽  
Plastid Evolution ◽  
Surface Distribution ◽  
Western Mediterranean Sea ◽  
Diazotrophic Cyanobacteria ◽  
The Mediterranean ◽  
Marine Areas

Abstract. The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has been formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH phylogenies. These genetic analyses were possible owning to the development of a new PCR protocol adapted for scarce microorganisms (0.2 cell ml−1). Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized with Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml−1 of Richelia were detected in the eastern basin, while small (0.7–1.5 μm) and large (2.5–3.2 μm) Nitro821-targeted cells were recovered at all stations and averaged 3.5 cell ml−1. The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. Surprisingly, the larger hybridized cells were not belonging to UCYN-B and C but to plastids of picoeukaryote. NifH gene was not recovered among picoeukaryotes, when rhizobia sequences, including the ones of Bradyrhizobia, were dominating nifH clone libraries from picoplanktonic size fractions. Few sequences of γ-proteobacteria were also detected in central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the development of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles and photosynthetic activity to acquire carbon for sustaining diazotrophy. Among UCYN further work will be necessary to understand their suggested role in plastid evolution.

scholarly journals Paleoenvironmental changes, climate and human impact in the Western Mediterranean Sea during the 4.2 Kyr event along a North-South Transect

2020 ◽  
Author(s):  
Nathalie Combourieu-Nebout ◽  
Vincent Coussin ◽  
Yannick Miras ◽  
Aurélie Penaud ◽  
Sandra Picard Casal ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Human Impact ◽  
Water Depth ◽  
Western Mediterranean ◽  
Time Lags ◽  
Central Mediterranean ◽  
Western Mediterranean Sea ◽  
Sequence Of Events ◽  
Dry Conditions ◽  
The Mediterranean

<p>The 4.2 ka event is considered a key-period of the Mediterranean climate because of its potential impact on human societies over the Holocene. Numerous records provide a detailed description on its expression in continental and marine archives (e.g. Bini et al, 2019). They generally indicate cold/dry conditions, although not uniformly expressed across the Mediterranean, and summer dryness reinforced by dry winters. Palynological data from the central Mediterranean basin show a complex response of the vegetation during this climatic event that seems to be more pronounced in the southern sites.</p><p>In this study, we developed a multidisciplinary approach on two sequences collected in the Western Mediterranean Sea to insight the response of the W-Mediterranean forest along a North-South transect. The two marine records, KSGC-31 (43°N - 3°17.9’E; 60 m water depth, Gulf of Lion margin at 20 km from the coast) and MD04-2801 (36°30.99’ N - 0°30.03’ W, 2067 m water depth, 12km from the Algerian coast) were used to document regional changes in the basin between 5 and 3 kyr BP at a multi-decadal to centennial scale temporal resolution.</p><p>Information derived from palynological (pollen, spores, dinocysts, microalgae and non-pollen palynomorphs) and marine proxy data (alkenone-derived SSTs, isotopes...) are combined to evaluate environmental and hydrological changes and how this relate to human activities. Our findings highlight coherent climatic patterns and time-lags along a South-North transect in the Western Mediterranean during the establishment of droughts. They also reveal the first indications of human impact in the two areas. Overall, our study shows the effectively of our approach based on cross-analysis of continental palynological and marine evidences to decipher the chronology of sequence of events embedded in multiproxy records.</p><p>Bini, M., Zanchetta, G., Perşoiu, A., et al. : The 4.2 ka BP Event in the Mediterranean region: an overview, Clim. Past, 15, 555–577, https://doi.org/10.5194/cp-15-555-2019, 2019.</p>

scholarly journals Alien species in the Mediterranean Sea by 2010. A contribution to the application of European Union’s Marine Strategy Framework Directive (MSFD). Part I. Spatial distribution

2010 ◽  
Vol 11 (2) ◽  
pp. 381 ◽  
Author(s):  
A. ZENETOS ◽  
S. GOFAS ◽  
M. VERLAQUE ◽  
M.E. CINAR ◽  
J.E. GARCIA RASO ◽  
...  
Keyword(s):  
Alien Species ◽  
Mediterranean Sea ◽  
Introduced Species ◽  
Cold Water ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Marine Strategy Framework Directive ◽  
Central Mediterranean ◽  
Total Species Richness ◽  
The Mediterranean

