reconciling the stommel box model with the stommel arons model a possible role for southern hemisphere wind forcing abstract in the stommel box model the strength of the overturning circulation is parameterized in terms of the density and hence the pressure difference between the two boxes straub has pointed out that this parameterization is not consistent with the stommel arons model for the abyssal circulation in particular the zonally averaged density field implied by the stommel arons model is unrelated to the strength or the direction of the meridional overturning circulation here the inconsistency is examined using the abyssal circulation model of kawase and a variant to include the effect of southern hemisphere wind forcing the important parameter is r the ratio of two timescales the timescale for a perturbation to the density field to propagate by either wave or advective processes from a high latitude source to the equator and the timescale for the dissipation of a perturbation to the density field by diapycnal mixing if the model is forced only by a deep water source in the northern basin it is

global adjustment of the thermocline in response to deepwater formation the global adjustment of the thermocline in response to deepwater formation is studied in a single mode model on a beta plane the signal is carried from ocean to ocean by kelvin waves which travel equatorward along western boundaries eastward across the equator poleward at the eastern boundaries and then eastward around the southern tip of continents into the next ocean basin the interior is filled by rossby waves emanating from eastern boundaries stronger weaker deepwater formation induces an upward downward motion of the main thermocline in the world oceans the adjustment is completed on centennial time scales

environmental significance of foraminiferal morphogroups in jurassic north sea deltas abstract the distribution of morphological groups of foraminifera has been analysed in toarcian and bajocian deposits of the northern north sea and the yorkshire coast the deposits are referred to prodeltaic lower delta front and interdistributary bay environments and contain mainly or entirely agglutinating assemblages of low to intermediate diversity a total of 33 agglutinating species are recognized in the studied material and these are arranged into eleven morphotypes composing seven subgroups and four morphogroups the categories are distinguished on the basis of main morphological features of the taxa combined with their life positions and micro habitats as inferred from modern analogues the prodelta deposits were formed in a normal saline and slightly stagnant depositional setting with foraminiferal faunas composed mainly of surficial and infaunal morphogroups the lower delta front and interdistributary bay sediments were deposited in shallow hyposaline waters strongly dominated by an epifaunal morphogroup with a partly phytal association a model of agglutinated morphotype distribution reveals increasing morphotype diversity and by inference ecological niche span from interdistributary bay through lower delta front to prodeltaic environments

234th based carbon export around free drifting icebergs in the southern ocean abstract the impact of free drifting icebergs on the efficiency of carbon export from the upper water column was measured using the disequilibrium of 234 th and its parent 238 u the study addressed the null hypothesis that free drifting icebergs do not alter 234 th deficiency and carbon export compared to surrounding waters upper water column inventories of 234 th were measured at six stations in the weddell sea concurrently with four deployments of lagrangian sediment traps lsts during a cruise in march april 2009 four stations were sampled ranging from 0 3 km to 60 km from c 18a temperature and salinity anomalies indicated enhanced upwelling and turbulent mixing extending downstream of the iceberg to a minimum of 20 km from the iceberg edge separate studies of the impact of c 18a on water column physical properties were used to define the extent of the iceberg s influence on surrounding waters the largest upper water column deficiencies in the inventories of 234 th were measured in close proximity and downstream of the iceberg and extending to below 100 m depth a steady state model was used to estimate the export of 234 th from the upper water column organic carbon export was calculated using c th from the concurrent lst collections comparison of stations within the iceberg s influence close proximity and downstream to within 20 km of the iceberg and far field greater than 60 km measurements showed a factor of 3 increase in organic carbon export near the iceberg the factor correlated well with the results from the near and far field lst measurements differences in the magnitude of carbon export at 100 and 600 m indicate that 90 percent of the exported material is regenerated by 600 m depth this study confirms that the increased abundance of large free drifting icebergs in the southern ocean can contribute to the drawdown of atmospheric co 2 through increased organic carbon export

response of middle jurassic benthic foraminiferal morphogroups to dysoxic anoxic conditions in the pieniny klippen basin polish carpathians abstract the distribution of foraminiferal morphological groups has been analyzed in upper aalenian lower bajocian black siltstones and mudstones of the pieniny klippen belt polish carpathians the deposits are assigned to middle neritic outer and upper bathyal zones represented by three succession and contain agglutinated and calcaeous foraminifera assemblages separate classifications of agglutinated and calcareous morphogroups are established and used for a palaeocological study the groups are distinguished on the basis of morphological features modes of life and feeding habits as inferred from modern analogues infaunal preferences of some foraminifera have been supported by comparison with other infaunal indicators such as trace fossil tiering and abundance of infaunal ostracods a new quantitative method to estimate dissolution of calcareous tests has been tested on the most common genus lenticulina it reveals a special survival strategy of this genus in suboxic muddy and flocculent substrate the distribution of morphogroups in comparison with other palaeoecological taphonomical and sedimentological indicators allows interpretations of organic input rate of sedimentation level of oxygenation position of the redox boundary and p h the studied deposits represent regional anoxic dysoxic event which occured within a semienclosed silled basin

