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The global impact of the Youngest Toba Tuff (YTT) supereruption ~74,000 years (ka) ago is still heavily debated, ranging from having insignificant effects on climate to severely affecting modern human evolution. Climate models and terrestrial proxy records show that the YTT eruption may have caused cooling of the Asian landmass, thus impacting regional climate such as the Indian monsoon system. However, the immediate effect of the eruption on the Indian monsoon has not been indisputably demonstrated in any proxy record. Here, we present a nearly annual phytoplankton-based primary productivity (PP) record from the northeastern Arabian Sea and show that PP increased by ~65% for about 10–20 years after the eruption. The elevated PP is most likely linked to the deepening of the ocean mixed layer driven by strengthened northeasterly Indian winter monsoon winds, supporting previous modeling studies and demonstrating unequivocal evidence from a marine record for an Indian monsoon response to the YTT eruption. Conversely, the intensified winds might have decreased PP off Somalia as observed today during winter and reduced the marine food supply of early humans in the region—a factor that may have contributed to the postulated migration window during this time.

Many have postulated that a specific microbial metabolism or the presence of microbes or/and their extracellular polymeric substances (EPS) can lead to the formation of dolomite. Although now there is the consensus that dolomite can be formed in the presence of microorganisms, the exact nature of the involvement of microbes in the dolomite nucleation remains a matter of debate. The focus is now in understanding how microbial mats determine the mineralogy of dolomite. Here we report the effect of the EPS extracted from phototrophic microbial mat isolated from a sabkha in Qatar dominated by cyanobacteria (Lyngbya aestuarii) in the formation of dolomite precursors at 25 °C and 40 °C. Both the temperature and the presence of EPS impact the size and morphology of minerals, promoting spherulitic and dumbbell growth in sulfate free solutions. The formation of proto-dolomite was enhanced by the abundance of carboxylated molecules in EPS which controlled the polymorphism of carbonates. Our study emphasizes the dual importance of organic matter and temperature in dolomite formation and their impact on mineral morphology and chemical composition in sabkhas.

Summary Here a work flow towards an accurate representation of interference colours (Michel-Levy chart) digitally captured on a polarised light microscope using dry and oil immersion objectives is presented. The work flow includes accurate rendering of interference colours considering the colour temperature of the light source of the microscope and chromatic adaptation to white points of RGB colour spaces as well as the colour correction of the camera using readily available colour targets. The quality of different colour correction profiles was tested independently on an IT8.7/1 target. The best performing profile was using the XYZ cLUT algorithm and it revealed a ΔE00 of 1.9 (6.4 no profile) at 5× and 1.1 (8.4 no profile) at 100× magnification, respectively. The overall performance of the workflow was tested by comparing rendered interference colours with colour-corrected images of a quartz wedge captured over a retardation range from 80–2500 nm at 5× magnification. Uncorrected images of the quartz wedge in sRGB colour space revealed a mean ΔE00 of 12.3, which could be reduced to a mean of 4.9 by applying a camera correction profile based on an IT8.7/1 target and the Matrix only algorithm (ΔE00 < 1.0 signifies colour differences imperceptible by the human eye). ΔE00 varied significantly over the retardation range of 80–2500 nm of the quartz wedge, but the reasons for this variation is not well understood and the quality of colour correction might be further improved in future by using custom made colour targets specifically designed for the analysis of high-order interference colours.

Rochin-Banaga, H.; Bollmann, J.; Cortes, M.Y., and Aguirre-Bahena, F., 2017. First account of Parmales (Chrysophyceae) in sediment trap samples from the Alfonso Basin, Gulf of California, Mexico. The flux of Parmales was analyzed from samples collected by a sediment trap deployed at 300 m depth in Alfonso Basin, Bay of La Paz. Twelve time-series samples were collected from September 2011 to September 2012 with a monthly resolution. Tetraparma insecta was the only species identified in this study. Its total fluxes varied considerably, with a minimum flux of 1 × 106 individuals m−2 d−1 in spring-summer and maximum flux of 66 × 106 individuals m−2 d−1 in autumn. The maximum flux was associated with warm water conditions (28°C). The observation of T. insecta in sediment traps suggests that this species might also be preserved in the sediment record at the Alfonso Basin.

This study presents a simple technique for the approximation of retardation, thickness and mass of birefringent particles with a retardation from 8 to 231 nm retardation. Tuning of the imaging system (standard light microscope equipped with a left and a right circular polarizer) to match grey values of polymer retarder films of known retardation with rendered grey values allows for a robust calibration and accurate approximation of retardation. In addition, a technique for accurate particle segmentation using a Canny-Deriche algorithm was used to minimize the bias on mass estimated from different thresholding techniques. The technique was tested using microscopic calcitic plates called coccoliths produced by the marine algal group coccolithophores, and the results compare well with published coccolith mass estimates obtained from volumetric analysis. LAY DESCRIPTION: Material with certain optical properties display interference colours when observed in a light microscope under circular polarized light. This study presents a simple technique for measuring the thickness and retardation of small particles within the 8 to 231 nm retardation range based on the grey values of their interference colours. Retardation is a measure of the distance between waves of two mutually perpendicular polarized light waves after passing through material. The technique involves the tuning of a standard light microscope system equipped with a left and a right circular polarizer and a digital camera to match grey values of polymer retarder films with a known retardation with grey values of a digitially rendered Michel-Levy chart. A technique for accurate isolation of particles from the image background using a Canny-Deriche algorithm is also described, which avoids possible biased results from thresholding. The techniques were tested using microscopic calcitic plates called coccoliths produced by the marine algal group coccolithophores, and the results compare well with published estimates obtained from volumetric analysis.

