Species Uvigerina Research Articles

Humid climate phases on the Island of Rhodes (Greece) during the late Pliocene at times of sapropel formation

The Island of Rhodes, located in the Eastern Mediterranean Sea, is affected by an active convergent plate boundary. In this context, marine sediments of Plio-Pleistocene age have been uplifted and are outcropping along the eastern coast of Rhodes. These archives provide an excellent opportunity to unravel the hydrological and climatic changes of the region during the late Pliocene. Our results provide new evidence for a more humid climate and an increased precipitation on the island during times of Northern Hemisphere summer insolation maxima and related sapropel formation in the Mediterranean deep sea. The periodic occurrence of eutrophic conditions at the shelf and upper slope off Rhodes is indicated by the recurrent dominance of eutrophic indicator species (of the genera Bolivina, Eubuliminella and Rectuvigerina), simultaneously with a decline in diversity and oligotrophic indicator species. These conditions resulted from higher primary productivity, triggered by local effects, such as enhanced precipitation and river run-off, which consequently favors the appearance of eutrophic taxa. The ∆δ13C records of the epibenthic foraminifera Cibicidoides pseudoungerianus and the shallow infaunal species Uvigerina peregrina indicate a slight productivity decrease towards younger times.

Uvigerina agglutinata n.sp. a new Holocene benthic foraminifer with an outer agglutinated layer from the central Red Sea

This paper describes a new deep-sea foraminifer which has possibly evolved a way to use sediment particles from its surroundings to increase its density. The benthic foraminifer recovered from Red Sea planktonic ooze shares some similarities with two well-established Uvigerina species Uvigerina auberiana d'Orbigny, 1826 and the extinct Uvigerina auberiana var. attenuata Cushman & Renz, 1941. However, it differs from the two species mainly by the incorporation of sediment grains into its external wall. Uvigerina agglutinata n.sp. is characterized by its initially triserial coiling, which changes to biserial in the middle part and eventually becomes uniserial in final whorl. The most diagnostic feature of this species is the incorporation of different shapes and sizes of detrital calcium carbonate grains into its outer wall.

Oxygen Isotope Offsets in Deep-Water Benthic Foraminifera

ABSTRACT Despite the extensive use of the benthic foraminiferal oxygen isotope composition (δ18O) as a proxy for paleoclimatic reconstructions, uncertainties remain regarding the consistency of interspecies offsets and the environmental factors controlling 18O fractionation. We investigated δ18O offsets of some frequently used Uvigerina, Bulimina, and Cibicidoides species in core top samples from different hydrographic and sedimentary regimes in the South China Sea, Makassar Strait, and Timor Strait/Eastern Indian Ocean. The δ18O values of the epifaunal taxa Cibicidoides mundulus and Cibicidoides wuellerstorfi showed no significant offset in all investigated regions, whereas shallow infaunal Cibicidoides species exhibited higher variability and were less reliable. We found no offsets between species of Uvigerina and Bulimina and assume that these genera can be measured together and/or substituted. Our results show that epifaunal taxa are close to equilibrium with ambient seawater and thus provide more reliable records of past ice volume and/or bottom water temperature variations than infaunal taxa. Offsets among equilibrium calcite, epifaunal taxa, and infaunal taxa are not constant “vital effects” but are influenced by changing gradients in bottom to pore water pH and carbonate ion concentrations that depend on deep-water ventilation and export flux of particulate carbonate and organic carbon. Offsets between epifaunal and infaunal taxa varied between 0.58 and 0.73‰, depending on regional bottom and pore water conditions. Our findings highlight the importance of regional and temporal variations in organic carbon flux/degradation and dissolution of calcite that may lead to slight under- or overestimates of the amplitude of δ18O fluctuations, especially during times of rapidly changing calcite-saturation of bottom and pore water.

