Anoxic basins of the eastern Mediterranean: geological framework

A brief review of the geological knowledge on the anoxic basins of the eastern Mediterranean is presented. Anoxic basins have been discovered in two different geological settings in the eastern Mediterranean. Bannock Basin belongs to the compressional style of the Mediterranean Ridge, and Tyro and Poseidon Basins belong to the transcurrent tectonic style of the Strabo Trench. The origin of the basins is subsurface salt dissolution triggered by tectonic deformation of the sediments on the Mediterranean Ridge, and tectonic subsidence (pull-apart mechanism) in the Strabo Trench. The onset of a deep-sea brine lake is always related to the outcrop of Messinian salts on the side-walls of the basin. The rate of basin subsidence controls the evolution of the brine lakes, which can also be completely diluted by bottom water circulation.     

Determination of inorganic sulphur speciation with polarographic techniques: Some preliminary results for recent hypersaline anoxic sediments

Polarographic techniques have been used to determine reduced inorganic sulphur speciation in recent anoxic marine sediments from two hypersaline basins, the Tyro and the Bannock Basins, in the Eastern Mediterranean. The following phases were determined: acid volatile sulphur (AVS), pyritic sulphur and zerovalent sulphur. The determination of AVS and pyrite was based respectively on the acidification and Cr(II) reduction of these sulphur components to H₂S. H₂S was collected in base and the sulphide concentration was measured by polarography. Standard Na₂S and pyrite gave recoveries of 99.6% ± 3.9% and 97% ± 12% respectively. Total zerovalent sulphur in a sediment sample was measured by the reaction of sulphite with thiosulphate. Thiosulphate was measured directly by polarography.

Pyrite is the main phase of inorganic reduced sulphur in the sediments from the Tyro and the Bannock Basins, and it has about the same average level (125 υmoles per gramme dry weight) in the cores recovered from the two areas. However, the distribution of pyrite in the top 100 cm of the two cores differs significantly. In the Bannock Basin a sharp increase is observed with depth, whereas in the Tyro Basin there is a small decrease with depth.

The total amount of reduced inorganic sulphur is less than the total amount of sulphur in the sediments. This indicates that there must be additional sulphur-bearing phases. One of these phases may be gypsum, and indeed, gypsum crystals have been observed in the Bannock Basin.

In neither basin is there a significant correlation between reduced sulphur and organic carbon. The pyrite that occurs in these basins may have been formed syngenetically at the interface of the anoxic brine and oxic seawater. Diagenetic pyrite may have been formed within the sediments of the basins. AVS and total zerovalent sulphur are still observed at depth. We therefore suggest that this may be due to the incomplete transformation of AVS and zerovalent sulphur into pyrite.     

Sulphate-related equilibria in the hypersaline brines of the Tyro and Bannock Basins, eastern Mediterranean

The Tyro and Bannock Basins, which are depressions in the eastern Mediterranean, contain hypersaline anoxic brines. These brines are of different composition: Tyro brine is primarily an early-stage halite (NaCl) brine, whereas Bannock brine includes the more soluble ions of late-stage evaporite minerals. Accordingly, the Bannock brine contains a much greater sulphate concentration than the Tyro Brine. This difference in sulphate concentration is reflected in the concentrations of ions such as Ca, Sr and Ba, which form sparingly soluble sulphate minerals.Equilibrium calculations using the Pitzer specific ion interaction model indicate that the brines in both basins are saturated with respect to gypsum (CaSO₄-2H₂O) and supersaturated to saturated with respect to dolomite (CaMg(CO₃)₂). The degree of saturation with respect to dolomite is greater in the Bannock Basin than it is in the Tyro Basin. Correspondingly, recent gypsum crystals and dolomite hardgrounds have been found in the Bannock Basin but not in the Tyro Basin.The Tyro brine is homogeneous in composition, whereas the Bannock brine demonstrates a clear two-layer brine structure. At the interface of the upper and the lower brine distinct positive anomalies occur in the total alkalinity and the concentration of phosphate, and negative anomalies occur in the concentrations of Mn²⁺ and the rare earth elements (REE). These anomalies and the observed association of gypsum/dolomite in the sediments are all consistent with a recent precipitation of dolomite and gypsum in the Bannock Basin. The brines in both basins are also saturated with respect to barite (BaSO₄).The ⁸⁷Sr/⁸⁶Sr and δ³⁴S ratios of the Bannock brines are amazingly consistent but differ dramatically from the values for modern or Messinian-age seawater. The Sr concentration and Sr and S isotope ratios in the gypsum crystals indicate that most of these crystals have resulted from precipitation/recrystallization from the brine and not from seawater. The observed variations between crystals are thought to reflect the recrystallization of (sub-) outcropping Messinian gypsum with a low ⁸⁷Sr/⁸⁶Sr ratio in the presence of seawater or brine fluids and with different extents of diagenesis.     

