phytodetritus entering the benthic boundary layer and aggregated on the sea floor in the abyssal ne pacific macro and microscopic composition abstract phytodetritus which can originate in surface waters following seasonal phytoplankton blooms is considered to be an important food resource for abyssal fauna we analyzed the composition of phytodetritus sampled discretely in situ at an abyssal station in the ne pacific the phytodetritus was collected during two time periods straddling a seasonal maximum in the flux of particulate matter into a sediment trap moored within the benthic boundary layer using the sediment trap record and concurrent time lapse photographs of the sea floor in addition to the results for the composition of sea floor phytodetritus we created a scenario for the origin accumulation and degradation of phytodetritus at the study site it appeared that the sediment trap record did not entirely account for the accumulation and composition of phytodetritus on the sea floor likely due to the undersampling of large sinking aggregates by the sediment trap within each sea floor sampling period two types of aggregated phytodetritus were identified based on macroscopic appearance loosely or strongly cohesive the loosely cohesive phyto detritus collected just before the maximum sinking flux was flocculent and contained large numbers of chain forming diatoms the bulk of the loosely cohesive phytodetritus collected one month later consisted of phaeodarians that appeared to have entrained both older and new diatom floc material the strongly cohesive discrete aggregates collected during both sampling periods appeared to be derived from zooplankton mucous webs although samples within each time period were heterogeneous microscopic composition of phytodetritus in terms of several phytoplankton and protozooplankton components differed significantly between sampling periods these results suggest that phytodetritus can change dramatically over a short time period this may have implications for the potential food resource and feeding behavior of abyssal fauna

how are benthic foraminiferal faunas influenced by cold seeps evidence from the miocene of italy abstract the miocene termina formation of the northern apennines italy hosts small marl bodies containing a fossil megafauna that is not seen elsewhere in the formation this fauna consists of concentrations of large lucinid clams having living representatives that occur in cold seep settings where they house chemosymbiotic bacteria together with the megafauna a 13 c depletion of their carbonate contents suggests a cold seep derived origin for these bodies they belong to the cluster of mostly carbonate oligo miocene bodies outcropping in the apennine range from piedmont to southern italy where they are included in deep marine units at different geological settings the relatively soft lithology of the bodies from the termina formation permitted the extraction of the microfossil component so that a taxonomically detailed investigation of benthic foraminifera was performed moreover a comparison with assemblages from nearby non seep deposits has allowed an evaluation of their use for recognizing fossil seeps a total of more than 200 species and subspecies of benthic foraminifera has been identified in seep bodies and surrounding non seep deposits and allowed paleodepth estimates within the middle bathyal zone 600 1000 m similarly to present day isobathyal settings the foraminiferal diversity is high with a major contribution by the accessory taxa that account for up to nearly 50 of the total assemblage based upon the microhabitat categories the epifaunal assemblages are largely outnumbered by the infaunal ones our results show that significant differences do not exist between the foraminiferal assemblages recovered from seep influenced bodies and the ones from the enclosing deposits these results agree with the findings from present day seep environments for which however a still limited and insufficient data set is at the moment available a further complication that should be considered is the effect of time averaging on fossil assemblages which would be responsible for some homogenization between foraminiferal stocks of normal marine non seep settings and adjacent assemblages controlled by short term events such as the ones produced by cold seepage

benthic foraminiferal recovery in the oslofjord norway responses to capping and re oxygenation abstract since 2001 the semi enclosed bekkelag basin inner oslofjord has been re oxygenated following decades of predominantly anoxic conditions additionally in 2007 parts of the polluted organic rich sediments in the basin were capped with uncontaminated post glacial clay this offered a unique opportunity to monitor the response recovery and colonization of the benthic community to re oxygenation and capping with uncontaminated sediments two sites 165 m apart at 50 m water depth in the bekkelag basin were regularly sampled for benthic foraminiferal and geochemical analyses between march 2008 and september 2010 one site rc5 capped was located in the middle and one rc9 re oxygenated uncapped just outside the capped area at the beginning of the study period the former had been exposed to colonization for one year and the latter for seven years maximum abundance of benthic foraminifera occurred in the surface 0 5 cm of sediment at both sites 60 occurred in the surface 0 1 cm and the majority of these were small 63 125 m forms the same taxa i e stainforthia fusiformis bulimina marginata textularia earlandi organic walled allogromiids were common at both sites indicating that the colonizers had rapidly immigrated from neighboring environments however their abundance showed pronounced differences between sites the dominance was lower and the species richness was significantly higher at the capped compared to the uncapped site throughout the study period these faunal characteristics probably reflect the fundamentally different environmental properties of the capping clay versus those of the formerly anoxic sediments nevertheless the absolute abundance increased at both sites and the assemblage compositions converged with time these results show that benthic foraminifera are well suited for monitoring ecological recovery and that colonization at the uncapped site where recovery was due to re oxygenation was slower than at the capped site

benthos communities in oxygen deficient shelf and upper slope areas of the peruvian and chilean pacific coast and changes caused by el nino

glaciation in the andes during the lateglacial and holocene this review updates the chronology of andean glaciation during the lateglacial and the holocene from the numerous articles and reviews published over the past three decades the andes which include some of the world s wettest and driest mountainous regions offer an unparalleled opportunity to elucidate spatial and temporal patterns of glaciation along a continuous 68 degree meridional transect the geographic and altitudinal extent of modern glaciers and the sensitivity of both modern and former glaciers to respond to changes in specific climatic variables reflect broad scale atmospheric circulation and consequent regional moisture patterns glaciers in the tropical andes and in the mid latitude andes are likely to have been far more sensitive to changes in temperature than glaciers in the dry subtropical andes broad scale temporal and spatial patterns of glaciation during the lateglacial are apparent in the southernmost andes the lateglacial chronology appears to have a strong antarctic signature with the best dated moraines correlating closely with the antarctic cold reversal the southernmost andes do not appear to have experienced a significant ice advance coeval with the younger dryas yd climatic reversal at the other end of the andes from w 0t o 9 n a stronger yd connection may exist but critical stratigraphic and geochronologic work is required before a yd ice advance can be fully demonstrated in the central andes of peru well dated moraines record a significant ice readvance at the onset of the yd but ice was retreating during much of the remaining yd interval the spatial temporal pattern of holocene glaciation exhibits tantalizing but incomplete evidence for an early to mid holocene ice advance s in many regions but not in the arid subtropical andes where moraines deposited during or slightly prior to the little ice age lia record the most extensive advance of the holocene in many regions there is strong evidence for neoglacial advances in the interval between 1 0 and 2 5 ka moraines that correlate with the lia of the northern hemisphere are seen in all presently glacierized mountain ranges most of these date to within the past 450 years outboard of these moraines in many regions are moraines of a slightly more extensive advance that occurred several hundred years prior to the onset of the lia priorities for future work include filling in several prominent spatial gaps in the distribution of chronologic studies for the lateglacial these gaps include the arid regions of northern chile and argentina the southern peruvian andes between 11 5 and 13 5 s and the andes of northern peru and

deep sea benthic foraminiferal species diversity in the ne atlantic and nw arabian sea a synthesis abstract we present a synthesis of species diversity data fishers alpha index shannon wiener log 2 es 100 rank 1 dominance for live stained foraminifera from five bathyal 1340 m depth and abyssal 4450 4950 m depth sites in the ne atlantic and a 3400 m deep site in the arabian sea three atlantic sites porcupine seabight biotrans porcupine abyssal plain are subject to seasonal phytodetritus inputs that support low diversity populations 8 17 species in other respects the foraminifera are highly diverse the meiofaunal fractions 45 or 63 m including fragmented and phytodetritus species of abyssal atlantic samples yielded 110 and 170 species in the 0 1 cm and 0 10 cm layers respectively the arabian sea sample 0 1 cm layer only yielded 232 species in both cases values for diversity measures were very high diversity was rather lower in bathyal porcupine seabight samples 0 1 cm layer which yielded 500 m porcupine and madeira abyssal plains was also speciose 113 133 species but diversity measures were lower and dominance higher than for the meiofauna all assemblages contained numerous undescribed species many belonging to poorly known monothalamous soft bodied taxa sample diversity was influenced by several factors combining phytodetrital and sediment populations reduced diversity and increased dominance slightly the inclusion of deeper sediment layers and finer sieve fractions had the opposite effect the inclusion of fragments had more impact on macrofaunal than on meiofaunal diversity although in both cases the effect was inconsistent either positive or negative porcupine and madeira abyssal plain multicore samples 63 m fraction contained substantially more foraminiferal species than nematode species the numbers of foraminiferal species in boxcore samples 500 m fraction were comparable to or greater than literature values for macrofaunal taxa such as polychaetes and isopods few of the more abundant species at our atlantic abyssal plain and arabian sea sites are endemic this is consistent with literature evidence that many common deep sea foraminiferal species are cosmopolitan and implies that global foraminiferal diversity may be more modest than the high sample diversity might suggest calcareous foraminifera which are well known taxonomically and have a good fossil record may provide a model for diversity patterns among the deep sea benthic biota in general

rapid growth of deep sea benthic foraminifera although benthic foraminifera are important components of the marine benthos and are widely used in paleoceanography for reconstructing deep and bottom water conditions relatively little is known about their growth rates in the deep sea here we present data for two species buliminella tenuata and nonionella stella from a coastal upwelling region that show abundance changes reflecting rapid growth of these taxa over a three month interval rapid growth indicates that the chemical composition of the calcareous foraminiferal test which is used extensively in paleoceanography may reflect environmental conditions over a relatively short interval i e months this observation suggests that it will be possible to reconstruct seasonal environmental conditions in certain areas of the oceans such as coastal upwelling regions

