Relative abundance of planktonic foraminifera in Pliocene and Pleistocene sediments of DSDP Hole 32-310 from Hess Rise, Central North Pacific (Table II)

Late Neogene planktonic foraminifera have been examined at Site 310 in the Central North Pacific and their stratigraphic ranges and frequencies are presented here. Blow's (1969) zonation developed for tropical regions has been applied where applicable. Where tropical index taxa are rare or absent in this temperate region, Globorotalia crassaformis, and the evolutionary bioseries G. conoidea - G. conomiozea and G. puncticulata - G. inflata have been found useful for zonal subdivisions. A correlation between stratigraphic ranges and frequency distributions of these species at Site 310 in the Central North Pacific, and Site 284 in the Southwest Pacific indicates that these species are relatively consistent biostratigraphic markers in temperate regions of both the North and South Pacific Oceans. An informal zonation for temperate latitudes of the Southwest Pacific has been established by Kennett (1973) and a similar zonal subdivision can be made at Site 310. Paleoclimatic/paleoceanographic interpretations based on coiling ratios, percent abundance, and phenotypic variations of Neogloboquadrina pachyderma indicate four major cold events during early, middle, and late Pliocene, and early Pleistocene. Faunal correlations of these events with similar events elsewhere in the Northeast and Southwest Pacific which have been paleomagnetically dated indicate the following approximate ages for these cold events: 4.7 Ma, 3.0 Ma, 2.6-1.8 Ma, and 1.2 Ma. Faunal assemblages have been divided into three groups representing cool, intermediate, and warmer water assemblages. Cool water assemblages are dominated by ~60% N. pachyderma; intermediate temperature faunas are dominated by species of Globigerina and Globigerinita and contain between 20% and 30% N. pachyderma. Warmer water assemblages are dominated by species of Globorotalia and contain <10% N. pachyderma. Frequency oscillations within these groups, in addition to paleotemperature parameters evident in N. pachyderma, afford refined paleoclimatic/paleoceanographic interpretations.

(Table 1) Relative abundance of planktonic foraminifers in ODP Hole 164-997A sediments

Hole 997A was drilled during Leg 164 of the Ocean Drilling Program at a depth of 2770 m on the topographic crest of the Blake Ridge in the western Atlantic Ocean. We report here an analysis of the faunal assemblages of planktonic foraminifers in a total of 91 samples (0.39-91.89 mbsf interval) spanning the last 2.15 m.y., latest Pliocene to Holocene. The abundant species, Globigerinoides ruber, Globigerinoides sacculifer, Neogloboquadrina dutertrei, Globorotalia inflata, and Globigerinita glutinata together exceed over ~70% of the total fauna. Each species exhibits fluctuations with amplitudes of 10%-20% or more. Despite their generally low abundance, the distinct presence/absence behavior of the Globorotalia menardii group is almost synchronous with glacial-interglacial climate cycles during the upper part of Brunhes Chron. The quantitative study and factor analysis of planktonic foraminiferal assemblages shows that the planktonic foraminiferal fauna in Hole 997A consists of four groups: warm water, subtropical gyre (mixed-layer species), gyre margin (thermocline/upwelling species), and subpolar assemblages. The subtropical gyre assemblage dominates throughout the studied section, whereas the abundance of gyre margin taxa strongly control the overall variability in faunal abundance at Site 997. In sediments older than the Olduvai Subchron, the planktonic foraminiferal faunas are characterized by fluctuations in both the subtropical gyre and gyre margin assemblages, similar to those in the Brunhes Chron. The upwelling/gyre margin fauna increased in abundance just before the Jaramillo Subchron and was dominant between 0.7 and 1.07 Ma. The transition from this gyre margin-dominated assemblage to an increase in abundance of the subtropical gyre and gyre margin species occurred around 0.7 Ma, near the Brunhes/Matuyama boundary. The presence of low-oxygen-tolerant benthic foraminifers, pyrite tubes, and abundant diatoms below the Brunhes/Matuyama boundary suggests decreased oxygenation of intermediate waters and more upwelling over the Blake-Bahama Outer Ridge, perhaps because of weaker Upper North Atlantic Deep Water ventilation. The changes in the relative composition of foraminifer assemblages took place at least twice, around 700 and 1000 ka, close to the ~930-ka switch from obliquity-forced climate variation to the 100-k.y. eccentricity cycle. The climate shift at 700 ka suggests a transition from relatively warmer conditions in the early Pleistocene to warm-cool oscillations in the Brunhes Chron.

