Mediterranean Black Sea Research Articles

NATO Public Diplomacy in the Mediterranean‒Black Sea Region

The article analyzes the main forms and methods of NATO’s public diplomacy in the Mediterranean-Black Sea region in the context of significant geopolitical processes taking place in this regional space. The aim of the study is to provide a comprehensive assessment of the policy of the North Atlantic Treaty Organization in the field of public diplomacy in one of the most strategically important regions of the world. The main objectives include the consideration of the key areas of the NATO Public Diplomacy Division’s work, the analysis of the projects implemented by the Alliance in the sphere of public diplomacy, as well as determining their impact on the geopolitical processes in the Mediterranean-Black Sea region. In order to achieve the overall goal general scientific theoretical methods such as analysis, synthesis, induction, deduction and comparison are used. The conclusion is made that in recent decades the North Atlantic Alliance has been trying to strengthen its potential in the sphere of public diplomacy in the Mediterranean-Black Sea region by various methods because of its strategic importance. Moreover, in the near future NATO will increase its activity in this regional area. Special attention will be paid to developing relations with potential candidates for membership, such as Bosnia and Herzegovina, Georgia, and Ukraine. Besides, in the medium term, NATO will continue to actively cooperate with Moldova and Serbia, which, despite their officially declared neutral status, are gradually moving closer to the Alliance. Most of the ongoing public diplomacy projects will be openly anti-Russian, because NATO initiatives will be aimed at ousting Russia from the humanitarian sphere of the Mediterranean-Black Sea region’s states.

High‐Resolution Climate Simulations Over the Eastern Mediterranean Black Sea Region Using the Pseudo‐Global Warming Method With a CMIP6 Ensemble

AbstractThe strong drying expected in the Eastern Mediterranean with climate change could cause mass migration of people already living under water shortages. On the other hand, precipitation is expected to increase toward the region’s north, particularly those along the interior of the eastern Black Sea coasts, which could worsen existing floods. However, this double‐sided adverse phenomenon and its underlying reasons have been investigated by relatively low‐resolution models in the Eastern Mediterranean Black Sea (EMBS) region, where orographic precipitation prevails. This study performs 4 km resolution Weather Research and Forecasting (WRF) model simulations with and without climate change signals retrieved from a CMIP6 GCM ensemble via pseudo‐global‐warming (PGW). The WRF simulations captured the large‐scale dynamics affecting the EMBS fairly well: an anticyclonic low‐level circulation and enhancing subsidence stem from anomalous ridge development over the central Mediterranean in winter (DJF), and a cyclonic low‐level circulation and weakening subsidence rise from heat‐low development over the Eastern Mediterranean in summer (JJA). The resulting picture of future warming and drying over the area generally supports the literature, although new insights emerge in anomalous precipitation increase, especially in the summer season over the Greater Caucasus and nearby regions. Most likely, the warmer‐than‐expected Caspian Sea induces a large increase in specific humidity and, thus, a large moisture source in the lower troposphere and an extension of the heat‐low effect in the mid‐troposphere. In addition, the high‐resolution WRF simulations provide added value over the complex topography of the Caucasian Mountain range for new insights into this region.

Earliest Records of Holocene Cetaceans in the Black Sea

ABSTRACTThe timing of the Holocene transition of the Black Sea from a brackish lake to a marine sea has long been debated. Here, we report on the earliest records of cetaceans in the Black Sea region as a proxy for the connection with the Mediterranean and the transition from a brackish to marine environment. We base our analysis on cetacean skeletal finds and archival data on cetacean skeletal remains from the Bosphorus, the western, northern and eastern Black Sea, and the Kerch Strait. We find that all three contemporary cetacean species in the Black Sea – the harbour porpoise, bottlenose dolphin and common dolphin – had migrated out of the Mediterranean to the Bosphorus and the Black Sea at least 8000–7000 years ago and reached the northern Black Sea by 5500 years ago at the latest. Our study suggests the establishment of a Mediterranean–Black Sea biogeographical connection for marine vertebrates at least 7000 years ago. The early presence of cetaceans in the Black Sea has implications for understanding its Holocene transition, as well as the evolutionary and ecological history of these species more generally.

