Foraminiferal Flux Research Articles

Western to Central Equatorial Pacific Planktic Foraminiferal Fluxes: Implication for the Relationship Between Their Assemblage and Warm Pool Migration from 1999 to 2002

ABSTRACT Time-series sediment trap experiments were carried out in the western to central equatorial Pacific (Sites MT3, MT4, MT5, and MT7) from 1999 to 2002, over the transitional time period from La Niña to El Niño conditions, in order to evaluate temporal variability in planktic foraminiferal fluxes and their assemblages. The foraminiferal test flux follows a trophic gradient from higher fluxes in the Equatorial Upwelling Region (EUR) and lower fluxes in the Western Pacific Warm Pool (WPWP) region. Globigerinoides ruber commonly dominates in all sites through the experimental period. Trilobatus sacculifer, Globigerinita glutinata, and Neogloboquadrina dutertrei occurred especially in the WPWP. In contrast, Globigerina bulloides and Pulleniatina obliquiloculata characterized the fauna in the EUR. A change in hydrologic conditions from La Niña to El Niño was documented along the sites during the sampled time interval. Simultaneous with an eastward advancement of the WPWP, the EUR retreated to the east. Rapid decreases in the fluxes of G. ruber, G. bulloides, and P. obliquiloculata were recognized immediately after the more oligotrophic WPWP conditions prevailed at Sites MT4, MT5, and MT7. Fluxes of the total planktic foraminifer assemblage increased both in the EUR and in the western side of the WPWP under full El Niño conditions during the second half of 2002. Such increases in test fluxes in the western side of the WPWP were mainly attributed to G. ruber and N. dutertrei, suggesting inputs of eutrophic waters from the northern coastal area of Papua New Guinea. Test fluxes under El Niño conditions in the WPWP were at the same level as those in the EUR, giving rise to strongly increased carbonate fluxes in the western equatorial Pacific.

Seasonal variation of fluxes of planktic foraminiferal tests collected by a time-series sediment trap in the central Bay of Bengal during three different years

Sediment trap samples from the southwestern Bay of Bengal were obtained at a water depth of about 900 m at sampling intervals of 17–27 days during three time periods (November 1988 to October 1989, December 1990 to October 1991, and January 1993 to October 1993). The planktic foraminifer abundances and assemblages of the samples were analyzed, and the factors governing the assemblages and their potential as indicators of climate and ocean processes in the sedimentary record were examined. We identified 28 species of planktic foraminifers in the samples, of which seven species accounted for more than 80% of each assemblage. The highest fluxes of planktic foraminifer tests were generally observed during the summer and winter monsoon seasons, and the lowest fluxes were observed during the intermonsoon seasons, especially from March to May. Periods of enhanced primary production during monsoons were accompanied by a sharp increase in the flux of Globigerina bulloides, whereas nutrient depletion in the surface ocean in spring led to subsurface small size plankton production and low planktic foraminifer test fluxes. The seasonality of foraminiferal assemblages and fluxes was controlled mainly by seasonal surface and subsurface primary production. The transition of abundant species from subsurface dwellers to surface ones throughout the monsoon season can be attributed to initial subsurface primary and secondary production being succeeded by enhanced surface production. The foraminiferal flux pattern differed among the three observation periods, especially in summer, because of interannual variation in the regional physical forces that induce nutrient replenishment at the surface. However, the consistent features of the flux pattern, with peaks during the monsoon seasons and minimal values in spring, suggest that our results reveal the essential, long-term flux pattern of planktic foraminifers in the southwestern Bay of Bengal.