Faunistické společenstvo kroměřížského souvrství na lokalitě Litenčice (karpatská předhlubeň, střední Morava)

The fossil assemblages of the foraminifers, bryozoans, molluscs, corals, decapods, sharks and teleosteans were analysed from the Litenčice sand pit in the middle part of the Carpathian Foredeep. The section can be assigned to the Karpatian Stage of the Central Paratethys regional stratigraphy (uppermost Lower Miocene) on the basis of species Uvigerina graciliformis Papp et Turn., Lampanyctus carpaticus (Brz.) and Agapilia pachii (Hoern.). Rich and diversified assemblages indicate mainly shallow water marine environment. Foraminifers and molluscs indicate salinity perturbations. Bryozoans and also molluscs document environment with relatively high dynamics and depth of water about 100 m. Foraminifers, fishes and sharks represent deeper water taxa and indicate a possible reworking of shallow-water elements. The studied sands and gravels of the Holešov Member of the Kroměříž Formation are interpreted as sediments of gravitational currents, more precisely dense turbidity currents (high-density turbidity currents) in the sense of Lowe (1982). The deposition environment can probably be placed on the submarine slope of the coarse-grained delta of the Gilbert type (so-called foresets). This study provided evidence of a number of fossil groups that occur at the site.

Faunal and stable isotopic analyses of benthic foraminifera from the Southeast Seep on Kimki Ridge offshore southern California, USA

We investigated the benthic foraminiferal faunal and stable carbon and oxygen isotopic composition of a 15-cm push core (NA075-092b) obtained on a Telepresence-Enabled cruise to the Southeast Seep on Kimki Ridge offshore southern California. The seep core was taken at a depth of 973 m in the vicinity of a Beggiatoa bacterial mat and vesicomyid clams (Calyptogena) and compared to previously published data of living assemblages from ~ 714 m, four reference cores obtained at ~ 1030 m, and another one at 739 m. All of the reference sites are also from the Inner Continental Borderland but with no evidence of methane seepage.No endemic species were found at the seep site and most of the taxa recovered there have been reported previously from other seep or low oxygen environments. Q- and R-mode cluster analyses clearly illustrated differences in the faunal assemblages of the seep and non-seep sites. The living assemblage at Southeast Seep was characterized by abundant Takayanagia delicata, Cassidulina translucens, and Spiroplectammina biformis, whereas the non-seep San Pedro Basin reference assemblage was comprised primarily of Chilostomella oolina and Globobulimina pacifica. Density and species richness were lower at the seep site compared to the non-seep site, reflecting the harsher living conditions there. The dead assemblage at the seep site was dominated by Gyroidina turgida compared to Cassidulina translucens at the ~ 1030 m non-seep site and Cassidulina translucens, Pseudoparrella pacifica, and Takayanagia delicata at the 739 m non-seep site. Density was three times lower at Southeast Seep than at the non-seep sites of comparable water depth but species richness was ~ 30% higher. Stable carbon isotopic values were considerably depleted in the seep samples compared to the non-seep samples, with a progression from lightest to heaviest average δ13C values evident at the seep site reflecting microhabitat preference and vital effect: the deep infaunal species of Globobulimina, the shallow infaunal species Uvigerina peregrina, the epifaunal species Cibicidoides wuellerstorfi, and the shallow infaunal but aragonite-shelled species Hoeglundina elegans. The δ13C values downcore among each benthic species indicates ongoing fluid seepage through at least the last 3800 cal yr B.P. at Southeast Seep. Besides the continual local seepage, evidence from δ13C values of planktic foraminifera in the seep core suggest two pulses of methane (at 3000 and 3700 cal yr B.P.) were released that were large enough to influence much of the water column. Paired benthic and planktic foraminiferal stable oxygen isotope records provide evidence that there were no paleoenvironmental changes such as increased bottom-water temperature or changes in oxygen isotopic composition of bottom and pore waters during this 3800-year record to induce the methane releases. Instead, Southeast Seep appears to be the result of local faulting providing pathways for fluid to flow to the seafloor at a fault stepover or transpressional bend in the regional strike-slip system.