ecostratigraphic trends of jurassic agglutinated foraminiferal assemblages as a response to sea level changes in shelf deposits of svalbard norway foraminiferal analysis proves to be a useful tool for the interpretation of major factors controlling the eco sedimentary environment changes in benthic foraminiferal features including morphogroups are mainly affected by variations in nutrient availability and oxygenation rate the integration of foraminiferal data with total organic carbon toc values together with differentiation of oxygen restricted biofacies orb based on sedimentological features and macroinvertebrate composition will improve the interpretations derived upper jurassic shelf deposits from svalbard norway are revealed to be particularly sensitive to the record of fluctuations in nutrients and oxygenation showing two extreme cases in toc content high toc concentrations are characterized by low values of the shannon weaver index h and diversity index in foraminifera pointing to a low diversity and dominance of r mode epifaunal foraminifera trochammina moreover differentiated orb can be characterized by parallel lamination in shales and an absence of macrobenthic invertebrates including trace fossils unfavourable benthic conditions are interpreted mainly related with a high consumption of oxygen by microbes in the sediment associated to the degradation of the organic matter low toc values are related to higher values of diversity h and diversity index and foraminiferal assemblages dominated by infaunal forms the differentiated orbs are characterized by coarse fabrics scarcity or absence of parallel lamination presence of trace fossils and abundance of macroinvertebrate shelly epifauna this is related to a better pore water circulation and higher oxygenation degree congruent with the comparatively more favourable conditions in the infaunal habitats ecostratigraphic trends along the studied section allow the differentiation of stratigraphic intervals reflecting variations in parameters related to the sea level dynamics transgressive phases reveal upward trends in palaeoenvironmental parameters characterized by decreasing grain size and increasing in both toc values and epifaunal foraminifera differentiated orb reveals diminution in abundance and diversity of trace fossils and benthic shelly macroinvertebrates upwards maximum flooding intervals show the maintenance or accentuation of the previously registered features the thinnest fabrics and the highest values in toc and in opportunistic epifaunal foraminifera with orb dominated by parallel lamination a regressive phase is characterized by coarsening upwards sediments decreasing toc values and increasing infaunal foraminifera orb reveals a diminution in parallel lamination together with an increase in trace fossil abundance and diversity as well as in benthic shelly macroinvertebrates

in situ measurement of mesopelagic particle sinking rates and the control of carbon transfer to the ocean interior during the vertical flux in the global ocean vertigo voyages in the north pacific abstract among the parameters affecting carbon transfer to the ocean interior particle sinking rates vary three orders of magnitude and thus more than primary production f ratios or particle carbon contents e g boyd p w trull t w 2006 understanding the export of marine biogenic particles is there consensus progress in oceanography 4 276 312 doi 10 1016 j pocean 2006 10 007 very few data have been obtained from the mesopelagic zone where the majority of carbon remineralization occurs and the attenuation of the sinking flux is determined here we report sinking rates from 300 m depth for the subtropical station aloha june 2004 and subarctic station k2 july 2005 north pacific ocean obtained from short 6 5 day deployments of an indented rotating sphere irs sediment trap operating as an in situ settling column peterson m l wakeham s g lee c askea m a miquel j c 2005 novel techniques for collection of sinking particles in the ocean and determining their settling rates limnology and oceanography methods 3 520 532 to separate the flux into 11 sinking rate fractions ranging from 820 to 2 m d 1 that are collected by a carousel for further analysis functioning of the irs trap was tested using a novel programming sequence to check that all particles have cleared the settling column prior to the next delivery of particles by the 6 hourly rotation cycle of the irs there was some evidence from the flux distribution among the cups and photomicroscopy of the collected particles that very slow sinking particles may have been under collected because they were unable to penetrate the brine filled collection cups but good evidence for appropriate collection of fast settling fractions approximately 50 of the particulate organic carbon poc flux was sinking at greater than 100 m d 1 at both stations at aloha more than 15 of the poc flux sank at 820 m d 1 but low fluxes make this uncertain and precluded resolution of particles sinking slower than 137 m d 1 at k2 less than 1 of the poc flux sank at 820 m d 1 but a large fraction 15 45 of the flux was contributed by other fast sinking classes 410 and 205 m d 1 pic and bsi minerals were not present in higher proportions in the faster sinking fractions but the observations were too limited to rule out a ballasting contribution to the control of sinking rates photographic evidence for a wide range of particle types within individual sinking rate fractions suggests that biological processes that set the porosity and shape of particles are also important and may mask the role of minerals comparing the spectrum of sinking rates observed at k2 with the power law profile of flux attenuation with depth obtained from other vertigo sediment traps deployed at multiple depths buesseler k o lamborg c h boyd p w lam p j trull t w bidigare r r bishop j k b casciotti k l dehairs f elskens m honda m karl d m siegel d silver m steinberg d valdes j van mooy b wilson s e 2007b revisiting carbon flux through the ocean s twilight zone science 316 5824 567 570 doi 10 1126 science 1137959 emphasizes the importance of particle transformations within the mesopelagic zone in the control of carbon transport to the ocean interior

diversity dynamics and mass extinctions of the early middle jurassic foraminifers a record from the northwestern caucasus abstract the early middle jurassic foraminiferal assemblages of the northwestern caucasus including a total of 315 species and 68 genera were analysed to establish the principal diversity patterns at substage level of resolution an overall conclusion is that the number of species varied significantly in contrast to the number of genera the most diversified were late sinemurian pliensbachian late toarcian early aalenian and late bajocian assemblages significant diversity drops have been documented in the early toarcian and in the middle aalenian the first of them corresponds to the well known mass extinction which regionally was initiated in the pliensbachian and terminated when rapid late toarcian diversification began the second event could be considered as a regional evidence of a new mass extinction that appeared in the middle aalenian and was most likely associated with the aalenian bajocian regional anoxic event also recorded in the carpathian part of the western tethys the most intense foraminiferal turnovers took place in the toarcian and in the middle aalenian early bajocian the lazarus effect in spite of its high value has not much influenced the estimation of principal diversity trends

