Holocene Paleoenvironments in the Western Mediterranean Sea: palynological evidences on the Algerian coast and climatic reconstructions

2020 ◽  
Author(s):  
Vincent Coussin ◽  
Aurelie Penaud ◽  
Nathalie Combourieu-Nebout ◽  
Odile Peyron ◽  
Yannick Miras ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Ocean Circulation ◽  
Environmental Changes ◽  
Regional Climate ◽  
Western Mediterranean ◽  
Climatic Conditions ◽  
Modern Analogue ◽  
Basin Scale ◽  
Algerian Coast ◽  
The Mediterranean

<p>Past and present oceanographic and climatic conditions along the Algerian coast involve complex mechanisms. Atlantic Ocean surface waters enter the Mediterranean Sea by the Gibraltar strait and become the Algerian current flowing along the North African coast forming a succession of eddies. Deep-water upwelling plumes is another recurrent feature of the ocean circulation along the Algerian margin. Past vegetation changes and the role of paleohydrological changes have been poorly described in this region. This work combines palynological (pollen and dinoflagellate cysts) and biomarker data to assess changing environmental and climatic conditions over the past 14 ka BP (late glacial and Holocene) acquired from the marine core MD04-2801 (Algerian coast, 2067 m water depth, Prisma cruise).</p><p>A total of 79 samples have been analyzed over the last 14 000 years BP. Palynological and organic biomarker proxy data were used to investigate the links between past sea surface temperature (SSTs) and hydrological changes on the observed regional environmental changes documented at centennial timescale resolution. Our data indicate (i) recurrent upwelling cells during relatively dry climatic conditions of the Younger Dryas (12.7 to 11.7 ka BP), the Early Holocene (11.7 to 8.2 ka BP) and from 6 ka BP onwards, (ii) an increase of fluvial discharges between 8.2 and 6 ka BP during the African Humid Period, and the concomitant colonization of coastlands by the Mediterranean forest. The comparison between our results and other western Mediterranean palynological records underlines the singularity of our results along the Algerian margin in terms of dinocyst assemblages and notably the over-representation of heterotrophic taxa. Palynological data shows direct links between continental dryness and marine hydrological conditions. Finally, we applied the Modern Analogue Technique to our pollen assemblages along the core in order to reconstruct seasonal and annual precipitations and temperatures and compare our local climatic patterns to regional climate signals at basin scale for the Holocene period.</p>

scholarly journals Inventory and the biogeographical affinities of Annelida Polychaeta in theAlgerian coastline (Western Mediterranean)

2020 ◽  
Vol 21 (1) ◽  
pp. 157
Author(s):  
ALI BAKALEM ◽  
PATRICK GILLET ◽  
JEAN-PHILIPPE PEZY ◽  
JEAN-CLAUDE DAUVIN
Keyword(s):  
Mediterranean Sea ◽  
World Ocean ◽  
Aegean Sea ◽  
Western Mediterranean ◽  
The Black Sea ◽  
Polychaete Species ◽  
Western Mediterranean Sea ◽  
Atlantic Origin ◽  
Algerian Coast ◽  
The Mediterranean

The data analyzed to inventory of all polychaetes in Algerian waters make it possible to estimate the diversity of this group to 534 species. The most diversified families are Syllidae (66 species), Spionidae (37 species) and Terebellidae (27 species).The presence of these listed species along the Algerian coast is compared with their occurrence in nine other areas of the Mediterranean Sea, in the Black Sea and in four other areas of the World Ocean. Comparison are also made with respect to the indications of the biogeographical origin for each species. The polychaete fauna of the Algerian coast is among the richest of the Mediterranean Sea and comparable to that reported for the French Mediterranean continental shelf  and the Aegean Sea, but higher that that found in the bordering coastlines of Morocco and Tunisia. Most of the species have an Atlantic origin and are present in the western Mediterranean Sea; this inventory includes eight Non-Indigenous Polychaete Species in the Algerian waters.

scholarly journals Subsurface iron accumulation and rapid aluminum removal in the Mediterranean following African dust deposition

2021 ◽  
Vol 18 (24) ◽  
pp. 6435-6453
Author(s):  
Matthieu Bressac ◽  
Thibaut Wagener ◽  
Nathalie Leblond ◽  
Antonio Tovar-Sánchez ◽  
Céline Ridame ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Comprehensive Evaluation ◽  
Vertical Mixing ◽  
Western Mediterranean ◽  
Surface Mixed Layer ◽  
Dust Deposition ◽  
Near Surface ◽  
Surface Ocean ◽  
Basin Scale ◽  
The Mediterranean

