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Antarctica is one of the most susceptible regions to climate change on Earth. Rising ocean temperatures, glacier melting, and disruptions of marine ecosystems make this polar region a focus of research on ecosystem transformation associated with ongoing climate change. Within the Antarctic ecosystem, diatoms, a key group of phytoplankton at the base of the marine food web, play a crucial role in maintaining marine ecosystem balance and functioning. Conventionally, fossil diatom assemblages have been investigated in marine sediment records to reconstruct paleoenvironmental conditions and understand climate change patterns of Antarctica. Recently, the application of ancient DNA techniques to ocean sediments (sedimentary ancient DNA, sed aDNA) has provided new insights into diatom community responses to environmental change over geological time scales. One benefit of sed aDNA analysis is that this technique can detect fragile diatom species that do not preserve well and are thus difficult to study via traditional microscopy techniques. In this paper, we review the importance of diatoms as indicators of Antarctic paleoenvironmental change, the novel use of diatom sed aDNA to assist Antarctic paleoenvironmental reconstruction, and the challenges and promises of using the sed aDNA approach. We propose that Fragilariopsis cylindrus , an extant polar diatom species, is an ideal model organism to study adaptation patterns of diatoms to changing climate due to its ecological success through time and the availability of whole-genome information for this species. Novel genetic information obtainable from ancient F. cylindrus, as well as other diatoms, will help us to better predict the evolutionary and adaptive dynamics of this important group of primary producers in the climatically vulnerable Antarctic region. • Climate change in Antarctica and the need to study this polar region. • Diatoms in Antarctic ecosystem and their role as paleoenvironmental indicators. • Using the novel technique of sedimentary ancient DNA (sed aDNA) in Antarctica. • Fragilariopsis cylindrus to study adaptation and evolution of diatoms in Antarctica. [ABSTRACT FROM AUTHOR]

Abstract: Palaeoenvironmental reconstructions of lake sediment records have been greatly facilitated by statistical comparisons with microfossil assemblages from the surface sediments of modern lakes. These modern sub-fossil assemblages from different lakes, which are often referred to as “training-sets”, attempt to incorporate gradients of environmental parameters, such as e.g., temperature and phosphorus, are of interest for paleoenvironmental reconstruction. One major assumption of quantitative palaeoenvironmental reconstructions requires that the environmental variable to be reconstructed is, or is linearly related to, an ecologically important determinant in the ecological system of interest, and that the joint distribution with other variables in the fossil set is the same as in the training-set. The motivation for this paper is that present-day diatom species abundances in surface-sediment samples are often influenced by several environmental gradients. Partial least squares (PLS) or weighted-averaging partial least squares (WA-PLS) regression methods can be used to adjust species optima, if the additional PLS components, which are orthogonal to previous PLS components, are included. This paper tests a reproducible approach for reducing the influence of background variables within a diatom training-set to produce a “screened” training-set, which focuses on the variable of interest. In our example total phosphorus (TP) is the variable of interest. The initial training-set consists of modern Swiss lakes along an elevation gradient spanning 2005 m (334 to 2339 m a.s.l.), which follows a TP gradient from 522 to 3 μg L−1. However, high-elevation lakes are not distributed equally along the TP gradient. They are meso-oligotrophic because high-elevation eutrophic lakes are rare in Switzerland. This leads to a potential confounding effect between the elevation and the nutrient gradients. These higher elevation lakes were selectively excluded, using Monte Carlo permutation tests, until the conditional effect with respect of covariables of elevation was no longer significantly related to the relative abundance of diatoms. The initial and screened inference models for log TP were applied to fossil assemblages from varved sediments at Greifensee (Switzerland), which cover the past century. The evaluation of the reconstructions with measured TP (1954–1994) demonstrates that the smaller (screened) subset performs better than the larger, more heterogeneous, initial data-set when the same number of components are included. The slope of the relation between measured and inferred log TP changed significantly for the reconstructions using partial least squares, with one and two components, and for reconstruction using weighted averaging partial least squares with two components. According to our interpretation, the accuracy of the reconstructions improved because modern diatom abundances of the smaller subset are controlled mainly by log TP and lakes are more equally distributed along the log TP gradient. This approach of reducing the influence of background variables is applicable to other heterogeneous training-sets, such as merged training-sets, in order to homogenise the background variables and to maintain the gradient of interest. [Copyright &y& Elsevier]