Early Eocene planktonic and benthic foraminifera from the Khangiran formation (northeast of Iran)

The Kopet-Dagh sedimentary basin is located in northeast of Iran and southeast of Turkmenistan in the Middle East. The Khangiran formation represents the last marine deposition in the Kopet-Dagh sedimentary basin. The early Eocene planktonic and benthic foraminifera from the Khangiran formation which belongs to the lower 376 m thickness of this formation are identified and biostratigraphically evaluated. Due to rarity of Morozovella species, planktonic foraminiferal zonation was difficult to determine in this formation. The determination of upper part of the late Paleocene for the lower 124 m of this formation is according to the lowest occurrence of Acarinina sibaiyaensis species. From E5 to near middle of E7 biozone, increasing trend of Acarinina frequency and a peak in Morozovella species and decreasing trend of frequency of Subbotina and Pseudohastigerina species indicate the warm and oligotrophic condition of the seawater during sedimentation of the studied interval. Toward the Ypresian-Lutetian boundary, the increasing trend of Pseudohastigerina and Subbotina species and decreasing in frequency of Acarinina species suggest the low-oxygen level, eutrophic and intermediate condition of the seawater. In this formation, the high abundance of the epifaunal taxa such as Anomalinoides spp., Cibicidoides spp., Gyroidinoides spp., and Lenticulina spp. from the base (late Paleocene sediments) up to E6 biozone reflects oligotrophic and oxic shallow water conditions. The occurrence of several peaks in abundance of Bulimina and Uvigerina species at the Ypresian/Lutetian boundary suggests eutrophic condition. These paleoecological conditions could be correlated with fluctuations in the numbers of the planktonic foraminifera.

Uptake of algal carbon and the likely synthesis of an "essential" fatty acid by <i>Uvigerina</i> ex. gr. <i>semiornata</i> (Foraminifera) within the Pakistan margin oxygen minimum zone: evidence from fatty acid biomarker and <sup>13</sup>C tracer experiments

Abstract. Foraminifera are an important component of benthic communities in oxygen-depleted settings, where they potentially play a significant role in the processing of organic matter. We tracked the uptake of a 13C-labelled algal food source into individual fatty acids in the benthic foraminiferal species Uvigerina ex. gr. semiornata from the Arabian Sea oxygen minimum zone (OMZ). The tracer experiments were conducted on the Pakistan margin during the late/post monsoon period (August–October 2003). A monoculture of the diatom Thalassiosira weisflogii was 13C-labelled and used to simulate a pulse of phytoplankton in two complementary experiments. A lander system was used for in situ incubations at 140 m water depth and for 2.5 days in duration. Shipboard laboratory incubations of cores collected at 140 m incorporated an oxystat system to maintain ambient dissolved oxygen concentrations and were terminated after 5 days. Uptake of diatoms was rapid, with a high incorporation of diatom fatty acids into foraminifera after ~ 2 days in both experiments. Ingestion of the diatom food source was indicated by the increase over time in the quantity of diatom biomarker fatty acids in the foraminifera and by the high percentage of 13C in many of the fatty acids present at the endpoint of both in situ and laboratory-based experiments. These results indicate that

Deep sea benthic foraminifera as proxies for palaeoclimatic fluctuations in the New Caledonia Basin, over the last 140,000years

abstract Article history:Received 17 September 2012Received in revised form 19 June 2013Accepted 28 August 2013Available online 4 September 2013Keywords:New Caledonia BasinTasman SeaQuaternarySouthwest PacificOceanforaminiferapalaeoenvironment The New Caledonia Basin (NCB), SW Pacific, a deep bathyal to abyssal basin bordered by the Lord Howe Rise tothe west and the Norfolk Ridge to the east, has received little scrutiny with regard to the taxonomic diversityofbenthicorganismsinitsQuaternarytoRecentdeepseasediments.In2001,GravityCore4(GC4)wasextractedfrom the NCB and the uppermost 141 cm, representing approximately the last 140,000 years, was investigatedfor chemical isotopic, carbonate, non-carbonate and trace element signatures. In this study, subsamples of thesame uppermost 141 cm of GC4 were picked and sorted for all foraminiferal taxa. At selected intervals in GC4,allbenthicspecieswereidentifiedandcountedformeasuresofrelativeabundance.Atotalof161speciesofben-thic foraminifera were obtained from the core and 46 species occurred in sufficient numbers to investigatechangingpatternsandtrendsinbiodiversityandrelativeabundance.Changesfoundwithintheforaminiferaldis-tribution down the core can be related to some oceanic and palaeoclimatic fluctuations during the last~140,000 years. Within GC4, two distinct foraminiferal assemblages were detected using Bray–Curtis clusteranalysis and Multidimensional Scaling (MDS) analysis. Foraminiferal Assemblage 1 occurs in lower bathyal toabyssal depths and was largely influenced by high oxygen levels at the sediment–water interface throughoutMarine Isotopic Stage (MIS) 6–3 (approximately 128 –25 ka). Foraminiferal Assemblage 2 dominated theupper bathyal shelf during MIS 2 (approximately 25–10 ka), with surface waters characterised by high sea sur-faceproductivity(SSP)andeutrophicconditions.DuringthetimecoveredbyGC4,thereareinstanceswheretherelative abundanceofthe dominanttaxonEpistominella exigua(Brady)and other key taxadecreasesand oppor-tunistic species of Uvigerina, adapted to lower oxygen levels, increase in relative abundance, indicating a shift ofconditions at the sediment–water interface. Factors that influence the foraminiferal assemblages include envi-ronmentalsetting,SSP,oxygenlevelsatthesediment–waterinterfaceandtransportationbyoceaniccurrentsys-tems operating within the region.© 2013 Elsevier B.V. All rights reserved.