Environmental variability off NE Greenland (western Fram Strait) during the past 10,600 years

To reconstruct the climatic and paleoceanographic variability offshore Northeast Greenland during the last ~10 ka with multidecadal resolution, sediment core PS93/025 from the outermost North-East Greenland continental shelf (80.5°N) was studied by a variety of micropaleontological, sedimentological and isotopic methods. High foraminiferal fluxes, together with high proportions of ice-rafted debris and high Ca/Fe ratios, indicate a maximum in bioproductivity until ~8 ka related to a low sea-ice coverage. Sortable silt values, planktic foraminifer associations, and stable isotope data of planktic and benthic foraminifers suggest a strong westward advection of relatively warm Atlantic Water by the Return Atlantic Current during this time, with a noticeable bottom current activity. This advection may have been facilitated by a greater water depth at our site, resulting from postglacial isostatic depression. For the following mid-Holocene interval (ca. 8–5 ka), isotope data, lower foraminiferal fluxes and a shift in grain size maxima point to a lasting but successively decreasing Atlantic Water inflow, a weakening productivity, and a growing sea-ice coverage which is also revealed by the PIIIIP25 index. A final stage in the environmental development was reached at ~5 ka with the establishment of pre-industrial conditions. Low Ca/Fe ratios, low foraminiferal fluxes, low sortable silt values and the sea-ice indicating PIIIIP25 index point to a limited productivity and a weak Atlantic Water inflow by the Return Atlantic Current to our research area, as well as a higher and/or seasonally more extended sea-ice coverage during the Late Holocene. Two intervals with somewhat enhanced Atlantic Water advection around 2.0 and 1.0 ka are indicated by slightly increased foraminiferal fluxes and the reoccurrence of subpolar foraminifers. These intervals may correlate with the Roman Warm Period and the Medieval Climate Anomaly, as defined in the North Atlantic region.

Does foraminiferal test size reflect changes in palaeoenvironmental conditions?—a case study from the southern Svalbard shelf

Although the environmental factors influencing the growth rate and reproduction of benthic foraminifera are known, the relationship between foraminifera test size and environmental variables remains unclear, especially on geological timescales. In this article, we present two records of benthic foraminiferal test size over the last 14 000 years from the southern Svalbard shelf. We use statistical correlation to relate test size changes with environmental conditions recorded by other proxies, including benthic δ18O and δ13C, foraminiferal flux and abundance, and relative abundances of different ecologically indicative foraminiferal groups. The general trends in test size were relatively consistent between the two cores. Still, we found that none of the analysed proxies was statistically correlated with the test size in both records. This leads to a conclusion that foraminifera size is primarily impacted by local oceanographic conditions. These local conditions are partly influenced by global oceanographic transitions. Therefore, large-scale changes can have a secondary impact on foraminiferal test size. The analysis of test size correlation between species similarly revealed that not all species react consistently to environmental changes. Our results indicate that foraminiferal test size cannot be used as a universal and straightforward proxy, but in combination with other methods it can yield valuable palaeoenvironmental information.

Sediment trap and deep sea coretop sediments as tracers of recent changes in planktonic foraminifera assemblages in the southeastern ultra-oligotrophic Levantine Basin

Sediment trap and core top sediments were used to study the seasonal and longer-term variability in the distribution and assemblage composition of planktonic foraminifera (PF) in the ultra-oligotrophic Eastern Mediterranean Levantine Basin (LB). A continuous time series of particulate flux sampled every 11–12 days were retrieved from a sediment trap deployed at 1300 m between May 2017 and May 2018. The core top sediments were collected close to the sediment trap mooring site at ~1500 m water depth. The average annual planktonic foraminiferal (PF) flux was 93 shells m-2 d-1, the lowest value yet recorded among traps located in tropical-subtropical oligotrophic regions. A bimodal increase in PF flux is observed, with highest numbers of 452 shells m-2 d-1 occurring in winter (February), responding directly to maxima in particulate mass flux. A lower flux occurs in late summer from mid-August to mid-September with up to 197 shells m-2 d-1.Ten species were found in the trap, the majority were symbiont-bearing spinose species that contribute 96% of the total flux. Globigerinoides ruber white predominate the assemblage composition during the winter peak together with Globoturborotalita rubsecens and Globigerinella calida. During the subordinate summer peak the dominating species were G. ruber white, Orbulina universa and Globigerinoides ruber pink.The relative abundance of G. bulloides and G. ruber pink is much lower in the sediment trap samples compared to their abundance in nearby coretop sediments. This trend seems to indicate a recent drop in their numbers. At the same time G. rubescens and Globoturborotalita tenella occur in higher numbers in the sediment trap compared with the coretop samples. These opposite trends may reflect the current adjustment of certain PF species to the ongoing sea surface warming and decrease in food availability in the LB.