High-latitude permafrost peatlands are sensitive to global warming, and understanding their paleohydrological evolution is critical for assessing future hydrological and environmental changes. This paper presents a diatom record from a peat deposit covering the past 3300 years to reconstruct the moisture and acidity conditions in the Tuqiang permafrost peatland in the northern Greater Khingan Mountains of northeast China. Our findings are integrated with previously published records of plant macrofossils, palynology, and geochemistry from the same profile. From 3300 to 2800 cal yr BP, planktonic and benthic diatoms were equally abundant, indicating relatively high moisture conditions, while the low abundance of acidophilous diatoms reflects relatively high pH during this interval. Pollen data show dominance by sedges with input from the surrounding Pinus forest, while LOI data and lithology suggest that the site was a non-peat accumulating wetland. During the period 2800–1100 cal yr BP, the dominance of planktonic diatoms indicates a wetter local environment, concurrent with the dominance of peat-forming sedges (Eriophorum), indicating the development of a peatland. Between 1100 and 500 cal yr BP, a short-lived increase in acidophilous diatoms (Eunotia) marks a decrease in pH. Since 500 cal yr BP, the dominance of benthic diatoms reflects a drier environment, while a vegetation shift from an Eriophorum -dominated rich fen to a Sphagnum- and Ericaceae-dominated poor fen. An increase in Eunotia diatoms prior to the Sphagnum peak may indicate that diatoms are more sensitive to local acidified habitats than moss. Peatland development in the northern Greater Khingan Mountains was likely induced by the onset of a cooler and wetter climate starting at approximately 2800 cal yr BP, a scenario supported by regional paleoclimate records. Since 700 cal yr BP, the peatland has been affected by both anthropogenic activities and climatic changes, as a drying climate and intensified human activities around the study area reduced diatom species diversity and peat accumulation. Under the background of future global warming and enhanced human activities, the decreasing species diversity and carbon accumulation rate of peatlands in high-latitude permafrost regions need more attention. • Diatoms can indicate local moisture and acidity in permafrost peatlands. • Diatoms are likely more sensitive to microhabitats than bryophytes. • TQ peatland formed after 2800 cal yr BP caused by the cooler and wetter climate. • Rich-fen shifted to poor-fen which co-influenced by deforestation and dry climate at LIA. [ABSTRACT FROM AUTHOR]

Diatom analysis of a sediment core recovered at IODP Site U1358 on the continental shelf off the Adélie Coast indicated that the lower section of the core contained an assemblage dating back to the Thalassiosira innura Zone of the lower Pliocene that ranges from 4.2 to 5.12 Ma. Based on lithological descriptions at both a macro- and micro-scale of this early Pliocene part of the core, four facies were interpreted from the diamictons representing the progressive advance and retreat of the grounding line over the site. Facies 1a and 1b contain a distinct directional signal from the orientation of the a-axis of clasts with several phases of fabric development along with both brittle and ductile deformation features that are common in sediments that have been subglacially deformed. Facies 1c and 1d are finely laminated and were deposited in open marine conditions. The four facies within the depositional model provide for the first time direct evidence for ice advancing across the shelf adjacent to the Wilkes Subglacial Basin on at least four occasions separated by three periods of open marine conditions indicating retreat of grounded ice inland of the site during a warmer than present early Pliocene. The times of open marine conditions are correlated with previous findings from the neighbouring rise sites that also indicated an oscillating ice margin. This has significant implications because firstly it suggests a dynamic East Antarctic Ice Sheet (EAIS) that is probably far more sensitive to climatic and oceanic forcing even during relatively short time periods than had previously been thought. Secondly it suggests that proxies used to interpret the advance and retreat of the grounding line from the rise can be linked with direct evidence of grounding line migration from the shelf. It also has important implications for the future behaviour and sensitivity of the EAIS under present continuing warming conditions. Together with results from the rise, this paper provides a crucial ice extent target for a new ice sheet model of this region during the Pliocene. [ABSTRACT FROM AUTHOR]

