factors influencing recent benthic foraminifera distribution on the guadiana shelf southwestern iberia abstract benthic foraminiferal assemblages in 24 sediment surface samples collected at water depths ranging from 9 to 103 m on the continental shelf off guadiana river were analysed leading to the identification of a total of 270 species cluster analyses performed on species with a relative abundance higher than 5 led to the identification of four assemblages the shallowest assemblage down to 12 m water depth is represented by ammonia beccarii asterigerinata mamila eggerelloides scaber mississipina concentrica planorbulina mediterranensis elphidium crispum and quinqueloculina laevigata a second assemblage between 12 and 40 m water depth is characterised by bulimina elongata cribrononion gerthi and nonion fabum the assemblage between 40 and 95 m water depth is characterised by bolivina dilatata epistominella vitrea bulimina aculeata bolivina ordinaria spiroloxostoma croarae and nonionella iridea finally below a depth of 95 m on the upper outer shelf an assemblage exists characterised by brizalina spathulata bulimina marginata cassidulina minuta brizalina subaenariensis cassidulina laevigata and uvigerina peregrina the spatial distribution of assemblages is closely associated with sea bottom sedimentary environments and bathymetry the number of benthic foraminiferal tests and the distribution of several nearshore species within the two shallowest assemblages are clearly influenced by the outflow of the guadiana estuary and by local hydrodynamic conditions the deeper water assemblages on the other hand were found to be more related to low levels of tidal energy low oxygen environments associated to fine grained sediments and cold water filaments related to seasonal upwelling

distribution of recent benthic foraminifera on the sunda shelf south china sea in this study we investigate the species composition and spatial distribution patterns of rose bengal stained and unstained benthic foraminifera from the central part of the sunda shelf in the south western south china sea in relation to environmental factors the uppermost centimetre of the surface sediments 150 mu m from 45 sites from inner 60 m to outer shelf 226 m water depths revealed 584 species including 443 stained species the univariate analyses of individual species abundances and community parameters and next canonical correspondence analysis were used to relate the faunal data to a set of measured environmental parameters four biofacies recognised on the sunda shelf are most strongly correlated to water depth primary production and sediment type of the habitat the inner shelf biofacies cca cluster a defined by ammomassilina alveoliniformis and asterorotalia pulchella occurs in fine grained sediments classified as modem terrigenous mud in the region with the highest primary production values the high energy inner shelf biofacies cca cluster b defined by heterolepa dutemplei and textularia lythostrota occurs in modem terrigenous sand and silt dominated sediments northeast from the natuna island the high energy outer shelf biofacies cca cluster c defined by cibicidoides pachyderma and textularia bocki is sandwiched between assemblages of biofacies d it occurs in the region characterised by neritic relict sand in the shallow waters on the sunda shelf the relationship of benthic foraminiferal faunal composition to grain size of sediments indirectly signals the prevailing bottom hydrodynamic conditions the dominance of the epibenthic foraminifera attached to bigger particles e g cibicides lobatulus planulina arimiensis and much higher abundances of empty tests suggest greater current velocities northeast of natuna island the outer shelf biofacies cca cluster d is defined by facetocochlea pulchra and bulimina marginata it occurs in an area covered with modem terrigenous silt and mud and is characterised by lower annual primary production but seasonally influenced by weak upwelling c 2006 elsevier b v all rights reserved

biofaciological zonation of benthic foraminifera of the continental shelf of campos basin se brazil data on the microbiofaciological zonation of benthic foraminifera were obtained from 82 sub samples from the subsurface sediments of the continental shelf of campos basin in southeastern brazil the abundance and distribution of the 93 species identified during the study were related to depth and temperature of the water as well as to sediment grain size four biofacies were established biofacies i represented by the sandier coastal sediments and dominated by pseudononion atlanticum and miliolids biofacies ii associated with carbonated substrates and represented by amphistegina lessonii and miliolids biofacies iii represented by mini cores a2 where bulimina marginata is predominant in all the samples and biofacies iv associated with the muddy substrates of the outer continental shelf dominated by b marginata discorbis orbicularis and globocassidulina subglobosa in general the miliolids were more abundant in sandy sediments except a2 while the bolivinids and buliminids predominated in the sediments with a silt fraction which were normally associated with higher levels of organic matter the highest species diversity and equitability and lowest dominance indices were recorded in the sandy sediments whereas the silty sediments were characterized by a predominance of opportunists such as bolivina spp and bulimina spp species that were abundant in one stratum of a mini core tended to be abundant throughout the core indicating stable conditions over long periods which guaranteed the settlement of these species 2014 elsevier ltd and inqua

