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A complete understanding of past El Niño–Southern Oscillation (ENSO) fluctuations is important for the future predictions of regional climate using climate models. One approach to reconstructing past ENSO dynamics uses planktonic foraminifera as recorders of past climate to assess past spatio-temporal changes in upper ocean conditions. In this paper, we utilise a model of planktonic foraminifera populations, Foraminifera as Modelled Entities (FAME), to forward model the potential monthly average δ18Oc and temperature signal proxy values for Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei from input variables covering the period of the instrumental record. We test whether the modelled foraminifera population δ18Oc and Tc associated with El Niño events statistically differ from the values associated with other climate states. Provided the assumptions of the model are correct, our results indicate that the values of El Niño events can be differentiated from other climate states using these species. Our model computes the proxy values of foraminifera in the water, suggesting that, in theory, water locations for a large portion of the tropical Pacific should be suitable for differentiating El Niño events from other climate states. However, in practice it may not be possible to differentiate climate states in the sediment record. Specifically, comparison of our model results with the sedimentological features of the Pacific Ocean shows that a large portion of the hydrographically/ecologically suitable water regions coincide with low sediment accumulation rate at the sea floor and/or of sea floor that lie below threshold water depths for calcite preservation.

The current geochronological state of the art for applying the radiocarbon (14C) method to deep-sea sediment archives lacks key information on sediment bioturbation. Here, we apply a sediment accumulation model that simulates the sedimentation and bioturbation of millions of foraminifera, whereby realistic 14C activities (i.e. from a 14C calibration curve) are assigned to each single foraminifera based on its simulation time step. We find that the normal distribution of 14C age typically used to represent discrete-depth sediment intervals (based on the reported laboratory 14C age and measurement error) is unlikely to be a faithful reflection of the actual 14C age distribution for a specific depth interval. We also find that this deviation from the actual 14C age distribution is greatly amplified during the calibration process. Specifically, we find a systematic underestimation of total geochronological error in many cases (by up to thousands of years), as well as the generation of age–depth artefacts in downcore calibrated median age. Even in the case of “perfect” simulated sediment archive scenarios, whereby sediment accumulation rate (SAR), bioturbation depth, reservoir age and species abundance are all kept constant, the 14C measurement and calibration processes generate temporally dynamic median age–depth artefacts on the order of hundreds of years – whereby even high SAR scenarios (40 and 60 cm kyr−1) are susceptible. Such age–depth artefacts can be especially pronounced during periods corresponding to dynamic changes in the Earth's Δ14C history, when single foraminifera of varying 14C activity can be incorporated into single discrete-depth sediment intervals. For certain lower-SAR scenarios, we find that downcore discrete-depth true median age can systematically fall outside the calibrated age range predicted by the 14C measurement and calibration processes, thus leading to systematically inaccurate age estimations. In short, our findings suggest the possibility of 14C-derived age–depth artefacts in the literature. Furthermore, since such age–depth artefacts are likely to coincide with large-scale changes in global Δ14C, which themselves can coincide with large-scale changes in global climate (such as the last deglaciation), 14C-derived age–depth artefacts may have been previously incorrectly attributed to changes in SAR coinciding with global climate. Our study highlights the need for the development of improved deep-sea sediment 14C calibration techniques that include an a priori representation of bioturbation for multi-specimen samples.

We use a single foraminifera enabled, holistic hydroclimate-to-sediment transient modelling approach to fundamentally evaluate the efficacy of discrete-depth individual foraminifera analysis (IFA) for reconstructing past sea surface temperature (SST) variability from deep-sea sediment archives, a method that has been used for, amongst other applications, reconstructing El Niño Southern Oscillation (ENSO). The computer model environment allows us to strictly control for variables such as sea surface temperature (SST), foraminifera species abundance response to SST, as well as depositional processes such as sediment accumulation rate (SAR) and bioturbation depth (BD), and subsequent laboratory processes such as sample size and machine error. Examining a number of best-case scenarios, we find that IFA-derived reconstructions of past SST variability are sensitive to all of the aforementioned variables. Running 100 ensembles for each scenario, we find that the influence of bioturbation upon IFA-derived SST reconstructions, combined with typical samples sizes employed in the field, produces noisy SST reconstructions with poor correlation to the original SST distribution in the water. This noise is especially apparent for values near the edge of the SST distribution, which is the distribution region of particular interest for, e.g., ENSO. The noise is further increased in the case of increasing machine error, decreasing SAR and decreasing sample size. We also find poor agreement between ensembles, underscoring the need for replication studies in the field to confirm findings at particular sites and time periods. Furthermore, we show that a species’ abundance response to SST could in theory bias IFA-derived SST reconstructions, which can have consequences when comparing IFA-derived SST from markedly different mean climate states. We provide a number of idealised simulations spanning a number of SAR, sample size, machine error and species abundance scenarios, which can help assist researchers in the field to determine under which conditions they could expect to retrieve significant results.