trace fossil model for reconstructing oxygenation histories of ancient marine bottom waters application to upper cretaceous niobrara formation colorado abstract trends of decreasing trace fossil diversity burrow size and penetration depth with diminishing oxygen availability in contemporary marine settings have been incorporated with the concept of trace fossil tiering to develop a model for reconstructing the oxygenation history of ancient basin bottom waters more sensitive than traditionally employed criteria the model permits detailed evaluation of relative degree of oxygenation through the recognition of oxygen related ichnocoenosis ori units or units of strata deposited under similar levels of bottom water oxygenation when employed in detailed vertical sequence analyses the model may also be used to construct interpreted oxygenation curves that reflect rates and magnitudes of temporal change in redox conditions the utility of the model is demonstrated by its application to rhythmically bedded calcareous strata of the niobrara formation upper cretaceous exposed in colorado non laminated strata of the niobrara are characterized by four recurring trace fossil suites referred to as the 1 chondrites 2 zoophycos teichichnus 3 planolites and 4 thalassinoides assemblages on the basis of trends in trace fossil diversity burrow diameter and penetration depth these assemblages are recognized as oxygen related ichnocoenoses interpreted oxygenation curves for the basal fort hays member reflect high magnitude redox cycles characterized by rapid deoxygenation events followed by gradual reoxygenation phases curves for the overlying smoky hill member reflect an overall lower degree of oxygenation with more irregular lower magnitude redox fluctuations significant correlation between interpreted levels of paleooxygenation and organic carbon content illustrate the model s potential for evaluating the distribution of organic rich fine grained strata co interpretation of these variables with carbonate content supports the premise that deposition was controlled by paleoceanographic perturbations modulated by milankovitch like climatic cycles comparison with traditionally emphasized macroinvertebrate body fossil criteria clearly demonstrates the greater utility of the trace fossil approach for evaluating paleo oxygenation

does iron fertilization lead to rapid carbon export in the southern ocean 1 the southern ocean has the potential to influence climate due to its large inventory of excess macronutrients such as nitrate and phosphate it has been hypothesized that if the supply of the micronutrient iron increased it would lead to enhanced uptake of atmospheric co2 and hence the sequestration of carbon via sinking particles martin 1990 while much has been learned about iron limitation and low phytoplankton biomass in high nutrient low chlorophyll regions martin 1991 coale et al 1996 less is known about the effect of fe on particle export here we present results from the first detailed study of particle export during a mesoscale iron fertilization experiment the southern ocean iron release experiment soiree measurements of the natural tracer thorium 234 indicate negligible particle export within 14 days after the initial infusion of iron we attribute this lack of response to colder water temperatures that promote slower cell metabolism in phytoplankton and hence slower secondary responses of herbivores and particle aggregation

benthic foraminiferal assemblages record major environmental perturbations during the late pliensbachian early toarcian interval in the peniche gssp portugal abstract this is the first ecostratigraphic and palaeoecological analysis of the benthic foraminiferal assemblages defined as morphogroups in the pliensbachian toarcian transition and the toarcian oceanic anoxic event t oae of the peniche section the toarcian global boundary stratotype section and point foraminiferal assemblages from the uppermost pliensbachian emaciatum zone reveal the presence of a stable benthic environment with good oxygen and availability of trophic resources as evidenced by the high diversity of specialists the pliensbachian toarcian transition reveals high foraminifera abundance mainly specialists although it is considered a slightly condensed interval the base of the levisoni zone shows dramatic changes in life style of foraminifera increase of epifauna and potentially deep infauna an increase in opportunistic forms and a decrease in diversity these changes suggest unfavourable conditions related to food availability diminution and depleted oxygenation corresponding to the beginning of the 13c negative excursion palaeoenvironmental conditions become severe in the lower to middle levisoni zone where there is a barren interval for foraminifera coincident with the highest values of total organic carbon after this interval foraminiferal assemblages experienced a recovery with increasing diversity and occurrence of specialists consistent with a well oxygenated environment and good food availability these changes observed in benthic foraminiferal fauna from the peniche section through the uppermost pliensbachian lower toarcian are comparable to what was reported previously on ostracods brachiopods and calcareous nannofossils foraminiferal assemblages from peniche section are comparable to other tethyan spain italy north africa and nw european sections england from the same stratigraphic interval with the suborder lagenina dominating the assemblages

palaeoenvironmental turnover across the cenomanian turonian transition in oued bahloul tunisia foraminifera and geochemical proxies abstract the integrated analysis of foraminiferal assemblages geochemical proxies and stable isotopes in the oued bahloul section tunisia allowed us to reconstruct the environmental turnover across the cenomanian turonian boundary an increase in palaeoproductivity proxies p ti u al sr al and in 13 c values and a decrease in foraminiferal diversity and 18 o values mark the beginning of the oceanic anoxic event 2 oae2 at the rotalipora cushmani and whiteinella archaeocretacea biozones boundary eutrophic conditions at the seafloor and in the water column are evidenced by high proportions of buliminids and the replacement of planktic oligotrophic specialist rotalipora by eutrophic opportunist hedbergella the enrichment in organic matter and redox sensitive elements together with the abundance of low oxygen tolerant benthic foraminifera indicate dysoxic conditions in the deep water column and at the seafloor higher u aut than mo aut among planktic foraminifera deep and intermediate dwellers disappear rotalipora and globigerinelloides and surface dwellers proliferate hedbergella the persistency of the poorly oxygenated conditions during the w archaeocretacea biozone locally produced euxinic conditions where mo ef and mo aut reach high values diversity presents minimum values and benthic foraminifera temporarily disappear the maximum percentage of heterohelicids indicates a stratified water column with a well developed oxygen minimum zone improved oxygen conditions returned in the upper part of the w archaeocretacea biozone and helvetoglobotruncana helvetica biozone with a slow recovery of foraminiferal assemblages decrease in eutrophic genera heterohelix and increase in mesotrophic genera whiteinella a gradual increase in 18 o values suggests decreased temperatures in surface waters the oae2 has been attributed to global temperature changes and palaeoceanographic reorganization the poor mixing of surface and deep waters and enhanced primary productivity related to global warming associated with increasing continental weathering and nutrient runoff may have favored the eutrophication of the ocean and the expansion of the oxygen minimum zone

