Holocene paleoecology and paleoceanography of the southwestern Black Sea shelf revealed by ostracod assemblages

The Holocene replacement of Ponto-Caspian ostracod assemblages by Mediterranean species is studied in two long composite cores, M02-45 (a composite of cores M02-45P, M02-45 T and M05-03P) and M05-50 (a composite of cores M05-50P and M05-51G), acquired at sites −69 m and −91 m deep on the southwestern Black Sea shelf. Composite core M02-45 was collected from the middle shelf and composite core M05-50 was acquired on the distal fringe of the eastern levée of a saline underflow channel emanating from the Strait of Bosphorus. Sixteen radiocarbon dates in M02-45 and nine in M05-50 are used to construct age models, which show recovery of sediments as old as 12,915 cal yr BP (M02-45 site) and 12,010 cal yr BP (M05-50 site). A total of 45 ostracod species are identified in the two cores. From ~12,000 to ~7425 cal yr BP, the ostracod assemblage is dominated by Ponto-Caspian species, mainly Loxoconcha sublepida, L. lepida and Tyrrhenocythere amnicola donetziensis. From ~7425 to ~6315 cal yr BP the assemblage consists of nearly equal abundances of Mediterranean species (Cytheroma variabilis in M02-45; Sagmatocythere littoralis in M05-50) and the Ponto-Caspian species. After ~6315 cal yr BP to the tops of the cores, the assemblage is dominated by Mediterranean species, including Palmoconcha agilis, Carinocythereis carinata, Hiltermannicythere rubra and Pterygocythereis jonesii. Cluster analysis further subdivides the stratigraphic succession into six bioecozones with different ostracod assemblages. The changes in the ostracod assemblages from one bioecozone to the next indicate that progressive environmental changes took place on the southwestern Black Sea shelf from at least 7500 cal yr BP to the present. The first hint of changing conditions at ~7500 cal yr BP lags the initial reconnection to the Mediterranean Sea through the Strait of Bosphorus by ~2000 yr, demonstrating that Black Sea salinity increased slowly and took that long to reach values tolerable to marine ostracod immigrants. Widespread colonization by Mediterranean species took even longer, ~3000 years from the time of the initial reconnection

Human Bocavirus NS1 and NS1-70 Proteins Inhibit TNF-α-Mediated Activation of NF-κB by targeting p65.

Human bocavirus (HBoV), a parvovirus, is a single-stranded DNA etiologic agent causing lower respiratory tract infections in young children worldwide. Nuclear factor kappa B (NF-κB) transcription factors play crucial roles in clearance of invading viruses through activation of many physiological processes. Previous investigation showed that HBoV infection could significantly upregulate the level of TNF-α which is a strong NF-κB stimulator. Here we investigated whether HBoV proteins modulate TNF-α-mediated activation of the NF-κB signaling pathway. We showed that HBoV NS1 and NS1-70 proteins blocked NF-κB activation in response to TNF-α. Overexpression of TNF receptor-associated factor 2 (TRAF2)-, IκB kinase alpha (IKKα)-, IκB kinase beta (IKKβ)-, constitutively active mutant of IKKβ (IKKβ SS/EE)-, or p65-induced NF-κB activation was inhibited by NS1 and NS1-70. Furthermore, NS1 and NS1-70 didn't interfere with TNF-α-mediated IκBα phosphorylation and degradation, nor p65 nuclear translocation. Coimmunoprecipitation assays confirmed the interaction of both NS1 and NS1-70 with p65. Of note, NS1 but not NS1-70 inhibited TNF-α-mediated p65 phosphorylation at ser536. Our findings together indicate that HBoV NS1 and NS1-70 inhibit NF-κB activation. This is the first time that HBoV has been shown to inhibit NF-κB activation, revealing a potential immune-evasion mechanism that is likely important for HBoV pathogenesis

Oscillating Quaternary water levels of the Marmara Sea and vigorous outflow into the Aegean Sea from the Marmara Sea Black Sea drainage corridor