Abstract: The long‐term responses of vegetation to climate variability are of relevance for predicting present and future vegetation change, and have implications for the management of savanna and riparian ecosystems. This paper explores the links between regional rainfall, hydrology and vegetation dynamics in the savannas and riverine forests of the lower Limpopo Valley, southern Africa, from 800AD to the present, reviewing palaeoecological data (fossil pollen, spores, diatoms and lithology) from several hydrological systems in Kruger National Park (KNP), South Africa and Limpopo National Park (PNL), Mozambique. The PNL–KNP records show that riverine arboreal taxa expanded during wetter periods, including 800–1400AD and after 1800AD. Between 1400 and 1800AD, grasses, savanna taxa and generalist taxa were favored over riparian taxa, a change that is linked with the onset of dry spells in the region (corresponding to the so-called Little Ice Age). The most extreme drought events around 1700AD resulted in a marked decline of riparian forest taxa near Lake Mapimbi, KNP. In contrast, many water-scarce sequences away from the riverine environment, such as Radio Pan, Mafayeni Pan, Malahlapanga Pan and Lake Makwadzi show stable grassland vegetation throughout the last 1200years. The results demonstrate the resilience of the grassland–savanna ecosystems to projected climate change with warmer and overall drier climate. The riverine forests are predicted to be more vulnerable especially as more extreme weather events are projected. [Copyright &y& Elsevier]

Abstract: Long-term evolution is thought to take opportunities that arise as a consequence of mass extinction (as argued, for example, by Gould, 2002) and the following biotic recovery, but there is absolutely no evidence for this being the case. However, our study shows that eutrophication by oceanic mixing also played a part in the enhancement of several evolutionary events amongst marine organisms, and these results could indicate that the rates of oceanic biodiversification may be slowed if upwelling becomes weakened by future global warming. This paper defines three distinct evolutionary events of resting spores of the marine diatom genus Chaetoceros, to reconstruct past upwelling through the analysis of several DSDP, ODP and land-based successions from the North, South and equatorial Pacific as well as the Atlantic Ocean during the past 40million years. The Atlantic Chaetoceros Explosion (ACE) event occurred across the E/O boundary in the North Atlantic, and is characterized by resting spore diversification that occurred as a consequence of the onset of upwelling following changes in thermohaline circulation through global cooling in the early Oligocene. Pacific Chaetoceros Explosion events-1 and -2 (PACE-1 and PACE-2) are characterized by relatively higher occurrences of iron input following the Himalayan uplift and aridification at 8.5Ma and ca. 2.5Ma in the North Pacific region. These events not only enhanced the diversification and increased abundance of primary producers, including that of Chaetoceros, other diatoms and seaweeds, but also stimulated the evolution of zooplankton and larger predators, such as copepods and marine mammals, which ate these phytoplankton and plants. Current thinking suggests new evolutionary niches open up after a mass extinction, but our study finds that eutrophication can also stimulate evolutionary diversification. Moreover, in the opposite fashion, our results show that as thermohaline circulation abates, global warming progresses and the ocean surface becomes warmer, many marine organisms will be affected by the environmental degradation. [Copyright &y& Elsevier]

Abstract: The paper presents the first paleontological data (pollen, plant macrofossil, diatom and ostracod) on the sediments of Lake Beloye, which is situated in the forest-steppe zone of Western Siberia. Our study contributes to better understanding of the Middle–Late Holocene regional to local environmental changes. Regionally, we recognized a cold stage of 3.4–2.3 calibrated ka BP and a dry stage of 2.8–1.7ka BP. The dry stage coincides with the climate-driven lowered level of the lake at 2.6–1.5ka BP. Later, the climate changed to warmer and wetter, which resulted in a highest stand of the lake at 1.3–0.2ka BP and was followed by the lowering of the lake. Forest-steppe persisted in this area during the whole period under consideration, but probably shifted southward. Such a shift is reflected in the environment around Lake Beloye similar to that of modern taiga, which existed at 3.2–1.3ka BP, however, compared to the colder and wetter climate of taiga, the conditions were colder and drier. The local plant associations and the lake ecosystem were affected by those events of climate and lake level changes. The initial eutrophic sedge-reed swamp evolved to the oligo-mesotrophic sphagnum bog, which existed around the lake at 3.2–1.3ka BP. Later, the bogging process was interrupted by the lake transgression, after which the dried bog around the lake was occupied by the birch forest. The lake ecosystem was strongly affected by the 3.4ka BP climate change: the low-alkaline eutrophic lake with abundant water higher plants and diatoms changed to the alkaline oligotrophic lake with calcium-fixing macrophytic algae and angiosperms. This resulted in total change of lake''s bio-geochemical and sedimentation patterns. [Copyright &y& Elsevier]