The translation of the original seawater signal (i.e. ambient temperature and δ18Osw) into distinct chambers of a single shell of a foraminifer during calcification can influence our interpretation of surface ocean conditions of the past, when based upon oxygen and carbon stable isotope geochemistry. In this study three different hypotheses were tested to gain more insight into biological and ecological processes that influence the resultant composition of stable isotopes of oxygen (δ18O) in the shells of planktonic foraminifera. These hypotheses were related to the shell size; the differences in isotopic composition between the final chamber and the remaining shell; and the differences between different species. Shells of Trilobatus sacculifer, Globigerinoides ruber white and Neogloboquadrina dutertrei were picked from the top of multi-core GS07-150-24, of modern age, offshore of north-eastern Brazil (3∘46.474′ S, 37∘03.849′ W) and analysed for single-shell and single-chamber stable isotope analysis. We show that the mean value of δ18O of the final chambers (δ18OF) is 0.2 ‰ ± 0.4 ‰ (1σ) higher than the mean value δ18O of the test minus the final chamber (δ18O

Measurements of δ18O on planktonic foraminifera represent an important geological archive. In the study of climate change on orbital time-scales, δ18O is used either as a proxy for temperature change, to construct age models through pattern matching, to deduce the drivers of climate change by looking at frequency power spectra or all of the above. The validity of these approaches hinges on a two-step assumption, namely that the signal of the orbital cycles is transferred unaltered from 1) solar radiation that reaches the top of the atmosphere, insolation, to the sea surface, and 2) from the sea surface translated into the δ18O composition of the foraminiferal shell. The complexity of these two steps make it difficult to validate the assumptions behind these major paleoclimatological approaches. In this research we aim to disentangle the problem, here focussing only on the latter part: how do species-specific living habitats of foraminifera in the water column and throughout the year shape the δ18O response were the Earth’s surfce climate to perfectly reflect the orbital forcing(s). To this end we combine an isotope-enabled climate model (iLOVECLIM) with a foraminifera growth model and investigate the response of δ18O from three species of foraminifera (Globigerinoides ruber, Neogloboquadrina pachyderma, and Globigerina bulloides) to obliquity and precessional cycles.Our results show that the planktonic foraminifera δ18O response to astronomical forcings is dominated by annual mean changes in sea-surface temperature, thus corroborating a key assumption underlying many geological climate reconstructions. However, in various places changes in the depth habitat, temperature-dependent growth rates, seasonality and δ18O of the sea water dominate the foraminifera δ18O signal. Because of these modulations, planktonic foraminifera δ18O time series can have very different characteristics compared to the orbital forcings, including limited spatial coherence as well as limited inter-species coherence at a single location.