carbon export associated with free drifting icebergs in the southern ocean abstract enrichment of the pelagic ecosystem associated with the proliferation of free drifting icebergs prompts questions about increased productivity and the export flux of organic carbon to the deep ocean with continued climate warming lagrangian sediment traps lst were deployed autonomously beneath a large tabular free drifting iceberg c 18a in the nw weddell sea during march and april 2009 to collect sinking particles at a depth of 600 m three lst deployments associated with c 18a within a 30 km radius collected sinking diatom frustules dominated by corethron pennatum and fragilariopsis nana euphausiid fragments crustacean and fish fecal material detrital aggregates and mineral grains one lst deployment at a control site 74 km away in open water devoid of icebergs collected diatom frustules euphausiid molts crustacean fecal material and detrital aggregates phytoplankton abundance microbial abundance and biomass were significantly higher in the lst samples than in open water collections at 500 m depth the mean mass flux and organic carbon flux associated with iceberg c 18a were twice as high 124 mg m 2 d 1 and 5 6 mg corg m 2 d 1 respectively than at the control site a similar trend was observed in corg 234th activity being highest near c 18a and lowest at the control site extrapolation of the area of enrichment to 30 km radius around c 18a 2826 km2 produces an estimated mass flux of 350 tons d 1 and carbon flux of 15 8 tons corg d 1 five similar sized icebergs to c 18a were identified in satellite images in a surrounding 47 636 km2 area at the same time of sampling assuming a 30 km radius as the area of influence around each of these five icebergs 46 of the total area would be enhanced with an export flux at 600 m of 122 4 tons corg d 1 the large numbers of smaller icebergs identified visually in this area would only increase this area of influence icebergs serve as areas of local enrichment and with increased proliferation must be considered in the cycling of carbon in the southern ocean

localization of abrupt change in the north atlantic thermohaline circulation 1 recent climate model experiments as well as paleoclimate records suggest that the meridional overturning circulation or thermohaline circulation in the atlantic ocean could change abruptly as a result of global warming and that this could have a significant impact on european climate we use a reduced gravity model to investigate the response of the atlantic overturning circulation to changes in forcing we find that variability at decadal and higher frequencies is confined to a single hemisphere this implies that a overturning variability resulting from high frequency changes in buoyancy forcing in the labrador and greenland seas will be limited to the north atlantic and b any observed decadal and higher frequency fluctuations in north atlantic overturning can only result from changes in the surface fluxes within the north atlantic basin itself these results suggest that southern ocean wind forcing is not important for north atlantic overturning on decadal and shorter timescales

coherent sea level fluctuations along the global continental slope signals in sea level or more properly sub surface pressure ssp sea level corrected for the inverse barometer effect are expected to propagate rapidly along the continental slope due to the effect of sloping topography on wave modes resulting in strongly correlated ssp over long distances observations of such correlations around the arctic and antarctic are briefly reviewed and then extended using satellite altimetry to the rest of the global continental slope it is shown that such long distance correlations are common especially in extra tropical regions simple correlations from altimetry cannot however establish the wave speed or whether waves are responsible for the correlations as opposed to large scale coherence in the forcing a case study around south america is used to highlight some of the complications and is found to strengthen the case for the importance of wave modes in such long distance ssp coherence although more detailed in situ data are required to resolve the cause of the correlations

linking ecosystem dynamics and biogeochemistry sinking fractionation of organic carbon in a swedish fjord we studied the growth and sedimentation of a phytoplankton bloom in the gullmar fjord in spring 2001 sinking fractionation as measured by differential sinking of components having varied carbon isotope signals was an important process in determining carbon fluxes within this complex coastal ecosystem large rapidly sinking diatoms aggregated with their own carbon exudates this exudate material was the single largest contributor to vertical carbon flux in the fjord over the study period and amounted to an order of magnitude greater carbon flux than the live biomass reaching the sediment traps we estimate that diatoms primary production contributed 75 of the total integrated production 100 of new production and 100 of the total sedimentary flux during the primary sedimentation event despite the fact that the surface bloom biomass was dominated by high concentrations of the flagellate chattonellasp diatoms carried a heavy carbon isotope signature 13c 19 to depth this moved downward as a layer through the water column distinct from other particular organic carbon poc at the surface having a very light signature 23 to 26 this light 13c signature at the surface coincided with a surface peak in particulate and dissolved organic carbon poc doc and transparent exopolymer particles tep and material carrying the low 13c signature had a negligible sinking rate this distinctive surface signature probably contained small poc typical of the microbial loop and its products a component of which was the very low 32 of the organic colloids measurable aggregation of these colloids occurred and they may have contributed up to 20 of the vertical flux very early in the study sinking fractionation of poc caused isotope composition shifts on the order of 3 7

the natural iron fertilization experiment keops kerguelen ocean and plateau compared study an overview when the first scientific voyages went to the southern ocean high levels of living biomass were observed in the vicinity of islands hart 1942 was the first to mention that the abundant biomass might be due to the release of oligoelements like iron from the island this hypothesis however remained unverified for more than half a century because of the experimental difficulties in properly manipulating water with subnanomolar iron concentrations when john martin formulated the iron hypothesis martin 1990 and provided the first supporting evidence of it he also suggested using the chlorophyll plume observed westward of the galapagos island in the equatorial pacific as a natural iron fertilization experiment