Trace elements in suspended matter from the anoxic hypersaline Tyro and Bannock Basins (eastern Mediterranean)

In the anoxic hypersaline Tyro and Bannock Basins of the eastern Mediterranean, extremely high concentrations of Co (0.015%), Cu (1.35%) and Zn (0.28%) were found in suspended matter collected at the sharp interface between seawater and the anoxic brine. The high particulate Co, Cu and Zn concentrations can be explained by the sharp increase in dissolved sulphide at these interfaces, and the resultant precipitation of metal sulphides. The particulate As, Sb and Mo concentrations also showed a sharp maximum at or close to the interface. However, the contributions of As, Sb and Mo contents in suspended matter to the total concentrations in the water column are small. Scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDAX) of suspended particulate matter from the Tyro Basin revealed spherical particles strongly enriched in Fe, Cu and Zn at the seawater-brine interface.     

Some chemical characteristics of the brines in Bannock and Tyro Basins: salinity, sulphur compounds, Ca, F, pH, At, PO4, SiO2, NH3

Results of the chemical investigation on the Bannock and Tyro Basins are reported.Both basins were found to be hypersaline ( 10 times higher than salinity of normal seawater) and anoxic. In all investigated basins a region of transition, a few meters thick, was identified at depths > 3327 dbar. It is characterized by a sharp gradient of salinity, and all concentrations of analysed species increase strongly except for dissolved oxygen and nitrate, which immediately drop to zero. This region appears as a sharp boundary that prevents mixing. As a result, in the presence of organic matter, an anoxic condition developed with the complete depletion of dissolved oxygen. At the same time, hydrogen sulphide and ammonium accumulated within the brine. Between the Bannock and the Tyro brines differences occur in the measured concentrations of H₂S, SO²⁻₄, Ca²⁺ and NH₃. There are some differences also within the Bannock area sub-basins.The Libeccio sub-basin, in the Bannock area, contains a double-layered brine: the upper layer is 140 dbar thick and the lower layer is 300 dbar thick. A second interface between upper and lower brines develops at a depth of 3500 dbar. Nearly all of the measured concentrations vs. depth show the double layer, with the exception of ammonium, the concentration of which remains nearly constant throughout the anoxic column. Profiles of the other species analyzed show remarkable differences on passing from the upper to the lower brine. Hydrogen sulphide, sulphate and fluoride concentrations appear constant and then increase at the second interface. The calcium concentration is also constant in the upper brine, but decreases at the second interface. Total alkalinity and phosphate concentrations show a maximum peak just below the first interface. However, after passing through the second interface all the chemical parameters exhibit an almost constant behaviour down to the bottom.Hypersaline conditions are attributed to the dissolution of Messinian evaporite, and anoxia is suggested to originate from the oxidation of organic matter present in sediments and from the absence of bottom water circulation in such a deep and enclosed environment.The chemical conditions can be summarized as follows: in the Libeccio Basin the values for the species analysed have the ranges: 39–321 psu for ‘salinity’, 8.2−6.5 for pH, 2.7–4.0 mM for total alkalinity, 0.2-0 mM for dissolved oxygen, 0–1669 μM for hydrogen sulphide, 0–198 μM for thiol, 31–99 mM for sulphate, 11–21 mM for calcium, 7–100 μM for fluoride, 0.2–3080 μM for ammonium, 5.8-0 μM for nitrite, 0.2–12 μM for phosphate and 8–130 μM for silicate.     

