scholarly journals Water column dynamics during the last interglacial anoxic event in the Mediterranean (sapropel S5)

2006 ◽  
Vol 21 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
E. J. Rohling ◽  
E. C. Hopmans ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Water Column ◽  
Last Interglacial ◽  
Anoxic Event ◽  
Column Dynamics ◽  
The Mediterranean

Radiocarbon dating of individual foram tests show that alleged Lessepsian species are of Holocene age

2021 ◽  
Author(s):  
Paolo G. Albano ◽  
Anna Sabbatini ◽  
Jonathan Lattanzio ◽  
Jan Steger ◽  
Sönke Szidat ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Red Sea ◽  
Native Species ◽  
Radiocarbon Dating ◽  
Suez Canal ◽  
Tropical Species ◽  
Indigenous Species ◽  
Last Interglacial ◽  
Sediment Depth ◽  
The Mediterranean

<p>The Lessepsian invasion – the largest marine biological invasion – followed the opening of the Suez Canal in 1869 (81 years BP). Shortly afterwards, tropical species also distributed in the Red Sea appeared on Mediterranean shores: it was the dawn of what would become the invasion of several hundred tropical species. The time of the Suez Canal opening coincided with an acceleration in natural history exploration and description, but the eastern sectors of the Mediterranean Sea lagged behind and were thoroughly explored only in the second half of the 20<sup>th</sup> century. Many parts are still insufficiently studied today. Baseline information on pre-Lessepsian ecosystem states is thus scarce. This knowledge gap has rarely been considered by invasion scientists: every new finding of species belonging to tropical clades has been assumed to be a Lessepsian invader.</p><p>We here question this assumption by radiocarbon dating seven individual tests of miliolids – imperforated calcareous foraminifera – belonging to five alleged non-indigenous species. Tests were found in two sediment cores collected at 30 and 40 m depth off Ashqelon, on the Mediterranean Israeli shelf. We dated one <em>Cribromiliolinella milletti </em>(core at 40 m, 20 cm sediment depth), three <em>Nodophthalmidium antillarum </em>(core at 40 m, 35 cm sediment depth), one <em>Miliolinella </em>cf. <em>fichteliana </em>(core at 30 m, 110 cm sediment depth), one <em>Articulina alticostata </em>(core at 40 m, 35 cm sediment depth) and one <em>Spiroloculina antillarum </em>(core at 30 m, 110 cm sediment depth). All foraminiferal tests proved to be of Holocene age, with a median calibrated age spanning between 749 and 8285 years BP. Only one test of <em>N. antillarum</em> showed a 2-sigma error overlapping the time of the opening of the Suez Canal, but with a median age of 1123 years BP. Additionally, a thorough literature search resulted in a further record of <em>S. antillarum</em> in a core interval dated 1820–2064 years BP in Turkey.</p><p>Therefore, these foraminiferal species are not introduced, but native species. They are all circumtropical or Indo-Pacific and in the Mediterranean distributed mostly in the eastern sectors (only <em>S. antillarum</em> occurs also in the Adriatic Sea). Two hypotheses can explain our results: these species are Tethyan relicts that survived the Messinian salinity crisis (5.97–5.33 Ma) and the glacial periods of the Pleistocene in the Eastern Mediterranean, which may have never desiccated completely during the Messinian crisis and which may have worked as a warm-water refugium in the Pleistocene; or they entered the Mediterranean Sea from the Red Sea more recently but before the opening of the Suez Canal, for example during the Last Interglacial (MIS5e) high-stand (125,000 years BP) when the flooded Isthmus of Suez enabled exchanges between the Mediterranean and the Indo-Pacific fauna. The recognition that some alleged Lessepsian invaders are in fact native species influences our understanding of the invasion process, its rates and environmental correlates.</p>

scholarly journals Excursions to C<sub>4</sub> vegetation recorded in the Upper Pleistocene loess of Surduk (Northern Serbia): an organic isotope geochemistry study

2013 ◽  
Vol 9 (3) ◽  
pp. 1001-1014 ◽  
Author(s):  
C. Hatté ◽  
C. Gauthier ◽  
D.-D. Rousseau ◽  
P. Antoine ◽  
M. Fuchs ◽  
...  
Keyword(s):  
General Pattern ◽  
Free Water ◽  
Circulation Pattern ◽  
Water Evaporation ◽  
C3 Plants ◽  
Mean Annual Precipitation ◽  
Glacial Cycle ◽  
Last Interglacial ◽  
The Balkans ◽  
The Mediterranean