Holocene vegetation dynamics of the Eastern Mediterranean region: Old controversies addressed by a new analysis

AbstractAimWe reconstruct vegetation changes since 12 ky in the Eastern Mediterranean to examine four features of the regional vegetation history that are controversial: the extent of non‐analogue vegetation assemblages in the transition from the Late Glacial to the early Holocene, the synchroneity of postglacial forest expansion, the geographical extent of temperate deciduous forest during the mid‐Holocene and the timing and trigger for the re‐establishment of drought‐tolerant vegetation during the late Holocene.LocationThe Eastern Mediterranean–Black Sea Caspian Corridor.TaxonVascular plants.MethodsWe reconstruct vegetation changes for 122 fossil pollen records using a method that accounts for within‐biome variability in pollen taxon abundance to determine the biome with which a sample has greatest affinity. Per‐biome affinity threshold values were used to identify samples that do not belong to any modern biome. We apply time series analysis and mapping to examine space and time changes.ResultsSites with non‐analogue vegetation were most common between 11.5 and 9.5 ky and mostly in the Carpathians. The transition from open vegetation to forest occurred at 10.64 ± 0.65 ky across the whole region. Temperate deciduous forest was not more extensive at 6 ky; maximum expansion occurred between 5.5 and 5 ky. Expansion of forest occurred between c. 4 and 2.8 k, followed by an abrupt decrease and a subsequent recovery. This pattern is not consistent with a systematic decline of forest towards more drought‐tolerant vegetation in the late Holocene but is consistent with centennial‐scale speleothem patterns linked to variations in moisture availability.Main ConclusionsWe show the occurrence of non‐analogue vegetation types peaked during early Holocene, forest expansion was synchronous across the region and there was an expansion of moisture‐demanding temperate trees around 5.5 to 5 ky. There is no signal of a continuous late Holocene aridification, but changes in forest cover appear to reflect climatic rather than anthropogenic influences.

Extreme Recreational Conditions in the Black Sea Resorts Associated with the North Atlantic Climate

The tourist and recreational conditions of the Mediterranean-Black Sea resorts are closely related to hydrometeorological anomalies, which in turn are largely associated with the North Atlantic climate. The aim of this paper was to study the change and variability of the bioclimatic indices and their extremes at the Black Sea resorts (on the example of Yalta, Southern coast of Crimea, and Sochi, Caucasian coast) associated with the North Atlantic Oscillation (NAO) and East Atlantic Oscillation (EAO). Using daily NCEP/NCAR (2.5° × 2.5°) and E-OBS (0.25° × 0.25°) reanalysis datasets, bioclimatic indices (wind cooling index, weight oxygen content, and equivalent-effective temperature) were calculated for January and July in 1950–2013/2018. The extreme index values were obtained using the 5th and 95th percentile relative thresholds. The results suggest that bioclimatic indices in Yalta are more sensitive to the global warming effect than those in Sochi, likely due to the geographical features. As a result, Yalta is becoming a year-round resort. It was shown for both resorts that negative EAO phase is significantly manifested in the increase of windy days in July versus the increase of windless days in the positive phase, and in the more frequent fresh and cold days in July (versus the opposite conditions in the positive phase only in Yalta). The NAO manifestations are mostly less pronounced than those of the EAO and are more significant in Sochi (mostly in January and in the negative NAO phase). Thus, it was shown that extreme values of bioclimatic indices occur at both resorts on the interannual scale depending on the NAO and EAO phases, but the conditions remain in the comfort range for now, even with the significant linear trends. The study can be expanded to other Mediterranean–Black Sea resorts for their sustainable development in a changing climate.