Iodine chemistry in deep anoxic basins and overlying waters of the Mediterranean Sea

Iodate (IO₃⁻) is the predominant dissolved species of iodine in the oxygenated waters of the Mediterranean Sea. Iodide (I⁻) is present in significant quantities (up to 65 nM) in oxygenated waters in the photic zone and near the interface above the anoxic and saline Bannock Basin. Lesser quantities of I⁻ (< 10 nM) are found throughout the rest of the oxic water column. An additional unidentified dissolved iodine species is present immediately above the anoxic interface.Total dissolved iodine (ΣI) increases dramatically across the seawater/brine interface. Part of this increase is undoubtedly the result of the dissolution of iodine-rich evaporites during formation of the brine bodies at the Tyro and Bannock Basins. The vertical distribution of ΣI and other dissolved chemical species (particularly PO₄³⁻) in the Bannock Basin brine, however, suggests an additional, present-day, diagenetic source of dissolved iodine to the brine. Based on the increase in the concentration of the most soluble major ions across the seawater/brine interface, 5–7 μM of the 11.5-μM increase in ΣI concentration must be attributed to diagenesis.     

Stable isotope study of water, gypsum and carbonate samples from the Bannock and Tyro Basins, eastern Mediterranean

Seawater and brine samples collected along vertical profiles above the Bannock and Tyro Basins (eastern Mediterranean), and gypsum samples collected by dredging and coring the anoxic section of the Bannock Basin, have been studied for their δ¹⁸O values. The following conclusions may be drawn from these data: (1) The water of the deep brines is isotopically slightly different from modern Mediterranean bottom water and might be a ‘fossil water’ possibly formed during a recent, climatically cooler stage or when the evaporation was slightly higher than nowadays. (2) The similarity between the δ¹⁸O values of the brine samples from the Bannock and Tyro Basins supports the possibility that the ages of the two basins are very close to each other. (3) Gypsum crystals on the bottom of the Bannock Basin are probably being formed by the dissolution and reprecipitation of sub-bottom (or outcropping) Messinian evaporites. This hypothesis is supported by the oxygen isotopic values exhibited by the gypsum crystallization water and by the oxygen and sulphur isotopic composition of gypsum. (4) The shells of pelagic organisms included in gypsum are probably very recent, but not contemporary, and may be referred to cooler environmental conditions.     

珠江口异养细菌时空分布特征及其调控机制

河口是海陆相互作用的重要地带, 往往呈现出独特的生物地球化学过程, 是研究碳循环过程的重要场所。在春季(2015年5月)、夏季(2015年8月)和冬季(2016年1月)分别对珠江口海域异养附生细菌和游离细菌时空分布及其各自高核酸(HNA)、低核酸(LNA)类群的相对贡献进行了调查研究, 并对其调控因子进行了相应探讨。结果表明, 珠江口异养细菌分布具有明显的时空差异。空间分布上, 珠江口异养细菌丰度自河口上游至下游呈递减趋势, 主要与上游污水输入以及珠江径流与高盐外海水在河口内的混合有关; 在雨季, 河口中下游盐度锋面区出现异养细菌丰度和叶绿素a质量浓度的高值区, 锋面区使营养物质停留时间增加, 促进浮游生物生长。垂直方向上, 表层异养细菌丰度略高于底层。时间尺度上, 异养细菌总丰度在春季最高(表层均值为2.94±1.23×10⁹个 •L^-1, 底层为2.81±1.50×10⁹个 •L^-1), 夏季次之(表层均值为2.32±0.43×10⁹个 •L^-1, 底层为1.90±0.50×10⁹个 •L^-1), 冬季最低(表层均值为1.06±0.33×10⁹个 •L^-1, 底层为9.76± 3.44×10⁸个 •L^-1)。珠江口海域异养细菌以附生细菌为主, 占异养细菌总丰度的16.56%~96.19%, 整体分布较稳定, 冬季最高(平均78.65%)、夏季(70.32%)与春季相近(68.17%)。附生细菌以代谢活跃的HNA类群为主, 游离细菌则主要以LNA类群为主, 代谢活性整体相对较低。     