acetate cycling in the water column and surface sediment of long island sound following a bloom a number of workers have suggested that rates of acetate cycling in sediments may approximate the rates of anaerobic decomposition of organic matter however few studies have examined whether this relationship holds over very short time scales such as those encountered during the deposition of the spring bloom into coastal sediments in this study we measured acetate concentrations and uptake rate constants in surface and bottom waters and in the top few centimeters of sediment in long island sound samples were collected every 2 3 weeks from early spring to early summer of 1993 acetate concentrations varied from 85 to 530 nm in the water column and from 2 to 29 8 fm in pore water acetate concentrations in pore water showed a strong depth variation with a concentration maximum in the surface few millimeters as well as a strong temporal variation the concentration of acetate averaged over the top 4 cm varied from about 5 pm in the early spring to 14 3 pm following the addition of spring bloom dcrivcd organic carbon acetate uptake rate constants in the water column varied from 0 0012 to 0 037 h l turnover time 33 4 to 1 13 d the avcragc uptake rate constants in the sediment over the top 4 cm varied from 0 07 to 0 59 h l turnover time 0 59 to 0 07 d and tended to increase over the course of the experiment in both the sediment and the water column in the water column acetate uptake rates calculated as rate constant times concentration varied from less than one nanomolc per liter per hour in the early spring to tens of nanomoles per liter per hour in the early summer in the sediment over the same period acetate uptake rates averaged over the top 4 cm varied from 0 13 to 5 25 pm i h i rates of acetate metabolism to co agreed within a factor of two to cstimatcs of the x0 flux from the sediments and both increased sharply following the deposition of the spring bloom however because temperatures were also increasing during this period we are unable to separate unambiguously the effects of supply of labile carbon and of temperature on the acetate uptake rate

ne atlantic benthic foraminifera modern distribution patterns and palaeoecological significance microfaunal evidence is presented from a region in the ne atlantic ocean characterized by well constrained and very uniform physiochemical water mass properties but a significant gradient in surface ocean productivity notable changes in the species composition of benthic foraminiferal assemblages can be directly related to surface productivity and particulate organic matter supply to the deep ocean floor because of the labile nature of much organic matter as it reaches the sea floor it is argued that benthic foraminifera which exhibit a high preservation potential in most marine sediments provide a better proxy for estimating past fluxes than bulk sediment organic carbon oc content three distinct assemblage groups are recognized a cassidulina laevigata group which is dominated by infaunal species and a relatively high sediment oc content a rhizammina spp group which is also dominated by infaunal species and an epistominella exigua group dominated by epifaunal taxa and falling sediment oc content significant faunal assemblage changes appear to be independent of grain size

upper quaternary deposits on the sao tome deep sea channel levee system south brazilian basin major turbidite versus contourite processes abstract this paper is an attempt to show how one may discriminate turbiditic and contouritic processes in the deposition of deep sea accumulations the case study is the sao tome deep sea channel levee system in the south brazilian basin this system is elongated parallel to the margin contour and was first interpreted as being controlled by contour current activity detailed analyses of 3 5 khz profiles and piston cores allowed to demonstrate that the upper quaternary sediments are predominantly deposited by turbidite and hemipelagic pelagic sedimentation processes on the levee and the transitional area towards the deeper rise frequent fine grained turbidites accounting for 25 45 of the entire depositional series are interbedded with the hemipelagic pelagic muds in the channel thicker and coarser turbidites 15 are associated with debris flows 20 deposit deformation in the form of slides slumps and diapir like structures largely affect the distal transitional area slight evidence of contour current activity only consists of some sediment wave fields and manganiferous rich layers or some top truncated sequences and foraminiferal sandy layers