Temporal variability in foraminiferal morphology and geochemistry at the West Antarctic Peninsula: a sediment trap study

Abstract. The West Antarctic Peninsula (WAP) exhibits strong spatial and temporal oceanographic variability, resulting in highly heterogeneous biological productivity. Calcifying organisms that live in the waters off the WAP respond to temporal and spatial variations in ocean temperature and chemistry. These marine calcifiers are potentially threatened by regional climate change with waters already naturally close to carbonate undersaturation. Future projections of carbonate production in the Southern Ocean are challenging due to the lack of historical data collection and complex, decadal climate variability. Here we present a 6-year-long record of the shell fluxes, morphology and stable isotope variability of the polar planktic foraminifera Neogloboquadrina pachyderma (sensu stricto) from near Palmer Station, Antarctica. This species is fundamental to Southern Ocean planktic carbonate production as it is one of the very few planktic foraminifer species adapted to the marine polar environments. We use these new data to obtain insights into its ecology and to derive a robust assessment of the response of this polar species to environmental change. Morphology and stable isotope composition reveal the presence of different growth stages within this tightly defined species. Inter- and intra-annual variability of foraminiferal flux and size is evident and driven by a combination of environmental forcing parameters, most importantly food availability, temperature and sea ice duration and extent. Foraminiferal growth occurs throughout the austral year and is influenced by environmental change, a large portion of which is driven by the Southern Annular Mode and El Niño–Southern Oscillation. A distinct seasonal production is observed, with the highest shell fluxes during the warmest and most productive months of the year. The sensitivity of calcifying foraminifera to environmental variability in this region, from weeks to decades, has implications both for their response to future climatic change and for their use as palaeoclimate indicators. A longer ice-free season could increase carbonate production in this region at least while carbonate saturation is still high enough to allow for thick tests to grow.

Seasonal and interannual changes in planktic foraminiferal fluxes and species composition in Guaymas Basin, Gulf of California

Abstract Paleoclimate records based on planktic foraminifera shells are reliant upon an understanding of how populations respond to annual and interannual changes in surface hydrography. In particular, annual and interannual flux variability would be expected to impact the interpretation of geochemical proxies from foraminifera shells. A seven-year time series from Guaymas Basin, Gulf of California reveals a seasonal progression of foraminiferal species flux, with faunal assemblages characteristic of winter, summer, and fall conditions. Observations of flux along with remotely sensed sea surface temperatures and previously published oxygen isotope data are used here to assess the range of environmental conditions each species would be expected to represent in the fossil record. We find that both species abundances and phenology are altered during negative El Nino Southern Oscillation (ENSO) phases, as occurred over the course of the study period. This observation is used in conjunction with published δ18O data to subsample fluxes in simulation of assemblages collected and analyzed by standard paleontological methods. This approach indicates that during periods more influenced by El Nino conditions, Globigerina bulloides would record warmer conditions, while Neogloboquadrina dutertrei would reflect cooler conditions.