北部湾养殖牡蛎体内异养细菌数量及其耐药性研究

为了探究北部湾养殖区域香港牡蛎(Crassostrea hongkongensis)体内的异养细菌和弧菌数量及其耐药概况变化, 对不同养殖场牡蛎体内的异养细菌进行分离培养, 并统计其数量, 通过药敏纸片扩散等方法研究了细菌的耐药状况。结果显示: 牡蛎在高死亡率养殖环境中体内的异养细菌[(8.6±0.4)×10⁶CFU·g^-1]和弧菌[(9.5±0.4)×10⁵CFU·g^-1]数量较高, 在中死亡率环境中体内的异养细菌[(6.9±0.2)×10⁶CFU·g^-1]和弧菌[(4.5±0.6)×10⁵CFU·g^-1]数量次之, 在低死亡率养殖环境中体内的异养细菌[(3.3±0.1)×10⁶CFU·g^-1]和弧菌[(2.5±0.6)×10⁵CFU·g^-1]数量最低。耐药细菌主要为革兰氏阴性菌, 对β-内酰胺类(青霉素)、糖肽类(万古霉素)的耐药率较高, 对四环素类(四环素、多西环素)的耐药率次之, 对氨基糖苷类(链霉素、庆大霉素、妥布霉素、新霉素)、大环内酯类(红霉素)、喹诺酮类(诺氟沙星、环丙沙星、氧氟沙星、恩诺沙星)的耐药率较低。在高死亡率环境中牡蛎体内的多重耐药菌占79.7%, 其耐药谱型(48种)较广; 在中度死亡率环境中牡蛎体内的多重耐药菌占66.2%, 其耐药谱型为30种; 在低死亡率环境中牡蛎体内的多重耐药菌占58.4%, 其耐药谱型为17种。本文探究了牡蛎死亡率与其体内异养细菌数量和细菌耐药性的关系, 结果显示牡蛎在高死亡率环境中体内的耐药细菌数量多、耐药谱型较广, 低死亡率环境中牡蛎体内的耐药细菌数量较少, 异养细菌数量与牡蛎死亡率呈正相关关系, 两者相关系数为0.996。     

Hardground formation in the Bannock Basin, Eastern Mediterranean

Twenty kilogrammes of crusts and slabs of indurated carbonate sediment, usually referred to as hardgrounds, were dredged along the eastern steep wall of the Bannock Basin during the 1984 cruise of R.V. Bannock.

The crusts range in thickness from one to a few centimetres and the fragments of these crusts are irregular in shape. Their surface is always uneven and their colour ranges from white to brownish dark grey. Some slabs are impregnated along one side by ferromanganese sesquioxides, and borings occur in several samples. Serpulid tubes have been observed in one instance. The borings and serpulids suggest formation of the hardgrounds at or close to the sediment/water interface and exposure at the seafloor.

The degree of lithification is generally different on the inferred upper and lower sides of the slabs. An upward increase of lithification across the slabs is reflected by mineralogy, ultrastructure and stable isotope composition of the carbonate. X-ray diffraction analyses indicate high-magnesian calcite as the predominant carbonate with minor amounts of low-magnesian calcite and dolomite. Occasionally, large gypsum crystals are attached to the hardgrounds and sometimes smaller ones are dispersed through the carbonate matrix.

An increase in diagenesis is reflected by the passage from friable, nodular nannofossil chalk to nannofossil limestone and hard xenotopic calcite micrite. Overgrowth of coccoliths and internal cementation of the tests of planktonic foraminifera by high-Mg calcite increase from chalk to limestone. In the hard, fully cemented micrites, coccoliths can no longer be recognised in the xenotopic fabric. Pteropods occur as dissolution moulds with aragonite preserved as only tiny relics.

Carbon and oxygen isotope analyses were performed on different samples. The progressive lithification to chalk and limestone is marked by a shift in the δ¹⁸O values from +1.2‰ to +5.4‰ (PDB). This change indicates that precipitation of high-Mg calcite and possibly also recrystallisation of the original biogenic carbonate took place within cold and hypersaline brines which were enriched in ¹⁸O. The oxygen isotope data suggest that lithification and gypsum precipitation occurred under identical conditions. The carbon isotope data show progressive diagenetic change from values near +1‰ to values of +3‰. This change may reflect a contribution of methanogenetic CO₂ to the hypersaline brine.     

Carbon and oxygen isotope composition of foraminifera in two cores from the Bannock Basin area, eastern Mediterranean

Two cores from the Bannock Basin in the eastern Mediterranean have been analysed for δ¹⁸0 and the δ¹³C in planktonic foraminifera. One core (02-PC) was extracted from the anoxic brine, the other (08-GC) from a plateau east of the brine.