Abstract: In northeastern Siberia, Russia, a 1.2m sediment core was retrieved and radiocarbon dated from a small and shallow lake located at the western side of the lower Lena River (N 69°24′, E 123°50′, 81ma.s.l.). The objective of this paper is to reconstruct the palaeoenvironmental variability and to infer major palaeoclimate trends that have occurred since ~13.3cal. kyr BP. We analysed the diatom assemblages, sedimentology (grain-size, total organic carbon (TOC), total nitrogen (TN)), and the elemental and mineralogical composition using X-ray fluorescence (XRF) and X-ray diffractometry (XRD) of the sediment core. Our results show parallel changes in the diatom species composition and sediment characteristics. Enhanced minerogenic sediment input and the occurrence of pyrite is indicative of a cold period between ~12.7 and 11.6cal. kyr BP. The diatom data enable a qualitative inference about the local ecological conditions to be made, and reveal an oligotrophic lake system with alkaline and cold conditions during the earliest Holocene. Moderately warmer climates are inferred for the period from ~9.1 to 5.7cal. kyr BP. The major shift in the diatom assemblage, from dominance of small benthic fragilarioid taxa to a more complex diatom flora with an influx of several achnanthoid and naviculoid diatom species, occurred after a transitional period of about 1400yr (7.1 to 5.7cal. kyr BP) at ~5.7cal. kyr BP, indicating a circumneutral and warmer hydrological regime during the Holocene thermal maximum (HTM). Diatom valve concentrations declined starting ~2.8cal. kyr BP, but have been rising again since ≤600cal. yr BP. This has occurred in parallel to the increased presence of acidophilous diatom taxa (e.g. Eunotia spp.) and decreased presence of small benthic fragilarioid species in the most recent sediments, which is interpreted as the result of neoglacial cooling and subsequent recent climate warming. Our findings are compared to other lake-inferred climate reconstructions along the Lena River. We conclude that the timing and spatial variability of the HTM in the lower Lena River area reveal a temporal delay from north to south. [Copyright &y& Elsevier]

Abstract: A quantitative biochronological study by Cody et al. (2008) integrates comprehensive diatom biostratigraphy, magnetostratigraphy, and tephrostratigraphy from 32 Neogene sections around the Southern Ocean and Antarctic continental margin. A recent method, known as Constrained Optimization (CONOP), which can be viewed as a multidimensional version of graphic correlation, is applied to that very interesting database. The goal of the present paper is to discuss some theoretical aspects of quantitative biochronology and to compare the constrained optimization with the deterministic method called Unitary Associations (UAM), a graph theoretical model. We illustrate the fact that the UAM is an extremely powerful and unique theory allowing an in-depth analysis of the internal conflicting inter-taxon stratigraphic relationships, inherent to any complex biostratigraphical database. [Copyright &y& Elsevier]

Abstract: This paper investigates changes in the vegetation and hydrology at Ljubljansko barje (Slovenia) using a multi-proxy approach (pollen, diatoms, geochemical and stable isotope analysis). During the Lateglacial Ljubljansko barje was a deep, oligotrophic lake surrounded by open woodland comprised predominantly of Pinus and Betula which in the early Holocene, when the lake became shallower and mesotrophic (Fragilaria pinnata, δ 15N~3.3‰, δ 13C~−33.7‰, C/N~7.9), was replaced by broadleaved tree taxa (Tilia, Ulmus, Quercus, Corylus) and Picea. This was followed by the spread of Fagus and after ~9200 cal yr BP Abies and planktonic and oligotrophic diatom taxa (Aulacoseira italica, Gomphonema angustum) as well as an increased allochthonous influx (silt, SiO2, Al2O3). Between ca. 6750 and 6000 cal yr BP the diatom data suggest shallower and oligotrophic conditions, whereas the stable isotope record (increased δ 13C and decreased δ 15N) indicates terrestrial input. Changes in forest composition (increase of Quercus, Alnus, Corylus) and the spread of herb taxa were probably advanced by human impact on the environment. The beginning of organic sedimentation, dated to 6000 cal yr BP, was followed by an increase of Fagus and Abies and by eutrophication and peat growth at ~5200 cal yr BP. [Copyright &y& Elsevier]

