Carbon and oxygen isotope geochemistry of live (stained) benthic foraminifera from the Aleutian Margin and the Southern Australian Margin

Comparisons of ambient bottom-water geochemistry and stable isotopic values of the tests of living (stained) calcareous benthic foraminifera from the North Pacific (on the Aleutian Margin, water depth 1988 m) and Murray Canyons group in the Southern Indian Ocean (Australian Margin, water depths 2476 m and 1634 m) provide modern environmental analogs to calibrate paleoenvironmental assessments. Consistent with the hypothesis that microhabitat preferences influence foraminiferal isotopic values, benthic foraminifera from both margins were depleted in ¹³C with respect to bottom-water dissolved inorganic carbon (DIC). The carbon isotope values of deep infaunal foraminifera (Chilostomella oolina, Globobulimina pacifica) showed greater differences from estimates of those of DIC than shallow benthic foraminifera (Bulimina mexicana, Bolivinita quadrilatera, Pullenia bulloides). This study provides new isotopic and ecological information for B. quadrilatera. The mean Δδ¹³C value, defined as foraminiferal δ¹³C values minus estimated ambient δ¹³C values from the Aleutian Margin, is 0.97‰ higher for G. pacifica than the mean from the Murray Canyon. This difference may result either from genetic or biological differences between the populations or from differences in environmental isotopic influences (such as pore water differences) that were not accounted for in the equilibrium calculations. These analyses provide calibration information for the evaluation of bottom water conditions and circulation patterns of ancient oceans based on fossil foraminiferal geochemistry.     

Spatial Patterns in the Distribution,Diversity and Abundance of Benthic Foraminifera around Moorea (Society Archipelago,French Polynesia)

Coral reefs are now subject to global threats and influences from numerous anthropogenic sources. Foraminifera, a group of unicellular shelled organisms, are excellent indicators of water quality and reef health. Thus we studied a set of samples taken in 1992 to provide a foraminiferal baseline for future studies of environmental change. Our study provides the first island-wide analysis of shallow benthic foraminifera from around Moorea (Society Archipelago). We analyzed the composition, species richness, patterns of distribution and abundance of unstained foraminiferal assemblages from bays, fringing reefs, nearshore and back- and fore-reef environments. A total of 380 taxa of foraminifera were recorded, a number that almost doubles previous species counts. Spatial patterns of foraminiferal assemblages are characterized by numerical abundances of individual taxa, cluster groups and gradients of species richness, as documented by cluster, Fisher α, ternary plot and Principal Component Analyses (PCA). The inner bay inlets are dominated by stress-tolerant, mostly thin-shelled taxa of Bolivina, Bolivinella, Nonionoides, Elongobula, and Ammonia preferring low-oxygen and/or nutrient-rich habitats influenced by coastal factors such as fresh-water runoff and overhanging mangroves. The larger symbiont-bearing foraminifera (Borelis, Amphistegina, Heterostegina, Peneroplis) generally live in the oligotrophic, well-lit back- and fore-reef environments. Amphisteginids and peneroplids were among the few taxa found in the bay environments, probably due to their preferences for phytal substrates and tolerance to moderate levels of eutrophication. The fringing reef environments along the outer bay are characterized by Borelis schlumbergeri, Heterostegina depressa, Textularia spp. and various miliolids which represent a hotspot of diversity within the complex reef-lagoon system of Moorea. The high foraminiferal Fisher α and species richness diversity in outer bay fringing reefs is consistent with the disturbance-mosaic (microhabitat heterogeneity) hypothesis.Calculations of the FORAM Index (FI), a single metric index to assess reef vitality, indicate that all fore- and most back-reef environments support active carbonate accretion and provide habitat suitability for carbonate producers dependent on algal symbiosis. Lowest suitability values were recorded within the innermost bays, an area where natural and increasing anthropogenic influences continue to impact the reefs. The presence of habitat specific assemblages and numerical abundance values of individual taxa show that benthic foraminifera are excellent recorders of environmental perturbations and good indicators useful in modern and ancient ecological and environmental studies.     