investigating the impact of anthropogenic land use on a hemiboreal lake ecosystem using carbon nitrogen ratios and coupled optical emission spectroscopy anthropogenic impacts on lake ecosystems have increased substantially towards the present however the strength and timing in most cases are not evaluated in detail missing valuable information on the response and recovery of an aquatic system in this study we use the sediment total organic carbon total nitrogen ratio c n and inductively coupled optical emission spectroscopy icp oes elements and the available information about the biological processes to explore anthropogenic land use impact on the lake ecosystem as a case study we selected a hemiboreal lake trik tas latvia ne europe the pearson correlation was used to statistically test the correlations of all variables our results show that the c n ratio lowered immediately with the onset of crop cultivation at 500 bce extensive forest clearance and an abrupt increase in land use are reflected through the associated chemical elements from icp oes and the increasing presence of herbivore dung spores since 1200 ce these changes concur with the excess of fish remains suggesting a decrease in fish populations interestingly anthropogenic land use driven erosion and accompanied calcium carbonate caco3 matter influx favoured the abundance of chara spp in lake trik tas since 500 ce which currently forms the protected specific habitat type h3140 of the european union at present specific submerged macrophyte chara habitat type diminished almost entirely due to increased nutrient input phytoplankton blooming hypertrophic conditions and reduced light availability the continued land use practices led to a switch in organic matter source in the lake from macrophytes to solely algal origin the current study underlines the need of additional methods used to detect the sensitivity of lake ecosystem to external disturbances such as minor anthropogenic land use that might not necessarily be apparent in more traditional analyses such as palynology

a deep sea benthic community exposed to strong near bottom currents on the scotian rise western atlantic abstract this paper gives an overview of the structure of a benthic community at 4626 m depth on the nova scotian continental rise here abundances of polychaetes bivalves isopods and tanaids are conspicuously high compared to those reported from comparable depths bacterial numbers and atp concentrations are also high we suspect that these anomalous abundances result from enhanced food availability caused by the strong near bottom currents that flow through the area the polychaete and bivalve faunas have few adults and high species dominance suggesting that currents create large scale sediment transporting disturbances the composition of the crustacean fauna supports this inference in that it is dominated by forms that can enter the seabed and thereby escape adverse conditions on the sediment surface

the benthic foraminiferal record of the medieval warm period and the recent warming in the gullmar fjord swedish west coast a high resolution study of benthic foraminiferal assemblages was performed on a ca eight metre long sediment core from gullmar fjord on the west coast of sweden the results of pb 210 and ams c 14 datings show that the record includes the two warmest climatic episodes of the last 1500 years the medieval warm period mwp and the recent warming of the 20th century both periods are known to be anomalously warm and associated with positive nao winter indices benthic foraminiferal successions of both periods are compared in order to find faunal similarities and common denominators corresponding to past climate changes during the mwp adercotryma glomerata cassidulina laevigata and nonionella iridea dominated the assemblages judging from dominance of species sensitive to hypoxia and the highest faunal diversity for the last ca 2400 years the foraminiferal record of the mwp suggests an absence of severe low oxygen events at the same time faunas and delta c 13 values both point to high primary productivity and or increased input of terrestrial organic carbon into the fjord system during the medieval warm period comparison of the mwp and recent warming revealed different trends in the faunal record the thin shelled foraminifer n iridea was characteristic of the mwp but became absent during the second half of the 20th century the recent skagerrak kattegat fauna was rare or absent during the mwp but established in gullmar fjord at the end of the little ice age or in the early 1900s also there are striking differences in the faunal diversity and absolute abundances of foraminifera between both periods changes in primary productivity higher precipitation resulting in intensified land runoff different oxygen regimes or even changes in the fjord s trophic status are discussed as possible causes of these faunal differences c 2011 elsevier b v all rights reserved less

changes in the water column structure and paleoproductivity in the western south atlantic ocean since the middle pleistocene evidence from benthic and planktonic foraminifera abstract based on an integrated approach planktonic and benthic foraminifera and stable isotopes carried out in two cores collected on continental slope of santos basin central brazil the paleoceanographic oscillations of the last 570 ka are documented benthic foraminiferal isotopic records coupled with foraminiferal assemblages analyses show 100 ky long term oscillation in the superficial productivity along the middle pleistocene these long term oscillations are interrupted by 30 ky short term changes that mark the transition periods of higher productivity 425 400 ka and 190 160 ka and lower 290 260 ka the planktonic foraminifera species allowed the recognition of changes in the water column structure and in the superficial productivity observed in the area those changes in the superficial waters promoting different organic matter export to the sea floor might have resulted in changes on the more abundant and phytodetritus opportunist benthic taxa epistominella exigua and alabaminella weddellensis

coupling of near bottom pelagic and benthic processes at abyssal depths in the eastern north pacific ocean a time series site was established in the eastern north pacific ocean to study the coupling between near bottom pelagic and benthic processes at abyssal depths in an area with well documented seasonality in surface water productivity particulate total mass ptm particulate organic c poc particulate total n ptn and particulate calcium carbonate p caco fluxes were measured from sediment trap collections at 600 and 50 m above bottom from february 1990 to october 199 1 606 d the sea floor at 4 100 m was concurrently monitored with a time lapse camera over a 386 d period from july 1990 to july 199 1 during this study in situ measurements of sediment community oxygen consumption scoc were made and surface sediment samples collected seasonally with a free vehicle grab respirometer ptm poc ptn and p cac0 fluxes exhibited a strong seasonal signal with episodic peaks from spring through fall and lows in winter scoc increased sharply between winter and summer coinciding with spring peaks in particulate fluxes detrital aggregates appeared on the sea floor in pulses over a 6 month period from july to december 1990 coinciding with periods when particulate fluxes were elevated but delayed 1 5 months after the initial peaks in particulate flux mobile epibenthic megafauna monitored with time lapse photography consisted primarily of holothuroids and echinoids and were twice as active when detrital aggregates were observed on the sea floor as during the rest of the year our results show a temporal relationship between the flux of particulate matter entering the benthic boundary layer the arrival and residence of detritus on the sea floor and the activity of the sediment community and mobile epibenthic megafauna

atlantic paleobathymetry paleoproductivity and paleocirculation in the late albian the benthic foraminiferal record spatial distribution patterns of benthic foraminifers in upper albian sediments from 25 dsdp odp sites and 31 onshore sections of the north and south atlantic ocean are used to generate paleobathymetric reconstructions and to identify areas of high primary production such as coastal and equatorial upwelling zones new paleobathymetric estimates are provided for dsdp odp sites and onshore locations that are not situated on oceanic crust paleobathymetric reconstructions indicate shallow water exchange between the north and south atlantic but show the existence of a deep water connection between the western and eastern tethys 2500 m through the gibraltar gateway strikingly there is no evidence for a strong latitudinal gradient in deep water benthic foraminiferal distribution during the late albian south atlantic assemblages show close affinity to north atlantic and tethyan assemblages exhibiting only a minor degree of provincialism biogeographic patterns reveal a distinct asymmetry in late albian paleoproductivity for the north atlantic as for the present day the eastern margins of the atlantic were generally more productive than the western margins and a belt of enhanced carbon aux export to the seafloor can be traced around the north african coast which probably corresponded to a zone of vigorous coastal upwelling by contrast assemblage composition in the south atlantic generally reflects mesotrophic to oligotrophic conditions benthic foraminiferal distribution patterns thus provide robust proxy data to test predictions from paleocirculation and paleobathymetric models for the mid cretaceous atlantic ocean and adjacent margins c 2001 elsevier science b v all rights reserved

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

benthic foraminiferal turnover across the cretaceous paleogene boundary at agost southeastern spain paleoenvironmental inferences abstract we studied upper cretaceous and lower paleogene benthic foraminifera from the agost section southeastern spain to infer paleobathymetrical changes and paleoenvironmental turnover across the cretaceous paleogene k p transition benthic foraminifera indicate uppermost bathyal depths at agost during the abathomphalus mayaroensis biochron from about 400 kyr before the k p boundary through the early plummerita hantkeninoides biochron about 120 150 kyr before that boundary the depth increased to middle bathyal for the remainder of the cretaceous and remained so for the danian part of the studied section parasubbotina pseudobulloides biochron at least 200 kyr after the k p boundary there were no perceivable bathymetrical changes at the k p boundary where 5 of the species became extinct and the species composition of the benthic foraminiferal fauna changed considerably below the boundary infaunal morphogroups constitute up to 65 73 of the faunas directly above the boundary in the black clays of the lower guembelitria cretacea biozone benthic foraminifera are rare several opportunistic taxa e g the agglutinant haplophragmoides sp have short peaks in relative abundance possibly reflecting low oxygen conditions as well as environmental instability with benthos receiving food from short lived local blooms of primary producers above the clays through the end of the studied interval epifaunal morphogroups dominate up to 70 of the assemblages or there is an even mixture or epifaunal and infaunal morphogroups infaunal groups do not recover to pre extinction relative abundances indicating that the food supply to the benthos did not recover fully over the studied interval about 200 kyr after the k p boundary the benthic foraminiferal faunal changes are compatible with the direct and indirect effects of an asteroid impact which severely destabilized primary producers and the oceanic food web that was dependent upon them

the global ocean flux of particulate organic carbon areal distribution and magnitude the magnitude and distribution of the particulate organic carbon poc rain rate to the seafloor in the atlantic pacific and indian ocean basins between 61 n and 61 s has been estimated from benthic oxygen flux estimates for water depths 1000 m only the calculation utilizes the extensive data sets of sedimentary organic carbon caco3 and accumulation rate to extrapolate between individual benthic flux measurement sites using an empirically derived correlation between the seafloor oxygen flux and these parameters the poc flux through the 1000 m depth horizon was then estimated from published correlations between sediment trap determined fluxes and water depth total oxygen utilization in the deep ocean is estimated to be 1 2 1014 mol o2 yr 1 a value that agrees well with previous estimates which were based on surface water primary productivity sediment trap and depth relationships and with deep water respiration rates estimated from apparant oxygen utilization aou 14c relationships on the basis of the derived global ocean flux distribution it is concluded that 1 dissolved organic carbon doc inputs are not required to account for estimated deep water respiration rates 2 the majority of the poc input to the deep ocean occurs within 30 of the equator 3 the proportion of primary production that reaches the deep sea does not vary greatly with latitude 4 gyre and continental margin regions contribute roughly equally to the deep poc flux with a relatively minor contribution from the equatorial divergence region 5 of the estimated 7 2 1013 mol c yr 1 of poc that sinks below the 1000 m depth horizon 45 3 3 1013 mol c yr 1 reaches the seafloor where it is oxidized 6 when normalized to basin area average deep flux rates in the atlantic and pacific are similar while highest rates are observed in the indian ocean and 7 the results can be fully reconciled only if the benthic flux of doc is significantly less than the benthic o2 flux