© 2020 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd Rationale: Oxygen (δ18O) and carbon (δ13C) isotope analysis of foraminifera and other CaCO3 samples has been a key technique for paleoceanographical and paleoclimatological research for more than 60 years. There is ongoing demand for the analysis of ever smaller CaCO3 samples, driven, for example, by the desire to analyse single specimen planktic foraminifera, or small samples of tooth enamel. Methods: We present a continuous-flow mass spectrometric technique that uses cryo-focusing of sample CO2 to analyse CaCO3 samples in a weight range between 10 and 3 μg. These are considerably lower sample weights than achievable on most currently available standard instrumentation. The technique is automated, so that sample throughput lies at >60 samples per day. The method involves an on-line vial-flushing routine designed to remove machine drift due to blank CO2 build-up in the sample vials. Results: In a series of experiments the effect of blank CO2 build-up is quantified, and outgassing from the chlorobutyl septa identified as the source. An improved flushing routine together with the use of a cryo-focusing step in the analysis is demonstrated to provide the analytical stability and sensitivity to analyse CaCO3 samples in a weight range between 10 and 3 μg at ≤0.1‰ precision (1σ) for both δ18O and δ13C values. The technique yields similarly precise results for the analysis of the structural carbonate fraction of small tooth enamel samples. Conclusions: This study demonstrates that high-precision oxygen and carbon isotope analysis is possible on CaCO3 samples smaller than 5 μg by use of a continuous-flow isotope technique. Of key importance are (1) the application of a cold trap that drastically reduces sample gas loss, and (2) a modified flushing regime that eliminates increasing background CO2 build-up in sample vials during longer automated sample runs., Rapid Communications in Mass Spectrometry, 34 (19), ISSN:1097-0231, ISSN:0951-4198

Oxygen (δWe present a continuous-flow mass spectrometric technique that uses cryo-focusing of sample COIn a series of experiments the effect of blank COThis study demonstrates that high-precision oxygen and carbon isotope analysis is possible on CaCO

Stable isotope analysis of biogenic carbonates has remained one of the most important tools in paleoceanography since Emiliani (1955) first described the fluctuation of oxygen isotopes in planktic foraminifers over the Pleistocene. Many laboratories now possess equipment with the capability to analyse foraminifer specimens singularly, at least for larger planktic forms.Being able to run single specimens of planktic foraminifers is significant, because it yields entirely different information than when one would analyse multiple specimens from the same species. Planktic foraminifers have an average life span of about one month, so analysing single specimens, makes paleoceanographic data at seasonal resolution available (e.g. Ganssen et al., 2011; Metcalfe et al 2019, and references therein).Most modern equipment for stable isotope analysis of CaCO3 samples yields good precision down to 10 microgram sample size. The smallest samples are generally measured with a dual inlet technique, because that quantitatively collects the CO2 gas sample in a cold trap before analysis, leading to a more efficient use of the sample gas. Modern dual inlet equipment has a sample size limit somewhere between 10 and 6 microgram CaCO3 sample weight, and in that range usually operates at increased analytical uncertainty when compared to larger samples (e.g. Ganssen et al., 2011). Smaller samples are problematic, because at small amounts of sample gas, the dual inlet system is not able to maintain viscous flow conditions required for precise isotope analysis. To circumvent that barrier, one can use continuous-flow (CF) mass spectrometry because in CF systems the carrier gas ensures proper flow conditions even if there is (virtually) no sample gas produced. Doing so has previously allowed for the isotope analysis of CaCO3 samples in the 10 – 6 microgram range at an external precision (1SD) of ~0.12‰ for both δ18O and δ13C (e.g. Metcalfe et al 2019).To further improve the performance of CF mass spectrometry for small CaCO3 samples, we ran experiments on a Thermo GASBENCH system, equipped with a cold trap (cf. Fiebig et al 2005) and interfaced with a Delta-V mass spectrometer. The experiments consisted of replicate analysis of CaCO3 standards between 10 and 3 micrograms in weight, which is the weight range of many of the smaller specimens of planktic foraminifers.Several hardware modifications were implemented to improve system stability and remove observed effects of contribution of blank CO2 building up in the sample vials. With these modifications, external reproducibility of the set-up for carbonate standard aliquots between 10 and 4 microgram reached a precision of ~0.10 ‰ for both δ18O and δ13C (1SD). This is similar to precisions typically attained for routine analysis of much larger samples in standard operation on the same equipment, and demonstrates that precise stable isotope analysis of smaller single-specimen planktic foraminifers than we could achieve so far is within reach of CF mass spectrometry.References:Emiliani, C. 1955, DOI: 10.1086/626295Fiebig, J., et al. 2005, DOI: 10.1002/rcm.2060Ganssen, G.M., et al., 2011, DOI:10.5194/cp-7-1337-2011Metcalfe, B., et al., 2019, DOI: 10.1029/2018PA003475