Abstract. Loess sequences have been intensively studied to characterize past glacial climates of the 40–50° north and south latitude zones. Combining different approaches of sedimentology, magnetism, geochemistry, geochronology and malacology allows the general pattern of the climate and environment of the last interglacial–glacial cycle in Eurasia and America to be characterized. Previous studies performed in Europe have highlighted the predominance (if not the sole occurrence) of C3 vegetation. The presence of C3 plants suggests a regular distribution of precipitation along the year. Therefore, even if the mean annual precipitation remained very low during the most extensive glacial times, free water was available for more than 2 months per year. Contrarily, the δ13C record of Surduk (Serbia) clearly shows the occurrence and dominance of C4 plants during at least 4 episodes of the last glacial times at 28.0–26.0 kyr cal BP, 31.4–30.0 kyr cal BP, 53.4–44.5 kyr cal BP and 86.8–66.1 kyr. The C4 plant development is interpreted as a specific atmospheric circulation pattern that induces short and dry summer conditions. As possible explanation, we propose that during "C4 episodes", the Mediterranean Sea would have been under the combined influence of the following: (i) a strong meridional circulation unfavorable to water evaporation that reduced the Mediterranean precipitation on the Balkans; and (ii) a high positive North Atlantic Western Russian (NA/WR)-like atmospheric pattern that favored northerlies over westerlies and reduced Atlantic precipitation over the Balkans. This configuration would imply very dry summers that did not allow C3 plants to grow, thus supporting C4 development. The intra-"C4 episode" periods would have occurred under less drastic oceanic and atmospheric patterns that made the influence of westerlies on the Balkans possible.

scholarly journals Fleshy Red Algae Mats Influence Their Environment in the Mediterranean Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Neele Schmidt ◽  
Yusuf C. El-Khaled ◽  
Felix I. Roßbach ◽  
Christian Wild
Keyword(s):  
Environmental Factors ◽  
Light Intensity ◽  
Water Temperature ◽  
Mediterranean Sea ◽  
Water Column ◽  
Red Algae ◽  
Water Movement ◽  
Ecosystem Engineer ◽  
Overlying Water ◽  
The Mediterranean

In the Mediterranean Sea, the fleshy red alga Phyllophora crispa forms dense mats of up to 15 cm thickness, mainly located on rocky substrates in water depths below 20 m. Because of the observed density of these mats and some first observations, we hypothesize that P. crispa is a yet undescribed ecosystem engineer that provides a multitude of ecological niches for associated organisms along small-scale environmental gradients. Therefore, we conducted an in-situ pilot study in the Western Mediterranean Sea to assess potential influence of the algae mats on the key environmental factors water movement, temperature and light intensity. We comparatively and simultaneously measured in P. crispa mats, in neighboring Posidonia oceanica seagrass meadows, on neighboring bare rocky substrates without algae mats, and in the directly overlying water column. We used several underwater logging sensors and gypsum clod cards. Findings revealed that P. crispa significantly reduced water movement by 41% compared to the overlying water column, whereas water movement was not affected by P. oceanica meadows and bare rocky substrates. Surprisingly, P. crispa increased the water temperature by 0.3°C relative to the water column, while the water temperature in P. oceanica and on bare rocky substrates was reduced by 0.5°C. Light intensity inside the red algae mats was reduced significantly by 69% compared to the water column. This was similar to measured light reduction of 77% by P. oceanica. These findings highlight the strong influence of the dense red algae mats on some key environmental factors. Their influence is obviously similar or even higher than for the well-known seagrass ecosystem engineer. This may be a factor that facilitates associated biodiversity similarly as described for P. oceanica.

Erosional landforms and biological structures in tectonically stable areas in the Mediterranean basin

2021 ◽  
Author(s):  
Valeria Vaccher ◽  
Stefano Furlani ◽  
Sara Biolchi ◽  
Chiara Boccali ◽  
Alice Busetti ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Mediterranean Basin ◽  
Vertical Position ◽  
Structural Constraints ◽  
Last Interglacial ◽  
Central Mediterranean ◽  
Biological Structures ◽  
The Mediterranean ◽  
The Mediterranean Basin