Simulating the Interconnected Eastern Mediterranean–Black Sea System on Climatic Timescales: A 30-Year Realistic Hindcast

Inter-basin water exchanges can be quite important in climatic-scale numerical studies simulating the circulation and hydrographic characteristics of neighboring oceanic basins connected through narrow straits. The crucial role of the interaction between the Mediterranean and the Black Seas is often overseen in simulations, which rely mostly on parameterizations to describe the exchange, essentially decoupling the two basins. In this study, the fully interconnected Eastern Mediterranean–Black Sea system is simulated for the historical period (1985–2015) using realistic boundary conditions (lateral, atmospheric and hydrological), with a hydrodynamic fully three-dimensional ocean modeling system. The setup of such a configuration is thoroughly described and the performance of the 30-year hindcast product is validated exhaustively against observations and model results, by evaluating the representation of surface fields, circulation, three-dimensional hydrographic characteristics, volumetric water exchanges, and the spatio-temporal variability of the above. The comparison shows exceptional performance, minimal drift, and substantial improvement compared to modeling studies that do not include the interaction. Moreover, due to the free-run configuration of the simulation (i.e., absence of assimilation schemes) no additional input is required other than the respective boundary conditions, making it possible to reliably extend the same setup for scenarios where observational data are not available, such as in future projections.

Mediterranean–Black Sea gateway exchange: scientific drilling workshop on the BlackGate project

Abstract. The MagellanPlus workshop “BlackGate” addressed fundamental questions concerning the dynamic evolution of the Mediterranean–Black Sea (MBS) gateway and its palaeoenvironmental consequences. This gateway drives the Miocene–Quaternary circulation patterns in the Black Sea and governs its present status as the world's largest example of marine anoxia. The exchange history of the MBS gateway is poorly constrained because continuous Pliocene–Quaternary deposits are not exposed on land adjacent to the Black Sea or northern Aegean. Gateway exchange is controlled by climatic (glacio-eustatic-driven sea-level fluctuations) and tectonic processes in the catchment as well as tectonic propagation of the North Anatolian Fault Zone (NAFZ) in the gateway area itself. Changes in connectivity trigger dramatic palaeoenvironmental and biotic turnovers in both the Black Sea and Mediterranean domains. Drilling a Messinian to Holocene transect across the MBS gateway will recover high-amplitude records of continent-scale hydrological changes during glacial–interglacial cycles and allow us to reconstruct marine and freshwater fluxes, biological turnover events, deep biospheric processes, subsurface gradients in primary sedimentary properties, patterns and processes controlling anoxia, chemical perturbations and carbon cycling, growth and propagation of the NAFZ, the timing of land bridges for Africa and/or Asia–Europe mammal migration, and the presence or absence of water exchange during the Messinian salinity crisis. During thorough discussions at the workshop, three key sites were selected for potential drilling using a mission-specific platform (MSP): one on the Turkish margin of the Black Sea (Arkhangelsky Ridge, 400 m b.s.f., metres below the seafloor), one on the southern margin of the Sea of Marmara (North İmrali Basin, 750 m b.s.f.), and one in the Aegean (North Aegean Trough, 650 m b.s.f.). All sites target Quaternary oxic–anoxic marl–sapropel cycles. Plans include recovery of Pliocene lacustrine sediments and mixed marine–brackish Miocene sediments from the Black Sea and the Aegean. MSP drilling is required because the JOIDES Resolution cannot pass under the Bosporus bridges. The wider goals are in line with the aims and scope of the International Ocean Discovery Program (IODP) “2050 Science Framework: Exploring Earth by Scientific Ocean Drilling” and relate specifically to the strategic objectives “Earth's climate system”, “Tipping points in Earth's history”, and “Natural hazards impacting society”.