Due to a lack of marine macrofossils in many sediment cores from the estuarine Baltic Sea, researchers are often forced to carry out 14C determinations on bulk sediment samples. However, ambiguity surrounding the carbon source pathways that contribute to bulk sediment formation introduces a large uncertainty into 14C geochronologies based on such samples, and such uncertainty may not have been fully considered in previous Baltic Sea studies. We quantify this uncertainty by analyzing bulk sediment 14C determinations carried out on densely spaced intervals in independently dated late-Holocene sediment sequences from two central Baltic Sea cores. Our results show a difference of ~600?14C?yr in median bulk sediment reservoir age, or R(t)bulk, between the two core locations (~1200?14C?yr for one core, ~620?14C?yr for the other), indicating large spatial variation. Furthermore, we also find large downcore (i.e., temporal) R(t)bulk variation of at least ~200?14C?yr for both cores. We also find a difference of 585?14C?yr between two samples taken from the same core depth. We propose that studies using bulk sediment 14C dating in large brackish water bodies should take such spatiotemporal variation in R(t)bulk into account when assessing uncertainties, thus leading to a larger, but more accurate, calibrated age range. (Less)

The current geochronological state-of-the-art for applying the radiocarbon (14C) method to deep-sea sediment archives lacks key information on sediment bioturbation. Here, we apply a sediment accumulation model that simulates the sedimentation and bioturbation of millions of foraminifera, whereby realistic 14C activities (i.e. from a 14C calibration curve) are assigned to each single foraminifera based on its simulation timestep. We find that the normal distribution of 14C age typically used to represent discrete-depth sediment intervals (based on the reported laboratory 14C age and measurement error) is unlikely to be a faithful reflection of the actual 14C age distribution for a specific depth interval. We also find that this deviation from the actual 14C age distribution is greatly amplified during the calibration process. We find a systematic underestimation of total geochronological error in many cases (by up to thousands of years), as well as the generation of age-depth artefacts in downcore calibrated median age. Specifically, we find that even in the case of perfect simulated sediment archive scenarios, whereby sediment accumulation rate (SAR), bioturbation depth, reservoir age and species abundance are all kept constant, the 14C dating and calibration process generates temporally dynamic median age-depth artefacts, on the order of hundreds of years – even in the case of high SAR scenarios of 40 cm ka−1 and 60 cm ka−1. Such age-depth artefacts can be especially pronounced during periods corresponding to dynamic changes in the Earth's Δ14C, where single foraminifera of varying 14C activity can be incorporated into single discrete-depth sediment intervals. In certain SAR scenarios, a discrete depth’s true median age can consistently fall outside the 95.45 % calibrated age range predicted by the 14C dating and calibration process. Our findings suggest the possibility of 14C-derived age-depth artefacts in the literature: since age-depth artefacts are likely to coincide with large-scale changes in global Δ14C, which themselves can coincide with large-scale changes in global climate (such as the last deglaciation), 14C-derived age-depth artefacts may have been previously been (partially) misinterpreted as due to changes in global climate. Our study highlights the need for the development of improved deep-sea sediment 14C calibration techniques that include an a priori representation of bioturbation for multi-specimen samples.

International audience; Planktonic foraminiferal species identification is central to many paleoceanographic studies, from selecting species for geochemical research to elucidating the biotic dynamics of microfossil communities relevant to physical oceanographic processes and interconnected phenomena such as climate change. However, few resources exist to train students in the difficult task of discerning amongst closely related species, resulting in diverging taxonomic schools that differ in species concepts and boundaries. This problem is exacerbated by the limited number of taxonomic experts. Here we document our initial progress toward removing these confounding and/or rate-limiting factors by generating the first extensive image library of modern planktonic foraminifera, providing digital taxonomic training tools and resources, and automating species-level taxonomic identification of planktonic foraminifera via machine learning using convolution neural networks. Experts identified 34,640 images of modern (extant) planktonic foraminifera to the species level. These images are served as species exemplars through the online portal Endless Forams (endlessforams.org) and a taxonomic training portal hosted on the citizen science platform Zooniverse (zooniverse.org/projects/ahsiang/ endless-forams/). A supervised machine learning classifier was then trained with~27,000 images of these identified planktonic foraminifera. The best-performing model provided the correct species name for an image in the validation set 87.4% of the time and included the correct name in its top three guesses 97.7% of the time. Together, these resources provide a rigorous set of training tools in modern planktonic foraminiferal taxonomy and a means of rapidly generating assemblage data via machine learning in future studies for applications such as paleotemperature reconstruction.