paleoclimate changes of the last 1000 yr on the eastern qinghai tibetan plateau recorded by elemental isotopic and molecular organic matter proxies in sediment from glacial lake ximencuo abstract total organic carbon corg and nitrogen ntot concentrations and isotope compositions and n alkane and n alkan ol molecular biomarker compositions were measured in two parallel sediment cores from lake ximencuo a typical glacial lake on the eastern qinghai tibetan plateau qtp to reconstruct local climatic variations during the past 1000 yr concentrations of corg and ntot vary similarly with changes in precipitation recorded by tree rings in dulan northeastern qtp indicating their close relation to precipitation carbon preference index cpi values of c22 c33 n alkanes and c22 c28 n alkan 1 ols and average chain length acl values of c27 c33 n alkanes generally negatively correlate with 13corg and 15ntot and also vary comparably with the oxygen isotope temperature record from the dunde ice core northeastern qtp these patterns indicate that high cpi values and negative shifts of the 13corg and 15ntot correspond to warmer conditions that favor the growth of vascular land plants and that lower values and positive shifts correspond to cooler conditions in the lake ximencuo locality this observation contradicts previous interpretations from peat and modern soil studies that conclude that the cpi indices were controlled by microbial degradation under different climate conditions here we propose that the changes of organic matter sources under different climate regimes combined with physiological adjustments of vascular plants to different air temperatures might yield different cpi responses to climate changes in glacial plateau lakes air temperature and precipitation increases and decreases reconstructed in this 1000 yr study were generally independent of each other but they both occurred at centennial or multi centennial scales the interaction between subtropical asian monsoon and mid latitude westerly atmospheric circulation systems probably dominated the local precipitation variations in the lake ximencuo catchment whereas solar insolation volcanism and greenhouse gas variations were likely responsible for the air temperature changes that are recorded in the lake sediments and that are consistent with regional temperature variations in the eastern qtp

environmental response to climatic and volcanic events in central europe during the weichselian lateglacial this paper reviews major results of the recent german research priority program changes of the geo biosphere during the last 15 000 years a contribution to pages focussing on changes of the geo biosphere during the weichselian lateglacial different continental archives such as annually laminated lacustrine sediments floodplain sediments and speleothems were used to reconstruct environmental response to climatic changes and the laacher see eruption event at ca 12 900 cal bp special emphasis is paid to establish a reliable time control using varve counting high precision radiocarbon dating of tree ring series and ams radiocarbon dating of terrestrial plant macrofossils recovered from lacustrine sediments to correlate and synchronize large scale environmental changes and events in central europe

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

deep sea benthic foraminiferal recolonization of the 1991 mt pinatubo ash layer in the south china sea a census count of rose bengal stained benthic foraminifera from the surface area on top of a 2 to 6 cm thick ashfall layer at three deep water stations along the western margin of the philippines exhibits a unique assemblage composition of benthic foraminifera the total number of benthic foraminifera is low and the ratio of living individuals to empty tests is high specific diversity is low with a significant dominance of infaunal morphotypes including species of the genus reophax r scorpiurus r bilocularis and r dentaliniformis which are regarded as successful recolonizers assemblages below the ash layers are diverse and contain many epifaunal suspension feeding agglutinated and calcareous foraminifera the 1991 mt pinatubo eruption caused mass mortality of benthic foraminifera in a vast area of the eastern south china sea followed by step wise recolonization of the ash substrate three years after the eruption the benthic foraminiferal community structure is still far from recovery to background levels

benthic foraminifera associated with cold methane seeps on the northern california margin ecology and stable isotopic composition release of methane from large marine reservoirs has been linked to climate change as a causal mechanism and a consequence of temperature changes during the quaternary and the paleocene these inferred linkages are based primarily on variations in benthic foraminiferal stable isotope signatures few modern analog data exist however to assess the influence of methane flux on the geochemistry or faunal characteristics of benthic foraminiferal assemblages here we present analyses of the ecology and stable isotopic compositions of living rose bengal stained and dead fossil foraminifera 150 mm from cold methane seeps on the slope off of the eel river northern california 500 525 m and discuss potential applications for reconstructions of methane release in the past and present calcareous foraminiferal assemblages associated with calyptogena clam bed seeps were comprised of species that are also found in organic rich environments cosmopolitan paleoceanographically important taxa were abundant these included uvigerina bolivina chilostomella globobulimina a ndnonionella we speculate that seep foraminifera are attracted to the availability of food at cold seeps and require no adaptations beyond those needed for life in organic rich reducing environments oxygen isotopic values of the tests of living foraminiferal assemblages from seeps had a high range up to 0 69 as did carbon isotopic values up to 1 02 many living foraminiferal isotope values were within the range exhibited by the same or similar species in non seep environments carbon isotopic values of fossil foraminifera found deeper in the sediments 18 20 cm however were 4 10 u peregrina and 3 60 b subargentea more negative than living d 13 c values these results suggest that d 13 c values of foraminiferal tests reflect methane seepage and species specific differences in isotopic composition and can indicate temporal variations in seep activity a better understanding of foraminiferal ecology and stable isotopic composition will enhance paleo seep recognition and improve interpretations of climatic and paleoceanographic change 2000 elsevier science b v all rights reserved

abyssal ne atlantic benthic foraminifera during the last 15 kyr relation to variations in seasonality of productivity abstract benthic foraminiferal faunas 63 m and stable isotopes from the last 15 kyr were studied in bengal programme high resolution temporal and spatial study of the benthic biology and geochemistry of a north eastern atlantic abyssal locality kasten core 13078 16 from the porcupine abyssal plain ne atlantic 48 49 91 n 16 29 94 w water depth 4844 m changes occurred in the accumulation rates species composition diversity and stable isotopes during the last 15 kyr today the area is strongly influenced by seasonal inputs of phytodetritus following the spring blooms in surface water primary productivity variations in the relative abundance of the two most abundant species epistominella exigua and alabaminella weddellensis which today show significant increases in abundance with the presence of phytodetritus on the sea floor are interpreted as resulting from changes in the seasonality of productivity seasonal productivity was higher during the holocene than during the last deglaciation and younger dryas probably coinciding with the retreat of the polar front to higher latitudes this hypothesis is consistent with simultaneous decreases in the percentage of the polar planktic foraminifera neogloboquadrina pachyderma s and increases in the percentage of globigerina bulloides a warmer water planktic foraminifera indicative of phytoplankton blooms and enhanced productivity the relative abundance of the phytodetritus species e exigua and a weddellensis covary between 14 7 and 8 1 kyr but not between 7 8 and 1 2 kyr major decreases in the numbers per gram and accumulation rates of planktic and benthic foraminifera occurred at 12 8 5 kyr and at 4 kyr which correspond to decreases in the sediment coarse fraction and published data on inorganic carbon contents suggesting that dissolution may have increased at these times relationships between benthic foraminiferal faunas and benthic stable isotope records suggest no simple relationship between faunal abundances and test isotope chemistry for example the abundances of phytodetritus species do not show strong correlations with either the 13c values of e exigua or the 13c e exigua p wuellerstorfi record which have previously been suggested as indicative of seasonality of productivity

relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in monterey bay california 1 as part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release we compared ambient pore water chemistry with the distribution and stable isotopic composition of living rose bengal stained foraminifera in mbari rov ventana tube cores taken from modern seepage areas about 1000 m water depth in monterey bay california benthic foraminiferal isotopic differences between sites clearly indicate that methane influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry carbon isotope signatures of living benthic foraminifera did not conform to the very negative 30 to 48 methane influenced carbon isotope values of the pore waters they live in instead the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published 13c values of foraminifera living in nonseep habitats it is not clear what relative influences biological ecological and physical factors have on the carbon isotopic signatures observed in seep foraminifera substantial carbon isotope differences can exist between individuals of the same seep species for instance 13c values of living globobulimina pacifica varied by as much as 2 9 between seeps within 8 km of each other whereas 13c values of living uvigerina peregrina varied by as much as 1 95 within the same seep provided there is no diagenetic alteration of the test carbonate isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage

trends in caribbean paleoproductivity related to the neogene closure of the central american seaway abstract this study tests the hypothesis that the late miocene to early pliocene constriction and closure of the central american seaway cas connecting the tropical atlantic and east quatorial pacific eep caused a decrease in productivity in the caribbean due to decreased coastal upwelling and an end to the connection with high productivity tropical pacific waters the present study compared paleoceanographic proxies for the interval between 8 3 and 2 5 ma in 47 samples from south caribbean odp site 999 with published data on eep dsdp site 503 proxies for site 999 include the relative abundance of benthic foraminiferal species representing bottom current velocity and the flux of organic matter to the sea floor the ratio of infaunal epifaunal benthic foraminiferal species and benthic foraminifer accumulation rates bfars in addition we calculated resistant planktic foraminifers species and used the previously published sand fraction and benthic carbon isotope values from site 999 during early shoaling of the isthmus 8 3 7 9 ma the caribbean was under mesotrophic conditions with little ventilation of bottom waters and low current velocity the pre closure interval 7 6 4 2 ma saw enhanced seasonal input of phytodetritus with even more reduced ventilation and enhanced dissolution between 6 8 and 4 8 ma during the post closure interval 4 2 2 5 ma in the caribbean paleoproductivity decreased current velocity was reduced and ventilation improved while the seasonality of phytodetrital input was reduced dramatically coinciding with the establishment of the atlantic pacific salinity contrast at 4 2 ma our data support the hypothesis that late miocene constriction of the cas at 7 9 ma and its closure at 4 2 ma caused a gradual decrease in paleoproductivity in the caribbean consistent with decreased current velocity and seasonality of the phytodetrital input