association of bathyal foraminifera with water masses in the northwestern gulf of mexico abstract q mode cluster analysis and r mode factor analysis of benthic foraminiferal data from 120 core tops from the northwestern gulf of mexico 87 1361 m 26 4 29 0 n 88 5 96 4 w distinguish separate thanatotopes and faunal assemblages related to the five water masses present within the depth range of the samples these water masses are the surface mixed layer sml gulf water gw oxygen minimum water omw subantarctic intermediate water saiw and caribbean midwater cmw reussella atlantica bigenerina irregularis and angulogenerina bella are particularly associated with sml bulimina spicata planulina foveolata and cibicidoides umbonatus with gw sphaeroidina bulloides bulimina mexicana and siphonina bradyana with omw epistominella exigua with saiw and gyroidinoides laevis cibicides wuellerstorfi pullenia subsphaerica bulimina aculeata gyroidinoides polius and laticarinina pauperata with cmw cluster analysis also indicates the presence of three faunal groups related to water depth and bottom water oxygen content within the omw assemblage an additional assemblage recognized in the mississippi river delta area may be related to low oxygen conditions above the normal depth for the oxygen minimum the close correspondence between the results of cluster and factor analyses suggests that similar numerical analyses of fossil data should be useful in deciphering ancient bathyal assemblages influenced by water mass properties

deep sea faunal provinces and their inferred environments in the indian ocean based on distribution of recent benthic foraminifera abstract multivariate analysis was performed on percentages of 46 species of unstained deep sea benthic foraminifera from 131 core top to near core top samples 322 5013 m from across the indian ocean faunal data are combined with geosecs geochemical data to investigate any relationship between benthic foraminifera assemblages and species and deep sea properties in general benthic foraminifera show a good correlation to surface productivity organic carbon flux to the sea floor deep sea oxygenation and to a lesser extent to bottom temperature without correlation with the water depths the foraminiferal census data combined with geochemical data has enabled the division of the indian ocean into two faunal provinces province a occupies the northwestern indian ocean arabian sea region where surface primary production has a major maximum during the summer monsoon season and a secondary maximum during winter monsoon season that leads to high organic flux to the seafloor making the deep sea one of the most oxygen deficient regions in the world ocean with a pronounced oxygen minimum zone omz this province is dominated by benthic foraminifera characteristic of low oxygen and high organic food flux including uvigerina peregrina robulus nicobarensis bolivinita pseudopunctata bolivinita sp bulimina aculeata bulimina alazanensis ehrenbergina carinata and cassidulina carinata province b covers southern southeastern and eastern parts of the indian ocean and is dominated by nuttallides umbonifera epistominella exigua globocassidulina subglobosa uvigerina proboscidea cibicides wuellerstorfi cassidulina laevigata pullenia bulloides pullenia osloensis pyrgo murrhina oridorsalis umbonatus gyroidinoides gyroidina soldanii and gyroidinoides cf gemma suggesting well oxygenated cold deep water with low oligotrophic and pulsed food supply

impact of interrelated and interdependent ecological controls on benthic foraminifera an example from the gulf of guinea living and dead benthic foraminiferal assemblages from two size fractions 63 250 m and 250 m were studied at 128 stations from the shelves down to abyssal plains of the gulf of guinea in the eastern equatorial atlantic the sample size ranged between 300 and 400 cm2 of the sediment water interface with a penetration depth of 1 cm environmental parameters were quantified for sediment composition food webs bottom water oxygen concentrations and benthic oxygen respiration seven major station groupings named g1 g7 are subdivided by factor analysis the three most abundant species therein are discussed with respect to their ecological requirements for both size classes and for living and dead counts for 49 living species the range of environmental gradients is established and for five species live observations are reported five station groupings can be attributed toward stepwise ranges scaled by bathymetry and flux rates of organic carbon g4 27 75 m g5 68 269 m g6 250 740 m g2 674 2007 m g1 1475 4970 m two geographically restricted station groupings locally interfinger with other groupings in the upper bathyal and abyssal water depths g7 82 451 m g3 1002 4658 m g7 shows lowered oxygen concentrations and benthic oxygen respirations whereas hemipelagic sediments are typical of g3 the interfingering of g7 and g3 however is not purely a result of the increasing number of species most perfectly adapted to these environments but rather that these groupings are structured by the decrease of species with lower tolerance towards environmental perturbation in fact the more common species have an environmental range much broader than the environmental frame of the groupings they dominate this observation holds for all size classes and for live and dead counts we conclude that species specific preferences and thresholds provide a more valuable and more consistent tool in environmental research than the environmental ranges observed for assemblages