EMP and SIMS studies on Mn/Ca and Fe/Ca systematics in benthic foraminifera from the Peruvian OMZ: a contribution to the identification of potential redox proxies and the impact of cleaning protocols

Abstract. In this study we present an initial dataset of Mn/Ca and Fe/Ca ratios in tests of benthic foraminifera from the Peruvian oxygen minimum zone (OMZ) determined with SIMS. These results are a contribution to a better understanding of the proxy potential of these elemental ratios for ambient redox conditions. Foraminiferal tests are often contaminated by diagenetic coatings, like Mn rich carbonate- or Fe and Mn rich (oxyhydr)oxide coatings. Thus, it is substantial to assure that the cleaning protocols are efficient or that spots chosen for microanalyses are free of contaminants. Prior to the determination of the element/Ca ratios, the distributions of several elements (Ca, Mn, Fe, Mg, Ba, Al, Si, P and S) in tests of the shallow infaunal species Uvigerina peregrina and Bolivina spissa were mapped with an electron microprobe (EMP). To visualize the effects of cleaning protocols uncleaned and cleaned specimens were compared. The cleaning protocol included an oxidative cleaning step. An Fe rich phase was found on the inner test surface of uncleaned U. peregrina specimens. This phase was also enriched in Al, Si, P and S. A similar Fe rich phase was found at the inner test surface of B. spissa. Specimens of both species treated with oxidative cleaning show the absence of this phase. Neither in B. spissa nor in U. peregrina were any hints found for diagenetic (oxyhydr)oxide or carbonate coatings. Mn/Ca and Fe/Ca ratios of single specimens of B. spissa from different locations have been determined by secondary ion mass spectrometry (SIMS). Bulk analyses using solution ICP-MS of several samples were compared to the SIMS data. The difference between SIMS analyses and ICP-MS bulk analyses from the same sampling sites was 14.0–134.8 μmol mol−1 for the Fe/Ca and 1.68(±0.41) μmol mol−1 for the Mn/Ca ratios. This is in the same order of magnitude as the variability inside single specimens determined with SIMS at these sampling sites (1σ[Mn/Ca] = 0.35–2.07 μmol mol−1; 1σ[Fe/Ca] = 93.9–188.4 μmol mol−1). The Mn/Ca ratios in the calcite were generally relatively low (2.21–9.93 μmol mol−1) but in the same magnitude and proportional to the surrounding pore waters (1.37–6.67 μmol mol−1). However, the Fe/Ca ratios in B. spissa show a negative correlation to the concentrations in the surrounding pore waters. Lowest foraminiferal Fe/Ca ratios (87.0–101.0 μmol mol−1) were found at 465 m water depth, a location with a strong sharp Fe peak in the pore water next to the sediment surface and respectively, high Fe concentrations in the surrounding pore waters. Previous studies found no living specimens of B. spissa at this location. All these facts hint that the analysed specimens already were dead before the Fe flux started and the sampling site just recently turned anoxic due to fluctuations of the lower boundary of the OMZ near the sampling site (465 m water depth). Summarized Mn/Ca and Fe/Ca ratios are potential proxies for redox conditions, if cleaning protocols are carefully applied. The data presented here may be rated as base for the still pending detailed calibration.