Sediment flux and recent paleoclimate in JordanBasin, Gulf of Maine

We report planktonic foraminiferal fluxes (accumulation rates) and oxygen isotopes (δ18O) from a nine-month sediment trap deployment, and δ18O from three sediment cores in Jordan Basin, Gulf of Maine. The sediment trap was deployed at 150m, about halfway to the basin floor, and samples were collected every three weeks between August 2010 and May 2011. The planktonic foraminiferal fauna in the trap is dominated by Neogloboquadrina incompta that reached a maximum flux in the second half of October. Oxygen isotope ratios on that species indicate that on average during the collecting period it lived in the surface mixed layer, when compared to predicted values based on data from a nearby hydrographic buoy from the same period. New large diameter piston cores from Jordan Basin are 25 and 28m long. Marine hemipelagic sediments are 25m thick, and the sharp contact with underlying red deglacial sediments is bracketed by two radiocarbon dates on bivalves that indicate ice-free conditions began 16,900 calibrated years ago. Radiocarbon dating of foraminifera indicates that the basin floor sediments (270–290m) accumulated at >3m/kyr during the Holocene, whereas rates were about one tenth that on the basin slope (230m). In principle, Jordan Basin sediments have the potential to provide time series with interannual resolution. Our results indicate the Holocene is marked by ~2°C variability in SST, and the coldest events of the 20th century, during the mid 1960s and mid 1920s, appear to be recorded in the uppermost 50cm of the seafloor.

Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic

Abstract. Oligotrophic regions represent up to 75% of Earth's open-ocean environments. They are thus areas of major importance in understanding the plankton community dynamics and biogeochemical fluxes. Here we present fluxes of total planktonic foraminifera and 11 planktonic foraminifer species measured at the Oceanic Flux Program (OFP) time series site in the oligotrophic Sargasso Sea, subtropical western North Atlantic Ocean. Foraminifera flux was measured at 1500 m water depth, over two ~ 2.5-year intervals: 1998–2000 and 2007–2010. We find that foraminifera flux was closely correlated with total mass flux, carbonate and organic carbon fluxes. We show that the planktonic foraminifera flux increases approximately 5-fold during the winter–spring, contributing up to ~ 40% of the total carbonate flux. This was primarily driven by increased fluxes of deeper-dwelling globorotaliid species, which contributed up to 90% of the foraminiferal-derived carbonate during late winter–early spring. Interannual variability in total foraminifera flux, and in particular fluxes of the deep-dwelling species (Globorotalia truncatulinoides, Globorotalia hirsuta and Globorotalia inflata), was related to differences in seasonal mixed layer dynamics affecting the strength of the spring phytoplankton bloom and export flux, and by the passage of mesoscale eddies. As these heavily calcified, dense carbonate tests of deeper-dwelling species (3 times denser than surface dwellers) have greater sinking rates, this implies a high seasonality of the biological carbonate pump in oligotrophic oceanic regions. Our data suggest that climate cycles, such as the North Atlantic Oscillation, which modulates nutrient supply into the euphotic zone and the strength of the spring bloom, may also in turn modulate the production and flux of these heavily calcified deep-dwelling foraminifera by increasing their food supply, thereby intensifying the biological carbonate pump.

Does the recent pool of benthic foraminiferal tests in fjordic surface sediments reflect interannual environmental changes? The resolution limit of the foraminiferal record

Benthic foraminifera tests (living + dead) and conductivity, temperature and depth (CTD) records in Hornsund Fjord (SW Spitsbergen) were studied over five non-consecutive summer seasons during 2002–2011. The data indicated significant changes in the abundance of benthic foraminifera, species composition and the variability of hydrological and micro-environmental conditions in this fjord. The increased inflow of Atlantic Water (AW) resulted in higher foraminiferal biodiversity and a greater number of rare species; however, many of these were fragile and were thus poorly preserved in the sediment. Cold years significantly reduced species richness in the fjord centre, while more stable hydrological conditions with a predominance of opportunistic foraminifera were noted at the fjord head. Elphidium excavatum f. clavata and Cassidulina reniforme exhibited sensitivity to salinity changes and food supply. The dynamic foraminiferal response to hydrological changes led to the conclusion that the annual foraminiferal flux, compounded by the poor preservation of fragile individuals, significantly changed the spatial and interannual composition of the foraminiferal tests remaining in the sediment. Furthermore, only mature individuals are representative of yearlong or multi-year fjord conditions, since the juveniles that bloom during their maximum growth periods in spring can die out under poor summer and winter conditions. The findings of this study indicated that the upper 8 cm of the sediment in the intense depositional systems of the Svalbard fjords provide good representation of recently departed benthic foraminifera, because of their mobility in surface sediments and further sediment compaction. Hence, the corresponding 10- to 15-year resolution in palaeoceanographic investigations seems to be the most reliable.