New insights into the pattern,timing, and duration of the evolutionary origin of the foraminiferal genus Hantkenina

A high-resolution study of the Tethyan Contessa Highway reference section (Gubbio, Italy) has produced a detailed, well-constrained and more complete pattern of the gradual evolutionary origin of the foraminiferal genus Hantkenina from Clavigerinella than hitherto shown. A nine-stage pattern is presented for this evolutionary lineage. The related time frame and duration are assessed using the astronomical calibration of the Contessa Highway record. The evolution of Clavigerinella caucasica to Hantkenina gohrbandti, the real ancestor of Hantkenina, leads in 333 kyr. The H. gohrbandti first appearance is dated at 45.564 Ma. Our findings show that during the middle Eocene, from 46 to 45.5 Ma and with a major pulse centered at 45.521 Ma deep-mesopelagic planktonic foraminifera may have developed different morphological modifications to tolerate temporary exceptionally stressful environmental conditions. These conditions are principally related to poorly oxygenated and usually food-poor waters. This suggests that sustained and expanded oxygen minimum zone conditions and associated enhanced eutrophication might have occurred during that time.     

Magnesium and strontium compositions of recent symbiont-bearing benthic foraminifera

Minor and trace elements in foraminiferal carbonates are potential paleo-proxies of climate, nutrient and seawater composition. There are very few reports of trace element composition of symbiont-bearing, larger foraminifera that are known to be important constituents of shallow-marine, modern and ancient carbonates. In this paper we examine the range of variation in Mg and Sr content of Recent species of these foraminifera from a lagoon of Lakshadweep Atoll (Indian Ocean) and Akajima Islands, Japan. Two hyaline species, Amphistegina lessonii and Neorotalia calcar,and two porcellaneous species, Amphisorus hemprichii and Marginopora vertebralis were collected live from Lakshadweep islands. Mg / Ca in these foraminifera is of an order of magnitude higher than the values reported for planktonic and symbiont-free benthic foraminifera. The Sr / Ca values are, however, comparable with the reported values in other foraminiferal taxa and they are found to vary within a narrow range. Electron-probe micro-analysis of three symbiont-bearing benthic species indicates spatial heterogeneity of high orders in Mg / Ca composition in all the species. The annual variation in temperature and pH of the lagoon water cannot explain the observed amplitude of the compositional variation. The photosynthesis and respiration of the symbionts and host foraminifera are possibly the major cause of compositional heterogeneity in individual tests, as has also been recently postulated for symbiont-bearing planktonic foraminiferal species. It highlights the need to isolate biological factors and necessitates species-specific paleotemperature scale in paleoclimatic analysis. We also analyzed δ¹⁸O, δ¹³C, Ca, Mg and Sr in carefully dissected chambers of a reef-dwelling, porcellaneous benthic foraminifer, Marginopora kudakajimaensis, collected live in four seasons. A moderate positive correlation is observed between Mg / Ca and temperature. However, large inter- and intra-test variation in Mg limits the precision of Mg / Ca as palaeotemperature proxy. The Sr / Ca of the test calcite is unrelated to temperature of the sea water. The δ¹³C of M. kudakajimaensis does not correlate with δ¹⁸O, Mg / Ca or Sr / Ca.     

Molecular Phylogeny and Morphology of Leannia veloxifera n. gen. et sp. Unveils a New Lineage of Monothalamous Foraminifera

Monothalamous (single‐chambered) foraminifera have long been considered as the “poor cousins” of multichambered species, which calcareous and agglutinated tests dominate in the fossil record. This view is currently changing with environmental DNA surveys showing that the monothalamids may be as diverse as hard‐shelled foraminifera. Yet, the majority of numerous molecular lineages revealed by eDNA studies remain anonymous. Here, we describe a new monothalamous species and genus isolated from the sample of sea grass collected in Gulf of Eilat (Red Sea). This new species, named Leannia veloxifera, is characterized by a tiny ovoid theca (about 50–100 μm) composed of thin organic wall, with two opposite apertures. The examined individuals are multinucleated and show very active reticulopodial movement. Phylogenetic analyses of SSU rDNA, actin, and beta‐tubulin (ß‐tubulin) show that the species represents a novel lineage branching separately from other monothalamous foraminifera. Interestingly, the SSU rDNA sequence of the new species is very similar to an environmental foraminiferal sequence from Bahamas, suggesting that the novel lineage may represent a group of shallow‐water tropical allogromiids, poorly studied until now.     