Relative contents of foraminifera species in bottom sediments of northern and southern seas

Correlation of paleoceanographic events in several key regions of the World Ocean: North Atlantic, Antarctic, West Arctic Seas, North Pacific and tropical Indo-Pacific has been carried out for the last 135 ka based on micropaleontological, stable isotope, geochronological (AMS-14C) and other data. It has been shown that the global thermohaline circulation controls remote climatic teleconnections on millennial-scale and partly on centennial-scale, while short-term climate changes are mainly transferred by the atmosphere. The basic information is given about the recent thermohaline circulation and stages of its development during Neogene.

Isotope age and relative abundance of planktonic foraminifera in Core Vulk-34-90, Sea of Okhotsk

Based on analyses of taxonomic composition of planktonic foraminifera and oxygen isotopic composition of their shells in the sediment core V34-90 from the eastern slope of the USSR Academy of Sciences Rise in the southeast Sea of Okhotsk the main climatic and hydrological variations over the past 20 Ka have been traced and dated by the radiocarbon method. The followed periods have been revealed: glacial (20-12.5 Ka), deglaciation (12.5-8.0 Ka) with a pronounced cooling event (Late Drias about 10.8 Ka) and post deglaciation (last 8.0 Ka).

Relative abundance of dinoflagellate cysts in surface sediments and dinoflagellate counts from three sediment cores from the Atlantic sector of the Southern Ocean

In this study we investigate the potential of organic-walled dinoflagellate cysts (dinocysts) as tools for quantifying past sea-surface temperatures (SST) in the Southern Ocean. For this purpose, a dinocyst reference dataset has been formed, based on 138 surface sediment samples from different circum-Antarctic environments. The dinocyst assemblages of these samples are composed of phototrophic (gonyaulacoid) and heterotrophic (protoperidinioid) species that provide a broad spectrum of palaeoenvironmental information. The relationship between the environmental parameters in the upper water column and the dinocyst distribution patterns of individual species has been established using the statistical method of Canonical Correspondence Analysis (CCA). Among the variables tested, summer SST appeared to correspond to the maximum variance represented in the dataset. To establish quantitative summer SST reconstructions, a Modern Analogue Technique (MAT) has been performed on data from three Late Quaternary dinocyst records recovered from locations adjacent to prominent oceanic fronts in the Atlantic sector of the Southern Ocean. These dinocyst time series exhibit periodic changes in the dinocyst assemblage during the last two glacial/interglacial-cycles. During glacial conditions the relative abundance of protoperidinioid cysts was highest, whereas interglacial conditions are characterised by generally lower cyst concentrations and increased relative abundance of gonyaulacoid cysts. The MAT palaeotemperature estimates show trends in summer SST changes following the global oxygen isotope signal and a strong correlation with past temperatures of the last 140,000 years based on other proxies. However, by comparing the dinocyst results to quantitative estimates of summer SSTs based on diatoms, radiolarians and foraminifer-derived stable isotope records it can be shown that in several core intervals the dinocyst-based summer SSTs appeared to be extremely high. In these intervals the dinocyst record seems to be highly influenced by selective degradation, leading to unusual temperature ranges and to unrealistic palaeotemperatures. We used the selective degradation index (kt-index) to determine those intervals that have been biased by selective degradation in order to correct the palaeotemperature estimates. We show that after correction the dinocyst based SSTs correspond reasonably well with other palaeotemperature estimates for this region, supporting the great potential of dinoflagellate cysts as a basis for quantitative palaeoenvironmental studies.

(Table 2) Relative abundance of planktonic foraminifera species in Pliocene - Early Quaternary sediments from ODP Hole 111-677A

Planktonic foraminifera from Pliocene - Early Quaternary sediments of ODP Hole 111-677A were studied in detail. It was shown that the majority of detected zonal taxa are reliable biostratigraphic reference points. Between 30 and 210 m in the core zones of planktonic foraminifera from PL1b to Pt1 (according to the W.A. Berggren scale) were distinguished. Changes of planktonic foraminifera complexes from sediments of Hole 111-677A are closely associated with climate-controlled development of surface water masses of the Eastern Equatorial Pacific during 4.6-0.65 million years ago. Sharp decrease in equatorial-tropical species about 3.4 million years ago correlated with cessation of surface water exchange between tropical regions of the Pacific and Atlantic oceans due to formation of the Central American isthmus. The paleotemperature method of M.S Barash was used for reconstructing surface temperatures. Maximum temperatures were reconstructed in late Early Pliocene (26.4°C) and in Late Pliocene (26.6°C) and minimum ones - in the beginning of Early Pliocene (18.4°C), in the middle of Late Pliocene (19.6°C). Cold events occurred: 4.6-4.3, 2.8-2.5, and 1.7-1.2 million years ago, and warm: 4.3, 4.18-3.4, 2.5-2.3, and 1 million years ago. In general, the middle of Early Pliocene, the middle of late Pliocene and early Pleistocene are characterized by cold-water conditions, and the end of Early and the end of Late Pliocene - by warm-water conditions.