A Late Glacial–Early Holocene multiproxy record from the eastern Fram Strait, Polar North Atlantic

The paleoceanographic development of the eastern Fram Strait during the transition from the cold Late Glacial and into the warm Early Holocene was elucidated via a multiproxy study of a marine sediment record retrieved at the western Svalbard slope. The multiproxy study includes analyses of planktic foraminiferal fauna, bulk sediment grain size and CaCO3 content in addition to Mg/Ca ratios and stable isotopes (delta C-13 and delta O-18) measured on the planktic foraminifer Neogloboquadrina pachyderma. Furthermore paleosubsurface water temperatures were reconstructed via Mg/Ca ratios (sSST(Mg/Ca)) and transfer functions (sSST(Transfer)) enabling comparison between the two proxies within a single record. The age model was constrained by four accelerator mass spectrometry (AMS) C-14 dates. From 14,000 to 10,300 cal yr B.P. N. pachyderma dominated the planktic fauna and cold polar sea surface conditions existed. The period was characterized by extensive sea ice cover, iceberg transport and low subsea surface temperatures (sSST(Transfer) similar to 2.1 degrees C; sSST(Mg/Ca) similar to 3.5 degrees C) resulting in restricted primary production. Atlantic Water inflow was reduced compared to the present-day and likely existed as a subsurface current. At ca. 10,300 cal yr B.P. Atlantic Water inflow increased and the Arctic Front retreated north-westward resulting in increased primary productivity, higher foraminiferal fluxes and a reduction in sea ice cover and iceberg transport. The fauna rapidly became dominated by the subpolar planktic foraminifer Turborotalita quinqueloba and summer sSST(Transfer) increased by similar to 3.5 degrees C. Concurrently, the sSST(Mg/Ca) recorded by N. pachyderma rose only similar to 0.5 degrees C. From ca. 10,300 to 8600 cal yr B.F. the average sSST(Mg/Ca) and sSST(Transfer) were similar to 4.0 degrees C and similar to 55 degrees C, respectively. The relatively modest change in sSST(Mg/Ca) compared to sSST(Transfer) can probably be tied to a change of the main habitat depth and/or shift in the calcification season for N. pachyderma during this period.

Seasonal variations in planktonic foraminiferal flux and oxygen isotopic composition in the western North Pacific: Implications for paleoceanographic reconstruction

The oxygen isotopic composition (δ 18 O) of planktonic foraminiferal shells in seafloor sediment provides information on past surface oceanography. Knowledge of seasonal and depth habitat, as well as the δ 18 O disequilibrium (vital effect), is essential to constrain the interpretation of sedimentary δ 18 O. Here, we present a 1-year time series of planktonic foraminiferal shell fluxes and δ 18 O from a sediment trap moored in the northwestern margin of the North Pacific. The vital effect and calcification depth for four species were estimated by comparing shell δ 18 O and the predicted values of equilibrium calcite calculated from temperature and estimated δ 18 O in seawater. Six major species ( Neogloboquadrina incompta , Neogloboquadrina dutertrei , Neogloboquadrina pachyderma , Globigerina quinqueloba , Globigerina bulloides , and Globorotalia scitula ) constituted 97% of the total foraminiferal flux. Most major species showed large fluxes in June and December, corresponding to periods of the development and disruption of the seasonal thermocline, implying the importance of nutrient injection and/or circulation for foraminiferal fluxes. Additional peaks in N. dutertrei and N. pachyderma were observed in August. The seasonal successions of foraminiferal fluxes corresponded to surface ocean stratification conditions and food availability, which are closely related to circulation of local currents. Vital effect estimations suggest that shells calcified in equilibrium for G. bulloides and N. pachyderma [sinistral (s)] and with a − 0.7‰ offset for N. dutertrei [dextral (d)], a − 1.0‰ offset for N.incompta (d), and a − 0.3‰ offset for N. pachyderma (d). The calculation of flux-weighted δ 18 O values reveals that the sedimentary δ 18 O values of G. bulloides , N. dutertrei (d), and N. incompta (d) reflect surface temperature in winter season, and those of N. pachyderma (s) and N. pachyderma (d) reflect summer and annual mean subsurface temperature, respectively. The shallow calcification depths for the four species suggest that δ 18 O between different species (Δδ 18 O) in the western North Pacific does not work for reconstructing past stratification conditions, unlike in other regions. Rather, the Δδ 18 O between N. pachyderma (s) and G. bulloides , N. dutertrei (d) or N. incompta (d) may be a more suitable proxy for past seasonality. • Seasonal variations in planktonic foraminiferal shell flux and δ 18 O are observed. • Stratification condition plays a major role in shell flux variations. • The δ 18 O vital effects and calcification depths for four species were determined. • Multi-species Δδ 18 O as a proxy of the past seasonality in the western North Pacific.

