Age model and ostracod countings from IODP Site 306-U1314

We present a detailed study of glacial/interglacial deep sea benthic ostracod assemblage variability at IODP Site U1314 (subpolar North Atlantic) in relation to the history of ice-rafting events and changes in deep ocean circulation over the past 170 ky. Our records of ostracod diversity, abundance and dissolution and sediment properties (IRD and CaCO3) show an excellent correspondence to high amplitude orbital and millennial variability observed in the climate records (d13C and d18O) from neighboring deep water sites, suggesting that the benthic meiofauna fluctuates synchronously with the prevailing oceanographic conditions (surface ocean conditions, deep ocean circulation and water temperature and food flux). Krithe (dominant), Argilloecia and Cytheropteron are the most abundant and diverse genera in association with Rockallia enigmatica. Three ostracod assemblages are recognized. The genera Pennyella, Argilloecia, Pelecocythere, Ambocythere, Pseudobosquetina, Bradleya and Nannocythere are associated with interglacials and interstadials, and possibly reflect increased flux of food to the sediments and more vigorous NADW formation. A transitional assemblage composed of species of Cytheropteron, Xestoleberis and Eucythere is restricted to climatic transitions and indicate moderate environmental conditions and seasonal productivity. A glacial/stadial assemblage is characterized by a temporal predominance of either intermediate-depth and shallow water Arctic/subarctic species (belonging to Cytheropteron, Polycope, Pedicythere, Swainocythere, Cluthia, Heterocyprideis, Elofsonella and Finmarchinella) or abyssal North Atlantic ostracods (Bythocythere, Dutoitella, Bathycythere and Bythocypris). The influx of high latitude taxa can be partially explained by ice-rafting, but may also represent a shift of the location of intermediate and deep water convection to the area south of Iceland. Therefore the combination of species characteristic of different watermasses during glacials may reflect shifts in the influence of high nutrient southern source water (e.g. AABW) vs. low nutrient GNAIW during glacials.

Effects of thallus disturbance on abundance and biomass of soft-bottom species in Kongsfjorden in summer 2013

The effects of biotic disturbances, like seaweed whiplash, on the diversity of benthic communities are well documented for temperate coastal systems, yet missing for Arctic benthos. In Arctic soft-bottom habitats, kelp thalli occur either continuously (e.g. trapped by sediment) or sporadically (by drifting on the sediment) after detachment from rocky shores. To explore whether a kelp thallus can disturb the structure and diversity of a coastal Arctic soft-bottom assemblage, we continuously fixed a single thallus of the kelp Saccharina latissima to or sporadically (i.e. biweekly) moved it on the sediment and compared treatment effects to unmanipulated plots (= controls). On 6 September 2013 (i.e. after 73 days of manipulation), one sediment core was taken from each of the 30 plots (n = 10), from which the number of individuals of each of the 45 encountered animal species were recorded. The continuous presence of an experimentally fixed kelp thallus significantly reduced the number of individuals on average by 27 %. This disturbance effect was even stronger, on average 49 %, where a kelp thallus was biweekly moved on the sediment. Likewise, taxon richness was lowered by an average of 19 and 36 % where a S. latissima thallus was continuously or sporadically present, respectively. While the composition of taxa was also significantly different among all treatment groups, evenness and biomass were unaffected by kelp treatments. We conclude that the presence and already movements of a single kelp thallus can promote small scale patchiness in near-shore soft-bottom assemblage structure and diversity and exemplify a significant connection between rocky and sedimentary coastal habitats.

Nannofossil datums of ODP Leg 165 holes and nannofossil abundance in ODP Hole 165-998A

A total of 53 calcareous nannofossil datums were detected in Quaternary and Neogene sections recovered during Ocean Drilling Program Leg 165 in the Caribbean Sea. Most of the low-latitude nannofossil zonal markers of Okada and Bukry could be determined at all of the sites. Additionally, size distribution patterns of specimens of Reticulofenestra, a common genus in Neogene and Quaternary sediments, were examined to interpret the biostratigraphic utility of changes in size.