BENTHONIC FORAMINIFERAL PALEOECOLOGY OF THE PLEISTOCENE IN DSDP HOLE 148, AVES RIDGE, EASTERN CARIBBEAN SEA

Deep Sea Drilling Project Hole 148 was drilled on the Aves Ridge, eastern Caribbean Sea at a lower-bathyal depth (1232 m) beneath the eastern edge of the Orinoco plume. The drillhole penetrated ~124 m of Pleistocene sediment, but core recovery was poor (66%). From 62 samples taken at ~2-m intervals, 17,259 >105-μm benthonic foraminifera were picked and 212 species were identified. Only four species accounted for >5% of the total recovery: Sigmoilopsis schlumbergeri , Uvigerina peregrina , U. auberiana , and Bulimina aculeata . Species of Uvigerina and Bulimina , indicative of organic loading and low dissolved-oxygen content, respectively formed 22.6% and 14.3% of total recovery. Cibicidoides bradyi formed 4.4% of total recovery and Globocassidulina subglobosa 3.3%. This indicates that, although the Caribbean Sea is bordered to the north, east, and west by oligotrophic waters, the Pleistocene in DSDP Hole 148 was deposited under organic-rich, low-oxygen conditions. The organic material was derived from high surface productivity within the nutrient-rich Orinoco plume. Uvigerina and Bulimina show a long-term ecostratigraphic signal, beginning with U. hispida and B. alazanensis being common in the lower part of the section, then U. peregrina and B. aculeata in the middle and U. peregrina and U. dirupta in the upper part. This succession may reflect temporal changes in surface productivity, possibly resulting from plate tectonic movement of DSDP Hole 148 relative to the Orinoco plume, as surface productivity generally decreases from the center to the margins of the plume. The Stilostomella Extinction , in which uniserial foraminifera decreased through the section, occurred through a gradual loss of specimens.

Badenian Pappinidae and Uvigerinidae from the South-western Badenian Pappinidae and Uvigerinidae from the South-western Badenian Pappinidae and Uvigerinidae from the South-western margin of the Pannonian Basin (Eastern Slovenia)

This study identifies fourteen foraminiferal species of families Pappinidae and Uvigerinidae, found in Badenian sediments of Eastern Slovenia (six sections in the Planina syncline). Two of the species, Uvigerina bellicostata and Angulogerina esuriensis are identified in Slovenia for the first time. Determined species show characteristic Central Paratethyan biostratigraphic distribution throughout the studied sections, allowing the positioning of a Late Middle Badenian foraminiferal Zone named after the species Uvigerina cf. pygmea.

STABLE CARBON ISOTOPES OF BENTHIC FORAMINIFERS FROM IODP EXPEDITION 311 AS POSSIBLE INDICATORS OF EPISODIC METHANE SEEP EVENTS IN A GAS HYDRATE GEOSYSTEM

Abstract Integrated Ocean Drilling Program (IODP) Expedition 311 at the Cascadia Margin, northeastern Pacific, provides an excellent opportunity to study the response of carbon isotopic compositions of benthic foraminifers to episodic methane seep events in a gas hydrate geosystem. The shallow infauna benthic foraminifer species Uvigerina peregrina and Bulimina mexicana collected from five sites (U1325, U1326, U1327, U1328, and U1329) exhibit dramatic negative carbon isotopic excursions (−0.75‰ to −2.74‰, −1.11‰ to −2.62‰, −0.51‰ to −2.75‰, −0.58‰ to −2.71‰, and −0.22‰ to −3.32‰ respectively) and positive oxygen isotopic anomalies (3.27‰ to 4.91‰, 3.16‰ to 4.78‰, 3.37‰ to 4.88‰, 3.45‰ to 4.88‰, and 3.4‰ to 4.88‰ respectively). Results indicate that gas hydrate dissociation influenced the dissolved inorganic carbon of the pore water via anaerobic oxidation of methane. SEM analysis of foraminifer tests and the comparative carbon isotopic analysis of previous works on this subject indicate minimal alteration...