International audience; The major control upon abundance of planktonic foraminifera and their stable oxygen isotope (δ 18 O) signature is the seasonally linked variation in water hydrography, key to the proliferation or attenuation of ecologically beneficial constraints. The range and variance σ(δ 18 O) of planktonic foraminifera can reflect changes in either the season or depth of calcification. For a detailed reconstruction of ocean changes we employed multispecies single-specimen analysis, which allows extraction of the isotopic variability within the species for the time covered by the sample. Previous studies with pooled specimens have shown that the multiannual temperature range may be extracted. Here we investigate how seasonality can be deduced from single-specimen analysis of planktonic foraminifera combined with multiple other proxies (IRD percent, faunal abundance) from Termination III. Our single-shell isotope results show that the variance in Globigerina bulloides oxygen isotope values corresponds to the insolation at the core site. Furthermore, faunal and isotopic analyses of the polar-subpolar neogloboquadrinid species, N. pachyderma (NPS) and N. incompta, reveal an intriguing result. These species are sister taxa, representing genetically distinct species, whose relative abundance reflects warm and cold conditions. While the difference between their isotopic means should reflect the temperature difference between their distinct growing seasons, we show that this difference also has a statistically significant relationship with the spread in individual NPS δ 18 O. At an appropriate core site, this approach could be used to further constrain the length of the growing season and therefore the inherent variability recorded within proxy records. Plain Language Summary Reconstructions of the past climate of the Earth have focused upon the average signal, either mean annual temperature or distinct seasons (e.g., average summer or winter), as recorded by the shells of planktonic organisms in deep-sea sediments. However, these records are biased by the waxing and waning of environmental variables that benefit or hinder the growth and proliferation of individual species. The spread in isotope values recorded by individual shells can therefore give more information as to the extent of the growing period as well as provide information upon the seasonality of the past.

A complete understanding of past El Niño-Southern Oscillation (ENSO) fluctuations is important for the future predictions of regional climate using climate models. Reconstructions of past ENSO dynamics use carbonate oxygen isotope ratios (δ18Oc) and trace metal geochemistry (Mg / Ca) recorded by planktonic foraminifera to reconstruct past spatiotemporal changes in upper ocean conditions. We investigate whether planktonic foraminifera-based proxies offer sufficient spatiotemporal continuity with which to reconstruct past ENSO dynamics. Concentrating upon the period of the instrumental record, we use the Foraminifera as Modelled Entities model to statistically test whether or not δ18Oc and the Temperature signal (Tc) in planktonic foraminifera directly records the ENSO cycle. Our results show that it is possible to use δ18Oc from foraminifera to disentangle the ENSO signal only in certain parts of the Pacific Ocean. Furthermore, a large proportion of these areas coincide with sea-floor regions exhibiting a low sedimentation rate and/or water depth below the carbonate compensation depth, thus precluding the extraction of a temporally valid palaeoclimate signal using long-standing palaeoceanographic methods.