Diatomeas bentonicas de ambientes someros depositadas a 300 m de profundidad en una cuenca del sur del Golfo de California Se registraron diatomeas bentonicas recolectadas con una trampa Technicap modelo PPS-3/3 con una abertura de 0.125 m 2 , la cual consta de un carrusel programable motorizado con doce botellas de 250 mL instalada a 300 m de profundidad en Cuenca Alfonso, Bahia de La Paz. Se contrasto la hipotesis de que diatomeas depositadas en la trampa de sedimento estarian relacionadas a ambientes de manglar de la Bahia de La Paz. Asi, con el objetivo de identificar las diatomeas bentonicas e inferir su procedencia, se reviso una muestra del periodo diciembre de 2011 a enero de 2012. La identificacion se realizo a partir de imagenes tomadas con un microscopio electronico de barrido Zeiss Supra Vp55. Se identificaron 38 taxa de diatomeas, 32 de las cuales fueron formas bentonicas entre las que se incluyen las especies: Actinoptychus vulgaris, Halamphora coffeaeformis, Delphineis surirella, Fragilariopsis doliolus y Nitzschia amabilis . Como estas, las diatomeas observadas corresponden principalmente a taxa bentonicos comunmente representadas en habitats de las zonas intermareal y submareal someras. Aunque la hipotesis fue respaldada, la composicion de especies de diatomeas no permitio mayor precision sobre el ambiente de procedencia.

Stable isotope ratios of carbon (δ13C) and oxygen (δ18O) from tree ring cellulose can provide valuable paleoclimatic information at annual and subannual resolution, from time periods long before instrumental climate records. Recently, mummified (non-permineralized) wood was discovered within Canadian Subarctic kimberlites, inviting paleoclimatic investigations of the time in which the trees grew. In the mummified wood, polysaccharides (hemicellulose, α-cellulose) are frequently preferentially degraded, in the low-silica anaerobic burial environment of the kimberlites, resulting in a lignin-rich material. However, some samples from the Ekati Panda kimberlite pipe (ca. 53.3 Ma) contain remnant cellulose, demonstrating the extraordinary preservation potential of kimberlites. Preservation of α-cellulose is important because it allows for the construction of stable isotopic proxy records of deep-time paleoclimates at annual to subannual resolution. Established α-cellulose extraction methods [i.e., using a 17.5% sodium hydroxide (NaOH) solution] were unsuitable for this material because all holocelluloses were dissolved. Therefore, we tested variants of two cellulose extraction methods [i.e., Brendel et al. (2000) and Jayme-Wise (Leavitt and Danzer 1993, Loader et al. 1997)] to optimize a procedure for extraction of a consistent yield of mummified wood cellulose for stable isotopic analysis. Stable carbon (δ13C) and oxygen (δ18O) isotopes were measured from cellulose from each extraction method, as well as Extractive-Free Wood and unextracted mummified wood. vitrinite reflectance, used to assess thermal alteration of the unextracted material to estimate post-burial temperatures within the kimberlite, suggested low post-burial peak temperatures (Tpeak = 60 °C). We detected no mineral contaminants (i.e., iron oxides) in the material using Energy-Dispersive X-ray Spectroscopy (EDX). Despite low cellulose yield (

Previous studies of deeply oxygenated (8–12 cm) sediments in Lake Superior revealed prominent iron (Fe)-rich layers, up to 2 cm thick. Whereas metal enrichments are common near the oxic–anoxic boundary in aquatic sediments, several geomicrobiological aspects of their formation remain unknown. In this study, we analyzed geochemical and microbiological signatures associated with the Fe-rich layer in Lake Superior at two locations (230 and 310-m water depth) in the Eastern Basin of the lake. We measured oxygen and metal contents in the sediment solid phase and imaged the Fe-rich layer with transmission and scanning electron microscope (TEM and SEM). Bacterial communities were characterized using tag-encoded FLX small subunit ribosomal gene amplicon pyrosequencing. The SEM images reveal filamentous structures encrusted with spheres of ca. 20 nm in diameter. TEM and energy dispersive X-ray spectroscopy observations of thin sections indicate that bacteria cells served as nucleation surfaces for Fe-oxide formation. The Fe-rich layers, in contrast to the layers directly above them, were dominated by members of the NC10 phylum, known for anaerobic methane oxidation, and also harbored a high proportion of Nitrospira species that were most similar to members of a Fe-rich seep. Taken together the results suggests that microorganisms, whose cell surfaces are serving as templates for iron oxide precipitates that might also be mediating the iron oxidation, support formation of the Fe-rich layers.

A circular polarizer is used for the first time to image coccoliths without the extinction pattern of crossed polarized light at maximum interference colour. The combination of a circular polarizer with retardation measurements based on grey values derived from theoretical calculations allows for the first time accurate calculations of the weight of single coccoliths thinner than 1.37 μm. The weight estimates of 364 Holocene coccoliths using this new method are in good agreement with published volumetric estimates. A robust calibration method based on the measurement of a calibration target of known retardation enables the comparison of data between different imaging systems. Therefore, the new method overcomes the shortcomings of the error prone empirical calibration procedure of a previously reported method based on birefringence of calcite. Furthermore, it greatly simplifies the identification of coccolithophore species on the light microscope as well as the calculation of the area and thus weight of a coccolith.

The discovery of exceptionally well-preserved Paleogene wood fossils (ca. 55–53 Ma) within Canadian Arctic diamond-bearing kimberlites prompted a paleoclimatic study of the Paleocene-Eocene Transition. The samples are not petrified, but have been “mummified” by their inclusion in pyroclastic debris and still contain primordial wood material. However, preferential cellulose loss has rendered the wood very fragile, precluding the use of standard dendrochronological methods of surface preparation. Similar to archaeological charcoal, breaking the mummified wood allows superior visualization of tree-ring boundaries and wood anatomy, but often produces irregular surfaces making microscopic examination difficult. Therefore, a simple aluminum clamp was constructed to break radial wood transects in a controlled manner for the purpose of collecting dendrochronological and wood-anatomical data for paleoclimatic reconstructions. Because it does not require the use of chemical treatments or stabilizing resins...