Benthic foraminiferal assemblage counts from the Gulf of California

Extensive CO2 vents have been discovered in the Wagner Basin, northern Gulf of California, where they create large areas with lowered seawater pH. Such areas are suitable for investigations of long-term biological effects of ocean acidification and effects of CO2 leakage from subsea carbon capture storage. Here, we show responses of benthic foraminifera to seawater pH gradients at 74-207 m water depth. Living (rose Bengal stained) benthic foraminifera included Nonionella basispinata, Epistominella bradyana and Bulimina marginata. Studies on foraminifera at CO2 vents in the Mediterranean and off Papua New Guinea have shown dramatic long-term effects of acidified seawater. We found living calcareous benthic foraminifera in low pH conditions in the northern Gulf of California, although there was an impoverished species assemblage and evidence of post-mortem test dissolution.

Biogeochemistry of the Eastern Weddell Gyre

The Southern Ocean (SO) plays a key role in modulating atmospheric CO2 via physical and biological processes. However, over much of the SO, biological activity is iron-limited. New in situ data from the Antarctic zone south of Africa in a region centered at -20°E - 25°E reveal a previously overlooked region of high primary production, comparable in size to the northwest African upwelling region. Here, sea ice together with enclosed icebergs is channeled by prevailing winds to the eastern boundary of the Weddell Gyre, where a sharp transition to warmer waters causes melting. This cumulative melting provides a steady source of iron, fuelling an intense phytoplankton bloom that is not fully captured by monthly satellite production estimates. These findings imply that future changes in sea-ice cover and dynamics could have a significant effect on carbon sequestration in the SO.

A high-resolution sedimentology and age determination of core PS2185 from the central Arctic Ocean

A high-resolution multiparameter stratigraphy allows the identification of late Quaternary glacial and interglacial cycles in a central Arctic Ocean sediment core. Distinct sandy layers in the upper part of the otherwise fine-grained sediment core from the Lomonosov Ridge (lat 87.5°N) correlate to four major glacials since ca. 0.7 Ma. The composition of these ice-rafted terrigenous sediments points to a glaciated northern Siberia as the main source. In contrast, lithic carbonates derived from North America are also present in older sediments and indicate a northern North American glaciation since at least 2.8 Ma. We conclude that large-scale northern Siberian glaciation began much later than other Northern Hemisphere ice sheets.

Estimation of sea surface temperature from sediment core PS1768-8

The quantitative diatom analysis of 218 surface sediment samples recovered in the Atlantic and western Indian sector of the Southern Ocean is used to define a base of reference data for paleotemperature estimations from diatom assemblages using the Imbrie and Kipp transfer function method. The criteria which justify the exclusion of samples and species out of the raw data set in order to define a reference database are outlined and discussed. Sensitivity tests with eight data sets were achieved evaluating the effects of overall dominance of single species, different methods of species abundance ranking, and no-analog conditions (e.g., Eucampia Antarctica) on the estimated paleotemperatures. The defined transfer functions were applied on a sediment core from the northern Antarctic zone. Overall dominance of Fragilariopsis kerguelensis in the diatom assemblages resulted in a close affinity between paleotemperature curve and relative abundance pattern of this species downcore. Logarithmic conversion of counting data applied with other ranking methods in order to compensate the dominance of F. kerguelensis revealed the best statistical results. A reliable diatom transfer function for future paleotemperature estimations is presented.

Investigations of artificial sediments from two deep-sea in situ recolonization experiments deployed for one year at the central HAUSGARTEN station IV during ARK-XIX/3c

Commercial exploitation and abrupt changes of the natural conditions may have severe impacts on the Arctic deep-sea ecosystem. The present recolonisation experiment mimicked a situation after a catastrophic disturbance (e.g. by turbidites caused by destabilized continental slopes after methane hydrate decomposition) and investigated if the recolonisation of a deep-sea habitat by meiobenthic organisms is fostered by variations innutrition and/or sediment structure. Two "Sediment Tray Free Vehicles" were deployed for one year in summer 2003 at 2500 m water depth in the Arctic deep-sea in the eastern Fram Strait. The recolonisation trays were filled with different artificial and natural sediment types (glass beads, sand, sediment mixture, pure deep-sea sediment) and were enriched with various types of food (algae, yeast, fish). After one year, meiobenthos abundances and various sediment related environmental parameters were investigated. Foraminifera were generally the most successful group: they dominated all treatments and accounted for about 87% of the total meiobenthos. Colonizing meiobenthos specimens were generally smaller compared to those in the surrounding deep-sea sediment, suggesting an active recolonisation by juveniles. Although experimental treatments with fine-grained, algae-enriched sediment showed abundances closest to natural conditions, the results suggest that food availability was the main determining factor for a successful recolonisation by meiobenthos and the structure of recolonised sediments was shown to have a subordinate influence.