controls on mesopelagic particle fluxes in the sub antarctic and polar frontal zones in the southern ocean south of australia in summer perspectives from free drifting sediment traps the saz sense project examined ecosystem controls on southern ocean carbon export during austral summer january february 2007 at three locations p1 in the low biomass subantarctic zone saz west of tasmania p3 in a region of elevated biomass in the saz east of tasmania fuelled by enhanced iron supply and p2 in high nutrient low chlorophyll hnlc polar frontal zone pfz waters south of p1 and p3 sinking particles were collected using i a cylindrical time series pps3 3 trap for bulk geochemical fluxes ii indented rotating sphere irs traps operated as in situ settling columns to determine the flux distribution across sinking rate fractions and iii cylindrical traps filled with polyacrylamide gels to obtain intact particles for image analysis particulate organic carbon poc flux at 150 m pps3 3 trap was highest at p1 lower at p2 and lowest at p3 3 3 1 8 2 1 0 9 and 0 9 0 4 mmol m 2 d 1 respectively biogenic silica bsi flux was very low in the saz 0 2 0 2 and 0 02 0 005 mmol m 2 d 1 at p1 and p3 respectively and much higher in the pfz 2 3 0 5 mmol m 2 d 1 at p2 hence the high biomass site p3 did not exhibit a correspondingly high flux of either poc or bsi separation of sinking rate fractions with the irs traps at 170 and 320 m depth was only successful at the pfz site p2 where a relatively uniform distribution of flux was observed with 1 3 of the poc sinking faster than 100 m d 1 and 1 3 sinking slower than 10 m d 1 analysis of thousands of particles collected with the gel traps at 140 190 240 and 290 m depth enabled us to identify 5 different categories fluff aggregates low density porous or amorphous aggregates faecal aggregates denser aggregates composed of different types of particles cylindrical and ovoid faecal pellets and isolated phyto cells chains and single cells faecal aggregates dominated the flux at all sites and were larger in size at p1 in comparison to p3 the pfz site p2 differed strongly from both saz sites in having a much higher abundance of diatoms and relatively small sized faecal aggregates overall the particle images suggest that grazing was an important influence on vertical export at all three sites with differences in the extents of large aggregate formation and direct diatom export further influencing the differences among the sites

the morphogroups of small agglutinated foraminifera from the devonian carbonate complex of the prague synform barrandian area czech republic abstract agglutinated foraminifera from the lower and lower part of the middle devonian predominantly limestones of the prague synform barrandian area were classified into five morphogroups morphogroup ed1 was divided to morphotype ed1a which is represented by foraminifera with straight tubular or branched tests irregularly coiled forms are separated to morphotype ed1b ed2 morphogroup includes genera with planoconvex tests which can be divided into morphotype ed2a characterized by planoconvex meandering tests and morphotype ed2b with subglobular tests the ed3 morphogroup contains genera with discoidal flattened planispirally coiled forms the ed4 group consists of globular forms whilst simple globular forms without marked tubular projections are representatives of morphotype ed4a and globular morphotypes ed4b with apertures on marked neck like projections and morphogroup ed5 is represented by very rare multilocular morphotypes the absence of the deep infaunal morphogroups is characteristic the morphogroup distribution has been strongly affected by oxygen concentration the energy of the environment nutrient availability and post mortem processes intervals with diversified and abundant foraminiferal assemblages can be correlated with positive 13 c excursions and also with the deposition of nodular limestones the devonian assemblages from the prague synform were compared with isochronous assemblages from other regions though the taxonomical composition of the early devonian assemblages from these areas are rather different the morphogroup composition is highly comparable and globally indicates similar life and feeding strategies of the early devonian foraminifera

optical imaging of mesopelagic particles indicates deep carbon flux beneath a natural iron fertilized bloom in the southern ocean we recorded vertical profiles of size distributions of particles ranging from 0 052 to several mm in equivalent spherical diameter in the natural iron fertilized bloom southeast of kerguelen island southern ocean and in surrounding high nutrient low chlorophyll hnlc waters with an under water video profiler during the kerguelen ocean and plateau compared study cruise jan feb 2005 total particle numerical abundance and total particle volume tpv in the 0 200 m layer were respectively 3 fold and 20 fold higher in the bloom and integrated tpv was correlated to integrated chlorophyll concentration the difference persisted well into the ocean interior with a 10 fold higher tpv at 400 m depth beneath the natural iron fertilized bloom below 400 m increases in tpv values at the bloom stations reflect the suspension of bottom sediments bloom waters had a greater proportion of large particles from the surface to 400 m and also exhibited an increase of this proportion with depth compared to hnlc waters multiple visits to the bloom reference sta a3 suggest preferential removal of large particles as the bloom declined comparing our particle abundance size spectra with those observed previously in polyacrylamide gel filled sediment traps allows us to estimate mesopelagic particle sinking rates these results suggest that particles sink faster in the hnlc waters than beneath the bloom the fact that sinking speeds were not a simple monotonic function of particle size and varied spatially highlights the need to go beyond parameterizations of sinking rate as a function of size alone

the barremian and aptian stepwise development of the oceanic anoxic event 1a oae 1a crisis integrated benthic and planktic high resolution palaeoecology along the gorgo a cerbara stratotype section umbria marche basin italy abstract the barremian and aptian were times of global plate reconfiguration and profound changes in the ocean climate system culminating in the worldwide deposition of lower aptian black shale layers oae 1a based on high resolution lithostratigraphic and micropaleontological analyses precursor conditions and timing of the anoxia are here reconstructed along a 33 06 m thick section in the proposed barremian aptian boundary gssp stratotype at gorgo a cerbara umbria marche basin italy a non uniform history of benthic foraminiferal diversification is interrupted by the selli level oae 1a and by three turnover points for both benthic and planktic organisms each highlighted by prominent breaks in lithology and outcrop morphology the first two points at 1 1 myr and 20 50 kyr prior to the onset of the oae 1a correspond respectively to the nannoconid bathypelagic calcareous nannofossils decline and crisis events and separate a pelagic limestone chert claystone lithological cycles of the uppermost maiolica formation showing frequencies reminiscent of orbital eccentricity and containing an oligotrophic barremian benthic and planktic assemblage dominated by k selected nannoconids and rhizammina b greenish grey cherty marls of the lowermost marne a fucoidi formation associated to declining sedimentation rates and eutrophic early aptian assemblages dominated by radiolarians and lituolid benthic foraminifera and c anoxic radiolarites and shales of the carbonate free selli level high magnitude and frequency assemblage fluctuations occur between the nannoconid crisis 25 cm below the lowermost oae 1a black shale layer and the selli level base with suggestions of bottom water acidification at 800 kyr after the oae 1a end a third turnover point in the basal reddish member of the marne a fucoidi highlights middle aptian assemblages characterized by a bloom of early macroperforate planktic foraminifera hedbergella spp and appearances of new benthic species marking a shift towards better oxygenation oae 1a oxygen and pelagic carbonate factory crises are here suggested to have been step wise and linked to global warming conditions