benthic foraminifera and environmental turnover across the cretaceous paleogene boundary at blake nose odp hole 1049c northwestern atlantic sediments recovered at lower bathyal odp site 1049 on blake nose northwestern atlantic offer an opportunity to study environmental changes at the cretaceous paleogene k p boundary relatively close to the chicxulub impact structure on the yucatan peninsula mexico in hole 1049c the boundary is located at the base of a 9 cm thick layer with abundant spherules considered to be impact ejecta uppermost maastrichtian oozes below and lowermost danian pelagic oozes above the spherulebed contain well preserved bathyal benthic foraminifera the spherule bed itself in contrast contains a mixture of shallow neritic and deeper bathyal species and specimens vary strongly in preservation this assemblage was probably formed by reworking and down slope transport triggered by the k p impact across the spherule bed i e the k p boundary only f7 of benthic foraminiferal species became extinct similar to the low extinction rates of benthic foraminifera worldwide quantitative analysis of benthic foraminiferal assemblages and morphogroups in the 63 am size fraction indicates a relatively eutrophic stable environment during the latest maastrichtian interrupted by a sudden decrease in the food supply to the benthos at the k p boundary and a decrease in diversity of the faunas followed by a stepped recovery during the earliest danian the recovery was probably linked to the gradual recovery of surface dwelling primary producers d 2004 elsevier b v all rights reserved

a 7000 year record of environmental change including early farming impact based on lake sediment geochemistry and pollen data from county sligo western ireland detailed chronologically tightly constrained lake sediment based geochemical and pollen records have enabled local changes in soil erosion woodland cover and composition and prehistoric farming impact to be reconstructed in considerable detail the profile opens shortly after 7800 bc when tall canopy trees were well established and presumably in equilibrium with their environment a distinct perturbation that involved an increase in pine and birch a decrease in oak and a minor opening up of the woodland is regarded as the local expression of the 8 2 ka climate anomaly lack of response in the geochemical erosional indicators is interpreted as evidence for drier conditions a short lived over compensation in climate recovery followed the 8 2 ka event neolithic farming impact is clearly expressed in both the pollen and geochemical data both datasets indicate that neolithic impact was concentrated in the early neolithic 3715 3440 bc in the interval 3000 2700 bc there appears to have been a break in farming activity the pollen data suggest substantially increased farming impact both arable and pastoral in the bronze age with maximum farming and woodland clearances taking place in the late bronze age 1155 935 bc these developments are poorly expressed in the geochemical record possibly due to within lake changes

accumulation of metals and changes in composition of freshwater lake organic sediments during the holocene abstract the distribution of metals in the strata of sediments deposited in the freshwater environment formed during the holocene in the territory of latvia has been studied rather insufficiently considering the large volume of accumulated organic matter in sediments studies on the content of metallic elements in sediments can help to determine the peculiarities of the metal accumulation process in limnic systems and the biogeochemical cycling of metals lake pilvelis which is located in the eastern part of latvia the northern part of europe was selected as the main study site lake pilvelis is a small lake of a glacial origin and 90 of its depression is filled with organic rich sediments the development stages of lake pilvelis since circa 10 000 cal bp are described in detail via reconstruction of the holocene palaeoenvironmental conditions using multi proxy sedimentary records the elemental composition and content of metallic elements in sapropel are analysed with the main objectives of characterising the accumulation rate of metals in the full profile of sapropel and determining the anthropogenic impact depending on the evolution of the lake and the genesis of sediment organic matter the correlation among the components characterising sediments such as sapropel and metallic elements revealed that the elemental distribution could be divided into three main groups according to the content of the elements associated with organic compounds e g for zn and mn and mineral compounds for ni co cr k fe mg and cu ni and co are partly associated with mineral compounds and partly associated with carbonates a principal component analysis revealed the main factors indicating the origin of metallic elements and the accumulation tendencies of metals in sediment layers the input of the mineral matter the characteristics of organic matter and human impact the content of metallic elements in sapropel from lake pilvelis is mainly affected by the composition of mineral matter not by the size of the particles

recent benthic foraminifera from the eastern south atlantic ocean dependence on food supply and water masses abstract sixty surface sediment samples from the eastern south atlantic ocean including the walvis ridge the angola and cape basins and the southwest african continental margin were analysed for their benthic foraminiferal content to unravel faunal distribution patterns and ecological preferences live stained with rose bengal and dead faunas were counted separately and then each grouped by q mode principal component analysis into seven principal faunal end members then multiple regression technique was used to correlate recent assemblages with available environmental variables and to finally differentiate between four principal groups of environmental agents acting upon the generation of benthic foraminiferal assemblages 1 seasonality of food supply and organic carbon flux rates together with oxygen content in the pore and bottom waters 2 lateral advection of deep water masses 3 bottom water carbonate corrosiveness and 4 energetic state at the benthic boundary layer and grain size composition of the substrate food supply and corresponding dissolved oxygen contents in the pore and bottom waters turned out to be the most important factors which control the distribution pattern of the recent benthic foraminifera at the continental margin in the zone of coastal upwelling and its mixing area benthic foraminiferal assemblages are dominated by stenobathic high productivity faunas characterized by elevated standing stocks low diversities and a large number of endobenthic living species at the continental shelf and upper continental slope the live assemblages are characterized by rectuvigerina cylindrica uvigerina peregrina s 1 uvigerina auberiana and rhizammina spp while the dead assemblages are characterized by cassidulina laevigata bolivina dilatata bulimina costata and b mexicana at the lower continental slope strong influence of high organic matter fluxes on the species composition is restricted to the area off the cunene river mouth where the live assemblage is dominated by uvigerina peregrina s 1 the corresponding dead assemblage by melonis barleeanum and m zaandamae in the adjacent areas of the lower continental slope the biocoenosis is characterized by reophax bilocularis and epistominella exigua which becomes dominant in the corresponding dead assemblage at the walvis ridge and in the abyssal angola and cape basins where organic matter fluxes are low and highly seasonal benthic foraminiferal assemblages reflect both the oligotrophic situation and the deep and bottom water mass configuration the top and flanks of the walvis ridge are inhabited by the rhizammina psammosphaera and r bilocularis live assemblages the corresponding dead assemblages are dominated by g subglobosa on the ridge top and e exigua on the flanks within the highly diverse e exigua dead assemblage several associated epibenthic species coincide with the core of nadw between about 1600 and 3700 m water depth these species include osangularia culter cibicidoides kullenbergi melonis pompilioides bolivinita pseudothalmanni and bulimina alazanensis the assemblages of the abyssal cape and angola basins are characterized by nuttallides umbonifer and a high proportion of agglutinated species these species are adapted to very low organic matter fluxes and a carbonate corrosive environment

evidence for control of abyssal agglutinated foraminiferal community structure by substrate disturbance results from the hebble area abstract deep sea agglutinated foraminifera have been quantitatively examined from 28 coretop samples from seven box cores collected in june 1983 at the hebble high energy benthic boundary layer experiment site 40 27 n 62 20 w 4815 4825 m depth and hebble shallow site 40 53 n 63 44 w 4185 m depth on the nova scotian continental rise samples from the relatively tranquil hebble shallow site can be distinguished from the hebble site on the basis of their microfauna a q mode varimax factor analysis of species frequency data delineates three major faunal assemblages 1 1 a faunal assemblage from the hebble site dominated by ammobaculties sp cf a americanus this assemblage exhibits lowest species diversity suggesting a disturbed community and strongly associated with box cores containing fine grained laminated sediments 2 2 an assemblage associated with box cores from the hebble meadow dominated by saccammina tubulata psammosphaera sp cf p fusca a coarsely grained species of psammosphaera and reophax sp 1 3 3 a fauna occurring at the hebble shallow site dominated by hormosinella distans with reophax bacillaris and ammobaculites agglutinans unique to the assemblage this fauna displays a higher ratio of calcareous to agglutinated species significantly higher species diversity lower variability and a greater proportion of hormosinids and species utilizing finer grains than samples from the hebble site which is interpreted as reflecting environmental stability marked heterogeneity exists among agglutinated foraminiferal assemblages within box cores at the hebble meadow within box core faunal variability exceeds between box core variability suggesting that environmental factors influencing the distribution of species are patchy on a scale of approximately 40 cm

benthic foraminiferal faunal turnover across the cretaceous tertiary boundary at agost southeastern spain paleoenvironmental inferences we studied upper cretaceous and lower paleogene benthic foraminifera from the agost section southeastern spain to infer paleobathymetrical changes and paleoenvironmental turnover across the cretaceous paleogene k p transition benthic foraminifera indicate uppermost bathyal depths at agost during the abathomphalus mayaroensis biochron from about 400 kyr before the k p boundary through the early plummerita hantkeninoides biochron about 120 150 kyr before that boundary the depth increased to middle bathyal for the remainder of the cretaceous and remained so for the danian part of the studied section parasubbotina pseudobulloides biochron at least 200 kyr after the k p boundary there were no perceivable bathymetrical changes at the k p boundary where v5 of the species became extinct and the species composition of the benthic foraminiferal fauna changed considerably below the boundary infaunal morphogroups constitute up to 65 73 of the faunas directly above the boundary in the black clays of the lower guembelitria cretacea biozone benthic foraminifera are rare several opportunistic taxa e g the agglutinant haplophragmoides sp have short peaks in relative abundance possibly reflecting low oxygen conditions as well as environmental instability with benthos receiving food from short lived local blooms of primary producers above the clays through the end of the studied interval epifaunal morphogroups dominate up to 70 of the assemblages or there is an even mixture or epifaunal and infaunal morphogroups infaunal groups do not recover to pre extinction relative abundances indicating that the food supply to the benthos did not recover fully over the studied interval about 200 kyr after the k p boundary the benthic foraminiferal faunal changes are compatible with the direct and indirect effects of an asteroid impact which severely destabilized primary producers and the oceanic food web that was dependent upon them 2003 elsevier science b v all rights reserved