Multiple proxies from a 319-cm peat core collected from the Hudson Bay Lowlands, northern Ontario, Canada were analyzed to determine how carbon accumulation has varied as a function of paleohydrology and paleoclimate. Testate amoeba assemblages, analysis of peat composition and humification, and a pollen record from a nearby lake suggest that isostatic rebound and climate may have influenced peatland growth and carbon dynamics over the past 6700 cal yr BP. Long-term apparent rates of carbon accumulation ranged between 8.1 and 36.7 g C m− 2 yr− 1 (average = 18.9 g C m− 2 yr− 1). The highest carbon accumulation estimates were recorded prior to 5400 cal yr BP when a fen existed at this site, however following the fen-to-bog transition carbon accumulation stabilized. Carbon accumulation remained relatively constant through the Neoglacial period after 2400 cal yr BP when pollen-based paleoclimate reconstructions from a nearby lake (McAndrews et al., 1982) and reconstructions of the depth to the water table derived from testate amoeba data suggest a wetter climate. More carbon accumulated per unit time between 1000 and 600 cal yr BP, coinciding in part with the Medieval Climate Anomaly.

A high-resolution study focussing on the distribution of calcareous nannofossils and carbon isotopes was carried out to improve the understanding of mid-Cretaceous black shale formation. The studied interval of the early Late Aptian is characterized by two major black shale couplets, the Niveau Noire 4 (NN4) and Niveau Noire Calcaire 2 (NNC2), of the Serre Chaitieu section in the Vocontian Basin (SE France; Breheret, 1997). This interval occurs within a long-term negative carbon isotope excursion of > 1.5‰ following the Early Aptian Oceanic Anoxic Event 1a (OAE1a). In contrast to the local NN4 black shales, the black shales of NNC2 are of regional significance and occur at the end of the major negative carbon isotope excursion of the early Late Aptian. Time equivalent black shales are suggested to be coeval with black shales found in the Western Tethys and Atlantic Ocean (Herrle et al., 2004). Calcareous nannofossil analyses and carbon isotopes indicate higher surface water productivity (mesotrophic), warmer surface water, and higher sea-level during the formation of the NN4 black shales. In contrast, the formation of the NNC2 black shales took place during a cooler phase, lower surface water productivity, and lower sea-level. A sea-level fall may cause a restriction of water mass exchange between the open-marine Western Tethys and the Vocontian Basin. This resulted in a longer residence time of the bottom water, decreased ventilation and less mixing of surface waters and thus enhanced preservation of organic matter at the sea floor. Our results indicate that the black shale formation of NN4 and NNC2 was caused by different processes such as increased surface water productivity and enhanced preservation of organic matter at the sea floor. Thus, we emphasize the role of different forcing factors which control the formation of local and regional black shales. The most important factors are sea-level fluctuations, increasing productivity, and changes in precipitation and evaporation rates.

In order to test whether morphological variations within Gephyrocapsa oceanica var. typica Kamptner 1943 reflect genotypic variation or phenotypic responses to environmental conditions, culture experiments of six strains of G. oceanica collected at different locations in the North Atlantic and Mediterranean have been carried out under different temperature and nutrients conditions. All morphological, and physiological data suggest the presence of two species or subspecies within G. oceanica var typica that correspond morphologically to Gephyrocapsa "Larger" and possibly to Gephyrocapsa "Equatorial" as previously defined from Holocene sediments. Given the importance of Gephyrocapsa species for the carbon cycle in the past, genetic studies on this group are of major interest to the understanding of past climate change and plankton evolution.

We analysed the morphology of Emiliania huxleyi from globally distributed plankton samples and demonstrate that the size of E. huxleyi placoliths is highly correlated to in-situ sea surface water salinity. We used multiple linear regression analysis to link morphological parameters of E. huxleyi to in-situ salinity and in-situ temperature. The best multiple regression model yielded an R 2 = 0.84 with a standard residual error of 0.65 for in-situ salinity over a gradient from 32.6 to 38.8. No significant correlation existed with temperature. Our results suggest that the morphology of E. huxleyi placoliths of recent and ancient sediments may provide a robust method to reconstruct sea surface salinities. One caveat is that the plankton-derived multiple regression model for in-situ salinities is different from that reported from previous work on Holocene sediments. This discrepancy is most likely caused by taphonomic processes or from the biogeographically biased data sets which were used (open ocean versus near shore). The cause of the tight relation between salinity and morphological response is not well understood but may be related to cell turgor regulation that affects the size of the cell and thus the size of a single coccolith.

Culture experiments were used to assess the applicability of Emiliania huxleyi coccolith morphology as a palaeo-sea-surface salinity (SSS) proxy. Coccolith morphology was dependent on salinity over a range reflecting present day marine conditions; both coccolith size and the number of coccolith elements increased linearly with increasing salinity. Using regression analysis, the effect of salinity on coccolith morphology was compared to those previously observed in sediment core-top and plankton data. No significant differences were found between the slopes of these data, suggesting that salinity is the primary control on E. huxleyi coccolith size and element number in the ocean. However, the intercepts of the culture data were significantly higher. A combination of experimental and literature analysis indicated that temperature and nutrients were unlikely to be the causes of this discrepancy. Literature analysis also highlighted that coccolith size data from marginal environments displayed different intercepts to those from the open-ocean data. This suggests that discrete morphotypes exist in these marginal locations. We, therefore, recommend that the original E. huxleyi coccolith morphology palaeo-SSS transfer function requires further evaluation before being routinely applied.

