Teofilo Abrajano

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 V30 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 V29.5 and 23.5 ka, and V10.5 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 benthic foraminiferal oxygen index shows that the onset of suboxic conditions in the Marmara Sea rapidly followed the establishment of fully marine conditions at V11^10.5 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 > 2002 Elsevier Science B.V. All rights reserved.

Molecular and isotopic characterization of polycyclic aromatic hydrocarbon distribution and sources at the international segment of the St. Lawrence River

Abstract This paper documents the molecular and compound-specific carbon isotope composition of polycyclic aromatic hydrocarbons (PAH) in St. Lawrence River sediments from the outflow of Lake Ontario (Kingston, ON) to the Massena area (NY). The sediment inventory of PAH is characterized by the dominance of 4 to 6 ring parent compounds, with the PAH ranging from 0.8 to 6700 μg/g. The high abundance of high molecular weight parent compounds, high parent/alkylated PAH ratios and 13C-enriched values recorded for individual PAH are consistent with a dominant combustion PAH source for the sediments upstream of the Massena area, but areas receiving higher petroleum contributions were also identified (e.g., Prescott-Ogdensburg, Cornwall). PAH contribution from aluminum smelting operations in the Massena area is pronounced in the southern bank of the St. Lawrence River, where sediment samples display the highest ΣPAH and higher 13C values for three ring PAH than for sediments immediately upstream. Thus, sediments at the international segment of the St. Lawrence River show localized enrichments in petroleum-related and aluminum smelter contributions against the regional backdrop of combustion-dominated PAH sources in sediments.

THE MARMARA SEA GATEWAY SINCE ~16 KY BP: NON-CATASTROPHIC CAUSES OF PALEOCEANOGRAPHIC EVENTS IN THE BLACK SEA AT 8.4 AND 7.15 KY BP

The Late Quaternary history of connection of the Black Sea to the Eastern Mediterranean has been intensely debated. Ryan, Pitman and coworkers advocate two pulses of outflow from the Black Sea to the world ocean at ~16–14.7 ky BP and ~11–10 ky BP. From ~14.7–11 ky BP and from ~10–8.4 ky BP, they suggest that the level of the Black Sea fell to ~ -100 m. At 8.4 ky BP, they further claim that a catastrophic flood occurred in a geological instant, refilling the Black Sea with saline waters from the Mediterranean. In contrast, we continue to gather evidence from seismic profiles and dated cores in the Marmara Sea which demonstrate conclusively that the proposed flood did not occur. Instead, the Black Sea has been at or above the Bosphorus sill depth and flowing into the world ocean unabated since ~10.5 ky BP. This conclusion is based on continuous Holocene water-column stratification (leading to sapropel deposition in the Marmara Sea and the Aegean Sea), proxy indicators of sea-surface salinity, and migration of endemic species across the Bosphorus in both directions whenever appropriate hydrographic conditions existed in the strait. The two pulses of outflow documented by Ryan, Pitman and coworkers find support in our data, and we have modified our earlier interpretations so that these pulses now coincide with the development of mid-shelf deltas: \Delta 2 (16–14.7 ky BP) and \Delta 1 (10.5–9 ky BP) at the southern end of the Bosphorus Strait. However, continued Black Sea outflow after 9 ky BP prevented the northward advection of Mediterranean water and the entry of open-marine species into the Black Sea for more than 1000 years. Sufficient Mediterranean water to change the Sr-isotopic composition of slope and shelf water masses was not available until ~8.4 ky BP (along with the first arrival of many varieties of marine fauna and flora), whereas euryhaline molluscs did not successfully populate the Black Sea shelves until ~7.15 ky BP. Instead of relying on catastrophic events, we recognize a slow, progressive reconnection of the Black Sea to the world ocean, accompanied by significant time lags.