The state-of-art on alien species in the Mediterranean Sea is presented, making distinctions among the four subregions defined in the EU Marine Strategy Framework Directive: (i) the Western Mediterranean Sea (WMED); (ii) the Central Mediterranean Sea (CMED); (iii) the Adriatic Sea (ADRIA); and (iv) the Eastern Mediterranean Sea (EMED). The updated checklist (December 2010) of marine alien species within each subregion, along with their acclimatization status and origin, is provided. A total of 955 alien species is known in the Mediterranean, the vast majority of them having being introduced in the EMED (718), less in the WMED (328) and CMED (267) and least in the Adriatic (171). Of these, 535 species (56%) are established in at least one area.Despite the collective effort of experts who attempted in this work, the number of introduced species remains probably underestimated. Excluding microalgae, for which knowledge is still insufficient, aliens have increased the total species richness of the Mediterranean Sea by 5.9%. This figure should not be directly read as an indication of higher biodiversity, as spreading of so many aliens within the basin is possibly causing biotic homogenization. Thermophilic species, i.e. Indo-Pacific, Indian Ocean, Red Sea, Tropical Atlantic, Tropical Pacific, and circum(sub)tropical, account for 88.4% of the introduced species in the EMED, 72.8% in the CMED, 59.3% in the WMED and 56.1% in the Adriatic. Cold water species, i.e. circumboreal, N Atlantic, and N Pacific, make up a small percentage of the introduced species, ranging between 4.2% and 21.6% and being more numerous in the Adriatic and less so in the EMED.Species that are classified as invasive or potentially invasive are 134 in the whole of the Mediterranean: 108 are present in the EMED, 76 in the CMED, 53 in the Adriatic and 64 in the WMED. The WMED hosts most invasive macrophytes, whereas the EMED has the lion’s share in polychaetes, crustaceans, molluscs and fish.

scholarly journals Particulate biogenic barium tracer of mesopelagic carbon remineralization in the Mediterranean Sea (PEACETIME project)

2020 ◽  
Author(s):  
Stéphanie H. M. Jacquet ◽  
Christian Tamburini ◽  
Marc Garel ◽  
Aurélie Dufour ◽  
France Van-Vambeke ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Western Mediterranean ◽  
Central Mediterranean ◽  
Particle Injection ◽  
Western Basin ◽  
Western Mediterranean Sea ◽  
Winter Convection ◽  
Carbon Remineralization ◽  
The Mediterranean ◽  
Heterotrophic Production

Abstract. We report on the sub-basins variability of particulate organic carbon (POC) remineralization in the central and western Mediterranean Sea during a late spring period (PEACETIME cruise). POC remineralization rates (MR) were estimated using the excess non-lithogenic particulate barium (Baxs) inventories in mesopelagic waters (100–1000 m) and compared with prokaryotic heterotrophic production (PHP). MR range from 25 ± 2 to 306 ± 70 mg C m−2 d−1. Results reveal larger MR processes in the Algerian (ALG) basin compared to the Tyrrhenian (TYR) and Ionian (ION) basins. Baxs inventories and PHP also indicates that significant remineralization occurs over the whole mesopelagic layers in the ALG basin in contrast to the ION and TYR basins where remineralization is mainly located in the upper 500 m horizon. We propose that this may be due to particle injection pumps likely driven by strong winter convection in the Western basin of the Mediterranean Sea. This implies significant differences in the remineralization length scale of POC in the central Mediterranean Sea relative to the western region.

eastern and western med Messinian salinity crisis : comparison scenarii and propositions

2020 ◽  
Author(s):  
Christian Gorini ◽  
Romain Pellen ◽  
jean-loup Rubino ◽  
Benoit Didier ◽  
Lucien Montader ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Nile Delta ◽  
Eastern Mediterranean ◽  
Phase 1 ◽  
Threshold Effect ◽  
Western Mediterranean ◽  
Messinian Salinity Crisis ◽  
Central Mediterranean ◽  
Western Basin ◽  
The Mediterranean