Abstract. Mineral dust deposition is an important supply mechanism for trace elements in the low-latitude ocean. Our understanding of the controls of such inputs has been mostly built on laboratory and surface ocean studies. The lack of direct observations and the tendency to focus on near-surface waters prevent a comprehensive evaluation of the role of dust in oceanic biogeochemical cycles. In the frame of the PEACETIME project (ProcEss studies at the Air-sEa Interface after dust deposition in the MEditerranean sea), the responses of the aluminum (Al) and iron (Fe) cycles to two dust wet deposition events over the central and western Mediterranean Sea were investigated at a timescale of hours to days using a comprehensive dataset gathering dissolved and suspended particulate concentrations, along with sinking fluxes. Dissolved Al (dAl) removal was dominant over dAl released from dust. The Fe / Al ratio of suspended and sinking particles revealed that biogenic particles, and in particular diatoms, were key in accumulating and exporting Al relative to Fe. By combining these observations with published Al / Si ratios of diatoms, we show that adsorption onto biogenic particles, rather than active uptake, represents the main sink for dAl in Mediterranean waters. In contrast, systematic dissolved Fe (dFe) accumulation occurred in subsurface waters (∼ 100–1000 m), while dFe input from dust was only transient in the surface mixed layer. The rapid transfer of dust to depth, the Fe-binding ligand pool in excess to dFe in subsurface (while nearly saturated in surface), and low scavenging rates in this particle-poor depth horizon are all important drivers of this subsurface dFe enrichment. At the annual scale, this previously overlooked mechanism may represent an additional pathway of dFe supply for the surface ocean through diapycnal diffusion and vertical mixing. However, low subsurface dFe concentrations observed at the basin scale (

scholarly journals Dynamic prokaryotic communities in the dark western Mediterranean Sea

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Catalina Mena ◽  
Rosa Balbín ◽  
Patricia Reglero ◽  
Melissa Martín ◽  
Rocío Santiago ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Community Composition ◽  
Environmental Changes ◽  
Spatial Dynamics ◽  
Deep Ocean ◽  
Western Mediterranean ◽  
Western Mediterranean Sea ◽  
Environmental Perturbations ◽  
Basin Scale ◽  
Major Increase

AbstractDark ocean microbial dynamics are fundamental to understand ecosystem metabolism and ocean biogeochemical processes. Yet, the ecological response of deep ocean communities to environmental perturbations remains largely unknown. Temporal and spatial dynamics of the meso- and bathypelagic prokaryotic communities were assessed throughout a 2-year seasonal sampling across the western Mediterranean Sea. A common pattern of prokaryotic communities’ depth stratification was observed across the different regions and throughout the seasons. However, sporadic and drastic alterations of the community composition and diversity occurred either at specific water masses or throughout the aphotic zone and at a basin scale. Environmental changes resulted in a major increase in the abundance of rare or low abundant phylotypes and a profound change of the community composition. Our study evidences the temporal dynamism of dark ocean prokaryotic communities, exhibiting long periods of stability but also drastic changes, with implications in community metabolism and carbon fluxes. Taken together, the results highlight the importance of monitoring the temporal patterns of dark ocean prokaryotic communities.

scholarly journals Subsurface iron accumulation and rapid aluminium removal in the Mediterranean following African dust deposition

2021 ◽  
Author(s):  
Matthieu Bressac ◽  
Thibaut Wagener ◽  
Nathalie Leblond ◽  
Antonio Tovar-Sánchez ◽  
Céline Ridame ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Comprehensive Evaluation ◽  
Western Mediterranean ◽  
Surface Mixed Layer ◽  
Dust Deposition ◽  
Near Surface ◽  
Surface Ocean ◽  
Supply Mechanism ◽  
Basin Scale ◽  
The Mediterranean