Calcite dissolution of planktic foraminifers that settle from the surface ocean to depths has been assessed using the weight/size relationship of tests and correlated to carbonate ion concentration ( [ CO 3 2 - ] ) of ambient sea water. Globigerina bulloides and Globigerinita glutinata were sampled from the North Atlantic and the Arabian Sea during different seasons (spring and fall and the monsoons, respectively). Test weight has been determined for single tests from narrow size classes ( 250 ± 8 μ m and 300 ± 7 μ m minimum test diameter). Initial test weight of both species in surface waters differs between regions and seasons. Weight loss of settling tests in the twilight zone between 100 and 1000 m water depths averaged 19%. Below the twilight zone (1000–2500 m) no weight loss occurs on average, and tests may even gain weight. Remineralization of settling planktic foraminiferal tests is most pronounced at maximum Δ CO 3 2 - . Accordingly, strong dissolution occurs in the twilight zone, at the depth of maximum decrease in Δ CO 3 2 - . It is assumed that dissolution of planktic foraminiferal calcite is caused by CO 3 2 - (under-) saturation inside the test, buffered by diffusive exchange of CO 3 2 - ions with the ambient sea water through the pores and aperture. Consequently, reconstruction of small-scale differences in seawater [ CO 3 2 - ] from test weight alone is not feasible and systematic correlation between test weight and Δ CO 3 2 - of the ambient sea water is statistically not significant. At constant [ CO 3 2 - ] , remineralization cannot be deduced from test weight, neither at high nor low CO 3 2 - saturation. In total, our data suggest that the global vertical planktic foraminiferal CaCO 3 flux is about 19% lower than calculated by Schiebel [2002. Planktic foraminiferal sedimentation and the marine calcite budget. Global Biogeochemical Cycles, 16 (4), 1065 [doi: 10.1029/2001GB001459]].

Morphometric analysis of coccoliths of various coccolithophore species from core top and culture samples has revealed that the morphology of single placoliths can be affected by environmental parameters such as temperature, salinity, and productivity. In this study, we have tested the morphological variations of placoliths of Emiliania huxleyi, the most common coccolithophore species in the modern ocean, with respect to environmental gradients. We have investigated especially the potential effect of salinity on the morphology, as it is known from culture studies that the growth of E. huxleyi placoliths is strongly influenced by varying salinities. Morphometric analysis of about 2150 placoliths from 37 globally distributed core top and plankton samples revealed that the morphology of E. huxleyi varies significantly along a sea surface salinity gradient from 33 to 38. Morphological parameters such as the mean size of placoliths are used as explaining variables in multiple regression analysis to reconstruct sea surface salinities (SSS). The best model for mean SSS yields an R 2 of 0.88 with a standard error of 0.49 whereas statistical models describing surface water temperature or productivity are less reliable and accurate. Application of the best model to plankton samples allows the prediction of in-situsalinitieswithingivenerrorestimates.TheapplicationofthebestmodeltofossilassemblagesfromtheLGM,however,ismore puzzling. Paleosalinity reconstructions in the South Atlantic, the Caribbean Sea, and the subtropical Atlantic are in good agreement with the published values. © 2007 Elsevier B.V. All rights reserved.

J. BOLLMANN, M.Y. CORTES ,A. K LEIJNE, J.B. O STERGAARD ANDJ.R. YOUNG. 2006. Solisphaera gen. nov. (Prymnesiophyceae), a new coccolithophore genus from the lower photic zone. Phycologia 45: 465-477. DOI: 10.2216/05-14.1 Solisphaera gen. nov. (Prymnesiophyceae) is described from the lower photic zone of the Pacific Ocean, the North Atlantic Ocean and the Gulf of Mexico. Differences in coccolith morphology between Solisphaera and members of Rhabdosphaer- aceae are certainly substantial enough to warrant the erection of a separate genus that should probably be categorised as incertae sedis aff. Rhabdosphaeraceae. The new genus accommodates three new species, S. emidasia sp. nov., S. blagna- censis sp. nov. and S. helianthiformis sp. nov. and the presence of a corona of process-bearing coccoliths around the cell is a key feature that unites the three species in the new genus Solisphaera, while the shape of these coronal coccoliths provides the main character for separating them at species level. A remarkable feature of this genus is the tight interlocking of the coronal coccoliths, in almost all collapsed coccospheres the circle of coronal coccoliths remains intact. This is evidently due to the presence of notches at the base of the process into which the rims of adjacent coccoliths lock. All three species are restricted to the lower photic zone in the areas studied and apparent preferences for different depth levels of S. emidasia and S. blagnacensis, as well as their nutrient and light requirements, have to be confirmed by further analysis.

Detailed analysis of the morphology of Florisphaera profunda from plankton samples collected at three sites in the Atlantic and Pacific Oceans reveals wide variation in this deep ocean-dwelling coccolithophore. In addition to the two varieties described previously, we found a third distinctive form, Florisphaera profunda var. rhinocera var. nov. All three varieties occur at each of the sampling sites. The analysis of monthly samples from different levels in the lower photic zone (LPZ) (100–200 m) at the Hawaii Ocean Time series station suggests that the varieties have similar distributions, which are correlated to primary productivity and the availability of light. The analysis of coccolith and coccosphere size in F. profunda reveals the existence of several size modes in Florisphaera profunda var. profunda and F. profunda var. elongata. The biological significance of these modes, or morphotypes is not known. However, their co-occurrence in single samples from different oceanic areas suggests that they ar...

The filtration technique is a widely applied method to calculate absolute coccolith abundances in paleoceanographic, paleoclimatic and ecological studies. Here, we have tested the accuracy and reproducibility of absolute coccolith abundance estimates obtained with the filtration method in combination with a rotary sample divider. The examination of two different filtration devices, a funnel and an in-line system, analysing a known number of microbeads per weight, revealed that counts obtained with funnel systems are up to O 18.6% too high. Repeated analyses (15×) of a fine-fraction sediment sample revealed a standard deviation of ±11.4% for the in-line system and ±15.2% for the funnel system, respectively. The comparison between three sub-samples (three splits of 1/30) showed a standard deviation of 4.6% for the in-line system and 9.9% for the funnel system, respectively. Therefore, we assume that the potential split error for the rotary splitter is ≤4.6%. The comparison of our results with estimates for the same samples analysed with the random settling and the “spiking with microbeads and spraying method” (SMS method) reveal that only the data obtained with the SMS and in-line filter method are statistically equal. The results obtained with the settling method are too low, whilst the results obtained with funnel filtration are too high in terms of coccolith absolute abundances. Our results confirm that the filtration method, including sample splitting with a rotary splitter, is a suitable method for the analysis of absolute coccolith abundances. However, the use of different filtration devices appears to affect the accuracy and reproducibility of the results. Furthermore, the number of splitting steps should be as small as possible to avoid an increase of error due to error propagation. In order to increase the reliability of the filtration method, we suggest calibrating a filtration device with microbeads as a standard measure. The reported reproducibility of the various preparation techniques may help to compare data sets obtained with different methods.