<p>The partial sequestration of the Mediterranean Sea from adjacent oceans at the end of the Miocene caused an evaporation surfeit that increased the water salinity above the seafloor of the deep basins and peripheral basins. As a result, an up to 2-3 km-thick sequence of evaporites was deposited in the center of the deep basins. This coincided with the concomitantly intense subaerial erosion of the adjacent margins and important Mass transport deposit events all around the peri- Mediterranean slopes. The volume of evaporites deposited in the deep basins implies a periodic connection with the world oceans concomitant with a huge evaporation during all the MSC. “Deep basins” refers to their position in the deep central parts of the extant Messinian basins in the western basin, the central basins (Ionian) and the eastern basins. The configuration of these basins and the distribution and thickness of the evaporites were very different 6 Myr ago due to the Africa Europe convergence. Evaporites deposition at the edge of the evaporites basins was affected by the geodynamic nature of the margins: Tertiary or Mesozoic passive or transform margins (North Africa), strike slip margins (northern and eastern Levant), convergent margins in the North of the East Mediterranean with evaporites subducted or stacked in a fore arc position. We propose a kinematic reconstruction of the central Mediterranean sea to discuss the connections between the Atlantic waters and the eastern Mediterranean Sea. In this presentation, we show that: (1) There is no opposition between the deposition of the first deep water evaporites and a sea level fall of more than 1000 m. (2) by a threshold effect the eastern Mediterranean could have been more restricted than the western Mediterranean during the phase 1 of the MSC, which could explain the two major incisions observed in the Nile delta (3). At the end of the MSC, this threshold effect could have been maximal with an accommodation space almost filled up and a bathymetry probably not exceeding 50 m in the western Mediterranean and in the Central Mediterranean with deposition of K and Mg evaporates, and almost zero in the Eastern Mediterranean as shown by the fluvial network developed on a wide-spread erosional surface on top of the Levant basin salt. (4) The Messinian salinity crisis (MSC) ended with the rapid re-flooding of the Mediterranean sea. A two-step flooding in the western Mediterranean could find its origin in this threshold effect.</p>

scholarly journals Errata to the Review Article (Medit. Mar. Sci. 11/2, 2010, 381-493): "Alien species in the Mediterranean Sea by 2010. A contribution to the application of European Union’s Marine Strategy Framework Directive (MSFD). Part I. Spatial distribution"

2011 ◽  
Vol 12 (2) ◽  
pp. 509 ◽  
Author(s):  
A. ZENETOS ◽  
S. GOFAS ◽  
M. VERLAQUE ◽  
M.E. CINAR ◽  
J.E GARCIA RASO ◽  
...  
Keyword(s):  
Alien Species ◽  
Mediterranean Sea ◽  
Introduced Species ◽  
Cold Water ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Marine Strategy Framework Directive ◽  
Central Mediterranean ◽  
Total Species Richness ◽  
The Mediterranean

The state-of-art on alien species in the Mediterranean Sea is presented, making distinctions among the four subregions defined in the EU Marine Strategy Framework Directive: (i) the Western Mediterranean Sea (WMED); (ii) the Central Mediterranean Sea (CMED); (iii) the Adriatic Sea (ADRIA); and (iv) the Eastern Mediterranean Sea (EMED). The updated checklist (December 2010) of marine alien species within each subregion, along with their acclimatization status and origin, is provided. A total of 955 alien species is known in the Mediterranean, the vast majority of them having being introduced in the EMED (718), less in the WMED (328) and CMED (267) and least in the Adriatic (171). Of these, 535 species (56%) are established in at least one area.Despite the collective effort of experts who attempted in this work, the number of introduced species remains probably underestimated. Excluding microalgae, for which knowledge is still insufficient, aliens have increased the total species richness of the Mediterranean Sea by 5.9%. This figure should not be directly read as an indication of higher biodiversity, as spreading of so many aliens within the basin is possibly causing biotic homogenization. Thermophilic species, i.e. Indo-Pacific, Indian Ocean, Red Sea, Tropical Atlantic, Tropical Pacific, and circum(sub)tropical, account for 88.4% of the introduced species in the EMED, 72.8% in the CMED, 59.3% in the WMED and 56.1% in the Adriatic. Cold water species, i.e. circumboreal, N Atlantic, and N Pacific, make up a small percentage of the introduced species, ranging between 4.2% and 21.6% and being more numerous in the Adriatic and less so in the EMED.Species that are classified as invasive or potentially invasive are 134 in the whole of the Mediterranean: 108 are present in the EMED, 76 in the CMED, 53 in the Adriatic and 64 in the WMED. The WMED hosts most invasive macrophytes, whereas the EMED has the lion’s share in polychaetes, crustaceans, molluscs and fish.

scholarly journals A massive update of non-indigenous species records in Mediterranean marinas