Severe Precipitation Phenomena in Crimea in Relation to Atmospheric Circulation

The increase in the frequency and intensity of hazardous hydrometeorological phenomena is one of the most dangerous consequences of climate instability. In this study, we summarize the data on severe weather phenomena using the data from 23 meteorological stations in Crimea from 1976 to 2020. Particular attention was paid to the precipitation phenomena descriptions. For the last 45 years, a significant positive trend of interannual variability of the annual occurrence of severe weather phenomena was estimated to be +2.7 cases per decade. The trend for severe precipitation phenomena was estimated to be +1.3 cases per decade. The probable maximum annual daily precipitation as a quantitative indicator of hazardous events was estimated for each station by using both the stationary and the non-stationary GEV models. For at least half of the meteorological stations, a non-stationary GEV model was more appropriate for the estimation of the precipitation extremes. An analysis of the main synoptic processes that drive severe weather phenomena of precipitation was carried out. The greatest contribution to the formation of severe precipitation was made by Mediterranean–Black Sea cyclones. At the same time, half of all of the cases of extreme precipitation were caused by cyclones generated over the Black Sea only, in all seasons apart from winter. In the mid-troposphere, four types of meridional circulation were identified depending on the location of troughs and ridges, with respect to the Black Sea region. More than 42% of severe precipitation phenomena were accompanied by an isolated high-altitude cyclone in the mid-troposphere over the Black Sea region. The main recommendation that can be drawn from this study is that long-term climatic non-stationarity should be taken into account whenever the risk assessment or hazard analysis is to be carried out. The results can also favor the designing of drainage and sewerage systems in urban areas. The findings of atmospheric patterns can be used for the improvement of extreme precipitation forecasts.

Present and Future Changes in Winter Cyclonic Activity in the Mediterranean–Black Sea Region in the 21st Century Based on an Ensemble of CMIP6 Models

A better understanding of expected future cyclonic activity, especially in winter in the Mediterranean basin, is essential in developing scientifically based adaptation and mitigation methods to study extreme precipitation and wind anomalies. The aim of this study was to analyze the changes in winter cyclonic activity in the Mediterranean–Black Sea region, as part of the North Atlantic–European sector, at three 15 year periods: the beginning, middle, and end of the 21st century. Our projections were based on an ensemble of seven Coupled Model Intercomparison Project (CMIP), phase 6, models, which showed the best agreement with NCEP/NCAR and ERA5 reanalyses under the intermediate SSP2-4.5 and highest-emission SSP5-8.5 scenarios. The results showed a consistent increase in the frequency of cyclones over Central Europe and the British Isles, which was associated with shifts in cyclone tracks: northward from the western Mediterranean region and southward from the Icelandic Low region. The latter shift led to a decrease in the frequency in the northern Atlantic–European region. At the same time, there was a reduction in the frequency of cyclones over the eastern region of the Mediterranean Sea, consistent with the decrease in cyclogenesis events. Area-averaged cyclone numbers in the western and eastern Mediterranean and Black Sea subregions reduced at the end of the century under the highest-emission scenario, but not constantly. There was a rise in the middle of the 21st century under both scenarios, which may be linked to long-term multidecadal variability or regional features. In general, our study showed that the future winter cyclonic activity in the Mediterranean–Black Sea region will respond unevenly to global climate changes, due to regional and monthly features and long-term quasiperiodic variability.

Example of Coastline Changes from the Last Glacier Maximum to the Present: Çanakkale Strait

Climate change emerges as an important problem for the earth today. Although the negative effects of this problem are not directly reflected in the time we live in, it is revealed by the scientists working on the subject that it will be observed in human life for decades-centuries and will be observed in detail on the earth for thousands of tens of thousands of years later. This predicted climate change can be considered a normal situation when considering the time that has passed from the formation of the earth to the present, approximately 4.5 billion years (except that the difference between the reasons for climate changes in the past geological times and the predicted climate change is the human effect). The effects of Quaternary climate change can be observed on the earth both on a global scale and on a regional scale. As an example of global climate change, the continuous change of sea level can be given, and the best indicators of this change are geological/geomorphological structures such as marine terraces or submarine canyons observed on the coasts on the regional scale. On the local scale, stalactites and stalagmites observed in caves, lake sediments, deep sea sediments, glacial cores are among the best examples of climate change. In this study, the land-sea boundary (coastal line) changes of the coasts of the Çanakkale Strait, which is the southern branch of the Turkish Straits System, have been investigated, considering the sea level changes that show the climate change best in the last 25 thousand years. In this context, the coastal changes of the Çanakkale Strait coasts from the Late Pleistocene to the present are modeled using geographic information systems programs, by using different global and regional sea level change charts showing climate changes. The most striking of these new maps is the one from 20 thousand years ago. At this time, it is known that the global sea level is 120 meters lower than today and the deepest point of the Çanakkale Strait is around -113 meters today. Therefore, it is not possible to mention a Mediterranean-Black Sea waterway connection through the Çanakkale Strait at these times.