Stratigraphic distribution of shallow-water benthic foraminifera from the Lower Cretaceous Taft formation,Central Iran (Yazd Block), with evidence for the importance of hiatuses

In this contribution, two stratigraphic sections are described through the Lower Cretaceous shallow-water platform sediments (Taft formation) from the northern Tethys, which are located in the Yazd Block, Central Iran. Benthic foraminifera are used to propose a biostratigraphy for these successions. They are grouped around several assemblage zones, and several genera and species are reported from the Yazd Block basin for the first time (e.g., Arenobulimina cochleata, A. meltae, Belorusiella sp., Bolivinopsis cf. labeosa, Decussoloculina barbui, Martinotiella jucunda, Myncina bulgarica, Novalesia cornucopia, Sabaudia briacensis, Simplorbitolina manasi). Their presence can provide a better understanding for the paleogeographic reconstruction of the Tethyan seaways. Furthermore, they represent candidates as potential index fossils in the Lower Cretaceous stratigraphy of the Yazd Block. The new biostratigraphic data allow to date the Lower Cretaceous successions between the probable Valanginian and the late Aptian. Based on the absence of early Barremian indicators and also late Aptian markers, two hiatuses are recognized through the Taft formation. This formation also displays a diachrony in ages at its base and top, which suggests the effect of long-term subsidence in the Yazd Block during the Early Cretaceous, following the Cimmerian phase of orogeny.     

Heading for New Shores: Projecting Marine Distribution Ranges of Selected Larger Foraminifera

The distribution of modern symbiont-bearing larger foraminifera is confined to tropical and subtropical shallow water marine habitats and a narrow range of environmental variables (e.g. temperature). Most of today''s taxa are restricted to tropical and subtropical regions (between 30°N and 30°S) and their minimum temperature limits are governed by the 14 to 20°C isotherms. However, during times of extensive global warming (e.g., the Eocene and Miocene), larger foraminifera have been found as far north as 50°N (North America and Central Europe) as well as towards 47°S in New Zealand. During the last century, sea surface temperatures have been rising significantly. This trend is expected to continue and climate change scenarios for 2050 suggest a further increase by 1 to 3°C. We applied Species Distribution Models to assess potential distribution range changes of three taxa of larger foraminifera under current and future climate. The studied foraminifera include Archaias angulatus, Calcarina spp., and Amphistegina spp., and represent taxa with regional, superregional and global distribution patterns. Under present environmental conditions, Amphistegina spp. shows the largest potential distribution, apparently due to its temperature tolerance. Both Archaias angulatus and Calcarina spp. display potential distributions that cover currently uninhabited regions. Under climate conditions expected for the year 2050, all taxa should display latitudinal range expansions between 1 to 2.5 degrees both north- and southward. The modeled range projections suggest that some larger foraminifera may colonize biogeographic regions that so far seemed unsuitable. Archaias angulatus and Calcarina spp. also show an increase in habitat suitability within their native occurrence ranges, suggesting that their tolerance for maximum temperatures has yet not been fully exploited and that they benefit from ocean warming. Our findings suggest an increased role of larger foraminifera as carbonate producers and reef framework builders in future oceans.     

Suitable sediment fraction for paleoenvironmental reconstruction and assessment of contaminated coastal areas based on benthic foraminifera: A case study from Augusta Harbour (Eastern Sicily,Italy)

Since the 1990s several studies noticed that, along coastal marine areas, the mean size of benthic foraminifera may be reduced due to heavy metal pollution, even if no biometric studies were carried out to quantify this aspect. The Augusta harbour (Sicily, Italy), is characterized by a strong contamination due to several anthropogenic activities, the most important of which are a petrochemical pole and an important industrial harbour. Taking into account the previous studies carried out in the area, which recorded small-sized foraminifera, the present study compared assemblage composition and faunal parameters in the >125 μm and >63 μm fractions of a sediment core collected in the most polluted sector of Augusta harbour. The aim was to understand if the two fractions have comparable environmental significance providing reliable information on the environmental status. In order to quantify the amount of smaller foraminifera in a community and to determine species loss between size fractions, two new indices are used: the Foraminiferal Size Index (FSI) and the Lost Species Index (LSI). Species richness, diversity and composition of the two assemblages were determined to characterize their structure. The results highlighted great depletion and different composition of the >125 μm assemblage with respect to the >63 μm one, showing a selective loss of particular ecological groups (stress-tolerant infaunal taxa). Also the better correlation of Foraminiferal Number (FN) and H’ index of >63 μm fraction with Polychlorobiphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), Barium (Ba) and Mercury (Hg), demonstrated the higher reliability of this size fraction for environmental assessment purposes.     