Abstract. Mineral dust deposition is an important supply mechanism for trace elements in the low-latitude ocean. Our understanding of the controls of such inputs has been mostly built onto laboratory and surface ocean studies. The lack of direct observations and the tendency to focus on near surface waters prevent a comprehensive evaluation of the role of dust in oceanic biogeochemical cycles. In the frame of the PEACETIME project (ProcEss studies at the Air-sEa Interface after dust deposition in the MEditerranean sea), the responses of the aluminium (Al) and iron (Fe) cycles to two dust wet deposition events over the central and western Mediterranean Sea were investigated at a timescale of hours to days using a comprehensive dataset gathering dissolved and suspended particulate concentrations, along with sinking fluxes. Dissolved Al (dAl) removal was dominant over dAl released from dust. Fe / Al ratio of suspended and sinking particles revealed that biogenic particles, and in particular diatoms, were key in accumulating and exporting Al relative to Fe. By combining these observations with published Al / Si ratios of diatoms, we show that adsorption onto biogenic particles, rather than active uptake, represents the main sink for dAl in Mediterranean waters. In contrast, systematic dissolved Fe (dFe) accumulation occurred in subsurface waters (~100–1000 m), while dFe input from dust was only transient in the surface mixed-layer. The rapid transfer of dust to depth (up to ~180 m d−1), the Fe-binding ligand pool in excess to dFe in subsurface (while nearly-saturated in surface), and low scavenging rates in this particle-poor depth horizon are all important drivers of this subsurface dFe enrichment. At the annual scale, this previously overlooked mechanism may represent an additional pathway of dFe supply for the surface ocean through diapycnal diffusion and vertical mixing. However, low subsurface dFe concentrations observed at the basin scale (< 0.5 nmol kg−1) questions the residence time for this dust-derived subsurface reservoir, and hence its role as a supply mechanism for the surface ocean, stressing the need for further studies. Finally, these contrasting responses indicate that dAl is a poor tracer of dFe input in the Mediterranean Sea.

Mediterranean Marine heatwaves: On the comparison of the physical drivers behind the 2003 and 2015 events

2020 ◽  
Author(s):  
Sofia Darmaraki ◽  
Samuel Somot ◽  
Robin Waldman ◽  
Florence Sevault ◽  
Pierre Nabat ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Large Scale ◽  
Climate Model ◽  
Heat Budget ◽  
Hot Spot ◽  
Regional Climate ◽  
Detection Algorithm ◽  
Heat Fluxes ◽  
Basin Scale ◽  
The Mediterranean

&lt;p&gt;Over the last decade, an intensification of extreme warm temperature events, termed as marine heatwaves (MHWs), has been reported in the Mediterranean Sea, itself a &amp;#8220;Hot Spot&amp;#8221; region for climate change. In the summer of 2003, a major MHW occurred in the Mediterranean with abnormal surface temperature anomalies of 2-3 C&amp;#186; persisting for over a month. In 2015, an undocumented but more intense summer MHW affected almost the entire Mediterranean Sea with regional temperatures anomalies reaching 4-5 C&amp;#186;. Here, we apply a MHW detection algorithm for long-lasting and large-scale summer events, on the hindcast output of a fully-coupled regional climate model (RCSM). We first examine the spatial variability and temporal evolution of both the 2003 and 2015 events. Then a basin-scale analysis of the mixed layer heat budget during each MHW is performed. The ocean and atmospheric components&amp;#8217; contribution is investigated separately during the onset, peak, and decay phases of both events, in order to disentangle the dominant physical processes behind each event. On the large-scale, our results indicate a key role of the wind forcing and the air-sea heat fluxes, while advection processes become more important at local scales. This study provides a comparison of the underlying mechanisms behind the two most intense MHW detected in the Mediterranean Sea during the last decade, constituting key information for the marine ecosystems of the region.&lt;/p&gt;

First record of Sphoeroides spengleri (Osteichthyes: Tetraodontidae) in the Mediterranean Sea

2004 ◽  
Vol 84 (5) ◽  
pp. 1089-1090 ◽  
Author(s):  
J.A. Reina-Hervás ◽  
J.E. García Raso ◽  
M.E. Manjón-Cabeza
Keyword(s):  
Alien Species ◽  
Mediterranean Sea ◽  
First Record ◽  
Western Mediterranean ◽  
Alboran Sea ◽  
Total Length ◽  
The Mediterranean ◽  
Alborán Sea

The capture of a specimen of Sphoeroides spengleri (Osteichthyes: Tetraodontidae), 17 December 2000 and 29·7 mm total length, from the Málaga coast (Alborán Sea, western Mediterranean) represents the first record of a new alien species for Mediterranean waters.