Palaeoenvironmental changes of the last two millennia on the western and northern Svalbard shelf

The western and northern Svalbard continental margins (European Arctic) are environmentally sensitive areas that are dependent on the northward flow of Atlantic Water, the largest heat source of the Arctic Ocean. Two marine sediment records from the Svalbard shelf: Kongsfjorden Trough and Hinlopen Trough, were analysed with regard to the benthic foraminiferal content and lithology to assess the palaeoceanographic evolution during the past two millennia with decadal to multi‐decadal temporal resolution. In both records, an overall gradual decrease of E. excavatum f. clavata during the past two millennia reflects a change towards generally warmer and less glacially influenced conditions, presumably related to enhanced inflow of Atlantic Water (AW). The influence of AW also varied on centennial time scales, as evidenced by faunal and sedimentary shifts occurring almost synchronously at both locations. The period from AD 700 to 1200 was characterized by enhanced inflow of AW, followed by the development of highly productive oceanographic fronts at both localities from AD 1200 to 1500. In contrast, the subsequent interval (AD 1500–1900) shows particularly harsh conditions in the Hinlopen Trough, with significantly reduced foraminiferal flux and sediment input related to perennial sea ice cover. In Kongsfjorden, less severe conditions were observed, indicating that the AW advection continued. The synchronicity of changes in both records demonstrates the effect of the variability in inflow of AW to the Svalbard region during the past 2000 years. Moreover, the records seem to follow climate anomalies, for example the Little Ice Age and Medieval Warm Period, found in the North Atlantic realm.

Marine calcium carbonate preservation vs. climate change over the last two millennia in the Fram Strait: Implications for planktic foraminiferal paleostudies

Abstract We present a high-resolution study of planktic foraminiferal distribution patterns in a deep sea core from the eastern Fram Strait (position 78° 55′ N; 06° 46′ E; water depth 1497 m). The sediment core is located below Atlantic water masses flowing into the Arctic Ocean and spans the last 2400 years. The investigation is based on planktic foraminiferal species distribution, stable isotopes, and sedimentological data. The mean shell weight of Neogloboquadrina pachyderma , %fragmentation, organic and inorganic carbon content and the presence of benthic organic linings were also investigated as an indication of preservation changes. The results indicate that the planktic foraminifera are affected by dissolution and point to five periods of especially poor preservation at ~ 200 BCE, ~ 300–650 CE, 700–850 CE, 1400–1500 CE and from 1800 CE to present. In the last century, small and fragile subpolar species Turborotalita quinqueloba and Globigerinita uvula are preserved. The increased percentage of these subpolar species together with increases in the %CaCO 3 , %TOC and total foraminiferal flux would point to surface water warming. However, our data suggest that these fragile species may not have been preserved in sediments older than 1900 CE due to selective dissolution. Consequently, the magnitude of the previously recorded recent surface water warming in the Fram Strait may be overestimated.