The absence of sapropelic muds in Core 08-GC from the two Holsteinian euxinic cycles, together with the presence of isotopic spikes, suggests that the plateau has risen during the last ca. 200,000 years by ca. 2.5 mm/yr.

The δ¹⁸0 amplitude of Globigerinoides ruber in eastern Mediterranean cores is only ca. 0.5%. larger than for this species in North Atlantic cores. This suggests that the surface oxygen isotopic composition of both bodies of water followed each other fairly closely during the Late Pleistocene, except during the stagnant phases.     

Facies analysis of Pleistocene sediments from the Bannock Basin area: A key to the reconstruction of its tectonic evolution

Facies analysis was carried out on 21 selected cores from the Bannock area in order to investigate the relationships between sedimentation and tectonism. Bannock Basin is a large, > 3500 m (uncorrected) deep subcircular depression near the deformation front of the Mediterranean Ridge facing the Sirte Abyssal Plain. The basin is divided into several sub-basins aligned along a rim-syncline surrounding a central elevated area (salt dome?). High-density brines and anoxic sediments occupy the deepest part of the depressions.

The facies distribution is controlled by the bottom configuration in that pelagic facies typically occur on plateaus and domes, debris-flow deposits in base-of-slope settings, and turbidites in basinal settings. The facies distribution may therefore be used to reconstruct the evolution of the various parts of the rim-syncline.

Erosional gaps may be related to tectonism or may be features created by the passage of major turbiditic events.

The results of our study of the facies associations, and of the rates of sediment accumulation, indicate that the collapse of the eastern part of the rim-syncline pre-dates the collapse of the western part. The western basins are deeper and larger than the eastern ones and (unlike the latter) are aligned at the foot of a strike-slip fault with a vertical offset of at least 700 m.     

利用遥感技术估算南海北部表层异养细菌丰度

常规异养细菌监测方法精度高但费时费力且不能连续观测, 而卫星遥感成本低、可以大面积同步、长时间周期观测, 可与常规方法互补。文章利用南海北部10个航次采集的表层异养细菌丰度和卫星遥感反射率, 采用统计回归的方法建立了异养细菌丰度的遥感模型, 其模型决定系数为0.81, 均方根误差为2.44×10⁸个·L^-1, 平均相对误差为21%, 具有较好表现。利用该模型估算南海北部表层异养细菌丰度, 结果显示: 从珠江河口到南海北部开阔海域, 异养细菌丰度逐渐减小。夏季河口地区平均异养细菌丰度最高, 春季最低; 近岸海域靠近珠江河口西侧的平均异养细菌丰度高于东侧; 冬季陆架地区平均异养细菌丰度最高, 夏季最低; 开阔海域的异养细菌丰度变化幅度较小。     

Evidence of relief inversion from the rim-syncline of Bannock Basin

The last steps in the geological exploration of Bannock Basin (cruises BAN-88 and BAN-89 of R.V. Bannock) provided direct evidence of an inversion of relief that was long suspected but hitherto never recorded.

Dolostones and dolomitic mudstones of probable Messinian age subcropping beneath the brine in the northern part of Bannock Basin and Zanclean oozes recorded on the sill separating two narrow and elongate satellite basins along the eastern part of the rim-syncline record a relief inversion during their evolution from cylindric folds to collapse structures.

In particular, the core from the eastern intrabasin sill contains two major unconformities: one separates early Zanclean oozes from late Piacenzian pelagic sediments characterized by winnowed layers, inclined bedding and incipient hardgrounds, and the second separates the latter from Middle Pleistocene pelagic sediments. The deepening is certainly post-late Piacenzian (post-M Pl 6 biozone) because sediments of that age record an actively uplifting structure.

Another argument in favour of the relief inversion, and of the youthful age of the deepening, is derived from a core raised from the northern part of the major western basins (large sill separating Maestro from Borea basins) which contains a coarse turbidite of North African origin representing an upflow turbidite similar to others recorded on the outer slopes of the Mediterranean Ridge. This unique finding in the area of Bannock Basin is preserved in the central part of the collapse basin, whereas in other settings an erosional gap is noticed at the equivalent stratigraphic position.     