High Molecular Weight Petrogenic and Pyrogenic Hydrocarbons in Aquatic Environments

Geochemistry is ultimately the study of sources, movement, and fate of chemicals in the geosphere at various spatial and temporal scales. Environmental organic geochemistry focuses such studies on organic compounds of toxicological and ecological concern. This field emphasizes not only those compounds with potential toxicological properties, but also the geological systems accessible to the biological receptors of those hazards. Hence, the examples presented in this chapter focus on hydrocarbons with known health and ecological concern in accessible shallow, primarily aquatic, environments.

Applicability of a high pressure digestion technique to the analysis of sediment and soil samples by inductively coupled plasma-mass spectrometry

As inductively coupled plasma-mass spectrometry (ICP-MS) expands its role in earth sciences, the concern about incomplete sample digestion remains. To address this problem, the use of high pressure dissolution was examined. High pressure digestion vessels (HPDVs) were fabricated and their use was compared with the existing method used at Memorial University of Newfoundland that utilizes screw top PTFE (STT) jars for digesting reference materials (RMs). ICP-MS analysis of solutions demonstrated more complete digestion of three marine sediment RMs, indicated by higher Y, Zr, Nb, heavy rare-earth element (HREE), Hf, and U concentrations when the HPDV was used. The results indicate better decomposition of resistant minerals, especially zircons that were likely in high abundance in the sediments. To evaluate its suitability to real samples, the method was applied to the ICP-MS analysis of sediment and soil samples from Cebu, Philippines. Good correlation for Nb and Pb, among other elements, was shown by the results from ICP-MS and X-ray fluorescence spectrometry. Barium recovery was relatively low for ICP-MS, possibly due to particle size difference. Mapping of data showed that the distribution of some elements, particularly the lighter rare-earth elements (REEs), in the soils corresponds to local geology; however, for others such as Zr, Nb, and Pb, results seem to correlate with anthropogenic activity.

Aspects of carbon isotope biogeochemistry of late Quaternary sediments from the Marmara Sea and Black Sea

Abstract The Marmara Sea is situated between the world’s largest permanently anoxic basin, the Black Sea, and an enclosed marginal sea, the Aegean Sea, which experienced quasi-periodic sapropel deposition since Miocene time. It is connected to the Black Sea and the Aegean Sea through the Straits of Bosphorus and Dardanelles, respectively. Sapropel M1, which contains from 1 to 2% total organic carbon, was deposited in the Marmara Sea between 6 and 10.5 ka. We inferred the carbon isotopic composition of dissolved inorganic carbon (DIC) in the water column of the Marmara Sea before, during and after the deposition of sapropel M1 from the carbon isotopic composition of a planktonic foraminifera ( Turborotalita quinqueloba ) and individual hexadecanoic and octadecanoic fatty acids. The period of sapropel deposition is marked by a depletion of 13 C in the water column DIC, contrary to what may be expected if sapropel deposition represents a period of enhanced primary productivity. Instead, we propose that both the relative 13 C depletion of DIC during sapropel deposition and the absolute values we estimated (δ 13 C=−13 to −14‰) are consistent with enhancement of the relative contribution of 13 C-depleted respired carbon to the water column DIC pool. Such enhancement possibly resulted from density stratification that existed during sapropel M1 deposition. The existence of density stratification is also argued from palynological and other lines of evidence (other papers in this issue), and is believed to have resulted from the encroachment of Black Sea water into the Sea of Marmara before 10 000 yr ago. Thus, sapropel M1 appears to have formed during periods of enhanced runoff and preservation and not enhanced primary productivity.