A comparison of spatial and temporal variability of living benthic foraminiferal faunas at 550m depth in the Bay of Biscay

We studied living (Rose Bengal stained) benthic foraminiferal faunas of four replicate cores sampled at a 550m deep station in the Bay ofBiscay in May 2004. After combining our new datawith those collected by Fontanier et al. (2003) at the same station between October 1997 and April 2000, we performed statistical analyses (Detrended Correspondence Analysis) to assess the extent of spatial variability in comparison to temporal variability in our dataset. Replicate cores taken from a single multi-corer deployment and from two deployments were compared so that we could gain insight into spatial variability both at a micro- (less than 1m apart) and meso-scale (around 100m apart). The statistical analyses suggest that the scale of spatial variability is similar to that of temporal variability. Only the most prominent features of temporal variability (i.e. responses to major bloom events) can be recognised. Especially the species Uvigerina peregrina, and to a smaller extent Cibicidoides pachydermus and Siphogenerina columellaris, appear to respond to bulk phytodetritus deposits following surface water primary production maxima. Uvigerina peregrina showed only elevated densities in autumn 1997 and spring 2004, but not in the samples from spring 1999 and 2000. We suggest that these differences could be explained by a difference in the composition of the phytoplankton exported to the seafloor.

Benthic foraminiferal assemblages as indicators of the paleoceanographic conditions in the eastern Equatorial Pacific

Five assemblages of benthic foraminifers reflecting the changes in the properties of the intermediate water masses and the biological productivity during different periods of the last glacial-interglacial cycle are defined based on the abundances and relative contents of indicative species in the upper 9 m of giant Core MD02-2529 from the Cocos Ridge. High bioproductivity and low oxygen content in the bottom water layer and sediments are established for the interstadial period based on the high abundance of the species Uvigerina peregrina, U. hispida, and C. pachyderma (Assemblage I) and especially for the Last Glacial Maximum (Assemblage II) with the dominant role of the same species and E. smithi. The transition from the glaciation to the current interglacial (Termination I, Assemblage III) is characterized by a high share of the epifaunal species C. wuellerstorfi and H. subhaidingeri, which indicates enhanced hydrodynamic activity and ventilation of the intermediate water washing the bottom. The end of Termination I was marked by strengthened selective dissolution of carbonate microfossils due to the increased influx of fresh organic matter to the bottom and/or advection of more aggressive intermediate waters. The diverse Early Holocene assemblage (Assemblage IV) points to variable ecological niches, while the abundance of the infaunal U. hispida in Assemblage V indicates low productivity of the surface waters and a low oxygen concentration in the bottom sediments of the Late Holocene.

Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean

Historically, the Holocene has been considered an interval of relatively stable climate. However, recent studies from the northern Arabian Sea (Netherlands Indian Ocean Program 905) suggested high‐amplitude climate shifts in the early and middle Holocene based on faunal and benthic isotopic proxy records. We examined benthic foraminiferal faunal and stable isotopic data from Ocean Drilling Program (ODP) Site 723 and total organic carbon data from ODP Site 724, Oman Margin (808 and 593 m water depths, respectively). At Site 723 the mid‐Holocene shift in δ18O values of infaunal benthic species Uvigerina peregrina (1.4‰) is 3 times larger than that of epifaunal benthic species Cibicides kullenbergi recorded at Site NIOP 905 off Somalia. However, none of the five other benthic species we measured at Hole 723A exhibits such a shift in δ18O. We speculate that the late Holocene δ18O decrease in U. peregrina represents species‐specific changes in ecological habitat or food preference in response to changes in surface and deep ocean circulation. While the stable isotopic data do not appear to indicate a middle Holocene climatic shift, our total organic carbon and benthic faunal assemblage data do indicate that the early Holocene deep Arabian Sea was influenced by increased ventilation perhaps by North Atlantic Deep Water and/or Circumpolar Deep Water incursions into the Indian Ocean, leading to remineralization of organic matter and a relatively weak early Holocene oxygen minimum zone in the northwest Arabian Sea in spite of strong summer monsoon circulation.