Intraspecific variation in Triassic Ophthalmidiid Foraminifera from Timor

Four ophthalmidiid species are described as free specimens extracted from mudstones and wackestones of Triassic age: Atsabella bandeiraensis nov. gen. nov. sp., Karaburunia atsabensis nov. sp., Ophthalmidium sp. cf. O. primitivum Ho and Spirophthalmidium grunaui nov. sp. Analysis of morphological variation found in large suites of specimens suggests that, as in modern miliolids, apertural characteristics, chamber shape and adult test size are features that vary within narrow limits and may be used to define species. In genera with milioline coiling in the post-embryonic stage, chamber arrangement may be highly variable. Post-embryonic coiling in K. atsabensis varies from quinqueloculine to almost spiroloculine and encompasses morphotypes that, in thin-section studies, have been attributed to a number of other genera. In Timor Leste, A. bandeiraensis, K. atsabensis and S. grunaui have been found with conodonts indicative of the Carnian, but the full local stratigraphic range of these species is uncertain. K. atsabensis occurs at another locality with conodonts suggestive of the Middle Triassic or less likely Carnian. Ophthalmidium sp. cf. O. primitivum has been found at one locality associated with A. bandeiraensis and K. atsabensis in a stratigraphic succession that suggests a correlation to the Carnian or Norian. The ophthalmidiids are found commonly associated with organic-cemented agglutinated and hyaline foraminifera and at some localities common to abundant ostracods and mollusc debris. They were most common in organic-rich carbonate mud of shallow-marine environments.     

Ecosystem indicators: Foraminifera,Thecamoebians and Diatoms from the Ologe Lagoon,Nigeria

The Ologe Lagoon in southwestern Nigeria is a natural habitat located closely to both residential and industrial estates. The lagoon is heavily affected by effluents of agricultural and industrial runoff including organochlorine compounds and heavy metals (chloropesticides, DDT and polychlorinated biphenyls, cadmium, manganese, zinc, copper, lead, iron and nickel). Ologe Lagoon is situated in a semi-isolated position and its brackish waters traverse several creeks and lagoons before it reaches the Atlantic Ocean. The lagoon experiences minor tidal but noticeable salinity and pH variations during the rainy season. During the dry season, however, the waters have a comparatively long resident time where sediments act as sink and aggregate contaminants over time. Investigations on benthic foraminifera, thecamoebian and diatom species were carried out to document the current status, composition, spatial distribution, and response of microfaunal assemblages to environmental stressors within the lagoon. The benthic foraminifer assemblage is composed of four highly specialized agglutinated species of Ammotium salsum, Miliammina fusca, Ammobaculites dilatatus and Ammobaculites aff. A. exiguus. They are present at all sample sites with varying abundances. The high abundance of Ammotium salsum is considered an indication of environmental stress. Thecamoebian species of Difflugia oblonga, Difflugia proteiformis and Pontigulasia compressa were also recorded in varying proportions and generally represent less than one percent of the total foraminifera/thecamoebian assemblage. The presence of marine brackish water larger siliceous diatoms of Actinoptychus and Campylodiscus species indicates an interaction between the lagoon and the marine waters although on the minimal scale with regards to actual salinity ranges. The faunal assemblages recovered are characterized by low species richness and alpha diversity indices and are typical of shallow, marginal-marine hyposaline environments. Numerical abundances and spatial distribution patterns suggest taxon-specific habitat preferences and highlight their potential for environmental monitoring studies.     