temporal variability in living deep sea benthic foraminifera a review the deep ocean environment is disturbed by various processes many of which involve episodic inputs of organic matter some inputs e g phytodetritus at mid high latitudes in the north atlantic and northeast pacific are seasonally pulsed others e g falls of whale carcasses are irregular and unpredictable but together they evoke a variety of responses from the benthic biota in the case of deep sea foraminifera only those responses arising from seasonal food pulses have been fairly well documented the population dynamics of deep sea benthic foraminifera total live populations and individual species appear to be controlled largely by two inversely related parameters the flux of organic matter to the seafloor and concentrations of oxygen in the sediment porewater organic matter food inputs are most intense along bathyal continental margins and their oxidation often leads to the depletion of oxygen in surface sediments under these conditions foraminiferal faunas are dominated by low oxygen tolerant infaunal species the abundance of which fluctuate in response to seasonally varying amounts of food and oxygen at some sites e g sagami bay off japan species migrate up and down in the sediments tracking critical oxygen concentrations where oxygen concentrations are consistently low less than about 0 5 ml l 1 as in parts of the california borderland foraminifera may undergo population increases solely in response to food pulses in the abyssal north atlantic and in some continental margin areas of this ocean organic matter inputs are weaker and do not lead to oxygen depletion within surface sediments these systems are food limited and seasonal population fluctuations reflect the availability of food phytodetritus rather than oxygen here the species which respond to phytodetritus are mainly epifaunal or shallow infaunal opportunists which represent a small proportion of highly diverse communities 2 or 3 out of 120 species per core of 25 5 cm2 surface area seasonal phytodetrital pulses to the deep seafloor and hence foraminiferal population dynamics are not entirely predictable being dependent on climatic and upper ocean processes they vary in intensity from year to year and occasionally e g at the porcupine abyssal plain pap in 1997 fail to materialise foraminiferal responses to irregular non seasonal organic matter inputs are poorly known however there is some evidence that whale falls turbidite deposits hydrothermal vents and seeps are exploited by species typical of organically enriched low oxygen environments rather than by a specialised fauna fossil foraminiferal assemblages from bathyal and abyssal environments may provide evidence for an increase or decrease in the seasonality of surface production as well as for longer term changes in palaeoproductivity however the accurate interpretation of this record depends on filling the many gaps which remain in our understanding of relations between benthic foraminiferal ecology and seasonal phenomena in the deep ocean

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

the fauna of the hebble site patterns in standing stock and sediment dynamic effects abstract at the high energy benthic boundary layer experiment hebble site at 4820 m depth on the nova scotia rise 40 27 n 62 20 w abundances of polychaetes bivalves tanaids and isopods were conspicuously greater than expected for the depth whereas those of nematodes and harpacticoids the two dominant meiofaunal taxa were not further the abundances of polychaetes bivalves tanaids and nematodes were consistent over time and appeared to be unaffected by the periods of strong near bottom flow that characterized the site in contrast isopods and harpacticoid copepods were less abundant in samples taken as a storm abated apparently because they were eroded during benthic storms we explore implications of the difference between macrofaunal and meiofaunal abundance for community structure in addition because a goal of the hebble project was the parameterization of sediment transport in the deep sea we summarize ways that the biota affects sediment transport at this high energy site

was it terra desolata conquering and colonizing the medieval prussian wilderness in the context of climate change pollen non pollen palynomorphs charcoal and geochemical analyses of sediments from lakes salet and ruskowiejskie ne poland were used to reconstruct vegetation changes in the former galindia territory old prussia related to human activity and the climatic instability of the medieval period among archaeologists and historians there is a widespread opinion that the permanent transformations of the environment in prussia south eastern baltic region began not earlier than after its conquest by the teutonic order and resulted from its economic activity and intensive colonization the impact of previous inhabitants of this land on the environment has been considered as definitely weak our results provide entirely contrasting evidence and demonstrate that strong and permanent deforestation started as early as in the early 11th century ad in the pre teutonic order time and were associated with the economic activity of the prussian galinditae tribes in this paper we also discuss a possible interpreta

phytodetritus at the abyssal seafloor across 10 of latitude in the central equatorial pacific fresh phytoplankton detritus or phytodetritus has been reported from numerous deep seafloor sites in the temperate north atlantic and pacific oceans following seasonal phytoplankton blooms here we report the first strong evidence for abyssal accumulations of phytodetritus in the tropics in the central equatorial pacific in november december 1992 we obtained photographs and or sediment core samples from 61 abyssal stations water depths of 4280 5012 m between 12 s and 9 n along 140 w greenish flocculent material was recovered from the top of multiple core samples from 5 s to 5 n this material was most abundant from 2 s to 2 n in some areas forming continuous layers at least 5 mm thick and individual aggregates 1 cm in diameter the greenish material was clearly visible in bottom photographs as a green veneer that covered 95 of the seafloor near the equator and as individual cm scale aggregates covering 1 of the seafloor occasionally thick accumulations of cm scale aggregates occurred in biogenic pits cleared trails and feeding traces suggest that surface deposit feeding holothurians and echiurans grazed the greenish material microscopic examination of greenish material recovered from core tops and a burrow lumen revealed relatively intact diatoms including rhizosolenia sp and other microalgae with chloroplasts containing chlorophyll the greenish material was 1 12 5 organic carbon by weight i e 5 39 times richer than associated seafloor sediments it also contained high excess activities of 234th suggesting arrival from the water column in the previous 100 days samples of the greenish flocculent material from 0 and 5 n incubated at simulated environmental pressure and temperature with 14c labeled glutamate exhibited 5 fold higher rates of microbial activity than underlying sediments or brown floc from 9 n surface sediment samples which included the greenish flocculent material from 5 s to 5 n also contained significant concentrations of chlorophyll a and other chloropigments the chloropigment concentrations were roughly comparable to deep sea phytodetritus collected in the north atlantic we conclude that fresh organic rich phytodetritus was present on the seafloor from 5 s to 5 n along 140 w in november december 1992 with highest concentrations within 2 3 of the equator this material is likely to be a concentrated high quality food resource for deep sea microbes and metazoans we estimate an upper limit for the standing stock of this phytodetritus to be 2 6 mmol corg m2 this corresponds to 3 of the annual flux of organic carbon to the seafloor at these latitudes in 1992 because the degradation rate of this material appears to be very high its presence at the seafloor for several months per year could yield significant phytodetrital contributions to the annual seafloor organic carbon budget we also suggest that the phytodetrital aggregates are formed at intense convergence zones resulting from seasonal passage of tropical instability waves within 5 of the equator if so phytodetrital accumulations are likely to recur seasonally over broad areas of the abyssal equatorial pacific

benthic foraminiferal distribution at middle valley juan de fuca ridge a northeast pacific hydrothermal venting site fourteen benthic foraminiferal bearing surface samples collected from the area of active venting aav in middle valley at a depth of 2430 m at the northern end of juan de fuca ridge northeast pacific ocean yielded 156 identifiable taxa sample sites were selected near active or recently active vents where temperatures up to 274 c have been measured the sea floor beyond hydrothermal mounds is characterized by unaltered soft hemipelagic mud and is dominated by a calcareous foraminiferal assemblage which includes numerous allochthonous species derived from the shelf via turbidite flows into the valley within the aav agglutinated foraminifera dominate with proximity to hydrothermal vent activity species of the family hormosinidae subfamily reophacinae dominate in the hydrothermal habitat because of their success at colonization attached agglutinated foraminifera densely colonize the indurated sediment in close proximity to vent sites however like the macrofauna observed near hydrothermal vents foraminifera do not venture into the extreme habitats where temperatures are greater than 20 c where clam beds are found in association with active hydrogen sulphide venting benthic foraminifera occur rarely these beds occur in loose pyritic mud that is toxic to all but species e g the clam culyp ena that co exist symbiotically with sulphur oxidizing bacteria the sparse distribution of calcareous benthic foraminifera in the vent areas is caused by enhanced carbonate dissolution at ph values of 5 2 low foraminiferal abundance and species diversity at the immediate site of active venting is attributed to rapid changes in physical and chemical conditions caused by circulating hydrothermal vent waters

the distribution of living benthic foraminifera on the continental slope and rise off southwest norway abstract surface sediment samples taken by corer from 45 stations on the norwegian continental margin and in the norway basin have been investigated for their benthic foraminiferal content unlike previous studies the living benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage factor analysis of both the living and dead faunal data reveals six living species assemblages and five corresponding dead assemblages the additional living assemblage is characterized by the arenaceous speciescribrostomoides subglobosum that dominates between 1400 and 2000 m water depth but is rare in the dead faunal data trifarina angulosa and to a lesser extent cibicides lobatulus characterize the shallowest foraminiferal assemblage from 200 to 600 m water depth where it is associated with strong bottom currents and warm saline atlantic water of the north atlantic drift on the slope between 600 and 1200 m water depth themelonis zaandami species assemblage dominates particularly in areas characterized today by rapid sedimentation of terrigeneous material between 1000 and 1400 m depth where the slope is covered by fine grained organic rich terrigeneous mud the living foraminiferal assemblage is characterized bycassidulina teretis andpullenia bulloides below 1400 m three foraminiferal assemblages are found c subglobosum is found from 1400 to 2000 m cibicidoides wuellerstorfi andepistominella exigua predominantly live from 2000 to 3000 m water depth and below 3000 m oridorsalis umbonatus andtriloculina frigida dominate the fauna all of theelphidium excavatum tests found in this study and thecassidulina reniforme tests found above 500 m water depth were found to be reworked analysis of the sediment grain size distribution and the organic carbon content in surface samples from the deepest stations suggest that the abundance ofc wuellerstorfi ande exigua is positively correlated to relatively coarse caused by planktic foraminifera and organic rich sediments whereas high frequencies ofo umbonatus andt frigida coincide with low organic carbon content we suggest thatc wuellerstorfi is adapted to deep sea environments with relatively high food supply tolerating relatively low interstitial water oxygen content whereaso umbonatus may tolerate lower food supply prefering well oxygenated interstitial waters