The Fauna of Floating Cyanobacterial Mats in the Oligohaline Eulittoral Zone off Hiddensee (South-west Coast of the Baltic Sea)

Abstract. The fauna — including macrofauna, meiofauna, and large ciliates — of floating cyanobacterial mats in a brackish shallow-water area was studied by analysing six 20 cm² pieces of mat. Although these microbial aggregations were scarcely 1 cm thick, their total meiofauna abundance was about five times as high as in the uppermost 4 cm of the adjacent sediment. The mat fauna was dominated by harpacticoids, although large ciliates, rotifers, nematodes, and oligochaetes were also markedly more abundant than in the sediment. All species occurring in the mats were members of the surrounding sediment fauna. Out of the 47 species found, only a few, among them predominantly the harpacticoid, Mesochra lilljeborgi B oeck , 1864, and the nematode Daptonema setosum ( bütschli , 1874), accounted for the majority of the individual abundance in the mats. Both are regularly found in sulphidic biotopes near Hiddensee. As SEM micrographs revealed, the oligochaete Paranais litoralis (O. F. M üller , 1788) and the harpacticoid Cletocamptus confluens (Schmeil, 1894) were apparently optimal substrates for dense lawns of cyanobacteria. This indicates possible close interactions between the meiofauna and these microbiota. The frequent predation of histophagous ciliates on nematodes and harpacticoids, which were probably weakened by oxygen deficiency and/or high sulphide concentrations, were not only a sign of a generally neglected pathway in the food chain, but also impressively emphasized the huge variety of interactions taking place between meio- and microfauna within this specific benthic microcosm. Because of their floating character, the mats can play an important role in the dispersal of benthic fauna.     

Carbon isotopic composition and lattice-bound carbonate of Peru-Chile margin phosphorites

New light-stable carbonate-carbon isotope and lattice-bound CO₂ data from Quaternary Peru-Chile margin phosphatic nodules, crusts and pelletal grains, and from associated dolomicritic concretions, are presented, which provide constraints on the timing and mechanisms of growth of these phases in organic carbon-rich sediments. Comparison of δ¹³C values from carbonate fluorapatite (CFA) nodules and pelletal grains (−4.8 to 0.0‰ and −2.9 to +1.0‰ PDB, respectively) with pore-water total dissolved δ¹³C values from these sediments suggests early authigenic CFA precipitation from pore waters within a few centimeters of the sediment-water interface in association with suboxic to perhaps anoxic microbial degradation of organic matter. In contrast, the dolomicritic cores of nodules recovered from about 12°S display both strongly negative to positive δ¹³C values (−10.8 to +6.1‰) characteristic of formation deeper in the sediments in association with methanogenic and perhaps sulfate reduction microbial processes.

The amount of structural carbonate in CFA suggests that carbonate substitution generally increases as δ¹³C in CFA decreases, a probable consequence of increasing carbonate and accompanying charge-balancing substitutions in the CFA lattice in response to increasing pore-water carbonate ion concentrations with depth below the sediment-water interface. In one buried upward-growing nodule, decreasing CFA δ¹³C and increasing structural CO₂ also correspond to decreasing CFA growth rates. These data suggest that in addition to other constraints such as pore-water phosphorus and fluoride availability, the lower limit of CFA precipitation in suboxic to anoxic sediments may be controlled by lattice poisoning due to excessive dissolved carbonate ion concentrations. In organic-rich Peru-Chile margin sediments this depth threshold appears to be at approximately 5–10 cm below the sediment-water interface where maximum CFA CO₂ contents of about 6 Wt.% occur; in less organic-rich settings, greater depths of precipitation of CFA may be anticipated. Below this relatively shallow depth of CFA precipitation on the Peru shelf, high pore-water alkalinity and associated elevated total dissolved carbon and carbonate ion concentration apparently favor the precipitation of authigenic carbonates.     

Variation in microbial biomass and community structure in sediments of peter the great bay (sea of japan/east sea), as estimated from fatty acid biomarkers