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

differential rates of benthic foraminiferal test production in surface and subsurface sediment habitats in the southern adriatic sea abstract live communities and corresponding dead assemblages of benthic foraminifera recovered in box cores from the southern adriatic sea differ significantly with respect to the relative abundances of species and higher order groups of foraminifera taphonomic destruction of disintegration prone arenaceous species is held responsible for the observed strong reduction in relative abundance of arenaceous foraminifera in the dead assemblage systematic differences in live and dead relative abundances of calcareous and calcite cemented arenaceous species may be due to differential rates of test production rather than selective taphonomic destruction we observed that epifaunal or shallow infaunal foraminifera are often overrepresented in the dead assemblage compared to their relative number in the live community whereas deeper infaunal species tend to be underrepresented on this basis we hypothesize that test production rate of benthic foraminiferal species may be related to their living depth in the sediment

post lgm sedimentation on the outer shelf upper slope of the northernmost part of the sao paulo bight southeastern brazil abstract sedimentary and isotope data as well as 14 c ams dating on 15 box cores were used to identify the main post last glacial maximum lgm processes in the outer shelf and upper slope of the northernmost part of the sao paulo bight southeastern brazil results show slight but significant variations in calcium carbonate total sulphur and nitrogen contents as well as carbon and oxygen isotope ratios sedimentation rates varying from 5 to 184 mm kyr 1 are controlled by the shelf and upper slope morphology the brazil current meander dynamics and the coastal water offshore motion

trophic control of benthic foraminiferal abundance and microhabitat in the bathyal gulf of lions western mediterranean sea surface sediment was sampled at two bathyal sites in the southwestern gulf of lions in the western mediterranean sea in february and august 1997 to study the distribution and microhabitat of living rose bengal stained deep sea benthic foraminifera both standing stock and diversity of the faunas and the microhabitat of distinct species mirror the trophic situation and the depth of the oxidised layer at the different sites our results suggest that the faunas do not comprise highly opportunistic species and are adapted to rather stable environments in the axial channel of the lacaze duthiers canyon organic matter fluxes are enhanced due to advective transport of organic matter resulting in elevated oxygen consumption rates in the surface sediment and a rather thin oxidised layer the corresponding benthic foraminiferal fauna is characterised by rather high standing stock and diversity and a well developed deep infauna in addition to freshly deposited phytodetritus more degraded organic matter seems to be an important food source in contrast at the open slope organic matter fluxes and oxygen consumption rates in the surface sediment are lower and the oxidised layer is much thicker than inside the canyon the corresponding benthic foraminiferal fauna comprises mainly epifaunal and shallow infaunal species with much lower standing stocks and clear differences between february and august in august standing stocks are higher and the average living depths of most species shift towards the sediment surface these differences can be attributed to patchiness or represent a seasonal trophic signal

marine sediments from southeastern brazilian continental shelf a 1200 year record of upwelling productivity abstract a sediment core from the cabo frio coastal shelf 23 19 s 41 8 w 117 m depth was analyzed for toc c n ratio organic petrography and planktonic foraminiferal content to evaluate variations in local productivity caused by changes in upwelling intensity and its relation to regional and global climatic variations during the last millennium the cabo frio core recorded the last 1200 years of sedimentation with rates varying from 0 11 to 0 32 mm yr 1 foraminiferal and organic geochemical analyses indicate the occurrence of three distinct periods of productivity from 850 ad until 1070 ad foraminifera fluxes consisting primarily of turborotalita quinqueloba indicate stronger south atlantic central water sacw transport onto the shelf which induced high biological productivity that was also recorded by high toc and marine palynomorphs content and a low c n atomic ratio this period coincided with a northward displacement of the atmospheric intertropical convergence zone itcz and south atlantic high sah systems driven by positive temperature anomalies in the north atlantic ocean during the medieval climate anomaly mca from 1070 until 1500 ad low toc flux and planktonic foraminifera fluxes and high c n atomic ratios suggest a reduction in marine productivity probably driven by reduced transport of sacw associated with the southward displacement of the sah and weakening of northeasterly winds the period between 1500 and 1830 ad which corresponds to the little ice age is marked by increased fluxes of planktonic foraminifera principally of globigerina bulloides and globigerinita glutinata these species mark an increase in productivity linked to sacw upwelling supported by the enhancement of northeasterly winds and southward displacement of the itcz and sah