Detailed interpretation of single-channel air-gun and deep-tow boomer profiles demonstrates that the Marmara Sea, Turkey, experienced small-amplitude (similar to 70 m) fluctuations in sea level during the later Quaternary, limited in magnitude by the sill depth of the Strait of Dardanelles. Moderate subsidence along the southern shelf and Quaternary glacio-eustatic sea-level variations created several stacked deltaic successions, separated by major shelf-crossing unconformities, which developed during the transitions from global glacial to integlacial periods. Near the Strait of Dardanelles, a series of sand-prone deposits are identified beneath an uppermost (Holocene) transparent mud drape. The sandy deposits thicken into mounds with the morphology and cross-sectional geometries of barrier islands, sand waves, and current-generated marine bars. All cross-stratification indicates unidirectional flow towards the Dardanelles prior to the deposition of the transparent drape which began similar to 7000 years BP, in strong support: of the notion that the Marmara Sea flowed westwards into the Aegean Sea through the Dardanelles at times of deglaciation in northern Europe. The global sea-level curve shows that, at similar to 11,000 and similar to 9500 years BP, sea level rose to the sill depths of the Straits of Dardanelles and Bosphorus, respectively. The effect from similar to 11,000 to similar to 9500 years BP was seawater incursion into the Marmara Sea, drowning and formation of algal-serpulid bioherms atop lowstand barrier islands, and transgression of shelves and lowstand deltas. At similar to 9500 years BP, glacial meltwater temporarily stored in the Black Sea lake, developed into a vigorous southward flow toward the Aegean Sea, forming west-directed sandy bedforms in the western Marmara Sea and initiating deposition of sapropel S1 in the Aegean Sea. This strong outflow persisted until similar to 7000 years BP, after which a mud drape began to accumulate in the Marmara Sea and euryhaline Mediterranean mollusks successfully migrated into a progressively more saline Black Sea where sapropel deposition began. Most eastern Mediterranean sapropels from S1 to S11 appear to correlate with periods of rising sea level and breaching, or near-breaching, of the Bosphorus sill. These events are believed to coincide with times of vigorous outflow of low-salinity (?fresh) surface waters transiting the Black Sea-Marmara Sea corridor, and ultimately derived from melting of northern European ice sheets. (C) 1999 Elsevier Science B.V. All rights reserved

Seismic stratigraphy of Late Quaternary deposits from the southwestern Black Sea shelf: evidence for non-catastrophic variations in sea-level during the last similar to 10,000 yr

Detailed interpretation of single channel seismic reflection and Huntec deep-tow boomer and sparker profiles demonstrates that the southwestern Black Sea shelf formed by a protracted shelf-edge progradation since the Miocene-Pliocene. Five seismic-stratigraphic units are recognized. Unit 1 represents the last phase of the progradational history, and was deposited during the last glacial lowstand and Holocene. It is divided into four subunits: Subunit 1A is interpreted as a lowstand systems tract, 1B and 1C are interpreted as a transgressive systems tract, and Subunit 1D is interpreted as a highstand systems tract. The lowstand systems tract deposits consist of overlapping and seaward-prograding shelf-edge wedges deposited during the lowstand and the subsequent initial rise of sea level. These shelf-edge wedges are best developed along the westernmost and easternmost segments of the study area, off the mouths of rivers. The transgressive systems tract deposits consist of a set of shingled, shore-parallel, back-stepping parasequences, deposited during a phase of relatively rapid sea-level rise, and include a number of prograded sediment bodies (including barrier islands, beach deposits) and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features. A number of radiocarbon dates from gravity cores show that the sedimentary architecture of Unit 1 contain a detailed sedimentary record for the post-glacial sea-level rise along the southwestern Black Sea shelf. These data do not support the catastrophic refilling of the Black Sea by waters from the Mediterranean Sea at 7.1 ka postulated by [Ryan, Pitman, Major, Shimkus, Maskalenko, Jones, Dimitrov, Gorur, Sakinc, Yuce, Mar. Geol. 138 (1997) 119-126], [Ryan, Pitman, Touchstone Book (1999) 319 pp.], and [Ballard, Coleman, Rosenberg, Mar. Geol. 170 (2000) 253-261]. Crown Copyright (C) 2002 Elsevier Science B.V. All rights reserved