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3954 ◽  
Author(s):  
Aylin Ulman ◽  
Jasmine Ferrario ◽  
Anna Occhpinti-Ambrogi ◽  
Christos Arvanitidis ◽  
Ada Bandi ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Indigenous Species ◽  
Central Mediterranean ◽  
Indigenous Status ◽  
Mediterranean Countries ◽  
Saccostrea Glomerata ◽  
The Mediterranean ◽  
Non Indigenous Species

The Mediterranean Sea is home to over 2/3 of the world’s charter boat traffic and hosts an estimated 1.5 million recreational boats. Studies elsewhere have demonstrated marinas as important hubs for the stepping-stone transfer of non-indigenous species (NIS), but these unique anthropogenic, and typically artificial habitats have largely gone overlooked in the Mediterranean as sources of NIS hot-spots. From April 2015 to November 2016, 34 marinas were sampled across the following Mediterranean countries: Spain, France, Italy, Malta, Greece, Turkey and Cyprus to investigate the NIS presence and richness in the specialized hard substrate material of these marina habitats. All macroinvertebrate taxa were collected and identified. Additionally, fouling samples were collected from approximately 600 boat-hulls from 25 of these marinas to determine if boats host diverse NIS not present in the marina. Here, we present data revealing that Mediterranean marinas indeed act as major hubs for the transfer of marine NIS, and we also provide evidence that recreational boats act as effective vectors of spread. From this wide-ranging geographical study, we report here numerous new NIS records at the basin, subregional, country and locality level. At the basin level, we report three NIS new to the Mediterranean Sea (Achelia sawayai sensu lato,Aorides longimerus,Cymodoceaff.fuscina), and the re-appearance of two NIS previously known but currently considered extinct in the Mediterranean (Bemlos leptocheirus, Saccostrea glomerata). We also compellingly update the distributions of many NIS in the Mediterranean Sea showing some recent spreading; we provide details for 11 new subregional records for NIS (Watersipora arcuata,Hydroides brachyacantha sensu latoandSaccostrea glomeratanow present in the Western Mediterranean;Symplegma brakenhielmi,Stenothoe georgiana,Spirobranchus tertaceros sensu lato,Dendostrea folium sensu latoandParasmittina egyptiacanow present in the Central Mediterranean, andW. arcuata,Bemlos leptocheirusandDyspanopeus sayiin the Eastern Mediterranean). We also report 51 new NIS country records from recreational marinas: 12 for Malta, 10 for Cyprus, nine for Greece, six for Spain and France, five for Turkey and three for Italy, representing 32 species. Finally, we report 20 new NIS records (representing 17 species) found on recreational boat-hulls (mobile habitats), not yet found in the same marina, or in most cases, even the country. For each new NIS record, their native origin and global and Mediterranean distributions are provided, along with details of the new record. Additionally, taxonomic characters used for identification and photos of the specimens are also provided. These new NIS records should now be added to the relevant NIS databases compiled by several entities. Records of uncertain identity are also discussed, to assess the probability of valid non-indigenous status.

scholarly journals Parasites of the head of Scomber colias (Osteichthyes: Scombridae) from the western Mediterranean Sea

2014 ◽  
Vol 59 (1) ◽  
Author(s):  
Salvatore Mele ◽  
Maria Pennino ◽  
Maria Piras ◽  
José Bellido ◽  
Giovanni Garippa ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Parasite Fauna ◽  
Point Of View ◽  
Published Data ◽  
Multivariate Techniques ◽  
Western Mediterranean Sea ◽  
Scomber Colias ◽  
Non Parametric

AbstractThe metazoan parasite assemblage of the head of 30 specimens of the Atlantic chub mackerel (Scomber colias) from the western Mediterranean Sea was analysed. Eight species of parasites were found, four mazocraeid monogeneans: Grubea cochlear (prevalence = 10%), Kuhnia scombercolias (59%), K. scombri (52%), Pseudokuhnia minor (86%); three didymozoid trematodes: Nematobothrium cf. faciale (21%), N. filiforme (41%), N. scombri (7%); and one laerneopodid copepod: Clavelissa scombri (7%). Results were compared with previously published data from 14 localities of the eastern Mediterranean Sea and the Atlantic Ocean, using non-parametric univariate and multivariate analyses, and the whole parasite fauna of S. colias was compared with that of the congeners (S. australasicus, S. japonicus and S. scombrus). Parasites showed to reflect the biogeographical and phylogenetic history of host. From a methodological point of view, the use of both non-parametric univariate and multivariate techniques proved to be effective tools to detect dissimilarities between parasite assemblages.