foraminiferal assemblages extinctions and appearances associated with the early toarcian oceanic anoxic event in the llanbedr mochras farm borehole cardigan bay basin united kingdom abstract the uppermost pliensbachian lower toarcian sediments recovered from llanbedr mochras farm borehole north wales uk were deposited in the cardigan bay basin and mainly consist of alternating marls and marly limestones the current study analyses the foraminiferal assemblages from the cored interval 143 m that has been assigned to the spinatum zone upper pliensbachian to the lower part of the bifrons zone middle toarcian the foraminiferal assemblages are dominated by the suborders lagenina and robertinina four main ecostratigraphic intervals have been identified based on changes in the foraminiferal assemblages that occurred before during and after the toarcian oceanic anoxic event t oae ecostratigraphic interval i upper part of the spinatum zone is characterized by a diverse assemblage with specialist opportunist and intermediate forms this assemblage is interpreted to represent a phase that pre dates the biotic crisis the ecostratigraphic interval ii tenuicostatum zone shows an abrupt increase in opportunist forms such as the genus reinholdella and a facultative opportunist such as paralingulina tenera which was tolerant to oxygen depleted conditions this second interval represents the initial biotic crisis phase in response to decreasing oxygenation the ecostratigraphic interval iii is considered the peak of the biotic crisis coincident with the negative carbon isotopic excursion at the base of the serpentinum zone and characterized by the dominance of the opportunist reinholdella 87 97 of the assemblage and low diversity the ecostratigraphic interval iv upper part of serpentinum zone and lower part of bifrons zone is characterized by an increase of diversity and an abrupt decrease in reinholdella this assemblage is interpreted to reflect the increased availability of oxygen from deep infaunal to epifaunal microhabitats and the return to normal conditions at the sea bottom ecostratigraphic fluctuations in the mochras foraminiferal assemblages across the t oae event are comparable with those from other parts of the uk the lusitanian basin portugal the umbria marche basin italy and the atlassic basin north africa in addition a foraminiferal turnover is evident across the pliensbachian toarcian boundary and the t oae and reflects the effects of the early jurassic biotic crisis on benthic foraminifera controlling factors of the biotic crisis are discussed regarding that anoxic conditions do not necessarily have a lethal effect on all foraminiferal species and other oceanographic and environmental factors need consideration fragmentation of epicontinental platforms sea level changes crisis of carbonate productivity and temperature changes

sinking particle properties from polyacrylamide gels during the kerguelen ocean and plateau compared study keops zooplankton control of carbon export in an area of persistent natural iron inputs in the southern ocean the kerguelen ocean and plateau compared study keops examined the origin of elevated phytoplankton biomass in naturally iron fertilized waters over the kerguelen plateau during midsummer january february 2005 we report sinking particle characteristics determined from image analysis of thousands of individual particles collected in viscous polyacrylamide gels placed in free drifting sediment traps at two sites a high phytoplankton biomass site over the central plateau a3 and a moderate biomass site at its periphery c5 the particles were divided into three types 1 oval fecal pellets 2 cylindrical fecal pellets and 3 aggregates the aggregates were most abundant and mainly consisted of agglomerations of the cylindrical fecal pellets conversion of the pellet and aggregate volumes to carbon contents suggests export fluxes of 50 60 mg c m22 d21 at 100 m depth in reasonable agreement with independent estimates from carbon and 234th measurements our observation that the majority of the particle flux was processed through the heterotrophic foodweb contrasts with the results of artificial iron fertilization experiments and with models for export from productive diatomdominated waters that emphasize direct export of phytoplankton detritus the keops results may offer more appropriate scaling for the response of ecosystem structure and carbon export to persistent iron fertilization in the southern ocean

in situ settling behavior of marine snow1 the settling velocities of undisturbed macroscopic aggregates known as marine snow were measured with scuba in surface waters off southern california and analyzed as a function of aggregate size mass and density the mean settling velocity was 74f39 m d l for aggregates ranging from 2 4 to 75 mm in maximum length sinking rates in the field varied exponentially with aggregate size and dry weight and were consistently up to four times slower than rates measured in the laboratory the excess densities of the 80 aggregates examined were calculated from volume and dry weight and ranged over four orders of magnitude with a median of 1 4 x 1o 4 g cm 3 aggregates of marine snow sank more slowly than predicted for either solid or porous spheres of equivalent volume and density although their velocities were within the range expected for equivalent sinking prolate ellipsoids no relationships between settling velocity and either excess density or particle shape were found drag coefficients of marine snow were also higher than predicted by theory for spheres of equivalent volume and density these deviations from theoretical expectations may be partially explained by errors in the estimation of the excess densities of aggregates variability in the densities of the heterogeneous primary particles comprising marine snow fecal pellets claymineral particlcs phytoplankton molts etc and the potential for buoyancy regulation by individual phytoplankton cells inhabiting aggregates make determination of excess density especially