Isotopic composition of fatty acids of extremely piezophilic bacteria from the Mariana Trench at 11,000 m

Two extremely piezophilic bacteria, DB21MT-2 and DB21MT-5, isolated from sediments of the Mariana Trench at 11,000 m, were grown in the laboratory under low-temperature (10 jC) and high-pressure (70 MPa) conditions. Phospholipid esterlinked fatty acids (PLFA) were analyzed by gas chromatography/mass spectrometry (GC/MS) and isotopic compositions of individual fatty acids were determined by gas chromatography isotope ratio mass spectrometry (GC-IRMS) in order to determine isotopic fractionation effects during biosynthesis. The piezophiles are characterized by fatty acids with carbon chains ranging from 14 to 22 carbons in length and by the presence of abundant polyunsaturated fatty acids (PUFA). Fatty acids from each culture exhibit a wide range of isotopic compositions (d 13 C vs. Pee Dee Belemnite (PDB)). With two exceptions (C15:0 and C17:1 from DB21MT-2), all fatty acids are depleted in 13 C relative to that of bulk carbon in the bacterial growth substrate. In addition, strain DB21MT-2 shows systematically higher (less negative) d 13 C values than strain DB21MT-5. The implications for isotope fractionation in fatty acid biosynthesis and the interpretation of isotopic composition of sedimentary fatty acids are discussed. It is suggested that the same type of microorganisms could have rather different d 13 C under the same growth conditions, and that sedimentary fatty acids with distinct d 13 C values do not necessarily have to originate from different organisms. Interpretation of d 13 C values of sedimentary biomarkers may be complicated by such large variations in d 13 Co f

TMAH thermochemolysis characterization of marine sedimentary organic matter in a Newfoundland fjord

Abstract Marine sedimentary organic matter of Trinity Bay and its associated fjord, the Northwest Arm (Newfoundland), was characterized by “batch-wise” tetramethyl ammonium hydroxide (TMAH) thermochemolysis. TMAH thermochemolysis products were characterized using GC/MS, and they included aromatic and aliphatic compounds determined as methyl esters and ethers. The dominant aliphatic compounds are fatty acids that ranged from C14 to C28, with a predominance of even carbon numbered species, and are either saturated, mono-unsaturated or branched. The aromatic compounds are phenols, of which the most abundant is 3,4-dimethoxybenzoic acid methyl ester, an important chemical marker in evaluating the terrestrial contribution to the organic carbon pool. The spatial variation of the thermochemolysates shows expected higher abundances of fatty acids and phenols in the near-shore sediments of the Northwest Arm compared to those of the offshore sediment cores. 210Pb dates of sediments of two near-shore cores enabled calculation of annual preserved fluxes of organic carbon, total fatty acids and phenols. The temporal and spatial input of phenols appear to be significantly influenced by saw-milling and logging activities of the local communities in the surrounding watershed.

Trimethylbenzoic acids as metabolite signatures in the biogeochemical evolution of an aquifer contaminated with jet fuel hydrocarbons

Evolution of trimethylbenzoic acids in the KC-135 aquifer at the former Wurtsmith Air Force Base (WAFB), Oscoda, MI was examined to determine the functionality of trimethylbenzoic acids as key metabolite signatures in the biogeochemical evolution of an aquifer contaminated with JP-4 fuel hydrocarbons. Changes in the composition of trimethylbenzoic acids and the distribution and concentration profiles exhibited by 2,4,6- and 2,3,5-trimethylbenzoic acids temporally and between multilevel wells reflect processes indicative of an actively evolving contaminant plume. The concentration levels of trimethylbenzoic acids were 3-10 orders higher than their tetramethylbenzene precursors, a condition attributed to slow metabolite turnover under sulfidogenic conditions. The observed degradation of tetramethylbenzenes into trimethylbenzoic acids obviates the use of these alkylbenzenes as non-labile tracers for other degradable aromatic hydrocarbons, but provides rare field evidence on the range of high molecular weight alkylbenzenes and isomeric assemblages amenable to anaerobic degradation in situ. The coupling of actual tetramethylbenzene loss with trimethylbenzoic acid production and the general decline in the concentrations of these compounds demonstrate the role of microbially mediated processes in the natural attenuation of hydrocarbons and may be a key indicator in the overall rate of hydrocarbon degradation and the biogeochemical evolution of the KC-135 aquifer.