Abstract: This paper reports new multi-proxy palaeoenvironmental data on the late Glacial-Holocene transition (c. 14.8–9.3 ka) in equatorial East Africa, in the form of microfossil assemblages (chironomids, diatoms and ostracods) recovered from the sediment record of Lake Emakat, Empakaai Crater, northern Tanzania. In the context of available palaeoclimatic and palaeoecological information from the region and previously published fossil pollen and carbon and nitrogen isotopic data for the same sediment sequence, we here reconstruct local lake-system response to regional climatic and hydrological instability during the period of post-glacial warming. The aquatic biological proxy indicators suggest that the water level and chemistry of Lake Emakat evolved, first from a shallow freshwater body at 14.8 ka to a deeper freshwater phase between c.14.4 and 10.3 ka and then to a markedly shallower, alkaline-saline environment after c.10.3 ka. The lake appears to have been deepest between 13.2 and 12.0 ka, at a time of climatic drying when moist montane forest vegetation within the lake''s crater catchment was being replaced by open wood-and scrubland. Some palaeohydrological changes reconstructed for Lake Emakat are in phase with lake evolution elsewhere in the region and thus apparently track broad-scale climate changes, but some are not. Collectively these multi-proxy paleolimnological data indicate a complex adjustment of the local aquatic ecosystem to temporal variations both in total annual effective precipitation and its seasonal distribution. The lake''s hydrological response was further conditioned by local factors, notably its geological and topographic setting. [Copyright &y& Elsevier]

Abstract: This paper examines the interdependence among the different forcing factors in the evolution of the Traba coastal wetland (Galicia, NW Spain) based on lithofacies and diatom analyses of three cores reaching the basement. According to radiocarbon data, the wetland originated 5700 cal yr BP, a time when similar systems on the Atlantic coast of the Iberian Peninsula were formed. Diatom assemblage data allow the estimation of the sea level position at 5700 cal yr BP at least 7 m below present-day mean sea level. Attenuation of the sea-level rise at that time was a major driving mechanism that permitted the establishment of an incipient beach–dune complex, causing water-logging in the Traba basin. However, the location of this incipient wetland on a basement high, which prevented an open connection to the sea, made topographic inheritance the main forcing factor in the subsequent evolution of the wetland. Thus, Traba was never a coastal lagoon system, as it has sometimes been defined. The maximum permeability of the beach–dune complex enclosing the wetland was recorded after its origin until 2900 cal yr BP, when increased stormy conditions affected the Galician shelf waters. Since then, the evolution of the wetland has been mainly controlled by more local factors, especially the continental sediment supply. Changes in land use in the basin have accelerated the infilling of the water body since the 19th century. This rapid infilling makes the whole system more prone to total encroachment in the short term, rather than to sea drowning. Palaeoenvironmental analyses showing the main trends in the long-term evolution of coastal wetlands can be of key importance in any management decisions aimed at preserving these kinds of sensitive coastal environments. [Copyright &y& Elsevier]