A new method based on surface-sample pollen data for reconstructing palaeovegetation patterns.

AimBiomisation has been the most widely used technique to reconstruct past regional vegetation patterns because it does not require an extensive modern pollen dataset. However, it has well‐known limitations including its dependence on expert judgement for the assignment of pollen taxa to plant functional types (PFTs) and PFTs to biomes. Here we present a new method that combines the strengths of biomisation with those of the alternative dissimilarity‐based techniques.LocationThe Eastern Mediterranean‐Black Sea Caspian Corridor (EMBSeCBIO).TaxonPlantsMethodsModern pollen samples, assigned to biomes based on potential natural vegetation data, are used to characterize the within‐biome means and standard deviations of the abundances of each taxon. These values are used to calculate a dissimilarity index between any pollen sample and every biome, and thus assign the sample to the most likely biome. We calculate a threshold value for each modern biome; fossil samples with scores below the threshold for all modern biomes are thus identified as non‐analogue vegetation. We applied the new method to the EMBSeCBIO region to compare its performance with existing reconstructions.ResultsThe method captured changes in the importance of individual taxa along environmental gradients. The balanced accuracy obtained for the EMBSeCBIO region using the new method was better than obtained using biomisation (77% vs. 65%). When the method was applied to high‐resolution fossil records, 70% of the entities showed more temporally stable biome assignments than obtained using biomisation. The technique also identified likely non‐analogue assemblages in a synthetic modern dataset and in fossil records.Main conclusionsThe new method yields more accurate and stable reconstructions of vegetation than biomisation. It requires an extensive modern pollen dataset, but is conceptually simple, and avoids subjective choices about taxon allocations to PFTs and PFTs to biomes.

European pollen-based REVEALS land-cover reconstructions for the Holocene: methodology, mapping and potentials

Abstract. Quantitative reconstructions of past land cover are necessary to determine the processes involved in climate–human–land-cover interactions. We present the first temporally continuous and most spatially extensive pollen-based land-cover reconstruction for Europe over the Holocene (last 11 700 cal yr BP). We describe how vegetation cover has been quantified from pollen records at a 1∘ × 1∘ spatial scale using the “Regional Estimates of VEgetation Abundance from Large Sites” (REVEALS) model. REVEALS calculates estimates of past regional vegetation cover in proportions or percentages. REVEALS has been applied to 1128 pollen records across Europe and part of the eastern Mediterranean–Black Sea–Caspian corridor (30–75∘ N, 25∘ W–50∘ E) to reconstruct the percentage cover of 31 plant taxa assigned to 12 plant functional types (PFTs) and 3 land-cover types (LCTs). A new synthesis of relative pollen productivities (RPPs) for European plant taxa was performed for this reconstruction. It includes multiple RPP values (≥2 values) for 39 taxa and single values for 15 taxa (total of 54 taxa). To illustrate this, we present distribution maps for five taxa (Calluna vulgaris, Cerealia type (t)., Picea abies, deciduous Quercus t. and evergreen Quercus t.) and three land-cover types (open land, OL; evergreen trees, ETs; and summer-green trees, STs) for eight selected time windows. The reliability of the REVEALS reconstructions and issues related to the interpretation of the results in terms of landscape openness and human-induced vegetation change are discussed. This is followed by a review of the current use of this reconstruction and its future potential utility and development. REVEALS data quality are primarily determined by pollen count data (pollen count and sample, pollen identification, and chronology) and site type and number (lake or bog, large or small, one site vs. multiple sites) used for REVEALS analysis (for each grid cell). A large number of sites with high-quality pollen count data will produce more reliable land-cover estimates with lower standard errors compared to a low number of sites with lower-quality pollen count data. The REVEALS data presented here can be downloaded from https://doi.org/10.1594/PANGAEA.937075 (Fyfe et al., 2022).