Antarctic sympagic meiofauna in winter

This study of Antarctic sympagic meiofauna in pack ice during late winter compares communities between the perennially ice-covered western Weddell Sea and the seasonally ice-covered southern Indian Ocean. Sympagic meiofauna (proto- and metazoans > 20 µm) and eggs > 20 µm were studied in terms of diversity, abundance and carbon biomass, and with respect to vertical distribution. Metazoan meiofauna had significantly higher abundance and biomass in the western Weddell Sea (medians: 31.1 * 10**3/m**2 and 6.53 mg/m**2, respectively) than in the southern Indian Ocean (medians: 1.0 * 10**3 /m**2 and 0.06 mg/m**2, respectively). Metazoan diversity was also significantly higher in the western Weddell Sea. Furthermore, the two regions differed significantly in terms of meiofauna community composition, as revealed through multivariate analyses. The overall diversity of sympagic meiofauna was high, and integrated abundance and biomass of total meiofauna were also high in both regions (0.6 - 178.6 * 10**3/m**2 and 0.02 - 89.70 mg/m**2, respectively), mostly exceeding values reported earlier from the western Weddell Sea in winter. We attribute the differences in meiofauna communities between the two regions to the older first-year ice and multi-year ice that is present in the western Weddell Sea, but not in the southern Indian Ocean. Our study indicates the significance of perennially ice-covered regions for the establishment of diverse and abundant meiofauna communities. Furthermore, it highlights the potential importance of sympagic meiofauna for the organic matter pool and trophic interactions in sea ice.

Weighted mean depth of zooplankton measured during various cruises to the Baltic Sea

The Baltic Sea is the largest brackish water area of the world. On the basis of the data from 16 cruises, we show the seasonal and vertical distribution patterns of the appendicularians Fritillaria borealis, Oikopleura dioica and the cyclopoid copepod Oithona similis, in the highly stratified Bornholm Basin. These species live at least temporarily below the permanent halocline and use different life strategies to cope with the brackish environment. The cold-water species F. borealis is abundant in the upper layers of the water column before the thermocline develops. With the formation of the thermocline abundance decreases and the specimens outlast higher temperatures below the halocline. Distribution and strategy suggest that F. borealis might be a glacial relict species in the Baltic Sea. Although Oikopleura dioica is only abundant during summer, O. similis is present all year round. Both species have in common that their vertical distribution is restricted to the waters below the halocline, most likely due to their requirements of higher salinities. We argue that the observed strategies are determined by ecophysiological constraints and life history traits. These species share an omnivorous feeding behaviour and the capability to utilise a spectra of small particles as food. As phytoplankton concentration is negligible below the halocline, we suggest that these species feed on organic material and heterotrophic organisms that accumulate in the density gradient of the halocline. Therefore, the deep haline waters in the Baltic Sea represent a habitat providing shelter from predation and food supply for adapted species that allows them to gather sufficient resources and to maintain populations.

Radiocarbon ages and pollen record of a sediment core from Lake Lyadhej-To

An 1180-cm long core recovered from Lake Lyadhej-To (68°15'N, 65°45'E, 150 m a.s.l.) at the NW rim of the Polar Urals Mountains reflects the Holocene environmental history from ca. 11,000 cal. yr BP. Pollen assemblages from the diamicton (ca. 11,000-10,700 cal. yr BP) are dominated by Pre-Quaternary spores and redeposited Pinaceae pollen, pointing to a high terrestrial input. Turbid and nutrient-poor conditions existed in the lake ca. 10,700-10,550 cal. yr BP. The chironomid-inferred reconstructions suggest that mean July temperature increased rapidly from 10.0 to 11.8 °C during this period. Sparse, treeless vegetation dominated on the disturbed and denuded soils in the catchment area. A distinct dominance of planktonic diatoms ca. 10,500-8800 cal. yr BP points to the lowest lake-ice coverage, the longest growing season and the highest bioproductivity during the lake history. Birch forest with some shrub alder grew around the lake reflecting the warmest climate conditions during the Holocene. Mean July temperature was likely 11-13 °C and annual precipitation-400-500 mm. The period ca. 8800-5500 cal. yr BP is characterized by a gradual deterioration of environmental conditions in the lake and lake catchment. The pollen- and chironomid-inferred temperatures reflect a warm period (ca. 6500-6000 cal. BP) with a mean July temperature at least 1-2 °C higher than today. Birch forests disappeared from the lake vicinity after 6000 cal. yr BP. The vegetation in the Lyadhej-To region became similar to the modern one. Shrub (Betula nana, Salix) and herb tundra have dominated the lake catchment since ca. 5500 cal. yr BP. All proxies suggest rather harsh environmental conditions. Diatom assemblages reflect relatively short growing seasons and a longer persistence of lake-ice ca. 5500-2500 cal. yr BP. Pollen-based climate reconstructions suggest significant cooling between ca. 5500 and 3500 cal. yr BP with a mean July temperature 8-10 °C and annual precipitation-300-400 mm. The bioproductivity in the lake remained low after 2500 cal. yr BP, but biogeochemical proxies reflect a higher terrestrial influx. Changes in the diatom content may indicate warmer water temperatures and a reduced ice cover on the lake. However, chironomid-based reconstructions reflect a period with minimal temperatures during the lake history.

