Hydrochemistry, phytoplankton pigment concentration and phytoplankton abundance in water samples obtained in the Kuroshio Extension Front in October 2009

This data was collected during a cruise to the Kuroshio Extension Front in October 2009. Several chemical and biological parameters were measured: dissolved nutrients, picophytoplankton (by flow cytometry), microphytoplankton (by light microscopy) and phytoplankton pigments (HPLC).

Temperature affects the morphology and calcification of Emiliania huxleyi strains

The global warming debate has sparked an unprecedented interest in temperature effects on coccolithophores. The calcification response to temperature changes reported in the literature, however, is ambiguous. The two main sources of this ambiguity are putatively differences in experimental setup and strain-specificity. In this study we therefore compare three strains isolated in the North Pacific under identical experimental conditions. Three strains of Emiliania huxleyi type A were grown under non-limiting nutrient and light conditions, at 10, 15, 20 and 25 ºC. All three strains displayed similar growth rate versus temperature relationships, with an optimum at 20-25 ºC. Elemental production (particulate inorganic carbon (PIC), particulate organic carbon (POC), total particulate nitrogen (TPN)), coccolith mass, coccolith size, and width of the tube elements cycle were positively correlated with temperature over the sub-optimum to optimum temperature range. The correlation between PIC production and coccolith mass/size supports the notion that coccolith mass can be used as a proxy for PIC production in sediment samples. Increasing PIC production was significantly positively correlated with the percentage of incomplete coccoliths in one strain only. Generally, coccoliths were heavier when PIC production was higher. This shows that incompleteness of coccoliths is not due to time shortage at high PIC production. Sub-optimal growth temperatures lead to an increase in the percentage of malformed coccoliths in a strain-specific fashion. Since in total only six strains have been tested thus far, it is presently difficult to say whether sub-optimal temperature is an important factor causing malformations in the field. The most important parameter in biogeochemical terms, the PIC:POC, shows a minimum at optimum growth temperature in all investigated strains. This clarifies the ambiguous picture featuring in the literature, i.e. discrepancies between PIC:POC-temperature relationships reported in different studies using different strains and different experimental setups. In summary, global warming might cause a decline in coccolithophore's PIC contribution to the rain ratio, as well as improved fitness in some genotypes due to less coccolith malformations.

Environmental controls on the Emiliania huxleyi calcite mass

Although ocean acidification is expected to impact (bio)calcification by decreasing the seawater carbonate ion concentration, [CO3]2-, there exists evidence of non-uniform response of marine calcifying plankton to low seawater [CO3]2-. This raises questions on the role of environmental factors other than acidification and on the complex physiological responses behind calcification. Here we investigate the synergistic effect of multiple environmental parameters, including temperature, nutrient (nitrate and phosphate) availability, and seawater carbonate chemistry on the coccolith calcite mass of the cosmopolitan coccolithophore Emiliania huxleyi, the most abundant species in the world ocean. We use a suite of surface (late Holocene) sediment samples from the South Atlantic and southwestern Indian Ocean taken from depths lying well above the modern lysocline. The coccolith calcite mass in our results presents a latitudinal distribution pattern that mimics the main oceanographic features, thereby pointing to the potential importance of phosphorus and temperature in determining coccolith mass by affecting primary calcification and possibly driving the E. huxleyi morphotype distribution. This evidence does not necessarily argue against the potentially important role of the rapidly changing seawater carbonate chemistry in the future, when unabated fossil fuel burning will likely perturb ocean chemistry beyond a critical point. Rather our study highlights the importance of evaluating the combined effect of several environmental stressors on calcifying organisms to project their physiological response(s) in a high CO2 world and improve interpretation of paleorecords.

(Table S1) Relative abundances of coccolithophore taxa in surface sediment samples from the Equatorial and Southeastern Pacific

This study aims to contribute to a more detailed knowledge of the biogeography of coccolithophores in the Equatorial and Southeastern Pacific Ocean. Census data of fossil coccoliths are presented in a suite of core-top sediment samples from 15°N to 50.6°S and from 71°W to 93°W. Following standard preparation of smear slides, a total of 19 taxa are recognized in light microscopy and their relative abundances are determined for 134 surface sediment samples. Considering the multivariate character of oceanic conditions and their effects on phytoplankton, a Factor Analysis was performed and three factors were retained. Factor 1, dominated by Florisphaera profunda and Gephyrocapsa oceanica, includes samples located under warm water masses and indicates the occurrence of calcite dissolution in the water column in the area offshore Chile. Factor 2 is related to cold, low-salinity surface-water masses from the Chilean upwelling, and is dominated by Emiliania huxleyi, Gephyrocapsa sp. < 3 µm, Coccolithus pelagicus and Gephyrocapsa muellerae. Factor 3 is linked to more saline, coastal upwelling areas where Calcidiscus leptoporus and Helicosphaera carteri are the dominant species.