Hydrological cycle of the Mediterranean-Black Sea system

The Mediterranean-Black Sea system consists of two semi-enclosed basins connected by the Turkish Straits. In turn, the Mediterranean Sea is connected to the Atlantic Ocean through the narrow Strait of Gibraltar. The hydrological cycle of the system is driven by fresh water exchanges between the atmosphere, continents and oceans, and by salty water mass exchange among the ocean basins. Monitoring such water fluxes, especially its time evolution, is essential to understand the water cycle in the region, which is very sensitive to global climate changes and influences the variability of the Atlantic Meridional Overturning Circulation (AMOC), which in turn affects the global climate. In this study, we have estimated the hydrological cycle of the Mediterranean-Black Sea system from the time-variable gravity observations performed by the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On satellites, and precipitation and evaporation from ERA5 atmospheric reanalysis data for the period 2002–2020. In the Black Sea, rivers introduce an average water volume of 391 ± 12 km3/year, one third of which escape through the atmosphere and two thirds go to the Mediterranean Sea. In the latter, 1787 ± 23 km3/year are lost via net evaporation. The rivers runoff (502 ± 27 km3/year), and the inflow of Atlantic waters (1020 ± 56 km3/year; 0.0323 ± 0.0018 Sv), finally restore the Mediterranean water budget. The balance is not reached instantaneously, and this delay introduces a seasonal variability in all the fluxes. In particular, the net water flux from the Atlantic Ocean increases up to 2660 ± 111 km3/year in August/September, and reverses to − 407 ± 140 km3/year in April/May. On top of the climatology, the mean annual Atlantic water flux varies significantly between 706 and 1262 km3/year.

Modelling present and future climate in the Mediterranean Sea: a focus on sea-level change

We present results of three simulations of the Mediterranean Sea climate: a hindcast, a historical run, and a RCP8.5 scenario simulation reaching the year 2100. The simulations are performed with MED16, a new, tide-including implementation of the MITgcm model, which covers the Mediterranean—Black Sea system with a resolution of 1/16°, further increased at the Gibraltar and Turkish Straits. Validation of the hindcast simulation against observations and numerical reanalyses has given excellent results, proving that the model is also capable of reproducing near-shore sea level variations. Moreover, the spatial structure of the elevation field compares well with altimetric observations, especially in the Western basin, due to the use of improved sea level information at the Atlantic lateral boundary and to the adequate treatment of the complex, hydraulically driven dynamics across the Gibraltar Strait. Under the RCP8.5 future scenario, the temperature is projected to generally increase while the surface salinity decreases in the portion of the Mediterranean affected by the penetration of the Atlantic stream, and increases elsewhere. The warming of sea waters results in the partial inhibition of deep-water formation. The scenario simulation allows for a detailed characterization of the regional patterns of future sea level, arising from ocean dynamics, and indicates a relative sinking of the Mediterranean with respect to the Atlantic more pronounced than the current one.