northeastern atlantic benthic foraminifera during the last 45 000 years changes in productivity seen from the bottom up we studied benthic foraminifera from the last 45 kyr in the 63 mu m size fraction in biogeochemical ocean flux studies bofs cores 5k 50 degrees 41 3 n 21 degrees 51 9 w depth 3547 m and 14k 58 degrees 37 2 n 19 degrees 26 2 w depth 1756 m at a time resolution of several hundreds to a thousand years the deepest site showed the largest fluctuations in faunal composition species richness and benthic foraminiferal accumulation rates the fluctuations resulted from changes in abundance of epistominella exigua and alabaminella weddellensis in the present oceans these species bloom opportunistically when a spring plankton bloom results in seasonal deposition of phytodetritus on the seafloor the phytodetritus species had very low relative abundances and accumulation rates during the last glacial maximum a strong increase in absolute and relative abundance of e exigua and a weddellensis during deglaciation paralleled the decrease in abundance of the polar planktonic foraminifer neogloboquadrina pachyderma s and the increase in abundance of warmer water planktonic species such as globigerina bulloides this strong increase in relative abundance of the phytodetritus species and the coeval increase in benthic foraminiferal accumulation rate were thus probably caused by an increase in the deposition of phytodetritus to the seafloor and thus probably of surface productivity when the polar front retreated to higher latitudes the abundance of phytodetritus species decreased during the younger dryas but not to the low levels of fully glacial conditions during heinrich events periods of excessive melt water formation and ice rafting benthic accumulation rates were very low as were the absolute and relative abundances of the phytodetritus species supporting suggestions that surface productivity was very low during these events in both cores pullenia and cassidulina species were common during isotope stages 2 3 and 4 as were bolivinid buliminid and uvigerinid species high relative abundances of these species have been interpreted as indicative either of sluggish deep water circulation or of high organic carbon fluxes to the seafloor in our cores relative abundances of these species are negatively correlated with benthic foraminiferal accumulation rates and we can thus not interpret them as indicative of increased productivity during glacials the percentage of these low oxygen species calculated on a phytodetritus species free basis decreased slightly at deglaciation at 5k but not at 14k this suggests that decreased production of north atlantic deep water during the last glacial might have slightly affected benthic foraminiferal faunas in the eastern north atlantic at 3547 m depth but not at 1756 m in conclusion major changes in deep sea benthic foraminiferal faunas over the last 45 000 years in our cores from the northeastern atlantic were the result of changes in surface water productivity not of changes in deep water circulation productivity was lower during the glacial probably because of extensive ice cover

the late miocene onset of high productivity in the benguela current upwelling system as part of a global pattern abstract we have examined the history of the elevated primary productivity associated with the benguela current upwelling system off southwest africa using sediments from 7 5 to 4 8 ma at ocean drilling program site 1085 in the middle cape basin sedimentation rates are low until 6 9 ma low accumulation rates of benthic foraminifers and organic carbon indicate that biological productivity was also low paleoproductivity dramatically increased at 6 7 6 5 ma and was highly variable until 4 8 ma with productivity maxima during cooler periods the presence of radiolarian opal only between 5 8 and 5 2 ma suggests an interlude of silica rich intermediate water in the cape basin the onset of heightened productivity under the benguela current is mirrored by similar increases reported between 6 9 and 6 7 ma in the tropical eastern pacific the western and northern pacific and the indian ocean the similarity between the patterns at site 1085 and in the pacific and indian oceans suggests that the dramatic productivity increase off southwest africa is part of a global response to paleoceanographic changes

oxygen minimum zone edge effects evidence from the central california coastal upwelling system geologic and biological data from box cores gravity cores and bottom photographs across the modern coastal upwelling system of central california reveal that biogeochemical activity increases along the edges of the oxygen minimum zone omz 0 5 ml 1 o2 macrofauna and benthic foraminifers as well as relative concentrations of calcium carbonate glauconite and fecal pellets all display edge effects the major controls appear to be a combination of dissolved oxygen concentration of near bottom waters bottom currents and possibly bacterially mediated nutrient recycling as well as food supplies omz edge effects should be recognizable in the rock record and may prove to be powerful paleoenvironmental paleoecological indicators

foraminiferal record and environmental changes during the deposition of the early middle pleistocene sapropels in southern italy a foraminiferal investigation documents the palaeoenvironmental changes across the sapropel units associated with insolation cycles 90 and 86 in the early middle pleistocene im fosso 5 agosto section basilicata southern italy three benthic foraminiferal fossil associations associations a b and c identified by performing hierarchical cluster analysis on the quantitative data can be considered diagnostic of the palaeoenvironmental conditions before during and after the sapropel intervals they indicate a gradual decrease of bottom water oxygenation prior to the onset of sapropel deposition and a rapid return to stable environmental conditions at the end of the sapropel events the constant presence of benthic foraminifera throughout the sapropels implies that the bottom environment was not totally anoxic the high resolution distributional pattern of planktonic and benthic foraminifera within the sapropel associated with i cycle 90 documents a surface water cooling with consequent rapid re oxygenation of bottom waters that subdivides this interval in two phases both of them are characterized by an early subphase with warm climate conditions a decrease of salinity in surficial water layers and dominated by the low oxygen tolerant benthic species globobulimina affinis the late subphase shows thermal stratification during summer and a relatively deep and oxygenated mixed layer during winter in this subphase the contemporaneous replacement of g affinis the bless opportunistic but more resistant to low oxygen conditionsq species with bolivina alata bolivina dilatata and brizalina spathulata the bless resistant to low oxygen conditionsq species indicates the relative oxygen improvement in sediment pore water the frequent changes detected in the sapropel associated faunal composition underline the unstable nature of bottom water oxygen content d 2004 elsevier b v all rights reserved

correlation frequency of emplacement and source directions of megaturbidites on the madeira abyssal plain abstract this paper describes the sediments of the whole madeira abyssal plain including the madcap area to the south previous studies have centred on the central sub basin which occupies most of the plain and which has become one of the most studied areas of seafloor the plain is made up of a series of large turbidites separated by thin pelagic layers which can be used to provide a high resolution stratigraphy back to about 750 000 years many of the turbidites were deposited close to oxygen isotope stage boundaries suggesting a strong relationship to sea level climate change although the exact initiation mechanism for the flows is not known data from the northern and southern extensions of the plain shows the effects of different entry points for the four main turbidite groups volcanic rich turbidites enter from the ne and e calcareous turbidites from the w one group of organic rich turbidites enters from the se and one group from the ne and e different turbidite sources operate for limited periods before switching to one of the other source areas it is very rare for two sources to provide turbidites at the same isotope stage boundary

paleoproductivity from benthic foraminifera abundance glacial to postglacial change in the west equatorial pacific surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep sea floor as a rule of thumb for each 1 mg of organic carbon arriving at the sea floor one benthic foram shell 150 m is deposited the correlation can be used to reconstruct organic flux to the sea floor in the past and hence the productivity of past oceans applying the appropriate equations to box core data from the ontong java plateau in the western equatorial pacific we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1 5 and 2 0 with intermediate values for the mid transition period accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period presumably because increased winnowing removed part of the food supply

reflections of pre and early agrarian human impact in the pollen diagrams of estonia high resolution pollen profiles based on 30 cores taken from estonian lake and mire deposits were used to reconstruct the extent and type of land use over most of the holocene biostratigraphical studies combining pollen records archaeological investigations conventional and accelerator mass spectrometry ams radiocarbon dates and numerical analysis were used to detect human impact on the landscape and vegetation indications of human activity were traced back to the mesolithic 9000 4900 cal bc and are reflected in the pollen diagram by a wide range of anthropogenic indicators which constitute nearly half of the total pollen sum together with high charcoal content human impact during the mesolithic is also indicated by the rarefaction analysis which shows a doubling of palynological diversity the neolithic 4900 1800 cal bc is regarded as a transitional period between the pre agrarian mesolithic and the agrarian bronze age 1800 500 cal bc changes in vegetation composition attributed to late mesolithic 6400 4900 cal bc land use were found in several of the sites investigated pollen records display the development and intensive use of a pastoral landscape in the middle neolithic 4150 3200 cal bc expressed in pollen diagrams as a drop in the frequencies of broad leaved trees and an increase in picea abies herb pollen and palynological diversity and in some cases increase in charcoal frequencies primitive tillage probably occurred during the middle neolithic at least in the alvar flat terrain with a thin soil cover on carbonaceous bedrock and coastal areas of estonia the earliest cerealia pollen finds are dated to ca 4000 cal bc and represented by avena type and hordeum type pollen during the bronze age crop cultivation played an important role in the farming economy the beginning of crop cultivation in estonia was almost simultaneous with southern sweden but more than 1000 years earlier than in finland the adoption of arable farming in estonia occurred much later than in southern sweden d 2004 elsevier b v all rights reserved