Abstract: The analysis of oxygen isotope ratios (δ 18O) from authigenic lake carbonates has become a well-established palaeoclimate technique. Less common is the use of δ 18O in biogenic silica (e.g. diatoms, sponge spicules, phytoliths), but the technique is being increasingly utilised for non-carbonate lakes. This paper aims to compare δ 18Odiatom with δ 18Ocarbonate in a low latitude, closed basin lake. Due to the influence of pH, rarely are both carbonate and diatoms preserved in lake sediments in concentrations high enough to measure oxygen isotopes. The δ 18O composition of both carbonate and silica should reflect the isotope composition and temperature of the lake water at the time of precipitation and hence theoretically they should be equivalent. Only one comparative study of δ 18Odiatom and δ 18Ocarbonate currently exists and that found differences between their δ 18O compositions, probably because they precipitated in different seasons. Unless there is evidence to suggest that silica and carbonate precipitate at the same time, their δ 18O records are likely to be different but complementary. In this study, we show that δ 18Odiatom and δ 18Ocalcite from Lake Tilo, Ethiopia show some similar broad climate trends. However, the δ 18Odiatom curve is generally more variable and does not record two regional arid events, picked up by the δ 18Ocalcite data. Several possible reasons for this are discussed: the precision of the δ 18Odiatom extraction technique, contamination of the diatom samples from tephra (volcanic glass), vital effects in the diatom samples, differences in their respective equilibrium isotope fractionation rates and the possibility that the dominant diatom, Aulacoseira granulata, and calcite precipitated in different seasons during this time. Currently, the problems associated with the cleaning and extraction of δ 18Odiatom suggests that details found in δ 18Ocalcite records may be lost in δ 18Odiatom records where contaminants such as tephra and clay minerals are difficult to remove. [Copyright &y& Elsevier]

Abstract: This paper describes a multi-core lake sediment study using pollen, diatoms, and chironomids, together with magnetics and sediment biogeochemistry, as biotic and abiotic proxies to infer lake development in response to environmental change during the Holocene at Lochnagar in the eastern Highlands of Scotland. Diatoms are used to infer pH, chironomids to infer temperature, with pollen and plant megafossils acting as an independent proxy to validate these records and to provide insights into changes in catchment vegetation and soils. Lipid biomarkers are explored for their potential to provide additional information on lake productivity. The results indicate highly distinctive fluctuations in the loss-on-ignition (LOI) record, which are in phase with changes in some biotic (chironomid head-capsule concentration) and abiotic (coarse silt particle size fraction, and lipid and chlorine fractions) variables. Catchment-driven changes due to the development and degredation of soils, and the natural succession and human intervention on terrestrial catchment vegetation have the strongest influence on the diatom and chironomid assemblages. These catchment processes resulted in the natural acidification of the lake water. Post-industrial acidification of the lake was also influential on the lake biota. Climate-driven temperature change appears to have had only a weak influence on the biota with declines in cold stenothermic chironomid taxa in response to Early Holocene warming and declines in thermophilic chironomids in response to cooling at about 2600 cal. yr BP. [Copyright &y& Elsevier]

In the southern tropical Andes, previous studies performed on lacustrine basins display large water-level fluctuations due to changes in the precipitation minus evaporation balance during the Holocene. Significant changes in groundwater levels were also inferred from river paleowetland deposits in northern Chile and the northern Bolivian Altiplano but the discrepancies which appeared in the data from paleolakes and paleowetlands are still not understood. In this paper we present stratigraphy and diatom analyses in new paleowetland records from non-glacial valleys. These data, compared with previous results, show that non-stormy precipitation (recorded by fine and/or organic sedimentation) dominated continuously from ∼11 200 to ∼1500 cal yr BP and that convective rainfall (recorded by strong erosion) occurred only episodically in the northern Altiplano. Convective rainfall was similar to the type of precipitation which nowadays occurs during the rainy season (austral summer) when the tropical easterlies from the Atlantic reach the Bolivian Andes. Non-stormy precipitation is interpreted as a result of an intensification of cold-air incursions from southern polar regions, in good agreement with data from Brazil. The maximum intensity in cold-air incursions occurred during the Early Holocene and coincided with a climatic optimum in Antarctica and a considerably reduced El Nin˜o Southern Oscillation (ENSO). During the Middle and Late Holocene, cold-air incursions decreased and the ENSO frequency increased. We suggest that the interactions between the southern high and low latitudes, by means of cold-air incursions and associated changes in the west wind flow, have been the main mechanisms involved in climatic changes at the latitudes of Bolivia. [Copyright &y& Elsevier]