The translation of the original seawater signal (i.e., ambient temperature, salinity and δ18Osw) into distinct chambers of a single shell of a foraminifer during calcification can influence our interpretation of surface ocean conditions of the past, when based upon oxygen and carbon stable isotope geochemistry. Three different hypotheses related to: the size; the composition of the final chamber vs. the remaining shell; and species-specific offsets were tested to gain more insight into biological and ecological processes that influence the resultant composition of stable isotopes of oxygen (δ18O) in the shells of planktonic foraminifera. Shells of Trilobatus sacculifer, Globigerinoides ruber white and Neogloboquadrina dutertrei were picked from the top of the RETRO multi-core GS07-150-24, of Modern age, offshore of North-East Brazil (3°46.474' S, 37°03.849' W) and analysed for single shell and chamber stable isotope analysis. We show that there is a significant difference, of 0.203 ‰ ± 0.40 ‰ (1σ), in δ18O between the final chamber (δ18OF) and the test minus the final chamber (δ18O) of T. sacculifer. The formation of the final chamber approximately 1 °C cooler than the chambers formed prior, suggests both ontogenetic depth migration to deeper water and a potential offset from the surface signal. However, we show that there is no statistical difference in the δ18O values of shells of three different size classes, based upon measured size as opposed to sieve size, of T. sacculifer, although the pattern between the different size classes indicates depth migration during the life and growth of T. sacculifer. Comparison between T. sacculifer, G. ruber white and N. dutertrei suggests that G. ruber has a shallower depth habitat (~ 90–120 m) than the other species (~ 100–130 m). Disentangling depth versus seasonal habitat is complicated given the commonality between isotopes values from similar depths but different seasons, for instance the same average isotope value will have a shallower depth habitat in May than September. Calculation of seasonal-depth habitat was therefore tested. Our results highlight the complicated nature of interpreting oxygen isotopes even for the modern record.

The oxygen-18 to oxygen-16 ratio recorded in fossil planktonic foraminifer shells has been used for over 50 years in many geoscience applications. However, different planktonic foraminifer species generally yield distinct signals, as a consequence of their specific living habitats in the water column and along the year. This complexity is usually not taken into account in model–data integration studies. To overcome this shortcoming, we developed the Foraminifers As Modeled Entities (FAME) module. The module predicts the presence or absence of commonly used planktonic foraminifers and their oxygen-18 values. It is only forced by hydrographic data and uses a very limited number of parameters, almost all derived from culture experiments. FAME performance is evaluated using the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) Late Holocene planktonic foraminifer calcite oxygen-18 and abundance datasets. The application of FAME to a simple cooling scenario demonstrates its utility to predict changes in planktonic foraminifer oxygen-18 to oxygen-16 ratio in response to changing climatic conditions.

Understanding the vertical distribution and migratory behaviour of shelled holoplanktonic gastropods is essential in determining the environmental conditions to which they are exposed. This is increasingly important in understanding the effects of ocean acidification and climate change. Here we investigated the vertical distribution of atlantid heteropods by collating data from publications and collections and using the oxygen isotope (?18O) composition of single aragonitic shells. Data from publications and collections show 2 patterns of migration behaviour: small species that reside in shallow water at all times, and larger species that make diurnal migrations from the surface at night to deep waters during the daytime. The ?18O data show that all species analysed (n = 16) calcify their shells close to the deep chlorophyll maximum. This was within the upper 110 m of the ocean for 15 species, and down to 146 m for a single species. These findings confirm that many atlantid species are exposed to large environmental variations over a diurnal cycle and may already be well adapted to face ocean changes. However, all species analysed rely on aragonite supersaturated waters in the upper 2.

Geochemical and morphological characteristics of Globorotalia truncatulinoides, a deep dwelling planktonic foraminifer, have been used since the mid-1950s to infer (paleo)oceanographic conditions of the upper ocean. The coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and/or season. Here we show that the isotopic composition of single specimens covering Termination III of multiple size fractions of North Atlantic G. truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to G. truncatulinoidesdextral as previously indirectly inferred in a plankton tow study. Furthermore, the change in coiling ratio from dominantly G. truncatulinoidesdextral (95%) to brief episodes of dominantly G. truncatulinoidessinistral (80%) gives a strong indication of deepening of the permanent thermocline during periods in which G. truncatulinoidessinistral was dominant. The position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the Atlantic meridional overturning circulation (AMOC), dominated by interglacial-glacial dynamics. We demonstrate that Glacial Heinrich (ice-rafted debris) events appear to proceed a permanent thermocline shoaling, whereas interglacial Heinrich events follow the shoaling of the permanent thermocline, likely a result of a weakened AMOC.