cenozoic deep sea benthic foraminifers tracers for changes in oceanic productivity from late middle eocene through earliest oligocene high latitude regions cooled and by the end of the period continental ice sheets existed in antarctica diversity of planktonic microorganisms declined and modern groups of terrestrial vertebrates originated coeval faunal changes in deep sea benthic foraminifers have been related to cooling of deep waters and increased oxygenation cooling however occurred globally whereas species richness declined at high latitudes and not in the tropics the late eocene and younger lower diversity high latitude faunas typically contain common epistominella exigua and alabaminella weddellensis opportunistic phytodetritus exploiting species that indicate a seasonally fluctuating input of organic matter to the sea floor we speculate that the species richness gradient and increase in abundance of phytodetritus exploiting species resulted largely from the onset of a more unpredictable and seasonally fluctuating food supply especially at high latitudes

a 370 ka paleoceanographic record from the hess rise central north pacific ocean and an indistinct kuroshio extension abstract a 5 m long core np36 collected from the hess rise in the central north pacific ocean 34 11 7 n 179 15 4 e water depth 2664 m was analyzed for benthic and planktonic foraminifera this core yields a continuous record for the last ca 370 000 years according to the oxygen isotope stratigraphy cross spectral analysis of down core variations in planktonic 18o values correlates well with the specmap reference scale allowing recognition of marine isotope stages mis down to mis 10 and the 18o variations coincide well with the changes in sea surface temperature derived using the modern analogue technique time series analyses of mass accumulation rates mar of planktonic and benthic foraminifera were also performed along with analysis of variations in faunal composition mar of planktonic foraminifera display maxima during glacial periods which together with coincident changes in lightness l of sediment measured with the spectrophotometer strongly suggests increasing flux of eolian dust to the hess rise due to strengthened westerly winds however mar of benthic foraminifera including epistominella exigua a common typical phytodetritus feeder also display highest increases during some interglacial periods i e mis 5 and 7 the benthic mar maxima are thought to reflect variations in consumption patterns between benthic and planktonic species a proposed hypothesis that vigorous grazing of phytoplanktons occurred during glacial periods reducing the flux of phytodetritus to the sea floor in turn impacting and limiting production of benthic foraminifera with the opposite effect prevailing during interglacial periods down core variations in right coiling neogloboquadrina pachyderma abundance and the composition of planktonic foraminiferal faunas indicate the subarctic front did not shift southward over the study site during the past 370 000 years alternatively variations in faunal composition indicate that subtropical water prevailed in the study area throughout this period no clear faunal evidence of the presence of the kuroshio extension was found in core np36 reflecting the loss of heat and tropical faunal elements from this water mass as it flowed eastward during late quaternary climatic maxima and minima

carbon and oxygen isotope geochemistry of live stained benthic foraminifera from the aleutian margin and the southern australian margin article comparisons of ambient bottom water geochemistry and stable isotopic values of the tests of living stained calcareous benthic foraminifera from the north pacific on the aleutian margin water depth 1988 m and murray canyons group in the southern indian ocean australian margin water depths 2476 m and 1634 m provide modern environmental analogs to calibrate paleoenvironmental assessments consistent with the hypothesis that microhabitat preferences influence foraminiferal isotopic values benthic foraminifera from both margins were depleted in 13 c with respect to bottom water dissolved inorganic carbon dic the carbon isotope values of deep infaunal foraminifera chilostomella oolina globobulimina pacifica showed greater differences from estimates of those of dic than shallow benthic foraminifera bulimina mexicana bolivinita quadrilatera pullenia bulloides this study provides new isotopic and ecological information for b quadrilatera the mean 13 c value defined as foraminiferal 13 c values minus estimated ambient 13 c values from the aleutian margin is 0 97 higher for g pacifica than the mean from the murray canyon this difference may result either from genetic or biological differences between the populations or from differences in environmental isotopic influences such as pore water differences that were not accounted for in the equilibrium calculations these analyses provide calibration information for the evaluation of bottom water conditions and circulation patterns of ancient oceans based on fossil foraminiferal geochemistry

a benthic foraminiferal proxy of pulsed organic matter paleofluxes in the temperate open ocean of the modern northeast atlantic the spring bloom of phytoplankton leads to a seasonal pulse of detrital organic material phytodetritus to the ocean floor opportunistic benthic foraminifera rapidly colonise this food resource producing large numbers of individuals whose tests are ultimately added to the sediment one of these taxa epistominella exigua shows periodic peaks in abundance in the fossil record at many open ocean sites previously such peaks have been commonly interpreted to result from changes in physicochemical properties of bottom water mass and thus deep sea circulation the main purpose of this paper is to propose thate exigua may be used as a proxy of pulsed organic matter inputs to the deep ocean and therefore as an indicator of relative changes in productivity

a top down and bottom up comparison of paleoproductivity proxies calcareous nannofossil sr ca ratios and benthic foraminiferal accumulation rates we investigate whether a relationship exists between organic matter production at the sea surface recorded by nannofossil carbonate sr ca and its consumption on the seafloor measured by benthic foraminiferal accumulation rates bfar a mid pliocene 3 67 3 90 ma section of ocean drilling program site 926 in the northwestern tropical atlantic was sampled where previous work established that the calcareous nannoplankton assemblages vary with insolation linked changes in surface water productivity our results reveal that coarse fraction nannofossil sr ca varies with changes in assemblage composition and may be predominantly controlled by the geochemistry of the warm water oligotrophic genus discoaster bfar also have a positive relationship with sr ca and discoaster abundances implying times of relatively low surface water nutrients coincide with enhanced bfar this result is opposite of what one would expect given the assumption of a direct relationship between primary and export production we speculate that the bfar are stimulated by enhanced organic carbon export associated with ballasting by nannofossil assemblages dominated volumetrically by large robust taxa such as discoaster species these results highlight the complexity of interpretations of bulk nannofossil sr ca ratios as well as bfar data with respect to paleoproductivity

early oligocene glaciation and productivity in the eastern equatorial pacific insights into global carbon cycling the onset of sustained antarctic glaciation across the eocene oligocene transition eot marks a pivotal change in earth s climate but our understanding of this event particularly the role of the

deep sea benthic foraminiferal assemblage response to a surface ocean productivity gradient a test a transect of samples from the eastern equatorial pacific where surface ocean productivity is the only changing environmental variable was used to test the response of benthic foraminiferal assemblages to an open ocean productivity gradient the transect runs along the east pacific rise from the highly productive waters near the equator to the oligotrophic south pacific subtropical gyre surface sediment benthic assemblages show progressive change along the transect with strong compositional shifts corresponding to the rapid productivity gradient near the equator and to the position of the southern convergence near 18 19 s the relationship of the assemblages to surface ocean productivity was tested by statistical regression of quantitative estimates of productivity on the assemblage principal component scores calculated for each sampling location the regression yielded an r squared of 0 87 demonstrating a clear relationship between surface ocean productivity and deep sea benthic foraminiferal assemblage composition the species most important to this relationship display a consistent response to oceanic productivity for long stretches of geologic time this conservative behavior and the results of the regression analysis indicate that benthic foraminiferal assemblages can be used to estimate surface ocean productivity for the geologic past

seasonal changes in bathyal foraminiferal populations in response to the flux of organic matter sagami bay japan benthic foraminiferal populations through 1991 94 were investigated by taking cores and in situ observations from the submersible shinkai 2000 in sagami bay japan 1450 m water depth at this location a strong spring bloom causes seasonal deposition of phytodetrital material to the sea floor the population size of benthic foraminifera is mainly controlled by this seasonal flux of organic matter which triggers rapid opportunistic reproduction of the shallow infaunal taxa bolivia pacifica and textularia kattegatensis we propose that these species have a one year life cycle the deep infaunal taxa globobulimina affinis and chilostomella ovoidea show less pronounced seasonal fluctuations in population size and seem to have a life cycle longer than two years the foraminifera migrate vertically through the sediment down to the maximum depth to which the sediment is oxygenated the seasonal flux of organic matter thus is the most important determinant of population size microhabitats and reproduction in sagami bay such foraminifera are extremely relevant in the functioning of the global carbon cycle especially at the interface of the hydrosphere and lithosphere

the δ13c in benthic foraminiferal tests of fontbotia wuellerstorfi schwager relative to the δ13c of dissolved inorganic carbon in southern ocean deep water implications for glacial ocean circulation models on a transect between 20 and 70 s in the eastern atlantic ocean and weddell sea water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon 13c co2 these measurements were compared to 13c values determined on live specimens of the benthic foraminifer fontbotia wuellerstorfi and closely related genera from the same stations in addition at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured general deepwater and bottom water mass circulation patterns as inferred from the 13c co2 are in close agreement with those known from other nonconservative tracers very low 13c values of upper circumpolar deep water 0 3 pee dee belemnite pdb in the polar front region and the eastern limb of the weddell gyre coincide with nutrient maxima however a significant decoupling of the dissolved phosphate signal from the 13c co2 signal is indicated in the abyssal weddell sea we attribute this to temperature dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom water formation multiple corer water from the sediment water interface is slightly 13c depleted relative to deepwater and bottom water 13 co2 the surface sediment organic carbon 13c is 3 to 4 lower south of the polar front than north of it and the 13corg in freshly accumulated phytodetritus is 3 to 4 lower than surface sediment organic carbon 13c comparison of live f wuellerstorfi 13c and related genera with bottom water 13c co2 exhibits at most stations between the subtropical front 41 s and the southern boundary of the antarctic circumpolar current 55 s a significant lowering of foraminiferal 13c values compilation of a mean last glacial interglacial 13c amplitude 13c from six published southern ocean cores results in a shift of 0 99 0 13 pdb this shift is greater than that in all other regions however all of these cores are from positions close to recent oceanic fronts thus for these peripheral areas of the southern ocean we suggest about half of the glacial interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production