&lt;p&gt;The Mediterranean basin displays a variety of neotectonics scenarios leading to positive or negative vertical displacement, which change the vertical position of former coastlines. As a result, the best locations to evaluate former sea levels and validate sea-level models are tectonically stable areas. There are a number of coastal areas considered to be stable based on the elevation of paleo sea-level markers, the absence of historical seismicity, and by their position far from major Mediterranean faults. We report here the results of swim surveys carried out at such locations following the Geoswim approach described by Furlani (2020) in nine coastal sectors of the central Mediterranean Sea (Egadi Island - Marettimo, Favignana, Levanzo, Gaeta Promontory, Circeo Promontory, North Sardinia - Razzoli, Budelli, Santa Maria, NW Sardinia &amp;#8211; Capocaccia, Maddalena Archipelago, Tavolara Island, East of Malta - Ahrax Point, Bugibba-Qawra, Delimara, Addura, Palermo, Ansedonia Promontory). All the sites are considered to be tectonically stable, as validated by the elevation of sea-level indicators. In fact, modern and MIS5.5 (last interglacial) m.s.l. altitudes fit well with accepted figures based upon field data and model projections. Starting from precise morphometric parameters such as the size of tidal notches and indicative landforms and biological structures, we have developed a procedure that integrates multiple geomorphological and biological descriptors applicable to the vast spectrum of locally diverse coastal situations occurring in the Mediterranean Sea. We took detailed measurements of features such as modern and MIS5.5 tidal notches at 146 sites in all the areas, the absence of modern tidal notch at Circeo promontory, shore platforms, and MIS5.5 marine terraces at Egadi islands, Malta, and Palermo. Biological structures were also measured. In particular, vermetid platforms at Egadi, Palermo and Malta. The morphometric characteristics of these indicators depend on 1) local geological and structural constraints, 2) local geomorphotypes, 3) climate, sea, and weather conditions that affect geomorphic and biological processes, and 4) the sea level change history.&lt;/p&gt;

On the lack of widespread bottom simulating reflectors in the Mediterranean Basin

2021 ◽  
Author(s):  
Cristina Corradin ◽  
Angelo Camerlenghi ◽  
Michela Giustiniani ◽  
Umberta Tinivella ◽  
Claudia Bertoni
Keyword(s):  
Water Column ◽  
Pore Water ◽  
Mediterranean Basin ◽  
Stability Field ◽  
Hydrocarbon Gases ◽  
Wide Range ◽  
Bottom Simulating Reflectors ◽  
Messinian Evaporites ◽  
The Mediterranean ◽  
The Mediterranean Basin

&lt;p&gt;In the Mediterranean Basin, gas hydrate bottom simulating reflectors (BSR) are absent, with very few and spatially limited exceptions occurring in Eastern Mediterranean mud volcanoes and in the Nile deep sea fan. This is in spite of widespread occurrence of hydrocarbon gases in the subsurface, mainly biogenic methane, from a wide range of stratigraphic intervals.&lt;br&gt;In this study we model the methane hydrate stability field using all available information on DSDP and ODP boreholes in the Western Mediterranean and in the Levant Basin, including the downhole changes of pore water salinity. The models take into account the consequent pore water density changes and use known estimates of geothermal gradient. None of the drilled sites were located on seismic profiles in which a BSR is present.&lt;br&gt;The modelled base of the stability field of methane hydrates is located variably within, below, or even above the drilled sedimentary section (the latter case implies that it is located in the water column). We discuss the results in terms of geodynamic environments, areal distribution of Messinian evaporites, upward ion diffusion from Messinian evaporites, organic carbon content, and the peculiar thermal structure of the Mediterranean water column. &lt;br&gt;We conclude that the cumulative effects of geological and geochemical environments make the Mediterranean Basin a region that is unfavorable to the existence of BSRs in the seismic record, and most likely to the existence of natural gas hydrates below the seabed.&lt;br&gt;&lt;br&gt;&lt;/p&gt;

scholarly journals Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

2020 ◽  
Author(s):  
Wytze K. Lenstra ◽  
Martijn Hermans ◽  
Marie J.M. Séguret ◽  
Rob Witbaard ◽  
Silke Severmann ◽  
...  
Keyword(s):  
Water Column ◽  
Column Dynamics ◽  
Iron And Manganese

Enhanced seasonality of precipitation in the Mediterranean during the early part of the Last Interglacial

Geology ◽  
2012 ◽  
Vol 40 (10) ◽  
pp. 919-922 ◽  
Author(s):  
Alice M. Milner ◽  
Richard E.L. Collier ◽  
Katherine H. Roucoux ◽  
Ulrich C. Müller ◽  
Jörg Pross ◽  
...  
Keyword(s):  
Last Interglacial ◽  
The Mediterranean
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