Investigations on sediment coring site PS1823 in the Riiser-Larsen Sea, Southern Ocean

Physical and sedimentological investigations were carried out on a 14 m long gravity core and a 0.5 m long box core from 4440 m water depth off Queen Maud Land, East-Antarctica. Strongly bioturbated hemipelagic muds of predominantly terrigenous origin and a very small biogenic part build up the 'Normal-Facies'. Several sandy to silty layers are inserted in the 'Normal-Facies'. These layers are seperated by lithology, structure and the investigated parameters of this study and are interpreted as turbidites. The source area for the turbidity currents is supposed to be at the uppermost continental margin, close to the shelf break and there is evidenee for this gravity transport within the erosive Ritscher-Canyon, which extends close to the core position. The distribution of biogenic components indicates an age of 1.3 million years or more, with an average sedimentation rate of about 1 cm/1000 years. Early diagenetic proeesses caused water loss by compaction, errosion and dissolution of biogenic components and precipitation and recrystallization of manganese micronodules. Cyclic fluctuations of the sediment-parameters within the 'Normal-Facies' enable the distinction of a 'Glazial'- and an 'Interglazial'-Facies. The 'Glazial'-Facies reflects glacial sedimentary conditions and shows a dark olive gray colour, high susceptibility, low silt/clay-ratios, only a few biogenic components and the regular occurence of interrelated turbidite layers. In contrast, the 'Interglazial'-Facies is dominated by a light olive or olive-brown colour, low susceptibility, high silt/clay-ratios and an increased number of biogenic components. This facies corresponds to interglacial conditions. Three main processes are supposed to have been responsible for the observed facies changes: (1) the bottom water mass circulation, (2) the gravity transport by turbidity currents and (3) the biogenic surface production. These processes are related to the quaternary climatic changes. The extension of the ice shelves directed the gravity transport to the deep sea and the formation of Antarctic Bottom Water, which in turn influenced the silt/clay-ratios in the sediment record. Fluctuations in sea ice coverage controlled the biogenic surface production.

Mineralogy and petrology of Black Sea Basin sediments

The origin and modes of transportation and deposition of inorganic sedimentary material of the Black Sea were studied in approximately 60 piston, gravity, and Kasten cores. The investigation showed that the sediment derived from the north and northwest (especially from the Danube) has a low calcite-dolomite ratio and a high quartz-feldspar ratio. Rock fragments are generally not abundant; garnet is the principal heavy mineral and illite is the predominant clay mineral. This sedimentary material differs markedly from that carried by Anatolian rivers, which is characterized by a high calcite-dolomite ratio and a low quartz-feldspar ratio. Rock fragments are abundant; pyroxene is the principal heavy mineral and montmorillonite is the predominant clay mineral. In generel, the clay fraction is large in all sediments (27.6-86.9 percent), and the lateral distributian indicates an increase in clay consent from the coasts toward two centers in the western and eastern Black Sea basin. Illite is the most common clay mineral in the Black Sea sediments. The lateral changes in composition of the clay mineral can easily be traced to the petrologic character of northern (rich in illite) and southern (rich in montmorillonite) source areas. In almost all cores, a rhythmic change of the montmorillonite-illite ratio with depth was observed. These changes may be related to the changing influence of the two provinces during the Holocene and late Pleistocene. Higher montmorillonite content seems to indicate climctic changes, probably stages of glaciation end permafrost in the northern area, at which time the illite supply was diminished to a large extent. The composition of the sand fraction is relatad to the different petrologic and morphologic characteristics of two major source provimces: (1) a northern province (rich in quartz, feldspars, and garnet) characterized by a low elevation, comprising the Danube basin area and the rivers draining the Russian platform; and (2) a southern province (rich in pyroxene and volcanic and metamorphic rocks) in the mountainous region of Anatolia and the Caucasus, characterized by small but extremely erosive rivers. The textural properties (graded bedding) of the deep-sea send layers clearly suggest deposition from turbidity currents. The carbonate content of the contemporary sediments ranges from 5 to 65 percent. It increases from the coast to a maximum in two centers in the western and eastern basin. This pattern reflects the distribution of the <2-µm fraction. The contemporary mud sedimentation is governed by two important factors: (1) the deposition of terrigenous allochthonous material of low carbonate content originating from the surrounding hinterland (northern and southern source areas), and (2) the autochthonous production of large quantities of biogenic calcite by coccolithophores during the last period of about 3,000-4,000 years.