diatoms preserved in surface sediments of the northeastern kerguelen plateau abstract an island mass effect was observed from the sedimentary distribution of diatoms on the northeastern kerguelen plateau five new samples placed in context to species distributions previously reported from the permanently open ocean zone pooz revealed a plateau community dominated by three species taxa fragilariopsis kerguelensis thalassionema nitzschioides f nitzschioides and chaetoceros hyalochaete resting spores intermediate abundances of thalassiosira antarctica were unique to the plateau sediment signature as were increased abundances of eucampia antarctica v antarctica the off plateau sediment sample contained typical pooz sediment distributions dominated by f kerguelensis thalassiosira lentiginosa and thalassiothrix antarctica the role of deposition from the surface waters to the sediments was investigated by comparison to the diatom thanatocoenose observed in surface waters these results suggest that the use of sediment abundances of c hyalochaete resting spores and f kerguelensis to determine past productivity events such as wind sourced iron enrichment of the southern ocean at the last glacial maximum is not straightforward the elevated abundance of t nitzschioides f nitzschioides on the plateau did not indicate an iron deplete regime but the converse for the evaluation of paleo productivity hypotheses for the open southern ocean we suggest caution in the use of subantarctic and kerguelen plateau sediment signatures and emphasize that there is a need to also study antarctic coastal and especially sea ice melt water stimulated blooms

latest cenomanian earliest turonian low oxygen tolerant benthonic foraminifera a case study from the sergipe basin n e brazil and the western anglo paris basin southern england abstract distinctive sedimentological geochemical isotopic and micropalaeontological response characterise the nature of sediments deposited under hypoxic anoxic bottom conditions during the latest cenomanian to earliest turonian of most of the world s basins the composition of the biota is a direct response to overall environmental conditions the recognition of distribution patterns of low oxygen tolerant microfauna is therefore of primary importance in evaluating and reconstructing the regional palaeoceanographic settings where such events took place a case study is presented from two coeval stratigraphic sequences the sergipe basin northeastern brazil and the western anglo paris basin southern england the associated benthonic foraminiferal assemblages from oxygen depleted environments consist mostly of opportunistic r selected species basic patterns in community trophic structures appear to have primarily dictated the composition of the biota the assemblages from outer shelf to upper slope oxygen depleted environments are commonly characterised by 1 low diversity 2 limited intraspecific variation 3 predominance c 40 60 of the total foraminiferal assemblage of epifaunal deposit feeding plano concavo convex trochospiral calcareous hyaline morphotypes gavelinellids conorboidids rosalinids and bagginids 4 variable numbers c 10 30 of infaunal bacterial detrital scavengers tapered and elongate morphotypes turrilinids bolivinids buliminellids fursenkoinids polymorphinids and caucasinids 5 epifaunal shallow infaunal deposit feeding lenticular morphotypes coiled vaginulinids c 5 19 6 variable numbers c 10 30 of agglutinated specimens lituolids discamminids eggerellids textulariids trochamminids ammodiscids tritaxiids and valvulinids and 7 dominance about 60 80 of minute c 100 200 m in maximum diameter width or length calcareous hyaline taxa during widespread dysaerobic quasi anaerobic episodes highly oxygen depleted bottom conditions are marked by the absence of benthonic microfauna minor taxonomic differences between the two studied areas are mostly due to palaeobiogeographic provincialism

miocene benthonic foraminiferal morphogroups in an oxygen minimum zone offshore cabinda this paper is part of the special publication no 153 the oil and gas habitats of the south atlantic eds n r cameron r h bate and v s clure two hundred and seventy eight benthonic foraminiferal species were recorded 126 agglutinating and 152 calcareous from cabgob 128 3 offshore angola this assemblage is comprised of a cosmopolitan fauna named the agua salada fauna known from the caribbean in the vienna basin west africa libya and borneo the fluctuating relative abundance of benthonic foraminiferal morphogroups in combination with total organic carbon toc data is suggested to reflect variation in the intensity of the oxygen minimum zone as it steadily increases upwards an infaunal agglutinated opportunistic r selected group moves from antiphase into phase with toc upwards in cabgoc 128 3 a morphologically comparative calcareous group displays the opposite trend moving from phase into antiphase with toc data planispiral agglutinated foraminifera emulate the steady increase in toc upwards in cabgoc 128 3 this group includes cyclammina cyclops previously only recorded in the arctic elongate flattened calcareous morphologies undergo a sudden expansion towards the top of the well and are apparently unaffected by toc this overall trend is supported by concurrent poor preservation amongst distinct calcareous groups susceptible to dissolution as expected in an area of dysaerobic conditions the disappearance of all agglutinated faunas in the late miocene is considered to be a reflection of oceanogrphic change

234th in different size classes of sediment trap collected particles from the northwestern pacific ocean abstract 234 th a surface area specific particle reactive radionuclide has been used to estimate particulate organic carbon poc export fluxes based on the poc 234 th ratio of sinking particles and the 234 th flux in the ocean the poc 234 th ratios from large particles 50 m are conventionally considered to represent sinking particles collected by sediment traps but this assumption has not been thoroughly tested more recently hung and gong 2010 separated sinking particles from the northern south china sea where diatoms are the most dominant group using different nitex screens and found that small 234 th and poc flux however the size distribution of sinking particles has seldom been measured in picoplankton dominated oligotrophic and upwelling conditions here we used nitex screens to separate sinking particles in oligotrophic and upwelling regions additionally images of selected bulk sinking particles not subject to sequential filtration were directly taken by scanning electron microscopy sem to determine the size distribution of sinking particles within the trap collected 234 th pool in the upwelling area the 1 10 and 10 50 m fractions had on average the highest amounts of 234 th while poc did not show significant variations among the different size fractions in the oligotrophic region the 10 50 and 1 10 m fractions had on average the highest amounts of 234 th while the 150 and 10 50 m had elevated shares of poc results thus demonstrate that 234 th was mainly carried by the smaller 234 th flux can be a major fraction of the total sinking flux of this isotope and thus particles smaller than 50 m cannot be ignored because the poc 234 th ratio that is often used is that of large 50 m particles obtained from pump systems not traps