Seasonal and interannual changes of planktic foraminiferal fluxes in the Gulf of Lions (NW Mediterranean) and their implications for paleoceanographic studies: Two 12-year sediment trap records

In order to investigate the seasonal and interannual variability of planktic foraminiferal fluxes in the NW Mediterranean, 266 samples from two 12-year-long sediment traps were analyzed. Two mooring lines were deployed at the east (Station Planier) and the west (Station Lacaze Duthiers) of the Gulf of Lions. The moorings were deployed at a water depth of around 1000m and were equipped with sediment traps at 500m above bottom (mab). In addition, an array of 13 core-tops recovered from different key areas of the Gulf of Lions is described. At Lacaze Duthiers, average foraminiferal fluxes were about double (411.8shellsm−2d−1) those found at the Planier sampling site (225.4shellsm−2d−1), probably due to the fertilizing effect of the Rhone river plume and the general oceanographic circulation. The annual total foraminiferal fluxes exhibited a unimodal trend, with maxima recorded during the winter–spring transition, i.e. the spring bloom, and minima during summer. Therefore, planktic foraminifers found in the sedimentary record in the Gulf of Lions may reflect the flux during the winter–spring period, rather than throughout the annual cycle. A total of eleven planktic foraminiferal species were identified in the sediment trap and core-top samples but only four species were dominant in the assemblages: Globigerina bulloides Neogloboquadrina pachyderma (dex.), Globorotalia inflata and Globorotalia truncatulinoides. The foraminiferal assemblages in the Gulf of Lions reflected the relatively cold conditions of the Northern Basin. No clear relationship between the NAO (North Atlantic Oscillation) and planktic foraminiferal fluxes was found in the sediment trap records. The low planktic foraminiferal fluxes recorded during the spring of 1998 were probably related to the anomalous environmental conditions triggered by the 1997–98 El Niño event. Furthermore, sediment trap samples were compared with surficial sediments recovered from different environmental and sedimentary settings of the Gulf of Lions and the application of these results in paleoceanographic reconstructions is discussed.

Short-term and small-scale variability in planktic foraminifera test flux in the Bay of Biscay

Test fluxes of planktic foraminifera in the Bay of Biscay were sampled in spring using drifting sediment traps deployed at 200m depth. At a temporal and spatial resolution of 3h and approximately 1km the foraminifer flux varied with a factor of 5. The consecutive deployments within the same area, at distances of ∼50km differed significantly in flux and relative species abundances. Flux sequences of the total foraminifer assemblage and individual species were significantly autocorrelated. The significance of autocorrelation analyses was affected by sample size of the flux sequences and limited to flux sequences with large fluxes. Autocorrelation in planktic foraminifer fluxes and standing stocks was restricted to distances <2km, and were not attributed to the temporal domain.

Flux dynamics of planktic foraminiferal tests in the south-eastern Bay of Biscay (northeast Atlantic margin)

The temporal and water depth related dynamics of planktic foraminiferal fluxes in the south-eastern Bay of Biscay are discussed for a two year sampling period (June 2006–June 2008). Two sediment traps deployed at 800m and 1700m water depth at a mooring in 2000m of water depth, were analyzed for the flux of planktic foraminiferal species >150μm, in comparison with the total mass flux. Total flux of planktic foraminifera shows seasonal maxima in spring/early summer (>2000Ind.m−2d−1) and minima from late summer through winter (<10 Ind.m−2d−1). The flux of planktic foraminiferal tests in the intermediate to deep water column at the inner Bay of Biscay comprises an intermittent and regionally variable signal of seasonal surface water primary productivity. Significant lateral transport and flux of particles superimposed on the downward mass flux indicate a decoupling of fluxes between the 800-m and 1700-m traps. The 210Pb budget and the presence of certain benthic foraminiferal species in the midwater column prove that the lateral flux originated from the upper continental slope. Despite the temporal and vertical variations of the particulate flux, a well-defined seasonal flux signal can be deduced from the frequency of planktic foraminiferal species.