Last glacial-Holocene paleoceanography of the Black Sea and Marmara Sea: stable isotopic foraminiferal and coccolith evidence

Multi-proxy data and radiocarbon dates from several key cores from the Black Sea and Marmara Sea document a complex paleoceanographic history for the last similar to 30 000 yr. The Marmara Sea was isolated from both the Black Sea and the Aegean Sea during glacial periods when global sea-level lowering subaerially exposed the shallow sills at the Straits of Bosphorus and Dardanelles (i.e. lake stage), and reconnected through both straits during interglacial periods, when rise of global sea level breached the shallow sills (i.e. gateway stage). Micropaleontological data show that during the 'lake stage' the surface-water masses in both the Marmara Sea and Black Sea became notably brackish; however, during the 'gateway stages' there was a low-salinity surface layer and normal marine water mass beneath. Two sapropel layers are identified in the Marmara Sea cores: sapropels M2 and M1 were deposited between similar to 29.5 and 23.5 ka, and similar to 10.5 and 6.0 ka, respectively. Micropaleontological and stable isotopic data show that the surface-water salinities were reduced considerably during the deposition of both sapropel layers M2 and M1, and calculation using planktonic foraminiferal transfer functions shows that sea-surface temperatures were notably lower during these intervals. The presence of fauna and flora with Black Sea affinities and the absence of Mediterranean fauna and flora in sapropels M1 and M2 strongly suggest that communication existed with the Black Sea during these times. A berithic foraminiferal oxygen index shows that the onset of suboxic conditions in the Marmara Sea rapidly followed the establishment of fully marine conditions at similar to 11-10.5 ka, and are attributed to Black Sea outflow into the Marmara Sea since 10.5 ka. These suboxic conditions have persisted to the present. The data discussed in this paper are completely at odds with the 'Flood Hypothesis' of Ryan et al. (1997), and Ryan and Pitman (1999). Crown Copyright (C) 2002 Elsevier Science B.V. All rights reserved

Deltas south of the Bosphorus Strait record persistent Black Sea outflow to the Marmara Sea since similar to 10 ka

At the southern exit of the Bosphorus Strait in the northeastern Marmara Sea, high-resolution seismic profiles reveal two lobate, progradational delta lobes in modem water depths of similar to40-65 m. The younger delta was active from similar to10 to 9 ka based on radiocarbon dates of equivalent prodelta deposits and the elevation of its topset-to-foreset transition. The topset-to-foreset transition climbs in the seaward direction because the delta prograded into a rising sea. Low abundances of marine fauna and flora in the 10-9-ka interval support a deltaic interpretation. There are no rivers in the area that could have fed the delta; instead, all evidence points to the strait itself as the source of sediment and water. When this outflow was strongest (similar to 10.6-6.0 ka), sapropels accumulated in basinal areas of both the Aegean and Marmara seas. Benthic foraminiferal and dinoflagellate cyst data from contemporary deposits elsewhere in the Marmara Sea point to the continual presence through the Holocene of a surface layer of brackish water that we ascribe to this same outflow from the Black Sea through the Bosphorus Strait. By similar to 9.1-8.5 ka, two-layer flow developed in the Bosphorus Strait as global sea level continued to rise, and the sediment supply to the younger delta was cut off because the outflowing Black Sea water ceased to be in contact with the, floor of the strait. The older delta lobe lies below a prominent lowstand unconformity and is tentatively interpreted to have formed from similar to 29.5 to 23.5 ka (oxygen-isotopic stage 3) when the Marmara Sea stood at similar to -55 m and a second sapropel accumulated in deep basinal areas. Crown Copyright (C) 2002 Elsevier Science B.V. All rights reserved