a time series study of the carbon isotopic composition of deep sea benthic foraminifera 1 variation of the 13c of living rose bengal stained deep sea benthic foraminifera is documented from two deep water sites 2430 and 3010 m from a northwest atlantic ocean study area 275 km south of nantucket island the carbon isotopic data of hoeglundina elegans and uvigerina peregrina from five sets of multicorer and soutar box core samples taken over a 10 month interval march may july and october 1996 and january 1997 are compared with an 11 5 month time series of organic carbon flux to assess the effect of organic carbon flux on the carbon isotopic composition of dominant taxa carbon isotopic data of hoeglundina elegans at 3010 m show 0 3 lower mean values following an organic carbon flux maximum resulting from a spring phytoplankton bloom this 13c change following the spring bloom is suggested to be due to the presence of a phytodetritus layer on the seafloor and the subsequent depletion of 13c in the pore waters within the phytodetritus and overlying the sediment surface carbon isotopic data of h elegans from the 2430 m site show an opposite pattern to that found at 3010 m with a 13c enrichment following the spring bloom this different pattern may be due to spatial variation in phytodetritus deposition and resuspension or to a limited number of specimens recovered from the march 1996 cruise the 13c of uvigerina peregrina at 2430 m shows variation over the 10 month interval but an analysis of variance shows that the variability is more consistent with core and subcore variability than with seasonal changes the isotopic analyses are grouped into 100 m size classes on the basis of length measurements of individual specimens to evaluate 13c ontogenetic changes of each species the data show no consistent patterns between size classes in the 13c of either h elegans or u peregrina these results suggest that variation in organic carbon flux does not preferentially affect particular size classes nor do 13c ontogenetic changes exist within the 250 to 750 m size range for these species at this locality on the basis of the lack of ontogenetic changes a range of sizes of specimens from a sample can be used to reconstruct 13c in paleoceanographic studies the prediction standard deviation which is composed of cruise core subcore and residual replicate variability provides an estimate of the magnitude of variability in fossil 13c data it is 0 27 for h elegans at 3010 m and 0 4 for u peregrina at the 2430 m site since these standard deviations are based on living specimens they should be regarded as minimum estimates of variability for fossil data based on single specimen analyses most paleoceanographic reconstructions are based on the analysis of multiple specimens and as a result the standard error would be expected to be reduced for any particular sample the reduced standard error resulting from the analysis of multiple specimens would result in the seasonal and spatial variability observed in this study having little impact on carbon isotopic records

ecology of deep sea benthic foraminifera in the north atlantic during the last glaciation food or temperature control abstract in this study we explore the paleoecology of nineteen species and two species groups of deep sea benthic foraminifera in relation to bottom water temperature and food supply in the central north atlantic during the last glaciation 60 000 28 000 years bp the study is based on core so82 02ggc taken from 1730 m water depth on the western flank of reykjanes ridge the climate of the investigated period was extremely unstable interrupted by thirteen warmings and coolings the so called dansgaard oeschger events at so82 02ggc surface and bottom water temperatures varied with up to 5 c between the warm interstadials and the cold stadials surface productivity as indicated by the flux of planktic foraminifera varied with a factor of up to ten the dansgaard oeschger events had a significant impact on the benthic foraminiferal faunas which experienced up to 70 replacement between the interstadials and stadials multivariate analysis reveals that the investigated species can be separated into two groups group 1 including bulimina costata brizalina subspinescens epistominella decorata and trifarina angulosa was attracted to higher temperatures and high food supply group 2 including pullenia bulloides valvulineria laevigata and melonis barleeanus was attracted to colder water and low food supply three species belonging to the cold group cibicidoides wuellerstorfi oridorsalis umbonatus and eponides tumidulus are almost exclusively confined to sediments rich in ice rafted detritus a few species including nonionella iridea and epistominella vitrea show opportunistic behaviour most species are epifaunal to shallow infaunal and live today in oligotrophic to mesotrophic habitats our investigations indicate that temperature was the primary factor responsible for the relative abundance and main grouping of species however four species show little influence by temperature and several perhaps most were clearly also affected by food supply

benthic environmental changes in the eastern mediterranean sea during sapropel s5 deposition abstract high resolution benthic foraminiferal analyses of sediment cores collected at different sites in the eastern mediterranean sea revealed that profound changes occurred in deep sea ventilation over the past 124 119 ka bp the three cores sin97 gc01 ban89 gc09 bd02 gc01 were selected in order to investigate middle and deep bathyal ecosystems in the eastern mediterranean basin at site sin97 gc01 933 m water depth urania basin the presence of benthic fauna in the sapropel layer and the gradual increase in benthic foraminiferal abundance from the middle part of the sapropel suggest that the sea floor was partially ventilated and that re oxygenation had increased considerably during the late phase of s5 deposition cores ban89 gc09 2011 m water depth napoli dome and bd02 gc01 2470 m water depth ionian sea show a different pattern during sapropel s5 benthic abundance and diversity strongly decrease and microfauna even disappears in some levels suggesting the establishment and maintenance of stagnant and anoxic conditions at the seafloor until the end of s5 deposition in the deepest part of the basin the re establishment of the benthic foraminiferal community at the top of the s5 layer indicates a relatively slow bottom re oxygenation at the southernmost site the foraminiferal assemblage records a short oxygenation pulse during the deposition of sapropel s5 linked to a short cold spell the results of this study suggest that the evolution of the dysoxic anoxic conditions as well as the re oxygenation pattern at the end of the stagnant period were characterised by spatial and temporal variability possibly controlled by basin physiography

living deep sea benthic foraminifera from the warm and oxygen depleted environment of the sulu sea the semi enclosed oligotrophic sulu sea is characterised by warm ca 10 c and oxygen depleted 32 m from 56 samples from surface down to 5 cm the stained foraminiferal assemblages of the sulu sea comprised 285 species including 137 agglutinated and 148 calcareous species standing stock values ranged from 595 individuals 10 cm2 on the continental slope to 100 individuals 10 cm2 in the abyssal zone generally in the low productivity and low oxygen environment of the sulu sea stained assemblages are characterized by low standing stock values moderate dominance and low diversity the combination of poor rates of c org flux and low dissolved oxygen content in bottom waters are the main factors controlling the deep sea benthic fauna in the sulu sea the foraminiferal abundances in the upper bathyal zone respond to both food fluxes and oxygen concentrations most of the epifaunal oxyphilic species have their lower limit of occurrence at a water depth of approximately 2000 m dissolved oxygen 1 25 ml l in the sulu sea at constantly dysoxic 1 ml l o2 sites from the lower bathyal and abyssal zone the assemblages comprised low oxygen tolerant species and are more dependant on c org fluxes the correlations between benthic foraminiferal faunas and c org flux and dissolved oxygen values are very good with correlation coefficients of r2 0 956r2 0 956 and 0 88 respectively the living deep sea foraminiferal assemblages consisted mainly of agglutinated tests with dominant species such as lagenammina difflugiformis ammoscalaria tenuimargo various reophax species and small 70 m trochamminaceans like portatrochammina wiesneri stained individuals of the calcareous parrelloides bradyi type 2 occurred in low numbers at oxygen poor sites down to a depth of 5 cm in the sediment column the only stained calcareous infaunal species found deeper than 4000 m was valvulineria mexicana average living depth of 3 cm the general microhabitat preferences of common species were consistent with those from other studies although due to the unique combination of poor food supply and dysoxic conditions most of the infaunal species had shallower average living depths than those reported from other dysoxic locations

detection of the askja ad 1875 cryptotephra in latvia eastern europe we report the first geochemically confirmed findings of the askja volcano iceland ad 1875 eruption cryptotephra in eastern europe the cryptotephra finding in latvia is the easternmost finding of

temporal variability in phytodetritus and megabenthic activity at the seabed in the deep northeast atlantic we report a ten year study of the abundance and activity of megabenthos on the porcupine abyssal plain northeast atlantic together with observations on the occurrence of phytodetritus at the deep sea floor 4850 m using the southampton oceanography centre time lapse camera system bathysnap we have recorded a radical change in the abundance and activity of megabenthos between the two periods of study 1991 1994 and 1997 2000 in 1991 1994 the larger megabenthos occurred at an abundance of c 71 6 ha and were dominated by large holothurians in addition there were very substantial populations of smaller megabenthic ophiuroids c 4979 ha together the total megabenthos are estimated to track over some 17 cm2 m2 d exploiting 100 of the surface of the seabed in c 2 5 years in 1997 2000 the larger megabenthos increased to an abundance of c 204 ha and were joined by exceptional numbers of a small holothurian species amperima rosea 6457 ha and ophiuroids principally ophiocten hastatum 53 539 ha the total megabenthos population was tracking at an estimnated rate of c 247 cm2 m2 d exploiting 100 of seabed in just 6 weeks coincident with these increases in the abundance and activity of the megabenthos there were apparently no mass depositions of aggregated phytodetritus to the seabed in the summers of 1997 1999 mass occurrences of phytodetritus had been noted during the summer months of the three years previously studied 1991 1993 and 1994 with covering between 50 and 96 of the sediment surface there is a statistically significant p 0 02 negative correlation between maximum extent of this seabed cover of phytodetritus and seabed tracking by megabenthos additional studies lampitt et al progr ocean 50 2001 indicate that there were no substantial changes in surface ocean primary productivity in export flux or in the composition of the flux that might otherwise account for the apparent absence of observable concentrations of phytodetritus during the summers of 1997 1999 we postulate that the marked increase in megabenthic tracking activity resulted in the removal via consumption disaggregation burial etc of the bulk of the incoming phytodetrital flux during these years a simple conceptual model based on the apparent phytodetrital fluxes observed in 1991 and 1993 suggests that the megabenthos tracking rates estimated for 1997 1999 are sufficient to account for near total removal of this flux however we are not able to estimate other processes removing phytodetritus i e other elements of the benthos that may also have increased between 1991 1994 and 1997 1999 other independent studies e g ginger et al progr ocean 50 2001 of flux constituents support the possibility that just a few species of megabenthos e g a rosea and o hastatum could well have consumed a major proportion of the incoming flux and so substantially modified the composition of the organic matter available to other components of the benthos