Late-glacial palaeoclimate reconstructions from deep-sea sediment archives provide valuable insight into past rapid changes in ocean chemistry. Unfortunately, only a small proportion of the ocean floor with sufficiently high sediment accumulation rate (SAR) is suitable for such reconstructions using the long-standing age–depth model approach. We employ ultra-small radiocarbon (14C) dating on single microscopic foraminifera to demonstrate that the long-standing age–depth model method conceals large age uncertainties caused by post-depositional sediment mixing, meaning that existing studies may underestimate total geochronological error. We find that the age–depth distribution of our 14C-dated single foraminifera is in good agreement with existing bioturbation models only after one takes the possibility of Zoophycos burrowing into account. To overcome the problems associated with the age–depth paradigm, we use the first ever dual 14C and stable isotope (δ18O and δ13C) analysis on single microscopic foraminifera to produce a palaeoclimate time series independent of the age–depth paradigm. This new state of the art essentially decouples single foraminifera from the age–depth paradigm to provide multiple floating, temporal snapshots of ocean chemistry, thus allowing for the successful extraction of temporally accurate palaeoclimate data from low-SAR deep-sea archives. This new method can address large geographical gaps in late-glacial benthic palaeoceanographic reconstructions by opening up vast areas of previously disregarded, low-SAR deep-sea archives to research, which will lead to an improved understanding of the global interaction between oceans and climate.

[1] Paleoceanographic studies routinely combine different foraminiferal proxies (i.e., weight, abundance, trace metal, and stable isotope measurements) into a cohesive narrative. The application of chemical treatment to disaggregate ocean sediments in the most efficient way to isolate the fossils of foraminifera from the other sediment components is dictated by the time available and the material used. Yet few studies have aimed to test both the physical and geochemical effects associated with such practices. In this study, we use samples with different sedimentological characteristics (i.e., varying percentages of CaCO3 and of terrigenous material) to test the impact upon these proxies of three processing methods and a control: (1) no chemicals (contol run); (2) soaking in sodium hexametaphosphate (Calgon®); (3) soaking in hydrogen peroxide; and (4) soaking in a sodium pyrophosphate. The samples were analyzed for faunal abundance, shell weight, stable isotope (δ18O, δ13C), and trace metal (Mg/Ca) geochemistry for four species of planktonic foraminifera (Globigerina bulloides, Globigerinoides ruber, Globorotalia inflata, and Globorotalia menardii). Results show that apart from the Calgon® solution, the values of faunal abundance, shell weight, Mg/Ca, and stable isotopes are similar irrespective of the cleaning treatment utilised and therefore warrant cross-comparison of results obtained with different preparation techniques. The use of Calgon® in pretreatment shows statistically different values for only foraminiferal shell weight.

The oxygen isotopic composition of planktonic foraminifera tests is one of the widest used geochemical tools to reconstruct past changes of physical parameters of the upper ocean. It is common practice to analyze multiple individuals from a mono-specific population and assume that the outcome reflects a mean value of the environmental conditions during calcification of the analyzed individuals. Here we present the oxygen isotope composition of individual specimens of the surface-dwelling species Globigerinoides ruber and Globigerina bulloides from sediment cores in the Western Arabian Sea off Somalia, inferred as indicators of past seasonal ranges in temperature. Combining the δ18O measurements of individual specimens to obtain temperature ranges with Mg/Ca based mean calcification temperatures allows us to reconstruct temperature extrema. Our results indicate that over the past 20 kyr the seasonal temperature range has fluctuated from its present value of 16 °C to mean values of 13 °C and 11 °C for the Holocene and LGM, respectively. The data for the LGM suggest that the maximum temperature was lower, whilst minimum temperature remained approximately constant. The rather minor variability in lowest summer temperatures during the LGM suggests roughly constant summer monsoon intensity, while upwelling-induced productivity was lowered.