Middle–late Miocene benthic foraminifera in a western equatorial Indian Ocean depth transect: Paleoceanographic implications

Middle through upper Miocene (17–5 Ma) benthic foraminiferal faunas (> 63 μm) from a depth transect in the western equatorial Indian Ocean (DSDP Site 237, ODP Sites 707, 709 and 710; water depth 1500–3800 m) underwent significant faunal changes at ∼ 14–13 Ma and 11–8 Ma. These faunal changes are not easily interpreted, because of the complex factors controlling benthic foraminiferal distribution and abundance. At ∼ 14–13 Ma, the relative abundance of ‘high-productivity’ taxa ( Bolivina, Bulimina, Melonis and Uvigerina species), although highly variable, generally increased at the two shallower sites (237 and 707), as did the percentage of Epistominella exigua (indicative of seasonal productivity) and Nuttallides umbonifera (indicative of corrosive bottom waters) at the two deeper sites (709 and 710); the latter species had a peak in abundance at the deepest site (710) between 11 and 9 Ma. Benthic foraminiferal accumulation rates (BFARs) increased strongly at the shallower sites starting at 11 Ma, peaking between 9 and 8 Ma, and increased weakly at the deeper two sites starting at 11 Ma. Elongate, cylindrical taxa decreased in abundance between 12 and 11 Ma at all sites. The abundance of planktic foraminiferal fragments was, as expected, overall higher at the deeper sites, with some high values after 12–13 Ma at the shallower sites. The faunal changes suggest that overall the food supply to the sea floor increased, but also became more pulsed or seasonal, peaking at 9–8 Ma, while deep and intermediate waters may have become more ventilated. The first phase of faunal change (14–13 Ma) was coeval with the global increase in benthic foraminiferal oxygen isotope values, worldwide turnover in benthic foraminiferal faunas, and possibly increased production of Antarctic Bottom Water (AABW) and Northern Component Water (NCW). The overall faunal turnover may reflect the composite faunal response to increased food input resulting from heightened productivity and increased bottom water ventilation associated with a combination of monsoonal intensification, global cooling and changes in ocean circulation, but there is no unequivocal evidence for the presence of Tethyan Outflow Water (TOW) over the studied time and depth range, in contrast to earlier publications.

Molecular phylogeny of the foraminiferal genus Uvigerina based on ribosomal DNA sequences

Uvigerina is a common genus of benthic foraminifera, often used as a proxy for paleoclimate and paleoenvironment reconstructions. Better understanding of the phylogeny of Uvigerina would improve its proxy value and would allow us to check whether its different morphospecies are real species or ecophenotypes only. Here, we used partial small-subunit ribosomal DNA (SSU rDNA) sequences to examine the phylogenetic relationships within Uvigerina and between this genus and other rotaliids. Our analyses show that the family Uvigerinidae forms a well supported clade branching as a sister group to Bolivinidae and Cassidulinidae. Studied individuals of Uvigerinidae include three species described as Uvigerina – U. mediterranea, U. elongatastriata and U. peregrina – as well as Rectuvigerina phlegeri and Trifarina earlandi. As U. peregrina is more closely related to R. phlegeri and T. earlandi than to the other two Uvigerina, the taxonomic status of these species needs to be revised. At the intraspecific level, we studied a morphologically highly variable population of U. peregrina from the Oslo Fjord. For the sequences obtained from this population of U. peregrina, we found almost no divergence inside the internal transcribed spacer (ITS), which is the most variable part of ribosomal DNA. This indicates a high morphological plasticity of Uvigerina species, which should be taken into consideration when using this genus as a proxy in paleoecological reconstructions.

Late Glacial to Recent distribution pattern of deep-water Uvigerina species in the north-eastern Atlantic