Magnetic state of ocean basalts (Table 1)

The natural remanent magnetization (NRM) of ocean basalts, giving rise to the pattern of marine magnetic anomalies, is known to be of comparatively low intensity for about 20 Ma old oceanic crust. The aim of this study is to detect possible peculiarities in the rock magnetic properties of ocean basalts of this age, and to establish a link between magnetomineralogy, rock magnetic parameters, and the low NRM intensity. Ocean basalts covering ages from 0.7 to 135 Ma were selected for rock magnetic experiments and their room temperature hysteresis parameters, Curie temperature and temperature dependence of saturation magnetization MS(T) was determined and complemented by reflected light microscopy. The majority of samples is magnetically dominated by titanomagnetite and titanomaghemite with increasing oxidation state with age. For these, a strong dependence of hysteresis parameters on the age of the samples is found. The samples have a minimum in saturation magnetization and a maximum in magnetic stability in the age interval ranging from approximately 10 to 40 Ma, coinciding with the age interval of low NRM intensity. The observed change in saturation magnetization is in the same order as that for the NRM intensity. A further peculiarity of the titanomaghemites from this age interval is the shape of their MS(T) curves, which display a maximum above room temperature (Neel P-type) and, sometimes, a self-reversal of magnetization below room temperature (Neel N-type). These special rock magnetic properties can be explained by titanomagnetite low-temperature oxidation and highly oxidized titanomaghemites in the age interval 10-40 Ma. A corresponding measurement of the NRM at elevated temperature allows to identify a maximum in NRM intensity above room temperature for the samples in that age interval. This provides evidence that the NRM is equally carried by titanomaghemites and that the low NRM intensities for about 20 Ma old ocean basalts are caused consequently by the low saturation magnetization of these titanomaghemites.

Event layer chronology from Lake Suigetsu (Japan, SG06 Project) for the last 40 kyr

Event layers in lake sediments are indicators of past extreme events, mostly the results of floods or earthquakes. Detailed characterisation of the layers allows the discrimination of the sedimentation processes involved, such as surface runoff, landslides or subaqueous slope failures. These processes can then be interpreted in terms of their triggering mechanisms. Here we present a 40 kyr event layer chronology from Lake Suigetsu, Japan. The event layers were characterised using a multi-proxy approach, employing light microscopy and µXRF for microfacies analysis. The vast majority of event layers in Lake Suigetsu was produced by flood events (362 out of 369), allowing the construction of the first long-term, quantitative (with respect to recurrence) and well dated flood chronology from the region. The flood layer frequency shows a high variability over the last 40 kyr, and it appears that extreme precipitation events were decoupled from the average long-term precipitation. For instance, the flood layer frequency is highest in the Glacial at around 25 kyr BP, at which time Japan was experiencing a generally cold and dry climate. Other cold episodes, such as Heinrich Event 1 or the Late Glacial stadial, show a low flood layer frequency. Both observations together exclude a simple, straightforward relationship with average precipitation and temperature. We argue that, especially during Glacial times, changes in typhoon genesis/typhoon tracks are the most likely control on the flood layer frequency, rather than changes in the monsoon front or snow melts. Spectral analysis of the flood chronology revealed periodic variations on centennial and millennial time scales, with 220 yr, 450 yr and a 2000 yr cyclicity most pronounced. However, the flood layer frequency appears to have not only been influenced by climate changes, but also by changes in erosion rates due to, for instance, earthquakes.

(Table 2) Relative contents of clay minerals in aeolian pelagic clays from the Pacific Ocean

For determining importance, composition, and history of aerosol material accumulation in formation of pelagic clays a study with use of light microscopy and scanning electron microscopy, X-ray diffractometry, and chemical methods has been carried out.

Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates - Collection of source datasets - Contribution to the MAREDAT World Ocean Atlas of Plankton Functional Types

The MAREDAT atlas covers 11 types of plankton, ranging in size from bacteria to jellyfish. Together, these plankton groups determine the health and productivity of the global ocean and play a vital role in the global carbon cycle. Working within a uniform and consistent spatial and depth grid (map) of the global ocean, the researchers compiled thousands and tens of thousands of data points to identify regions of plankton abundance and scarcity as well as areas of data abundance and scarcity. At many of the grid points, the MAREDAT team accomplished the difficult conversion from abundance (numbers of organisms) to biomass (carbon mass of organisms). The MAREDAT atlas provides an unprecedented global data set for ecological and biochemical analysis and modeling as well as a clear mandate for compiling additional existing data and for focusing future data gathering efforts on key groups in key areas of the ocean. The present collection presents the original data sets used to compile Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates

Chlorophyll-a, primary production rates, carbon concentrations and cell counts of coccolithophores, diatoms and microzooplankton measured in water samples from the North Atlantic during the M87/1 cruise in April 2012

The Deep Convection cruise repeatedly sampled two locations in the North Atlantic, sited in the Iceland and Norwegian Basins, onboard the RV Meteor (19 March - 2 May 2012). Samples were collected from multiple casts of a conductivity-temperature-depth (CTD) - Niskin rosette at each station. Water samples for primary production rates, community structure, chlorophyll a [Chl a], calcite [PIC], particulate organic carbon [POC] and biogenic silicic acid [BSi] were collected from predawn casts from six light depths (55%, 20%, 14%, 7%, 5% and 1% of incident PAR). Additional samples for community structure and ancillary parameters were collected from a second cast. Carbon fixation rates were determined using the 13C stable isotope method. Water samples for diatom and micro zooplankton counts, collected from the predawn casts, were preserved with acidic Lugol's solution (2% final solution) and counted using an inverted light microscope. Water samples for coccolithophore counts were collected onto cellulose nitrate filters and counted using polarising light microscopy. Water samples for Chl a analysis were filtered onto MF300 and polycarbonate filters and extracted in 90% acetone. PIC and BSi samples were filtered onto polycarbonate filters and analysed using an inductively coupled plasma emission optical spectrometer and a SEAL QuAAtro autoanalyser respectively.

Coccosphere geometry measurements from culture experiments on the coccolithophore species Calcidiscus leptoporus, Calcidiscus quadriperforatus and Helicosphaera carteri

Coccolithophores are a key phytoplankton group that exhibit remarkable diversity in their biology, ecology, and calcitic exoskeletons (coccospheres). An understanding of the physiological processes that underpin coccosphere architecture is essential for maximizing the information that can be retrieved from their extensive fossil record. Using culturing experiments on four modern species from three long-lived families, we investigate how coccosphere architecture responds to population shifts from rapid (exponential) to slowed (stationary) growth phases as nutrients become depleted. These experiments reveal statistical differences in cell size and the number of coccoliths per cell between these two growth phases, specifically that cells in exponential-phase growth are typically smaller with fewer coccoliths, whereas cells experiencing growth-limiting nutrient depletion have larger coccosphere sizes and greater numbers of coccoliths per cell. Although the exact numbers are species-specific, these growth-phase shifts in coccosphere geometry are common to four different coccolithophore families (Calcidiscaceae, Coccolithaceae, Isochrysidaceae, Helicosphaeraceae), demonstrating that this is a core physiological response to nutrient depletion across a representative diversity of this phytoplankton group. Polarised light microscopy was used for all coccosphere geometry measurements.

Seawater carbonate chemistry and Emiliania huxleyi mass and size, 2011

About one-third of the carbon dioxide (CO2) released into the atmosphere as a result of human activity has been absorbed by the oceans, where it partitions into the constituent ions of carbonic acid. This leads to ocean acidification, one of the major threats to marine ecosystems and particularly to calcifying organisms such as corals, foraminifera and coccolithophores. Coccolithophores are abundant phytoplankton that are responsible for a large part of modern oceanic carbonate production. Culture experiments investigating the physiological response of coccolithophore calcification to increased CO2 have yielded contradictory results between and even within species. Here we quantified the calcite mass of dominant coccolithophores in the present ocean and over the past forty thousand years, and found a marked pattern of decreasing calcification with increasing partial pressure of CO2 and concomitant decreasing concentrations of CO3. Our analyses revealed that differentially calcified species and morphotypes are distributed in the ocean according to carbonate chemistry. A substantial impact on the marine carbon cycle might be expected upon extrapolation of this correlation to predicted ocean acidification in the future. However, our discovery of a heavily calcified Emiliania huxleyi morphotype in modern waters with low pH highlights the complexity of assemblage-level responses to environmental forcing factors.