So-called "vital effects" are a collective term for a suite of physiologically and metabolically induced variability in oxygen (δ18O) and carbon (δ13C) isotope ratios of planktonic foraminifer shells that hamper precise quantitative reconstruction of past ocean parameters. Correction for potential isotopic offsets from equilibrium or the expected value is paramount, as too is the ability to define a comparable life stage for each species that allows for direct comparison. Past research has focused upon finding a specific size range for individual species in lieu of other identifiable features, thus allowing ocean parameters from a particular constant (i.e. a specific depth or season) to be reconstructed. Single-shell isotope analysis of fossil shells from a mid-latitude North Atlantic Ocean piston core covering Termination III (200 to 250 ka) highlight the advantage of using a dynamic size range, i.e. utilising measurements from multiple narrow sieve size fractions spanning a large range of total body sizes, in studies of palaeoclimate. Using this methodology, we show that isotopic offsets between specimens in successive size fractions of Globorotalia inflata and Globorotalia truncatulinoides are not constant over time, contrary to previous findings. For δ18O in smaller-sized globorotalids (212–250 μm) it is suggested that the offset from other size fractions may reflect a shallower habitat in an early ontogenetic stage. A reduction in the difference between small and large specimens of G. inflata between insolation minima and maxima is interpreted to relate to a prolonged period of reduced water column stratification. For the shallow-dwelling species Globigerina bulloides, no size–isotope difference between size fractions is observed, and the variability in the oxygen isotopic values is shown to correlate well with the seasonal insolation patterns. As such, patterns in oxygen isotope variability of fossil populations may be used to reconstruct past seasonality changes.

Efficient searching is crucial for timely location of food and other resources. Recent studies show that diverse living animals use a theoretically optimal scale-free random search for sparse resources known as a Lévy walk, but little is known of the origins and evolution of foraging behavior and the search strategies of extinct organisms. Here, using simulations of self-avoiding trace fossil trails, we show that randomly introduced strophotaxis (U-turns)--initiated by obstructions such as self-trail avoidance or innate cueing--leads to random looping patterns with clustering across increasing scales that is consistent with the presence of Lévy walks. This predicts that optimal Lévy searches may emerge from simple behaviors observed in fossil trails. We then analyzed fossilized trails of benthic marine organisms by using a novel path analysis technique and find the first evidence, to our knowledge, of Lévy-like search strategies in extinct animals. Our results show that simple search behaviors of extinct animals in heterogeneous environments give rise to hierarchically nested Brownian walk clusters that converge to optimal Lévy patterns. Primary productivity collapse and large-scale food scarcity characterizing mass extinctions evident in the fossil record may have triggered adaptation of optimal Lévy-like searches. The findings suggest that Lévy-like behavior has been used by foragers since at least the Eocene but may have a more ancient origin, which might explain recent widespread observations of such patterns among modern taxa.

[Brayard et al. (2010)][1] assert that their study of late Early Triassic gastropods provides evidence against the post-extinction Lilliput effect. Regrettably, their data provide no such evidence. The Lilliput effect as defined by [Urbanek (1993)][2] is a quantifiable, temporary decrease in the

Marine invertebrate taxa that survived the late Permian (latest Changhsingian) mass extinction event are all much smaller than they were prior to the event, an example of the Lilliput effect. New taxa that first appeared in the immediate extinction aftermath are also small compared to their size in younger strata. The Lilliput effect is a temporary phenomenon, with most surviving taxa returning to pre-extinction size in the first two conodont zones of the Triassic. In this study, the growth rates, of some of the Early Triassic Lilliput animals, estimated by growth-line analysis, were compared from different stratigraphic levels to determine how this variable fluctuated as body size returned to pre-extinction values after the event. Specimens were collected from the Mazzin and Siusi members of the Werfen Formation in northern Italy, from facies deposited in a tropical, mixed siliciclastic-carbonate ramp setting. Measurements of the bivalves Unionites and Claraia, the gastropod Bellerophon and the brachiopod '. Lingula' were made in the field, with subsequent growth-line analysis conducted on well-preserved specimens of 'Lingula'. Specimens collected from the basal Triassic Mazzin Member were smaller than those from the younger Siusi Member. Growth-line analysis indicates that the smaller Mazzin Member specimens had a greater number of more closely spaced growth lines than the larger Siusi Member specimens. The small, 'Lilliput' animals living in the immediate aftermath of the Late Permian event therefore suffered more interruptions to growth and had overall slower growth rates than larger individuals living in later recovery times. Frequent interruptions to growth and an overall slower growth rate in specimens from the Hindeodus parvus and Isarcicella isarcica zones of the Mazzin Member (lower Induan) reflects suboptimal environmental conditions, such as the frequency or severity of low-oxygen episodes, temperature extremes, and/or disruptions to primary productivity. © 2010 Elsevier B.V.