Distribution of ostracod and benthic foraminiferal assemblages during the last 550 kyr in the East-Corsica basin,western Mediterranean Sea: A paleo-environmental reconstruction

The study of Quaternary sediments covering the last 550 kyr from the borehole GDEC-4-2, East-Corsica basin, was performed through the study of benthic meiofaunal assemblages (ostracoda and benthic foraminifera) whose distribution responds to climate changes, and glacial–interglacial variability in particular. The interglacial ostracod group is mainly composed of the Argilloecia acuminata, Cytheropteron alatum, Henryhowella sp., Polycope sp. and Cytherella sp., which indicate an enhanced surface productivity and possibly high bottom water temperature during these warm intervals. Benthic foraminifera, such as Hoeglundina elegans, Sigmoilopsis schlumbergeri, Bigenerina nodosaria and Hyalinea balthica are predominant during interglacial periods and also show an increasing surface productivity associated to warm intervals. Increase in surface productivity would contribute to an enhanced export of organic matter to sea floor at the GDEC-4-2 site during interglacial periods. The bottom temperature drop coupled with the important sedimentary inputs (associated to a significant quantity of refractory organic matter) during glacial periods was highlighted by the predominance of ostracoda, such as Paradoxostoma sp., Cytheropteron testudo, Bathycythere vanstraateni, Macrocypris sp., Echinocythereis echinata and benthic foraminifera as Bolivina spathulata, Bulimina costata, and Bulimina marginata. The distribution of some benthic foraminifera species describing a turnover system allowed the characterization of the last three climate cycles (MIS 8–9, MIS 6–7, MIS 1–5) probably marked by changes of bottom water paleoceanographic conditions in terms of temperature, salinity, bottom current intensity and surface productivity. The cyclic variations of the allochthonous group recorded over the last 550 kyr suggest a major role played by the eustatic factor, with the latter possibly favouring down slope transport. The distribution of this group allowed thus establishing a link between shelf-basin sediment transfer and climate, with enhanced shelf-basin sediment transfer during glacial low stands.     

Abyssal NE Atlantic benthic foraminifera during the last 15 kyr: Relation to variations in seasonality of productivity

Benthic foraminiferal faunas (> 63 μm) and stable isotopes from the last 15 kyr were studied in BENGAL programme (high-resolution temporal and spatial study of the BENthic biology and Geochemistry of a north-eastern Atlantic abyssal Locality) kasten core 13078#16 from the Porcupine Abyssal Plain, NE Atlantic (48°49.91 N, 16°29.94 W, water depth 4844 m). Changes occurred in the accumulation rates, species composition, diversity, and stable isotopes during the last 15 kyr. Today, the area is strongly influenced by seasonal inputs of phytodetritus following the spring blooms in surface water primary productivity. Variations in the relative abundance of the two most abundant species, Epistominella exigua and Alabaminella weddellensis, which today show significant increases in abundance with the presence of phytodetritus on the sea-floor, are interpreted as resulting from changes in the seasonality of productivity. Seasonal productivity was higher during the Holocene than during the last deglaciation and Younger Dryas, probably coinciding with the retreat of the polar front to higher latitudes. This hypothesis is consistent with simultaneous decreases in the percentage of the polar planktic foraminifera Neogloboquadrina pachyderma (s), and increases in the percentage of Globigerina bulloides, a warmer water planktic foraminifera indicative of phytoplankton blooms and enhanced productivity. The relative abundance of the ‘phytodetritus species’ (E. exigua and A. weddellensis) covary between 14.7 and 8.1 kyr, but not between 7.8 and 1.2 kyr. Major decreases in the numbers per gram and accumulation rates of planktic and benthic foraminifera occurred at ∼ 12–8.5 kyr and at ∼ 4 kyr which correspond to decreases in the % sediment coarse fraction and published data on inorganic carbon contents suggesting that dissolution may have increased at these times. Relationships between benthic foraminiferal faunas and benthic stable isotope records suggest no simple relationship between faunal abundances and test isotope chemistry. For example, the abundances of phytodetritus species do not show strong correlations with either the δ¹³C values of E. exigua or the Δδ¹³C _{E. exigua − P. wuellerstorfi} record, which have previously been suggested as indicative of seasonality of productivity.     