foraminifera from the aalenian and the bajocian gssp middle jurassic of murtinheira section cabo mondego west portugal biostratigraphy and paleoenvironmental implications the detailed study of benthic foraminifera in 28 samples from late toarcian aalenian early bajocian hemipelagic sediments of the murtinheira section cabo mondego lusitanian basin west portugal has permitted the recognition of the assemblage composition and the analysis of their evolution throughout this time interval the representatives of the suborder lagenina dominate all the assemblages and in the majority of them the most abundant species is lenticulina munsteri the late toarcian and early aalenian assemblages are very similar from the comptum subzone a gradual replacement of the early jurassic forms by characteristic middle jurassic taxa takes place during the late aalenian early bajocian interval a significant number of last occurrences los of taxa are recorded the assemblages composition the estimation of the relative taxa abundances and the data obtained from the calculation of several diversity indexes together with the previous sedimentological and paleontological works in this area indicate that these assemblages were developed in a shelfal basin environment this platform showed normal marine salinity values good oxygenation and was always located above calcite compensation depth ccd however the environmental conditions were not always the best for the development of rich and diverse foraminiferal assemblages these conditions were probably unstable during the late toarcian aalensis subzone early aalenian lower part of the comptum subzone from the comptum subzone to the lower part of the limitatum subzone late aalenian conditions were more stable and more favourable for the development of foraminiferal communities however in the aalenian bajocian transition the environmental conditions changed again and affected the development of this group in the limitatum subzone a decrease in the diversity of the assemblages was recorded this fact seems to be related to a global perturbation in the carbon cycle that could have affected the foraminifera together with other marine and continental organism groups

planktic foraminifera from the mid cretaceous barremian early albian of the north sea basin palaeoecological and palaeoceanographic implications abstract a marine cretaceous succession barremian albian of a cored borehole bgs 81 40 located in the central north sea basin has been examined with respect to its planktic and benthic foraminiferal content as well as for calcareous nannofossils the distribution patterns of foraminifera and calcareous nannofossils allow for a two fold division of the investigated interval 1 the barremian earliest aptian interval which reflects a marine temporary restricted setting this is indicated by sporadic occurrences of planktic foraminifera with very rare planispiral forms suggesting short term connections of the boreal and tethyan realms the benthic foraminiferal assemblages indicate aerobic sometimes dysaerobic bottom water conditions high abundances of nannoconids in the barremian suggest enhanced stratification and or warm oligotrophic surface water 2 the late aptian early albian interval which was characterised by an open oceanic environment with cool and aerobic surface water conditions planktic foraminifera are more abundant and diverse than in the lower interval trochospiral hedbergellids dominate the foraminiferal assemblages the episodic occurrences of planispiral clavate and trochospiral flattened planktic morphotypes indicate the existence of a seaway between the boreal and the tethyan realms aerobic to dysaerobic bottom water conditions are suggested by the composition of the benthic foraminiferal assemblages high abundances of cool water taxa within the calcareous nannofossil assemblages indicate a cooling trend across the latest aptian and earliest albian

a theory for the surface atlantic response to thermohaline variability abstract the response of the upper warm limb of the thermohaline circulation in the north atlantic to a rapid change in deep water formation at high latitudes is investigated using a reduced gravity ocean model changes in deep water formation rate initiate kelvin waves that propagate along the western boundary to the equator on a timescale of months the response in the north atlantic is therefore rapid the southern hemisphere response is much slower limited by a mechanism here termed the ldquo uatorial buffer since to leading order the flow is in geostrophic balance the pressure anomaly decreases in magnitude as the kelvin wave moves equatorward where the coriolis parameter is lower together with the lack of sustained pressure gradients along the eastern boundary this limits the size of the pressure field response in the southern hemisphere interior adjustment is by the westward propagation of rossby waves but only a small fraction of the change in thermohaline circulation strength is commun

progress on the formation dynamics of the layered circulation in the south china sea abstract in the south china sea scs an alternating cyclonic anticyclonic cyclonic cac circulation is recognized in the upper middle deep layers based on the principle of stokes theorem the cac circulation is driven extrinsically by the east asia monsoonal winds a vertical sandwich like inflow outflow inflow through luzon strait ls and intrinsically by the slope current topography interaction the understandings on the formation mechanisms of cac circulation have been achieved based on different principles and the physically solid interpretation on the cac circulation need to be further clarified in this paper we review different dynamic perspectives from recent researches that describe the combined effects of surface wind forcing lateral external forcing and the intrinsic coupling among different layers our aim is to obtain a consistent understanding of the dynamics of the circulation in the scs the cac circulation forms largely from the planetary vorticity flux that is extrinsically induced by the inflow outflow inflow through ls which is predominantly balanced by the interaction between the cac flow and bottom topography inside basin the vertical motion dynamically links the circulation in three layers and its spatial pattern has a strong impact on the basin circulation particularly in the middle and deep layers vertical coupling of the layers occurs mainly over the slope because of the cross slope motion due to interaction between strong slope current and topography the internal layered circulation and intensified mixing in turn affect and maintain the layered current structure in ls based on the review of the forcing mechanisms we offer perspectives for further investigations

the late cretaceous early paleocene palaeobathymetric trends in the southwestern barents sea palaeoenvironmental implications of benthic foraminiferal assemblage analysis the late cretaceous foraminiferal assemblages from five wells drilled in the southwestern barents sea were analysed using morphogroup analysis in order to understand the palaeoenvironment and palaeobathymetry of the study area morphogroup analysis of assemblages in the upper cretaceous kveite formation suggests stable possibly middle to lower bathyal mesotrophic and relatively well oxygenated environments in the tromso basin during the late cretaceous the depositional setting of upper cretaceous kviting formation in the tectonically more stable hammerfest basin was probably shallower but still represents a deep water environment similar to that of the kveite formation a shallowing regional bathymetry in the southwestern barents sea is indicated by the general decreasing trend in the relative abundance of tubular forms and the species diversity of assemblages which reflects the regional late cretaceous paleocene uplift prior to the break up of the greenland norwegian sea changes in the relative abundance of morphogroups and in the main constituent in the cumulative length of tubular taxa from rhizammina to rhabdammina near the top of kveite formation agree with the possible existence of bottom water currents c 2011 elsevier b v all rights reserved