The distribution of diatoms, coccolithophores and planktic foraminifers mirrored the hydrographic and trophic conditions of the surface ocean (0–100 m) across the upwelling area off the Oman coast to the central Arabian Sea during May/June 1997 and July/August 1995. The number of diatoms was increased in waters with local temperature minimum and enhanced nutrient concentration (nitrate, phosphate, silicate) caused by upwelling. Vegetative cells of Chaetoceros dominated the diatom assemblage in the coastal upwelling area. Towards the more nutrient depleted and stratified surface waters to the southeast, the number of diatoms decreased, coccolithophore and planktic foraminiferal numbers increased, and floral and faunal composition changed. In particular, the transition between the eutrophic upwelling region off Oman and the oligotrophic central Arabian Sea was marked by moderate nutrient concentration, and high coccolithophore and foraminifer numbers. Florisphaera profunda, previously often referred as a ‘lower-photic-zone-species’, was frequent in water depths as shallow as 20 m, and at high nutrient concentration up to 14 mol NO3 l?1 and 1.2 mol PO4 l?1. To the oligotrophic southeast of the divergence, cell densities of coccolithophores declined and Umbellosphaera irregularis prevailed throughout the water column down to 100 m depth. In general, total coccolithophore numbers were limited by nutrient threshold concentration, with low numbers ( 70×103 cells l?1) at low [NO3] and [PO4]. The components of the complex microplankton succession, diatoms, coccoliths and planktic foraminifers (and possibly others), should ideally be used as a combined paleoceanographic proxy. Consequently, models on plankton ecology should be resolved at least for the seasonality, to account for the bias of paleoceanographic transfer calculations.

Recently a new palaeotemperature proxy was developed, based on the morphology of the coccolithophore genus Gephyrocapsa . Here we apply and validate this new methodology by comparing Gephyrocapsa -derived palaeotemperature estimates with temperature estimates obtained from alkenone ratios, Mg/Ca ratios in foraminiferal calcite, and planktic foraminifera assemblages. We investigated a downcore record off Cape Blanc (GeoB 1048; 20°55′N, 19°43′W), spanning the last 28 000 years, in the vicinity of BOFS core 31K (19°00′N, 20°10′W), for which a detailed multiproxy palaeotemperature record has already been established. Our data show an especially good correspondence between the Gephyrocapsa - and alkenone-derived palaeotemperatures, and thus validate the great potential of the new Gephyrocapsa proxy to reconstruct sea surface water temperatures (SSTs). Both indicate a glacial drop in SST of ∼3°C compared to Holocene values, similar to the Mg/Ca palaeotemperature record, although the latter is consistently ∼2.5°C cooler. Largest discrepancies, both in terms of downcore amplitude changes and same-age sample estimates, are found with available planktic foraminifera transfer function data. This can be due to fundamental differences in the season of production, ecologic preferences and habitats, and/or preservation. On the other hand, it may be a result of differences inherent to the transfer functions used, and their original calibration, i.e. regional vs. global approach or different temperature ranges covered. In addition to the downcore record off Cape Blanc, sediment samples corresponding to the Last Glacial Maximum (LGM) were selected from a dispersed set of eighteen well-dated gravity cores, in order to derive palaeo-SST maps off Northwest Africa during this time-slice. By applying a regional Gephyrocapsa transfer function for the first time, we show that mean SSTs in the Canary Islands region during the LGM were 4–6°C colder than today. We found lowest glacial temperatures (14–15.5°C) offshore Morocco and south of the volcanic Canary Islands, likely due to intensified upwelling related to stronger trade winds, consistent with estimates from CLIMAP and other palaeotemperature reconstructions for the same region. In contrast, for offshore Cape Blanc, today’s centre of perennial upwelling, our temperature estimates for the LGM are significantly warmer (ΔT [today–LGM] 2.5–4°C) than proposed by CLIMAP (ΔT [today–LGM] 6–10°C). However, our results consistently support temperature reconstructions based on alkenones that also indicate rather small temperature changes (ΔT [today–LGM] 2–4°C) in this area. We show that Gephyrocapsa morphotypes may also provide useful qualitative information about relative changes in primary productivity, although no linear relationship is apparent. In summary, our palaeotemperature and palaeoproductivity data support the observation that enhanced glacial productivity appears geographically limited to the northernmost latitudes of the NW African upwelling system, whilst upwelling intensity off Cape Blanc was reduced, despite overall enhanced trade wind intensity.

The size of any organism is influenced by the surrounding ecological conditions. In this study, we investigate the effects of such factors on the size spectra of planktic foraminiferal assemblages from Holocene surface sediments. We analyzed assemblages from 69 Holocene samples, which cover the major physical and chemical gradients of the oceans. On a global scale, the range of sizes in assemblages triples from the poles to the tropics. This general temperature-related size increase is interrupted by smaller sizes at temperatures characteristic of the polar and subtropical fronts, at 2°C and 17°C, respectively, as well as in upwelling areas. On a regional scale, surface water stratification, seasonality and primary productivity are highly correlated with the size patterns. Such environmentally controlled size changes are not only characteristic for entire assemblage, but also for the dominant single species.