Environmental and climatic changes in the central Mediterranean Sea (Siculo–Tunisian Strait) during the last 30 ka based on dinoflagellate cyst and planktonic foraminifera assemblages

A high resolution micropalaeontological study of the core MD 04-2797 CQ recovered in the Sicilian–Tunisian Strait provides insights into the paleoclimatic history of the Mediterranean Sea at the transition between the western and eastern basin over the last 30 ka. Using the analysis of dinoflagellate cyst and planktonic foraminiferal assemblages, we reconstruct the paleoenvironmental changes that took place in this region. High abundances of cold temperate dinocyst species (Nematosphaeropsis labyrinthus, Spiniferites elongatus, Bitectatodinium tepikiense) and the polar planktonic foraminifera Neogloboquadrina pachyderma (left coiling) reveal three major cooling events synchronous with North Atlantic Henrich events 1 and 2 (H1 and H2) and the European and North Atlantic Younger Dryas event. During the Holocene, the presence of warm dinocyst species (Spiniferites mirabilis and Impagidinium aculeatum) and planktonic foraminifera (Globorotalia inflata and Globigerinoides ruber), reflects a significant increase of sea surface temperatures in the western Mediterranean basin, but a full warming was not recorded until 1500 years after the onset of the Holocene. Moreover, our results show that the Holocene was interrupted by at least four brief cooling events at ~ 9.2 ka, ~ 8 ka, ~ 7 ka and ~ 2.2 ka cal. BP, which may be correlated to climatic events recorded in Greenland ice cores and in the Atlantic Ocean.     

Influence of the mode of macrofauna-mediated bioturbation on the vertical distribution of living benthic foraminifera: First insight from axial tomodensitometry

We investigated the influence of bioturbation by macrofauna on the vertical distribution of living (stained) benthic foraminifera in marine intertidal sediments. We investigated the links between macrofaunal bioturbation and foraminiferal distribution, by sampling from stations situated on a gradient of perturbation by oyster-farming, which has a major effect on benthic faunal assemblages. Sediment cores were collected on the French Atlantic coast, from three intertidal stations: an oyster farm, an area without oysters but affected by oyster biodeposits, and a control station. Axial tomodensitometry (CT-scan) was used for three-dimensional visualization and two-dimensional analysis of the cores. Biogenic structure volumes were quantified and compared between cores. We collected the macrofauna, living foraminifera, shells and gravel from the cores after scanning, to validate image analysis. We did not investigate differences in the biogenic structure volume between cores. However, biogenic structure volume is not necessarily proportional to the extent of bioturbation in a core, given that many biodiffusive activities cannot be detected on CT-scans. Biodiffusors and larger gallery-diffusors were abundant in macrofaunal assemblage at the control station. By contrast, macrofaunal assemblages consisted principally of downward-conveyors at the two stations affected by oyster farming. At the control station, the vertical distribution of biogenic structures mainly built by the biodiffusor Scorbicularia plana and the large gallery-diffusor Hediste diversicolor was significantly correlated with the vertical profiles of living foraminifera in the sediment, whereas vertical distributions of foraminifera and downward-conveyors were not correlated at the station affected by oyster farming. This relationship was probably responsible for the collection of foraminifera in deep sediment layers (> 6 cm below the sediment surface) at the control station. As previously suggested for other species, oxygen diffusion may occur via the burrows built by S. plana and H. diversicolor, potentially increasing oxygen penetration and providing a favorable microhabitat for foraminifera in terms of oxygen levels. By contrast, the absence of living foraminifera below 6 cm at the stations affected by oyster farming was probably associated with a lack of biodiffusor and large gallery-diffusor bioturbation. Our findings suggest that the effect of macrofaunal bioturbation on the vertical distribution of foraminiferal assemblages in sediments depends on the effects of the macrofauna on bioirrigation and sediment oxidation, as deduced by Eh values, rather than on the biogenic structure volume produced by macrofauna. The loss of bioturbator functional diversity due to oyster farming may thus indirectly affect infaunal communities by suppressing favorable microhabitats produced by bioturbation.     