Aeolian Dust Inputs in the Mediterranean and Black Sea Marine System

<p>The aim of this paper is to estimate the amount of aeolian dust, deposited by dry and wet processes, that is deposited to the eleven marine regions of the Mediterranean-Black Sea Marine System (MBMS) and to compare it to the riverine influxes (i.e. suspended and dissolved sediment loads). This research is based on information for aeolian dust deposition at several coastal stations, around the MBMS, following an extended research of the available literature. For data elaboration, processing, and visualization a G.I.S. environment was utilized. The total annual amount of dust input for the whole system has been estimated to 59.9 × 106 tonnes, of which 57.2 × 106 tonnes are deposited in the Mediterranean Sea and only 2.7 ×106 tonnes in the Black Sea. The contribution of dust input (load), corresponding to 6.2% and 0.8% of the total amount of suspended and dissolved load, for the Mediterranean and Black Sea respectively, reveals the significant role of the aeolian dust inputs to the MBMS marine environment, in particular, at its southern Mediterranean domain.</p>

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

The Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

Climate-driven connectivity changes of the Black Sea since 430 ka: Testing a dual palynological and geochemical approach

The Black Sea experienced multiple episodes of connection with both the Mediterranean and Caspian seas during the Quaternary. Global sea-level variation has been proposed as the main driver of changes in Mediterranean-Black Sea connectivity, while positive water budgets drove Caspian overspill. We present a new, two proxy, low-resolution record from the Black Sea that allows reconstruction of connectivity history from 430 to 50 ka: dinoflagellate cysts (dinocysts) provide direct evidence for properties of surface waters and strontium isotopes constrain the source(s) of water entering the basin. Dinocysts and 87Sr/86Sr suggest that the Black Sea was isolated from the Mediterranean during global sea-level lowstands associated with glacials MIS 4, 8 and 10. Both proxies also strongly suggest that marine (Mediterranean) water flowed into the Black Sea during the eustatic highstands associated with peak interglacials during MIS 5 and 9. However, while the contribution of marine waters during MIS 5e was similar to the present day, lower 87Sr/86Sr during MIS 9 suggests lower than present input. Connectivity during MIS 11, MIS 7 and MIS 6 is more enigmatic. Lower 87Sr/86Sr than those of the isolated Black Sea and dinocyst assemblages dominated by species of Paratethyan lineage are compatible with input from the Caspian Sea. Dinocyst taxa recovered in MIS 11 can be found in both the Caspian Sea and the Black Sea today. All four interglacials studied contain different dinocyst assemblages, suggesting that different conditions may have prevailed during each warm period. However, high-resolution studies are needed to confirm this observation. Further work on the same sequence could be valuable in elucidating the connectivity history of the Black Sea over the glacial-interglacial cycles of the late Quaternary.

Investigation of mechanisms underlying chaotic genetic patchiness in the intertidal marbled crab Pachygrapsus marmoratus (Brachyura: Grapsidae) across the Ligurian Sea

BackgroundStudies on marine community dynamics and population structures are limited by the lack of exhaustive knowledge on the larval dispersal component of connectivity. Genetic data represents a powerful tool in understanding such processes in the marine realm. When dealing with dispersion and connectivity in marine ecosystems, many evidences show patterns of genetic structure that cannot be explained by any clear geographic trend and may show temporal instability. This scenario is usually referred to as chaotic genetic patchiness, whose driving mechanisms are recognized to be selection, temporal shifts in local population dynamics, sweepstakes reproductive success and collective dispersal.In this study we focused on the marbled crab Pachygrapsus marmoratus that inhabits the rocky shores of the Mediterranean Sea, Black Sea and East Atlantic Ocean, and disperses through planktonic larvae for about 1 month. P. marmoratus exhibits unexpectedly low connectivity levels at local scale, although well-defined phylogeographic patterns across the species’ distribution range were described. This has been explained as an effect of subtle geographic barriers or due to sweepstake reproductive success. In order to verify a chaotic genetic patchiness scenario, and to explore mechanisms underlying it, we planned our investigation within the Ligurian Sea, an isolated basin of the western Mediterranean Sea, and we genotyped 321 individuals at 11 microsatellite loci.ResultsWe recorded genetic heterogeneity among our Ligurian Sea samples with the occurrence of genetic clusters not matching the original populations and a slight inter-population divergence, with the geographically most distant populations being the genetically most similar ones. Moreover, individuals from each site were assigned to all the genetic clusters. We also recorded evidences of self-recruitment and a higher than expected within-site kinship.ConclusionsOverall, our results suggest that the chaotic genetic patchiness we found in P. marmoratus Ligurian Sea populations is the result of a combination of differences in reproductive success, en masse larval dispersion and local larval retention. This study defines P. marmoratus as an example of marine spawner whose genetic pool is not homogenous at population level, but rather split in a chaotic mosaic of slightly differentiated genetic patches derived from complex and dynamic ecological processes.