This paper discusses the techniques used to sample and analyse living marine calcareous phytoplankton. The various methods are described and tested within several research projects aimed at the determination of coccolithophore cell densities in seawater. In addition, the potential advantages and drawbacks associated with the application of light and scanning electron microscopic techniques to the quantitative analysis of coccolithophores are discussed. Several tests have been carried out in order to quantify potential errors related to: (1) homogeneity of material distribution on filter membranes; (2) use of different microscopes (scanning electron microscope versus light microscope); (3) use of different filter membranes (cellulose mixed-ester membranes versus polycarbonate membranes); and (4) Utermohl settling versus filtration method. These tests revealed that major errors in cell density calculations could result from the uneven distribution of coccolithophore specimens on a filter membrane. The error resulting from the use of a light microscope arises from its low resolution, which restricts the identification of species, especially of small coccospheres. The use of different filter membranes does not show a statistically significant difference in cell density calculations, although polycarbonate membranes can be examined much more efficiently with the scanning electron microscopy than cellulose mixed-ester membranes. The Utermohl method, however, gives lower cell densities consistently (several times) than the filtration method.

Particle supply and sediment accumulation in the Canary Basin are strongly modified by seasonal coastal upwelling and dust input from the Sahara. Along an E–W depth profile and fertility gradient north of the Canary Islands, we demonstrate an increase in total mass accumulation rates from a low of 1–2 g cm−2 ka−1 in the outer oceanic domain to 6–12 g cm−2 ka−1 closer to the Moroccan shelf in Holocene sediments. During the Last Glacial Maximum (LGM, oxygen isotopic event 2.2), a steeper gradient was found, with two to four times higher mass accumulation rates at the near-shore sites. Total mass accumulation rates during the Last Interglacial Climax (LIC, isotopic event 5.5) and end of the Penultimate Glaciation (ePG, isotopic event 6.2) resemble Holocene values, with lowered near-shore maxima of 3 and 4 g cm−2 ka−1, respectively. Analyses of separate sediment components show that total organic carbon, total carbonate, lithogenic and diatom accumulation rates were generally enhanced during glacial times, especially during the LGM. In contrast, glacial accumulation rates of biogenic carbonate particles (coccoliths and planktic foraminifera shells) remained constant or were lowered with respect to interglacial time periods at the site closest to the Moroccan shelf, despite a doubling of bulk carbonate accumulation. This could indicate lowered supply from the productive euphotic zone or a latitudinal, offshore shift of the main sedimentary depocentre. However, enhanced carbonate dissolution could by itself account for this decrease in biogenic carbonate accumulation. Increased glacial input of detrital carbonate, derived from the exposed Moroccan shelf, appears to be responsible for the overall enhanced carbonate accumulation at the same sites, east of Lanzarote.

The recent discovery of well-preserved mummified wood buried within a subarctic kimberlite diamond mine prompted a paleoclimatic study of the early Eocene "hothouse" (ca. 53.3 Ma). At the time of kimberlite eruption, the Subarctic was warm and humid producing a temperate rainforest biome well north of the Arctic Circle. Previous studies have estimated that mean annual temperatures in this region were 4–20 °C in the early Eocene, using a variety of proxies including leaf margin analysis and stable isotopes (δ13C and δ18O) of fossil cellulose. Here, we examine stable isotopes of tree-ring cellulose at subannual- to annual-scale resolution, using the oldest viable cellulose found to date. We use mechanistic models and transfer functions to estimate earliest Eocene temperatures using mummified cellulose, which was well preserved in the kimberlite. Multiple samples of Piceoxylon wood within the kimberlite were crossdated by tree-ring width. Multiple proxies are used in combination to tease apart likely environmental factors influencing the tree physiology and growth in the unique extinct ecosystem of the Polar rainforest. Calculations of interannual variation in temperature over a multidecadal time-slice in the early Eocene are presented, with a mean annual temperature (MAT) estimate of 11.4 °C (1 σ = 1.8 °C) based on δ18O, which is 16 °C warmer than the current MAT of the area (−4.6 °C). Early Eocene atmospheric δ13C (δ13Catm) estimates were −5.5 (±0.7) ‰. Isotopic discrimination (Δ) and leaf intercellular pCO2 ratio (ci/ca) were similar to modern values (Δ = 18.7 ± 0.8 ‰; ci/ca = 0.63 ± 0.03 %), but intrinsic water use efficiency (Early Eocene iWUE = 211 ± 20 μmol mol−1) was over twice the level found in modern high-latitude trees. Dual-isotope spectral analysis suggests that multidecadal climate cycles somewhat similar to the modern Pacific Decadal Oscillation likely drove temperature and cloudiness trends on 20–30-year timescales, influencing photosynthetic productivity and tree growth patterns.

A method for non-destructive disaggregation of coccoliths contained in fecal pellets, marine snow and on coccospheres is described. It consists of repeated chemical oxidation of organic material with (NaClO and H2O2) combined with brief periods of ultrasonification.

After the article has been published online, the authors noticed that the Table 1a in the Supplementary material is not the table from the accepted manuscript. Table 1a should be corrected to the following: Two rows for 20.5 % and 3.5 % Reads should be exchanged as shown in the table below. For the rows Reads 4.7 %: FJ497180 Uncultured bacterium clone Pm_planulaeLM_G11; Coverage, Max Identity: 99, 86; Habitat: Associate of coral should be exchanged with DQ404779 Uncultured bacterium clone 661230; Coverage, Max Identity: 98, 91; Habitat: Contaminated sediment. The first set of Coverage, Max Identity values (98, 91) should be removed, and the remaining values 86, 94 and 96, 89 should be moved up so that they correspond with the correct bacterial classifications. Reads 3.7 %: JX825743.1 Uncultured bacterium clone GD2::G9RA0RH03GJRTH; Coverage, Max Identity: 94, 99; Habitat: Lava Caves should be exchanged with AM909970 Uncultured bacterium clone LM63; Coverage, Maximal Identity: 100, 96; Habitat: Rhizosphere soil from rice field, China.