Hétérochronies du développement sensu Gould chez les foraminifères planctoniques cénomaniens : exemple de néoténie dans le bassin du Western Interior américain

Development heterochronies sensu Gould in the Cenomanian planktonic foraminifera: case of neotony in the American Western Interior Basin. During the Cenomanian–Turonian boundary, the anoxic event OAE2 has involved the disappearance of Rotalipora, complex keeled planktonic foraminifera which had conquered deep oceanic water. In the Western Interior basin, the last rotalipores are associated with Anaticinella, morphotypes without keel. The heterochronical relationship between these morphotypes is investigated. The loss of the keel would be a selective advantage enabling them to remain in the surface water, less reached by oceanic anoxia. Thus, two endemic species, only known in the American seaway, are observed: A. multiloculata (Morrow) and A. planoconvexa (Longoria). These species would respectively result by neoteny from R. greenhornensis and R. cushmani. To cite this article: D. Desmares et al., C.R. Palevol 2 (2003).     

Cenomanian ostracods of the Tarfaya upwelling region (Morocco) as palaeoenvironmental indicators

Changes in ostracod occurrence and assemblage composition from the Cenomanian of the Tarfaya Basin (Morocco) are investigated in order to evaluate their potential for palaeoenvironmental analyses of Cretaceous upwelling regions. Most frequent genera found at Tarfaya are Brachycythere, Veenia, Reticulocosta, Cytherelloidea, and Nigeroloxoconcha. Assemblages found at Tarfaya are characterised by low diversities. Successive appearance of assemblages dominated by these genera represents a depth gradient, corresponding to the results of the performed correspondence analysis. Ostracods are most abundant if associated either with moderate food supply and sufficient oxygenation or high food supply and high oxygenation. They disappear almost completely during permanent oxygen deficiency and are, contrary to benthic foraminifera, less frequent during periods of enhanced food supply. Species of the genus Brachycythere appear to be more sensitive to oxygen deficiency than other genera. Reticulocosta and Cytherelloidea avoid strong food pulses and are probably better adapted to oxygen depletion than other genera. Ostracods appear to be powerful environmental indicators for sea-level changes, oxygenation or food supply in Late Cretaceous upwelling settings, such as in the Cenomanian Tarfaya Basin.     

Biogeographic distribution of rudists and benthic foraminifera: An approach to Campanian-Maastrichtian palaeobiogeography of Turkey

Transgressive sequences of Campanian-Maastrichtian Stages in Turkey generally begin with medium- to coarse-grained clastics and continue with shallow marine limestones, reefal limestones and then open marine rhythmic fine-grained clastics. These mixed siliciclastic-carbonate sequences are observed on three main platforms known as Rhodope-Pontide (RPP), Anatolide-Tauride (ATP) and Arabian (AP). New species of the rudist genera Gorjanovicia, Radiolites, Sauvagesia, Durania and Sabinia are observed on the RPP. Yvaniella and Ugarella are only found on this platform. Orbitoides gruenbachensis Papp is the most abundant species of benthic foraminifera on the RPP. Cideina soezerii (Sirel), Dizerina anatolica Meriç, Helicorbitoides boluensis Sirel, Ilgazina unilateralis Erdo?an, Nummofallotia kastamonica Özgen-Erdem, Selimina spinalis ?nan, Sirelina orduensis Meriç and ?nan, Smoutina cruysi Drooger are also observed on this platform. Rudist and benthic foraminifera on the ATP have both high diversity and abundance in comparison with RPP and AP faunas. Genus and species diversity of the rudist fauna is quite high: 17 genera and 36 species are described. New rudist genera such as Darendeella, Kurtinia and Balabania and many new species of Radiolitidae and Hippuritidae may be restricted to this platform. Characteristic larger benthic foraminifera contain 18 genera and 37 species. Among benthic foraminifera Loftusia ketini Meriç, L. turcica Meriç and Av?ar, Postomphalocyclus merici ?nan and Pseudoedomia hekimhanensis Görmü? are also likely restricted to this platform. Rudist diversity on the AP is poor. Four endemic genera (Vautrinia, Dictyoptychus, Paracaprinula and Hatayia) and two species (Hippurites syriaca Vautrin, Pironaea syriaca Vautrin) characterize the fauna on this platform. Loftusia diversity and abundance among the benthic foraminifera is quite high. Arnaudella grossouvreii Douvillé, Discyclina schlumbergeri Munier-Chalmas, Loftusia harrisoni Cox, L. elongata Cox, L. matsumaruii Meriç and Görmü? and Pseudorbitolina marthae Douvillé are only documented from southeastern Anatolia. Biogeographic distributions of rudist and benthic foraminifera show different faunal associations on the three main platforms (RPP, ATP and AP). Our data from both rudist and benthic foraminifera indicate that different faunal associations and existence of restricted genera and species may be associated with a deep marine barrier to circulation during the Campanian-Maastrichtian. Southern and northern branches of the Neotethyan Ocean are considered to be barriers in preventing migration of the species.     