Physio-geographical characteristics of the marine regions and their catchment areas of the Mediterranean Sea and Black Sea marine system

ABSTRACT The Mediterranean Sea and the Black Sea comprise a semi-enclosed intercontinental Marine System (MBMS), bordered by the Eurasian and African continents. Its total marine surface is circa 3 × 106 km2, while its drainage basin exceeds 7 × 106 km2; the latter includes the watersheds of 39 large (>104 km2) river systems, which correspond to about 83% of its total area. The MBMS includes four basins, that is, Western, Central, Eastern Mediterranean (WMED, CMED, EMED) and Black Sea (BLS), which are subsequently divided into 11 marine regions. Thus, the WMED includes the Alboran (ALB), the West MED (WEST) and the Tyrrhenian (TYR); the CMED consists of the Adriatic (ADR), the Ionian (ION) and the Centric MED (CEN); the EMED includes the Levantine (LEV), the Aegean (AEG) and the Marmara (MAR) and the BLS except of the Black Sea (BLA) includes the Azov Sea (AZOV). The present work aims to: (i) describe geographically the MBMS marine regions and their boundaries according to International Hydrographic Office and the common practice for environmental studies; (ii) provide and compare key-morphometric characteristics of all marine regions and their catchment areas and (iii) examine the possibility of a better separation of the existing marine regions.

Classification of European and Mediterranean coastal dune vegetation

AbstractAimsAlthough many phytosociological studies have provided detailed local and regional descriptions of coastal dune vegetation, a unified classification of this vegetation in Europe and the Mediterranean Basin has been missing. Our aim is to produce a formalized classification of this vegetation and to identify the main factors driving its plant species composition at a continental scale.LocationAtlantic and Baltic coasts of Europe, Mediterranean Basin and the Black Sea region.MethodsWe compiled a database of 30,759 plots of coastal vegetation, which were resampled to reduce unbalanced sampling effort, obtaining a data set of 11,769 plots. We classified these plots with TWINSPAN, interpreted the resulting clusters and used them for developing formal definitions of phytosociological alliances of coastal dune vegetation, which were included in an expert system for automatic vegetation classification. We related the alliances to climatic factors and described their biogeographic features and their position in the coastal vegetation zonation. We examined and visualized the floristic relationships among these alliances by means of DCA ordination.ResultsWe defined 18 alliances of coastal dune vegetation, including the newly described Centaureo cuneifoliae‐Verbascion pinnatifidi from the Aegean region. The main factors underlying the differentiation of these alliances were biogeographic and macroclimatic contrasts between the Atlantic–Baltic, Mediterranean and Black Sea regions, along with ecological differences between shifting and stable dunes. The main difference in species composition was between the Atlantic–Baltic and Mediterranean–Black Sea regions. Within the former region, the main difference was driven by the different ecological conditions between shifting and stable dunes, whereas within the latter, the main difference was biogeographic between the Mediterranean and the Black Sea.ConclusionsThe first formal classification of the European coastal dune vegetation was established, accompanied by an expert system containing the formal definitions of alliances, which can be applied to new data sets. The new classification system critically revised the previous concepts and integrated them into a consistent framework, which reflects the main gradients in species composition driven by biogeographic influences, macroclimate and the position of the sites in the coast–inland zonation of the dune systems. A revision of the class concept used in EuroVegChecklist is also proposed.