(Table 2) Relative contents of clay minerals in aeolian pelagic clays from the Pacific Ocean

For determining importance, composition, and history of aerosol material accumulation in formation of pelagic clays a study with use of light microscopy and scanning electron microscopy, X-ray diffractometry, and chemical methods has been carried out.

Relative abundance of prokaryotes in sediments of the Håkon Mosby mud volcano (Z1-Z3, all habitats)

CARD-FISH was performed as previously described in Ruff et al., (2013; doi:10.1371/journal.pone.0072627) with the following modifications. 4-6 µl of 25-fold diluted sediment were used for filtration. Archaeal cell walls were permeabilized with 0.1M HCl for 2 min to detect ANME-3 cells, or Proteinase K solution (15 µg ml-1 (Merck, Darmstadt, Germany) in 0.05 M EDTA (pH 8), 0.1 M Tris-HCl (pH 8), 0.5 M NaCl) for 2-4 min at room temperature for all other archaea. Bacterial cell walls were permeabilized with lysozyme solution (1000kU/ml) for 60 min at 37°. Cells were stained with DAPI (1µg/ml), embedded in mounting medium and counted in 40-60 independent microscopic fields using an Axiophot II epifluorescence microscope (Carl Zeiss, Jena, Germany).

Relative abundance of anaerobic methanotrophic archaea in bacterial mat Cascadia margin off Oregon

The microbially mediated anaerobic oxidation of methane (AOM) is the major biological sink of the greenhouse gas methane in marine sediments (doi:10.1007/978-94-009-0213-8_44) and serves as an important control for emission of methane into the hydrosphere. The AOM metabolic process is assumed to be a reversal of methanogenesis coupled to the reduction of sulfate to sulfide involving methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) as syntrophic partners which were describes amongst others in Boetius et al. (2000; doi:10.1038/35036572). In this study, 16S rRNA-based methods were used to investigate the distribution and biomass of archaea in samples from sediments above outcropping methane hydrate at Hydrate Ridge (Cascadia margin off Oregon) and (ii) massive microbial mats enclosing carbonate reefs (Crimea area, Black Sea). Sediment samples from Hydrate Ridge were obtained during R/V SONNE cruises SO143-2 in August 1999 and SO148-1 in August 2000 at the crest of southern Hydrate Ridge at the Cascadia convergent margin off the coast of Oregon. The second study area is located in the Black Sea and represents a field in which there is active seepage of free gas on the slope of the northwestern Crimea area. Here, a field of conspicuous microbial reefs forming chimney-like structures was discovered at a water depth of 230 m in anoxic waters. The microbial mats were sampled by using the manned submersible JAGO during the R/V Prof. LOGACHEV cruise in July 2001. At Hydrate Ridge the surface sediments were dominated by aggregates consisting of ANME-2 and members of the Desulfosarcina-Desulfococcus branch (DSS) (ANME-2/DSS aggregates), which accounted for >90% of the total cell biomass. The numbers of ANME-1 cells increased strongly with depth; these cells accounted 1% of all single cells at the surface and more than 30% of all single cells (5% of the total cells) in 7- to 10-cm sediment horizons that were directly above layers of gas hydrate. In the Black Sea microbial mats ANME-1 accounted for about 50% of all cells. ANME-2/DSS aggregates occurred in microenvironments within the mat but accounted for only 1% of the total cells. FISH probes for the ANME-2a and ANME-2c subclusters were designed based on a comparative 16S rRNA analysis. In Hydrate Ridge sediments ANME-2a/DSS and ANME-2c/DSS aggregates differed significantly in morphology and abundance. The relative abundance values for these subgroups were remarkably different at Beggiatoa sites (80% ANME-2a, 20% ANME-2c) and Calyptogena sites (20% ANME-2a, 80% ANME-2c), indicating that there was preferential selection of the groups in the two habitats.