Environmental stress and human life history strategy development in rural and peri-urban South India

Few studies have examined the role of early vs. later environment in the development of life history (LH) strategies, whether age at sexual debut mediates LH development, or whether LH indicators contribute to environmental stress in adulthood. In the current study, we addressed these gaps cross-culturally using data from Jenu Kurubas who live in the rural outskirts of Mysore (n = 133), India, and mixed-caste peri-urban residents in Mysore city (n = 222). Research took place from October 2016–July 2017. First, participants engaged in semi-structured interviews to formulate quantitative measures of current environmental stress (n = 60). Next, participants (n = 355) completed structured questionnaires that measured demographics; early and current environmental stress; and LH indicators including age at sexual debut, facets of impulsivity, education, and number of children. Structural equation modeling was used to test for the developmental cascade reported in Western studies of psychosocial acceleration (e.g., indirect effect of early environmental stress on number of children through age at sexual debut). Consistent with Western findings, environmental stress appeared to hasten sexual debut, decrease self-regulation and educational attainment, and increase current environmental stress in the peri-urban sample. Early environmental stress forecasted younger age at sexual debut in both samples; however, no other effects of early environmental stress nor any associations with current environmental stress were consistent between samples. Although age at sexual debut appeared to translate early environmental stress into greater numbers of children and current environmental stress in the peri-urban and rural samples, respectively, it was associated with different outcomes between the samples and forecasted adult environment only in the rural sample. Taken together, our findings indicate more research is needed to determine whether the developmental cascade suggested by most applications of LH theory to humans generalizes across cultures and rural and peri-urban environments.     

The niche of benthic foraminifera,critical thresholds and proxies

Ecological studies of benthic foraminifera are carried out to explain patterns of distribution and the dynamics of communities. They are also used to provide data to establish proxy relationships with selected factors. According to niche theory, the patterns of distribution of benthic foraminifera are controlled by those environmental factors that have reached their critical thresholds. For each species, in variable environments, different factors may be limiting distributions both temporally and spatially. For a species or an assemblage to be useful as a proxy its abundance must show a strong correlation with the chosen factor. Since numerous factors influence each species, it is only in those environments where the majority of factors show little variation but one particular factor shows significant variation that the proxy relationship for that factor can be determined. On theoretical grounds, the reliability of using foraminiferal abundance as a proxy of a selected environmental factor should be restricted to the range close to the upper and lower thresholds. For oxygen, foraminifera are potential proxies for the lower limits but once oxygen levels rise to values of perhaps >1 or 2 ml l⁻¹, there is no longer a relationship between oxygen levels and abundance. By contrast, the flux of organic matter over a large range shows a sufficiently close relationship with foraminiferal assemblages so that transfer functions can be derived for the deep sea. However, the relationship at species level is far less clear cut. Much more accurate estimates of primary productivity and modern organic flux rates are required to improve the determination of past flux rates.     

Modelling the temperature dependent growth rates of planktic foraminifera

The temperature influence on foraminifera growth rate was analysed using a mechanistic formulation that take into account enzyme inactivation at extreme temperatures. Growth rates are calculated using available published and unpublished laboratory culture experiments for eight species, including Neogloboquadrina pachyderma (sinistral and dextral forms), Neogloboquadrina dutertrei, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinella siphonifera and Orbulina universa. Modeled growth formulas readily reproduce the observed growth patterns for all species. Similar growth patterns are observed for the species that have the same symbiotic algae G. ruber, G. sacculifer, and O. universa. However, different growth patterns are observed for herbivorous species (Neogloboquadrina genus) compared to carnivorous species with or without symbionts. Our growth estimates correspond well to in situ observations from both plankton tows and sediment traps. These estimates will help to improve the quantification of the effects of environmental parameters on foraminifera species distribution and abundance.