Individual species of marine calcareous phytoplankton are known to occur in blooms in today's ocean and to have dominated fossil assemblages. Interest in the study of marine phytoplankton-ocean-climate interactions has increased because of the potential influence of phytoplankton species like Emiliania huxleyi on global climate and on the global carbon cycle. There is evidence that Gephyrocapsa caribbeanica, which is closely related to E. huxleyi, was globally dominant in the late Pleistocene (480–262 ka). Morphological analyses of Gephyrocapsa coccoliths reveal that only two of six Holocene morphological associations occurred during this time interval. We examine three potential causes for the dominance: preservation, environment, and evolutionary adaptation. We conclude that evolutionary adaptation was the likely process responsible for Gephyrocapsa dominance, although there are indications in the mid-Brunhes for warmer climates than today.

Morphological analysis of 70 globally distributed Holocene sediment assemblages of the calcareous marine phytoplankton genus Gephyrocapsa (Prymnesiophyta) displays significant correlations between the measured morphological parameters and environmental gradients. By extrapolating these essential findings, paleoecological and evolutionary interpretations can be obtained for the Pleistocene period. Measurements of various morphometric parameters of 3600 coccoliths showed that the morphologically most distinct features arc bridge angle and placolith length. Bridge angle ranged from 120 ° to 3 ° and placolith length from 6.2 μm to 0.9 μm. The combination of the mean bridge angle and the mean length of each sediment assemblage (Holocene) leads to six morphological groups which characterise different environments and geographic areas: Equatorial associations have a mean bridge angle larger than 56 ° and a mean size between 3.1 μm and 3.9 μm. The temperature range of these associations is 25 °C to 29.5 °C mean sea surface temperature (MSST). Abbreviation GE: Gephyrocapsa Equatorial. Subtropical central water-mass associations have a mean bridge angle between 27 ° and 56 ° and a mean length larger than 3.1 μm. These associations are only found in oligotrophic central gyre regions with a MSST between 22 °C and 25 °C. Abbreviation GO: Gephyrocapsa Oligotrophic. Transitional associations have a mean bridge angle between 27 ° and 56 ° and a mean length between 2.4 μm and 3.1 μm. These associations are only found in areas with a mean SST between 19 °C and 20 °C. Abbreviation GT: Gephyrocapsa Transitional. Transitional to subarctic cold associations have a mean bridge angle less than 27 ° and a mean length larger than 2.4 μm. These associations are found in moderately productive regions with a mean SST lower than 21 °C. Abbreviation GC: Gephyrocapsa Cold. Moderately productive temperate associations have a mean bridge angle larger than 56 ° and a mean length larger than 3.9 μm. These associations are dominant in upwelling regions, but also occur in non-upwelling areas. Their temperature range is 18 °C to 23 °C. The relative abundance of these associations within the Gephyrocapsa complex in individual samples decreases with increasing distance from the coast. Abbreviation: GL Gephyrocapsa Larger. Associations consisting of small placoliths with a mean bridge angle between 20 ° and 50 ° and a mean length less than 2.4 μm show no well defined environmental or geographic preference. Such forms seem to be frequent near islands and coasts (neritic) in tropical to subtropical regions. Abbreviation: GM: Gephyrocapsa Minute. The observed morphological discontinuities along the environmental gradients are suggestive of distinct and possibly genetically isolated species populations. In individual assemblages, however, considerable morphological variability is observed and characteristic morphological traits show gradual change along environmental gradients. These features could be expected, if a single, globally homogeneous genotypic species Gephyrocapsa oceanica should show high phenotypic plasticity. Future morphological analysis of plankton samples from various areas and taken at various seasons are expected to confirm the conclusion of environmental dependence of Gephyrocapsa morphology drawn from this analysis.

A new method for weight estimates of single coccoliths using the birefringence of calcite is described. The weight estimates of 364 Holocene coccoliths using this new method are in good agreement with published volumetric estimates. A robust calibration method based on the measurement of a calibration target of known retardation enables the comparison of data between different imaging systems. Therefore, the new method overcomes the shortcomings of the error prone empirical calibration procedure of a previously reported method based on birefringence of calcite. In addition, the new method includes the application of a circular polariser that eliminates the extinction pattern in crossed polarised light. This imaging method allows for the first time the imaging of complete coccoliths on a light microscope at maximum interference colours without moving any mechanical part of the microscope. Therefore, it greatly simplifies the identification of coccolithophore species on the light microscope as well as the calculation of the area and thus weight of a coccolith.

Morphological analysis of Gephyrocapsa spp. in plankton samples confirms the existence of five out of six morphotypes that were previously reported from Holocene sediments. Our data suggest a much higher diversity within the genus Gephyrocapsa than the currently accepted species circumscriptions. Furthermore, we confirm the morphological species delineations made by Kamptner that allow the separation of three morphological groups within the genus Gephyrocapsa: one group with large bridge angles (G. oceanica var. typica Kamptner 1943), a second group with small bridge angles (G. oceanica var. californiensis Kamptner 1956) and a third group of small coccoliths (G. aperta Kamptner 1963). However, a seemingly continuous transition from small to large coccoliths within G. oceanica var. typica along a temperature gradient points either to a high phenotypic plasticity of G. oceanica var. typica or numerous sibling species highly adapted to specific environmental conditions. Testing of these hypotheses is of utmost importance to understanding the diversity of marine plankton and its evolution, and to assessing the impact of future and past environmental change on primary producers such as coccolithophorids.