A Near-Uniform Basin-Wide Sea Level Fluctuation of the Mediterranean Sea

2007 ◽  
Vol 37 (2) ◽  
pp. 338-358 ◽  
Author(s):  
Ichiro Fukumori ◽  
Dimitris Menemenlis ◽  
Tong Lee
Keyword(s):  
Atlantic Ocean ◽  
Mediterranean Sea ◽  
Sea Level ◽  
Ocean Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Level Fluctuation ◽  
Strait Of Gibraltar ◽  
Sea Level Fluctuation ◽  
The Mediterranean

Abstract A new basin-wide oscillation of the Mediterranean Sea is identified and analyzed using sea level observations from the Ocean Topography Experiment (TOPEX)/Poseidon satellite altimeter and a numerical ocean circulation model. More than 50% of the large-scale, nontidal, and non-pressure-driven variance of sea level can be attributed to this oscillation, which is nearly uniform in phase and amplitude across the entire basin. The oscillation has periods ranging from 10 days to several years and has a magnitude as large as 10 cm. The model suggests that the fluctuations are driven by winds at the Strait of Gibraltar and its neighboring region, including the Alboran Sea and a part of the Atlantic Ocean immediately to the west of the strait. Winds in this region force a net mass flux through the Strait of Gibraltar to which the Mediterranean Sea adjusts almost uniformly across its entire basin with depth-independent pressure perturbations. The wind-driven response can be explained in part by wind setup; a near-stationary balance is established between the along-strait wind in this forcing region and the sea level difference between the Mediterranean Sea and the Atlantic Ocean. The amplitude of this basin-wide wind-driven sea level fluctuation is inversely proportional to the setup region’s depth but is insensitive to its width including that of Gibraltar Strait. The wind-driven fluctuation is coherent with atmospheric pressure over the basin and contributes to the apparent deviation of the Mediterranean Sea from an inverse barometer response.

scholarly journals Ecological opportunities and specializations shaped genetic divergence in a highly mobile marine top predator

2014 ◽  
Vol 281 (1795) ◽  
pp. 20141558 ◽  
Author(s):  
Marie Louis ◽  
Michael C. Fontaine ◽  
Jérôme Spitz ◽  
Erika Schlund ◽  
Willy Dabin ◽  
...  
Keyword(s):  
Population Structure ◽  
Mediterranean Sea ◽  
Environmental Changes ◽  
Demographic History ◽  
World Ocean ◽  
Ecological Niches ◽  
Morphological Divergence ◽  
Evolutionary Diversification ◽  
The Mediterranean ◽  
Population Demographic

Environmental conditions can shape genetic and morphological divergence. Release of new habitats during historical environmental changes was a major driver of evolutionary diversification. Here, forces shaping population structure and ecotype differentiation (‘pelagic’ and ‘coastal’) of bottlenose dolphins in the North-east Atlantic were investigated using complementary evolutionary and ecological approaches. Inference of population demographic history using approximate Bayesian computation indicated that coastal populations were likely founded by the Atlantic pelagic population after the Last Glacial Maxima probably as a result of newly available coastal ecological niches. Pelagic dolphins from the Atlantic and the Mediterranean Sea likely diverged during a period of high productivity in the Mediterranean Sea. Genetic differentiation between coastal and pelagic ecotypes may be maintained by niche specializations, as indicated by stable isotope and stomach content analyses, and social behaviour. The two ecotypes were only weakly morphologically segregated in contrast to other parts of the World Ocean. This may be linked to weak contrasts between coastal and pelagic habitats and/or a relatively recent divergence. We suggest that ecological opportunity to specialize is a major driver of genetic and morphological divergence. Combining genetic, ecological and morphological approaches is essential to understanding the population structure of mobile and cryptic species.

scholarly journals First record of Solea (Microchirus) boscanion (Osteichthyes: Soleidae) in the Mediterranean Sea, with data on other sympatric soleid species

2002 ◽  
Vol 82 (5) ◽  
pp. 907-911 ◽  
Author(s):  
Enric Massutí ◽  
J.A. Reina-Hervás ◽  
Domingo Lloris ◽  
L. Gil de Sola
Keyword(s):  
Climate Change ◽  
Mediterranean Sea ◽  
First Record ◽  
Western Mediterranean ◽  
The Other ◽  
The Mediterranean

The capture of five specimens of Solea (Microchirus) boscanion (Osteichthyes: Soleidae), a species previously unrecorded in the Mediterranean, is reported from the Iberian coast (western Mediterranean). The main morphometric and meristic measurements of this species with data of the other sympatric, and morphologically very similar, soleids Microchirus variegatus and Buglossidium luteum are also given. The record is discussed in relation to climate change and competition between species.

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.

Sign in / Sign up

Export Citation Format

Share Document