scholarly journals Further spreading of the non-indigenous bryozoan Celleporaria brunnea in the Mediterranean Sea: port to port morphological variations

2015 ◽  
Author(s):  
Jasmine Ferrario ◽  
Agnese Marchini ◽  
Martina Marić ◽  
Dan Minchin ◽  
Anna Occhipinti-Ambrogi
Keyword(s):  
Mediterranean Sea ◽  
Western Mediterranean ◽  
Indigenous Species ◽  
Large Variability ◽  
Morphometric Characters ◽  
Morphological Variations ◽  
The North ◽  
Western Mediterranean Sea ◽  
The Pacific ◽  
The Mediterranean

The Pacific cheilostome bryozoan Celleporaria brunnea (Hincks, 1884), a non-indigenous species already known for the Mediterranean Sea, was recorded in 2013-2014 from nine Italian port localities (Genoa, Santa Margherita Ligure, La Spezia, Leghorn, Viareggio, Olbia, Porto Rotondo, Porto Torres and Castelsardo) in the North-western Mediterranean Sea; in 2014 it was also found for the first time in the Adriatic Sea, in the marina “Kornati”, Biograd na Moru (Croatia). In Italy, specimens of C. brunnea were found in 44 out of 105 samples (48% from harbour sites ad 52% from marinas). These data confirm and update the distribution of C. brunnea in the Mediterranean Sea, and provide evidence that recreational boating is a vector responsible for the successful spread of this species. Previous literature data have shown the existence of differences in orifice and interzooidal avicularia length and width among different localities of the invaded range of C. brunnea. Therefore, measurements of orifice and avicularia were assessed for respectively 30 zooids and 8 to 30 interzooidal avicularia for both Italian and Croatian localities, and compared with literature data, in order to verify the existence of differences in the populations of C. brunnea that could reflect the geographic pattern of its invasion range. Our data show high variability of orifice measures among and within localities: zooids with broader than long orifice coexisted with others displaying longer than broad orifice, or similar values for both length and width. The morphological variation of C. brunnea in these localities, and above all the large variability of samples within single localities or even within colonies poses questions on the reliability of such morphometric characters for inter and intraspecific evaluations.

scholarly journals The effect of cyclones crossing the Mediterranean region on sea level anomalies at the Mediterranean Sea coast

2019 ◽  
Author(s):  
Piero Lionello ◽  
Dario Conte ◽  
Marco Reale
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Eastern Mediterranean ◽  
Storm Track ◽  
Western Mediterranean ◽  
Residual Water ◽  
Positive Anomaly ◽  
Western Basin ◽  
Sea Level Anomalies ◽  
The Mediterranean

Abstract. Large positive and negative sea level anomalies at the coast of the Mediterranean Sea are linked to intensity and position of cyclones moving along the Mediterranean storm track, with dynamics involving different factors. This analysis is based on a model hindcast and considers nine coastal stations, which are representative of sea level anomalies with different magnitude and characteristics. When a shallow water fetch is present, the wind around the cyclone center is the main cause of sea level positive and negative anomalies, depending on its onshore or offshore direction. The inverse barometer effect produces a positive anomaly at the coast near the cyclone pressure minimum and a negative anomaly at the opposite side of the Mediterranean Sea, because a cross-basin mean sea level pressure gradient is associated to the presence of a cyclone. Further, at some stations, negative sea level anomalies are reinforced by a residual water mass redistribution within the basin, which is associated with a transient response to the atmospheric pressure forcing. Though the link between presence of a cyclone in the Mediterranean has comparable importance for positive and negative anomalies, the relation between cyclone position and intensity is stronger for the magnitude of positive events. Area of cyclogenesis, track of the central minimum and position at the time of the event differ depending on the location where the sea level anomaly occurs and on its sign. The western Mediterranean is the main cyclogenesis area for both positive and negative anomalies, overall. Atlantic cyclones mainly produce positive sea level anomalies in the western basin. At the easternmost stations, positive anomalies are caused by Cyclogenesis in the Eastern Mediterranean. North Africa cyclogeneses are a major source of positive anomalies at the central African coast and negative anomalies at the eastern Mediterranean and North Aegean coast.

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