Sedimentology and faunal compositions of surface sediments from the southern Florida Strait

The water masses in the Florida Straits and Bahamas region are important sources for the Northern Atlantic surface ocean circulation. In this study, we analyse carbonate preservation in surface sediments located above the chemical lysocline in the Florida Straits and Bahamas region and discuss possible reasons for supralysoclinal dissolution. Calcite dissolution proxies such as the variation of the foraminiferal assemblage, Fragmentation Index, Benthic Foraminifera Index, and Resistance Index displayed a good preservation in both areas. The pteropod species Limacina inflata showed very good preservation in sediments of inter-platform channels from the Great Bahama Bank (Providence Channel, Exuma Sound) above the aragonite lysocline. Supralysoclinal aragonite dissolution, however, was observed at two water depth levels (800-1000 m and below 1500 m) in the Florida Straits. Our observations suggest that the supralysoclinal dissolution in the Florida Straits is due to the degradation of organic material. The presence of Antarctic Intermediate Water (AAIW) may be a contributing factor for the significant aragonite dissolution in 800-1000 m. The comparison of modern preservation patterns of the surface sediments with hydrographical measurements shows that the L. inflata Dissolution Index (LDX) might be an adequate proxy to reconstruct paleo-water mass conditions in an area which is highly saturated with respect to calcium carbonate.

X-ray diffraction analysis, binocular component analysis and radiocarbon dating of sediment cores from the NW Iberian shelf system

Based on a well-established stratigraphic framework and 47 AMS-14C dated sediment cores, the distribution of facies types on the NW Iberian margin is analysed in response to the last deglacial sea-level rise, thus providing a case study on the sedimentary evolution of a high-energy, low-accumulation shelf system. Altogether, four main types of sedimentary facies are defined. (1) A gravel-dominated facies occurs mostly as time-transgressive ravinement beds, which initially developed as shoreface and storm deposits in shallow waters on the outer shelf during the last sea-level lowstand; (2) A widespread, time-transgressive mixed siliceous/biogenic-carbonaceous sand facies indicates areas of moderate hydrodynamic regimes, high contribution of reworked shelf material, and fluvial supply to the shelf; (3) A glaucony-containing sand facies in a stationary position on the outer shelf formed mostly during the last-glacial sea-level rise by reworking of older deposits as well as authigenic mineral formation; and (4) A mud facies is mostly restricted to confined Holocene fine-grained depocentres, which are located in mid-shelf position. The observed spatial and temporal distribution of these facies types on the high-energy, low-accumulation NW Iberian shelf was essentially controlled by the local interplay of sediment supply, shelf morphology, and strength of the hydrodynamic system. These patterns are in contrast to high-accumulation systems where extensive sediment supply is the dominant factor on the facies distribution. This study emphasises the importance of large-scale erosion and material recycling on the sedimentary buildup during the deglacial drowning of the shelf. The presence of a homogenous and up to 15-m thick transgressive cover above a lag horizon contradicts the common assumption of sparse and laterally confined sediment accumulation on high-energy shelf systems during deglacial sea-level rise. In contrast to this extensive sand cover, laterally very confined and maximal 4-m thin mud depocentres developed during the Holocene sea-level highstand. This restricted formation of fine-grained depocentres was related to the combination of: (1) frequently occurring high-energy hydrodynamic conditions; (2) low overall terrigenous input by the adjacent rivers; and (3) the large distance of the Galicia Mud Belt to its main sediment supplier.