Variation in the microbial biomass and community structure found in sediment of heavily polluted bays and the adjacent unpolluted areas were examined using phospholipid fatty acid analysis. Total microbial biomass and microbial community structure were responding to environmental determinants, sediment grain size, depth of sediment, and pollution due to petroleum hydrocarbons. The marker fatty acids of microeukaryotes and prokaryotes - aerobic, anaerobic, and sulfate-reducing bacteria -were detected in sediments of the areas studied. Analysis of the fatty acid profiles revealed wide variations in the community structure in sediments, depending on the extent of pollution, sediment depth, and sediment grain size. The abundance of specific bacterial fatty acids points to the dominance of prokaryotic organisms, whose composition differed among the stations. Fatty acid distributions in sediments suggest the high contribution of aerobic bacteria. Sediments of polluted sites were significantly enriched with anaerobic bacteria in comparison with clean areas. The contribution of this bacterial group increased with the depth of sediments. Anaerobic bacteria were predominantly present in muddy sediments, as evidenced from the fatty acid profiles. Relatively high concentrations of marker fatty acids of sulfate-reducing bacteria were associated with organic pollution in this site. Specific fatty acids of microeukaryotes were more abundant in surface sediments than in deeper sediment layers. Among the microeukaryotes, diatoms were an important component. Significant amounts of bacterial biomass, the predominance of bacterial biomarker fatty acids with abundance of anaerobic and sulfate-reducing bacteria are indicative of a prokaryotic consortium responsive to organic pollution.     

Shallow-Water Gasohydrothermal Vents of Ushishir Volcano and the Ecosystem of Kraternaya Bight (The Kurile Islands)

Abstract. A marine ecosystem in the crater of the Ushishir Volcano (Kraternaya Bight, Yankich Island, the Kuriles) showing gasothcrmal activity was studied for hydrographical, hydrochemical, and biological characteristics. Maximal changes in chemical and biological characteristics were observed in the surface water layer of 0–5 m. This layer had higher water temperature, was saturated with volcanogcnic carbon dioxide (up to 2000 10^-6 torr), ovcrsaturatcd with oxygen (up to 200 %), and contained high concentrations of chlorophyll a. Hydrogen sulfide was found in the surface water layer and at a depth of 15 m in the area of maximal effect of volcanic effluents.
The planktonic community is characterized by high rates of production and destruction of organic matter only in the 0–5 m layer. Daily vertical migrations of the ciliatc Mesodinium rubrum were observed, which caused "red tides".
Bacterial, algobacterial, and diatom mats developed on the bottom of the bight in the zone of gasohydrothermal vents and in areas of volcanic water seeping. The rate of organic matter production in algobacterial mats reached 33.4g C-rrr²-d^-l, chcmolithotrophy predominating. Bottom settlements had high population density and great animal biomass, which reached 10 kg m^-2 in gasohydrothermal fields. They obtain sufficient energy from primary production of microphy-tobenthos, algobacterial, and bacterial mats. Bcnthic species dominant in the bight were not found off the Ushishir Islands.
Some species of macrobenthos inhabiting the Kraternaya Bight differ markedly in size and biomass from the same species found beyond the bight.     

In situ Bicarbonate Uptake by Bacteria-Alvinella Associations

Abstract. Three species of Alvinellidae are found on walls of some hydrothermal chimneys at 13^o N on the East Pacific Rise (EPR); numerous epibiotic bacteria were associated with two of these polychaetes, Alvinella pompejana and Alvinella caudata , but not with the third, Paralvinella grasslei. Many studies suggest that chemoautotrophic bacteria play a prominent role in deep-sea hydrothermal vent ecosystems. Particularly important are the intracellular bacteria present in the giant pogonophores and bivalve molluscs.
The abundant epibioses observed on these Alvinella species are unusual and the relationships between these bacteria and the worms are unknown. Previous results, including ¹³C values, morphological insertion of the bacteria on the epidermis, presence of ribulose biphosphate carboxylase, and fixation of ¹⁴C bicarbonate in some bacteria and in the dorsal epidermis, suggest that a trophic relationship could exist between Alvinella and its epibiotic bacteria. The present study compared the incorporation area of ¹⁴C bicarbonate in the 3 species. Paralvinella , which is devoid of epibiotic bacteria, served as a control.     

基于多种培养基和不同培养温度的马里亚纳海沟异养细菌多样性分析

马里亚纳海沟具有低温、高压、永久黑暗以及营养匮乏等深海环境特征,其中的细菌多样性对深海环境具有极为重要的作用.为研究马里亚纳海沟海水中异养细菌的物种多样性,采用多种培养基、不同培养温度同步筛选,单菌落16S rRNA基因序列鉴定,邻近法系统发育树构建分析等方法,对25个海水样品进行异养细菌多样性分析.共获得细菌531株...