북서태평양 아열대 해역에서 침강입자 플럭스의 시·공간 변동

Time-series sediment traps were deployed at 1,000 m water depth of the northwestern subtropical Pacific from July 2009 to June 2010, with the aim of understanding temporal and spatial variations of sinking-particle fluxes. The opening and closing of the traps was synchronized at 18-day periods for 20 events. Total mass fluxes showed distinct seasonal variations with high values for the summer-fall seasons and relatively low values for winter-spring. This seasonal variation at two stations was characterized by a distinct difference in <TEX>$CaCO_3$</TEX> fluxes between the two seasons. The enhanced <TEX>$CaCO_3$</TEX> flux in the summer - fall seasons might be attributed to an increased planktonic foraminiferal flux. Total mass flux at FM10 station was nearly 50% higher than that at FM1 station. The difference in <TEX>$CaCO_3$</TEX> fluxes between two stations contributed nearly 70% of the difference of total mass fluxes. The <TEX>$CaCO_3$</TEX> flux was a major component controlling temporal and spatial variation of sinking - particle fluxes in the western subtropical Pacific Ocean.

Atlantic Water advection to the eastern Fram Strait — Multiproxy evidence for late Holocene variability

A multiproxy data set of an AMS radiocarbon dated 46 cm long sediment core from the continental margin off western Svalbard reveals multidecadal climatic variability during the past two millennia. Investigation of planktic and benthic stable isotopes, planktic foraminiferal fauna, and lithogenic parameters aims to unveil the Atlantic Water advection to the eastern Fram Strait by intensity, temperatures, and salinities. Atlantic Water has been continuously present at the site over the last 2000 years. Superimposed on the increase in sea ice/icebergs, a strengthened intensity of Atlantic Water inflow and seasonal ice-free conditions were detected at ~ 1000 to 1200 AD, during the well-known Medieval Climate Anomaly (MCA). However, temperatures of the MCA never exceeded those of the 20th century. Since ~ 1400 AD significantly higher portions of ice rafted debris and high planktic foraminifer fluxes suggest that the site was located in the region of a seasonal highly fluctuating sea ice margin. A sharp reduction in planktic foraminifer fluxes around 800 AD and after 1730 AD indicates cool summer conditions with major influence of sea ice/icebergs. High amounts of the subpolar planktic foraminifer species Turborotalia quinqueloba in size fraction 150–250 μm indicate strengthened Atlantic Water inflow to the eastern Fram Strait already after ~ 1860 AD. Nevertheless surface conditions stayed cold well into the 20th century indicated by low planktic foraminiferal fluxes. Most likely at the beginning of the 20th century, cold conditions of the terminating Little Ice Age period persisted at the surface whereas warm and saline Atlantic Water already strengthened, hereby subsiding below the cold upper mixed layer. Surface sediments with high abundances of subpolar planktic foraminifers indicate a strong inflow of Atlantic Water providing seasonal ice-free conditions in the eastern Fram Strait during the last few decades.

Seasonal variations of particle fluxes in the northeastern equatorial Pacific during normal and weak El Niño periods

A moored time-series sediment trap was deployed at the Korea Ocean Research and Development Institute Long-term Monitoring (KOMO) Station in the northeastern equatorial Pacific from July 2003 to June 2005. A weak El Nino event was recorded from June 2004 to February 2005, and normal conditions were observed in the remaining periods. The normal period was divided into two seasons based on the cycles of environmental properties in the surface ocean: cold (December–May) and warm (June–November) season. During the normal period, the total mass flux was 1.7 times higher in the cold season than in the warm season. Particularly, the CaCO3 flux was nearly three times higher in the cold season. The enhanced CaCO3 flux in the cold season was attributed to an increased foraminiferal flux, which may have influenced the seasonal variability of the total mass flux at the KOMO station. The enhanced foraminiferal flux during the cold season may have been caused by the environmental changes of the surface ocean in response to wind-driven mixing resulting in supply of subsurface nutrient-enriched water. Particle fluxes during the weak El Nino period were lower by 30% than those during the normal period, which was consistent with previous findings in the central and eastern equatorial Pacific.