Phases with massive abundances of Uvigerina species recorded in North Atlantic deep-sea cores were previously attributed to water mass properties or to extended high productivity during the last Glacial. We investigated the Uvigerina distribution in 53 sediment cores and 555 surface samples from the north-eastern Atlantic ranging from 30° to 70°N and 1 to 4410 m water depth. Our results showed that Uvigerina pigmea dominated in late Pleistocene assemblages whereas Uvigerina peregrina and Uvigerina peregrina parva were common during the Holocene. Uvigerina pigmea lives today in the Gulf of Guinea and South Atlantic only (9°N to 17°S), but was present up to 54°N during the Last Glacial Maximum. The species retreated north- and southwards during Termination I and disappeared in the north-eastern Atlantic off northern Portugal 6100 years ago. Uvigerina peregrina and U. peregrina parva spread out from isolated occurrences along the continental slope off western Iberia at the onset of Termination I. Uvigerina peregrina exhibited Recent abundance maxima at Goban Spur, Plateau des Landes, and the Iberian Margin. These areas are subjected to strong lateral advection by downslope transport and sediment focusing. The actual flux rate of particulate organic matter is locally raised by a factor of 4 to 5. Comparable flux rates were otherwise recorded at U. peregrina maxima under the NW-African coastal upwelling regime. The Recent distribution of U. pigmea and evidence from sediment cores show an organic carbon flux of 3.5 g C m − 2 yr − 1 as minimum for a sustainable population of this species. Alkenone, pigment and planktonic foraminiferal records from cores MD952039 and MD952040 revealed that a spring bloom dominated productivity dynamics and a balanced food particle composition of haptophyteae algae and diatoms were limiting environmental factors for U. pigmea during the Pleistocene. A widespread change from glacial to modern productivity characteristics during the last Deglaciation may have triggered the early Holocene disappearance of U. pigmea from the north-eastern Atlantic.

Late-Holocene changes in ocean circulation and climate: foraminiferal and isotopic evidence from Sulafjord, western Norway

A 278 cm long sediment core spanning the last 5500 years was collected from 440 m water depth in Sulafjorden, western Norway. Detailed analyses of benthonic foraminfera, stable isotopes and lithology have been performed on the core, and a chronology based on five AMS dates on benthonic foraminifera has been established. The foraminiferal assemblages consist of species that are common in the North Sea region today. The benthonic fauna seems to respond to changes in oxygenation of the bottom water in the fjord indicating relatively low dissolved oxygen contents prior to c. 2000 cal. bc followed by a gradual increase until c. 700 cal. bc. The oxygen levels in the water masses are assumed to reflect the ingress of oceanic water from the shelf. Downcore variations in the oxygen isotope ratios in the benthonic species Uvigerina mediterranea in Sulafjorden are interpreted to reflect temperature variations with a minimum amplitude of 2°C. The isotopic data indicate five cold periods at c. 2150–1800 cal. bc, c. 850–600 cal. bc, 150 cal. bc to cal. ad 150, c. cal. ad 500–650, and one in the top of the core corresponding to the ‘Little Ice Age’ ( c. cal. ad 1625). These periods are characterized by 1.5–2°C reduction in the bottom-water temperatures in Sulafjorden. Some of the cold periods in the fjord record are contemporaneous with the Holocene ice-rafting events in the North Atlantic and glacier fluctuations in western Norway and Northern Scandinavia. This implies that late-Holocene climate fluctuations in Scandinavia are caused by circulation changes in the North Atlantic region.

Characteristics ofUvigerina in the Northwestern Indian Ocean: Paleo-environmental implications

Coretop sediment samples covering water depth from 247 to 1474 m in the Northwestern Indian Ocean were analyzed. 6 species ofUvigerina among 77 species and 11 species-complexes were found in all 26 samples. They areUvigerina auberiana d’Orbigny,Uvigerina hispida Schwager,Uvigerina peregrina Cushman,Uvigerina proboscidea Schwager,Uvigerina spinicostata Cushman and Jarvis, andUvigerina sp. Characteristics ofUvigerina are (1) high abundance due to rich food supply and less competitors; (2) low diversity because only those eurytopic / opportunistic forms can survive environment of low dissolved oxygen value; (3) various test shapes and ornamentations which are controlled by respiration or gas exchange of the cell; and (4) abundance ofUvigerina is well related with environmental factors such as water depth, oxygen content and productivity or food supply. TheseUvigerina species can be used as paleo-environmental proxy of low oxygen and rich organic matter supply related to high-surface productivity upwelling caused by Indian monsoons. Analysis ofUvigerina in Hole 723B of ODP Leg 117 showed that upwelling was intensified 9, 18, 50, 100, 200, 240, 340, 440, 480, 600 and 700 ka ago, which implies the increasing in global changes effect from the uplift of the Tibetan Plateau.