benthic foraminifera off west africa 1 n to 32 s do live assemblages from the topmost sediment reliably record environmental variability abstract recent benthic foraminifera 125 m were investigated from multicorer samples on a latitudinal transect of 20 stations between 1 n and 32 s along the upper slope off west africa samples were selected from a narrow water depth interval between 1200 and 1500 m so that changes in water masses are minimized but changes in surface productivity are important and the only significant environmental variable live rose bengal stained benthic foraminifera were counted from the surface sediment down to a maximum of 12 cm dead foraminifera were investigated in the top 5 cm of the sediment only five live and five dead benthic foraminiferal assemblages were identified using q mode principal component analysis matching distinct primary productivity provinces characterized by different systems of seasonal and permanent upwelling differences in seasonality quantity and quality of food supply are the main controlling parameters on species composition and distribution of the benthic foraminiferal faunas to test the sensitivity of foraminiferal studies based on the uppermost centimeter of sediment only a comparative q mode principal component analysis was conducted on live and dead foraminiferal data from the top 1 cm of sediment it has been demonstrated that on the upper slope off west africa most of the environmental signals as recorded by species composition and distribution of the total live and dead assemblages i e including live and dead foraminifera from the surface sediment down to 12 cm and 5 cm respectively can be extracted from the assemblages in the top centimeter of sediment only on the contrary subsurface abundance maxima of live foraminifera and dissolution of empty tests strongly bias quantitative approaches based on the calculation of standing stocks and foraminiferal numbers in the topmost centimeter

living benthic foraminifera of the okhotsk sea faunal composition standing stocks and microhabitats live rose bengal stained benthic foraminifera were investigated in surface sediment samples from the okhotsk sea to reveal the relationship between faunal characteristics and environmental parameters live benthic foraminifera were quantified in the size fraction 125 m in the upper 8 cm of replicate sediment cores recovered with a multicorer at five stations along the sakhalin margin and at three stations on the southwestern kamchatka slope the stations are from water depths between 625 to 1752 m located close or within the present okhotsk sea oxygen minimum zone with oxygen levels between 0 3 and 1 5 ml l 1 at the high productivity and ice free kamchatka stations live benthic foraminifera are characterized by maximal standing stocks about 1700 3700 individuals per 50 cm2 strong dominance of calcareous species up to 87 91 of total live faunas and maximal habitat depths down to 5 2 6 7 cm depth vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments at the sakhalin stations which are seasonally ice covered and less productive live benthic foraminifera show lower standing stocks about 200 1100 individuals per 50 cm2 lower abundance of calcareous species 10 64 of total live faunas and shallower habitat depths down to 2 5 5 4 cm depth faunal vertical distributions are characterized by maximum in the uppermost surface sediments it is suggested that 1 lower and strongly seasonal organic matter flux caused by the seasonal sea ice cover and seasonal upwelling 2 lower bottom water oxygenation 0 3 1 1 ml l 1 and 3 more pronounced influence of carbonate undersaturated bottom water along the sakhalin margin are the main factors responsible for the observed faunal differences according to species downcore distributions and average living depths common calcareous species were identified as preferentially shallow intermediate and deep infaunal foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments

paleoproductivity changes during the holocene in the inner shelf of cabo frio southeastern brazilian continental margin benthic foraminifera and sedimentological proxies abstract sedimentological and benthic foraminifera analyses carried out on a core length 4 15 m collected at 22 56 31 s and 41 58 48 w at a water depth of 43 m sampled from the inner shelf of cabo frio southeastern brazilian continental margin allowed identification of different hydrodynamic and productivity regimes related to sea level fluctuations and or climatic changes during the last 9 4 ka cal bp prior to 7 0 ka cal bp a less intense hydrodynamic and lower productivity regime occurred at lower sea levels and under drier climatic conditions between 7 0 and 5 0 ka cal bp relatively stronger local oceanic circulation and relatively high productivity were observed in a scenario of rising sea levels and more humid conditions from 5 0 to 3 0 ka cal bp bottom currents weakened and input of nutrients increased with productivity levels similar to the previous phase at lower sea level and in a drier climate from 3 0 ka cal bp up to the present stronger hydrodynamic conditions and a higher productivity regime are linked to the establishment of the upwelling process in cabo frio from 2 5 ka cal bp to the present upwelling enhancement has been recognized resulting from the combined action of ne winds and the intensification of the meandering pattern of the brazil current bc

development of accretionary orogens preface abstract this special issue celebrates the career of cees van staal an icon of appalachian geology who retired from the geological survey of canada in 2017 the issue is an outcome of the symposium entitled development of accretionary orogens a symposium celebrating the career of cees van staal that was held in cees s honour at the 2017 geological association of canada mineralogical association of canada gac mac meeting in kingston ontario the papers in this special issue simultaneously demonstrate recent advances in the understanding of accretionary orogens cees s influence on this understanding as well new data and concepts concerning their development in keeping with the global reach of cees s research this vsi is a contribution to the international geological correlation program 648 supercontinent cycles and global geodynamics

mid lower bathyal benthic foraminifera of the campos basin southeastern brazilian margin biotopes and controlling ecological factors abstract the benthic foraminiferal assemblages recovered from 41 surface sediment samples of the campos basin southeastern brazilian continental margin were analyzed in order to understand their distribution patterns and ecological preferences living and dead specimens of benthic foraminifera were selected for identification and quantitative analysis from the 63 to 125 m the 125 m and the combined 63 m size fractions q mode cluster and canonical correspondence analyses for all size fractions show the dissimilarity between the samples collected on the middle slope group 1 750 to 1050 m water depth and those collected on the lower slope group 2 1350 to 1950 m water depth food supply energy state stability at the benthic pelagic boundary and the grain size of the substrate seem to be the most important environmental factors determining the distribution pattern of the benthic foraminiferal assemblages in the deep sea the middle slope between 750 and 1050 m water depth is characterized by the dominance of different species of the genus bolivina cassidulina laevigata and globocassidulina subglobosa the occurrence of these species in association with cibicidoides kullenbergi epistominella exigua and uvigerina proboscidea seems to be related to seasonal organic matter fluxes relatively oxic bottom waters strong bottom currents and sandy sediments the lower slope between 1650 and 1950 m water depth is inhabited by a microfauna with different characteristics composed of preferentially epifaunal or shallow infaunal deposit feeding species e g bolivina spp eponides weddellensis lenticulina cultrata and suspension feeders that are adapted to oligotrophic conditions and high dissolved oxygen levels in the bottom waters e g rhabdammina spp rhizammina sp

benthic foraminifera as proxies of organic matter flux and bottom water oxygenation a case history from the northern arabian sea abstract benthic foraminifera have been quantified in two sediment cores from a topographic high murray ridge in the northern arabian sea one core is from a station within the present day oxygen minimum zone omz the other from a station below the omz changes in the intensity of the omz linked to monsoonal climate variability had a strong impact on benthic foraminiferal composition and accumulation rates at the shallower omz station 920 m an intensification of the omz resulted in lower diversities and high dominances of low oxygen tolerant species the deeper station 1470 m was far less affected though at least once during the last 225 000 years the benthic faunal composition and accumulation rates show evidence for a deepening of the base of the omz to a level close to or even below 1470 m we suggest that percentages of miliolids can be used for rapid reconstruction of periods of increased ventilation in the northern arabian sea and are a promising proxy for tracing changes in bottom and pore water oxygenation in general omz conditions are characterised by high abundances of deep infaunal species and increased burial efficiency of organic matter the proportion of deep infaunal species appears to be a measure for the anoxic burial efficiency of organic matter and not a direct measure for the arriving flux at the seabed results furthermore show that benthic foraminiferal accumulation rates cannot be used as a proxy for surface water productivity under the prevalence of severe dysoxia