In this chapter we discussed image calibration, filtering, and processing techniques, which are used to prepare an image for subsequent data extraction and analysis. Size measurements from a digital image are calibrated by imaging objects with a known size. Pixel intensity is a measure for the composition of the imaged object and can be calibrated by imaging objects with known composition. Methods depend on the type of material and imaging technique. We discuss colour calibration, as colour is one of the most widely used types of data in image analysis. Filtering is performed on an image to remove artefacts that are unrelated to the object of study. The challenge is to find the best filter, one that removes all noise with minimum change to the actual information in the image. Described are techniques to remove the effects caused by uneven illumination during imaging, and methods to filter camera related noise. Image processing involves modification and/or enhancement of the image in such a way that the required numerical data can be extracted more easily. Processing techniques that are outlined include edge detection, segmentation, and processing of binary images.

In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.

We characterize the evolutionary radiation of planktic foraminifera by the test size distributions of entire assemblages in more than 500 Cenozoic marine sediment samples, including more than 1 million tests. Calibration of Holocene size patterns with environmental parameters and comparisons with Cenozoic paleoproxy data show a consistently positive correlation between test size and surface-water stratification intensity. We infer that the observed macroevolutionary increase in test size of planktic foraminifera through the Cenozoic was an adaptive response to intensifying surface-water stratification in low latitudes, which was driven by polar cooling.

In this chapter we present a revision of the biogeographical distribution of five coccolithophorid species (Coccolithus pelagicus, Calcidiscus leptoporus, Heli-cosphaera carteri, Syracosphaera pulchra and Umbilicosphaera sibogae) and the genus Gephyrocapsa in the Atlantic Ocean. The mapping is based on surface sediment samples. Each of the taxa considered here constitutes an unambiguous morphological group ideal for rapid low taxonomic resolution analysis of assemblages, which is a tempting strategy for ecological and paleoecological analysis of assemblages. However, in each case recent research has indicated that these broad taxa are in fact composed of several discrete species, or sub-species. The clearest example is C. pelagicus, with discrete morphotypes in sub-Arctic and temperate upwelling areas. For Gephyrocapsa and Umbilicosphaera the separation is less obvious but still unambiguous. Species separation is manifestly essential to understanding the biogeography of these taxa. For H. carteri and S. pulchra the mapped distributions are relatively straightforward and we do not yet know how they relate to the recently proven genotypic variation within the taxa.

Coccolithophores are an ideal test group for investigating fine-scale differentiation within the phytoplankton since their taxonomy is rather well-documented and their biomineralised periplasts – the coccoliths – provide a rich suite of qualitative and quantitative morphological characters and a uniquely extensive fossil record. In addition, extant coccolithophore species can be grown in culture and hence are available for studies of morphological variability under controlled conditions, molecular genetic studies and cytological research.

A quick new method is described for the quantification of absolute nannofossil proportions in deep-sea sediments. This method (SMS) is the combination of Spiking a sample with Microbeads and Spraying it on a cover slide. It is suitable for scanning electron microscope (SEM) analyses and for light microscope (LM) analyses. Repeated preparation and counting of the same sample (30 times) revealed a standard deviation of10.5%. The application of tracer microbeads with different diameters and densities revealed no statistically significant differences between counts. The SMS-method yielded coccolith numbers that are statistically not significantly different from values obtained from the filtration-method. However, coccolith counts obtained by the random settling method are three times higher than the values obtained by the SMS- and the filtration-method. © 1999 Elsevier Science B.V. All rights reserved.

This is the first description of a combination coccosphere of the heterococcolithophore species Coronosphaera mediterranea (Lohmann 1902) Gaarder in Gaarder & Heimdal (1977) and the holococcolithophore species Calyptrolithophora hasleana (Gaarder 1962) Heimdal in Heimdal & Gaarder (1980) (Figs 1, 2). A single specimen of this new combination coccosphere was found within 53000 analysed cells in one of 189 samples collected at the JGOFS time series station ALOHA, Hawaii, during 1993 to 1996. The specimen was in a sample collected during autumn 1996 at a water depth of 5 m at a temperature of 26·1 °C, salinity of 35·0 psu, phosphate of 0·002 μmol/kg and in nitrate-depleted water (for details see Cortes, 1998; Cortes et al., 2001).

[1] A global sea surface temperature calibration based on the relative abundance of different morphotypes within the coccolithophore genus Gephyrocapsa in Holocene deep-sea sediments is presented. There is evidence suggesting that absolute sea surface temperature for a given location can be calculated from the relative abundance of Gephyrocapsa morphotypes in sediment samples, with a standard error comparable to temperature estimates derived from other temperature proxies such as planktic foraminifera transfer functions. A total of 110 Holocene sediment samples were selected from the Pacific, Indian, and Atlantic Oceans covering a mean sea surface temperature gradient from 13.6° to 29.3°C. Standard multiple linear regression analyses were applied to this data set, linking the relative abundance of Gephyrocapsa morphotypes to sea surface temperature. The best model revealed an r2 of 0.83 with a standard residual error of 1.78°C for the estimation of mean sea surface temperature. This new proxy provides a unique opportunity for the reconstruction of paleotemperatures with a very small amount of sample material due to the minute size of coccoliths, permitting examination of thinly laminated sediments (e.g., a pinhead of material from laminated sediments for the reconstruction of annual sea surface temperature variations). Such fine-scale resolution is currently not possible with any other proxy. Application of this new paleotemperature proxy may allow new paleoenvironmental interpretations in the late Quaternary period and discrepancies between the different currently used paleotemperature proxies might be resolved.

We describe a device for random settling preparation of calcareous nannoplankton (coccolith) samples. The device allows easy draining and cleaning, as well as sedimentation at different heights of the water column through the use of different slide carriers. Reproducibility and accuracy of the device has been tested with standardised microbeads as spiking material. In applying counting techniques with different equations for determining absolute abundances, we discovered major anomalies in the calculated results that we interpreted as being due to the effect of convection currents within the device and the usage of elevated cover slides. A modified formula that corrects for the influence of elevated cover slides in random settling experiments is therefore proposed. Although the settling method is more time-consuming than standard smear-slide techniques, additional information is gained about the spatial and temporal distribution of coccoliths. These are important for palaeoecological and palaeobiogeographical interpretations.