The Eocene sediment successions of the East Pisco Basin (southern Peru) host an exceptionally rich and well-preserved assemblage of vertebrate fossils. However, due to the dearth of geochronological and biostratigraphic controls as well as of stratigraphic correlations, our understanding of these rocks and their fossil content remains elusive. This paper provides a comprehensive calcareous nannofossil, diatom, and silicoflagellate biostratigraphic framework for the Eocene strata exposed at four localities along the Ica River Valley, permitting a robust chronological calibration of the marine vertebrate fauna entombed therein and a better definition of important appearance/ extinction events. The Paracas Formation, deposited directly on top of the Proterozoic and Paleozoic rocks of the crystalline basement, is formed by a siliciclastic-bioclastic sand-sized deposit (Los Choros member) and calcareous-terrigenous siltstone (Yumaque member) that was deposited from the Lutetian (47.8–41.2 Ma) through the Bartonian (41.2–37.7 Ma) to the early Priabonian (37.7–33.9 Ma). The unconformably overlying Otuma Formation consists of a basal sandstone, followed by calcareous siltstone intercalated by diatomite layers towards the top. In the study area, the Otuma Formation is Priabonian in age and is truncated at the top by an unconformity at the base of the overlying Miocene Chilcatay Formation. Due to the angular nature of the unconformity, the upper Otuma strata reach the Oligocene elsewhere. Average sedimentation rates range from 17 to 24 m/My in the Yumaque member of the Paracas Formation and increase to 147–170 m/My in the Otuma Formation. The microfossil assemblages witness a coastal setting with warm-temperate conditions for the Paracas Formation that become slightly cooler (though still temperate) in the upper Otuma Formation. Diatomaceous layers in the upper Otuma Formation indicate an overall increase in nutrient availability, which could reflect the global reorganization of ocean currents at the Eocene-Oligocene transition. However, the taxonomic composition of the diatom assemblage suggests seasonal rather than persistent upwelling conditions. • Calcareous nannofossils constrain the Paracas Fm to the Lutetian-early Priabonian • Calcareous nannofossils and diatoms indicate that the Otuma Formation is Priabonian • The East Pisco Basin was warm-temperate in the Lutetian-Bartonian • Slight cooling and seasonal upwelling occur in the basin in upper Priabonian [ABSTRACT FROM AUTHOR]

Evaluating and understanding bio-environmental relationships at different spatial and temporal scales is important for accurately assessing marine productivity in relation to oceanographic conditions in changing Arctic ecosystems. In this paper, we compare four different bio-environmental datasets, in order to shed new light on the complex marine ecosystem of the Baffin Bay-Labrador Sea region, as well as the historical links between environmental changes and the ecosystem. Satellite dataset was used to describe the regional distribution of chlorophyll a , sea ice concentration (SIC), sea surface temperature (SST) and sea surface salinity (SSS). Chlorophyll a data were also analysed together with shrimp assessment dataset to examine the relationship between marine pelagic productivity and bottom feeders off the Greenland coast. A microfossil dataset (diatom valves) from 57 surface sediment stations was used to describe diatom concentration and diversity across the study region. It was also used in combination with satellite data from the same sites to analyse species-environment relationships and develop a diatom-based transfer function for reconstructing past changes in SIC, SST and SSS. Subsequently, we applied the diatom transfer function on three short sediment cores from off SW and W Greenland spanning the last few centuries. A monitoring dataset of sea ice observations and instrumental measurements of water temperature and salinity, together with atmospheric data (air temperature and wind conditions) from Greenland, were used to develop a more complete picture of 20th and 21st century changes in ocean-climate conditions. Our comparative analyses show clear spatial distribution patterns of marine phytoplankton and identify key ecological groups linked to oceanic conditions. In addition, we find a significant correlation between the different trophic levels, culminating in a 'productivity boom' in 2001 CE. On a longer temporal scale, the transfer function reconstructions reveal a good correlation with the satellite, monitoring and observational trends, as well as a consistent, long-term decrease in sea ice linked to ocean-climate variability. • Satellite, monitoring, microfossil and shrimp survey datasets were studied. • Present-day marine biotal environment in Baffin Bay-Labrador Sea was described. • SW-W Greenland sea ice and temperature-salinity conditions were reconstructed. • Satellite, monitoring, microfossil ocean-climate datasets were compared. • Marine productivity and shrimp data were correlated for trophic link. [ABSTRACT FROM AUTHOR]