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Saccammina minimus sp. nov., a spherical agglutinated organism presumed to be a foraminiferan, is described from the Kaplan Central site in the abyssal eastern Equatorial Pacific (5042 m water depth). The new species is minute in size (32 μm of samples collected at the KC site. In six subcores (6.6 cm2 surface area, 0–1 cm layer) from two cores obtained during a single deployment of a multiple corer, it represented 59% of all stained foraminifera in the samples. However, it had an extremely patchy small-scale distribution on a scale of centimetres; for example, 3, 285 and 1090 specimens were extracted from three subcores. A separate study has reported similar patterns among other minute indeterminate monothalamous foraminifera at the Kaplan East site (4032–4089 m water depth) located to the east, c. 1200 km from our study site. The reason for these very patchy distributions is not clear.

Specimens of the benthic foraminifer Ammonia beccarii were cultured in the laboratory in order to determine the relation between temperature and Mg/Ca and oxygen isotope values in their tests. Asexual reproduction in this species provides a large number of juveniles that were allowed to grow into maturity at temperatures ranging from 10 to 27 °C and at salinities ranging from 18 to 33 PSU. The Mg/Ca in a calcite increase exponentially and δ18O decreases linearly with the temperature. Salinity has no significant impact on either Mg/Ca or δ18O. We show how the combination of these two parameters can be used to reconstruct seawater δ18O and temperature in shallow marine habitats.

Foraminifera are an important faunal element of the abyssal ecosystem and largely depend on deposited particulate organic matter from the photic zone to sustain their metabolism for growth and reproduction. However, their role in the carbon cycle in deep-sea sediments is insufficiently studied. We investigated benthic foraminifera at Station M (4000 m depth) in the Northeast Pacific and assessed the response of individual species to a simulated phytodetritus pulse during an in situ feeding experiment. Sediments were incubated for 4 d with 13C-labeled diatoms (Thalassiosira weissflogii) applied to the sediment surface. The living foraminiferal community (>0.063 mm) of the upper 3 cm contained >100 species and was strongly dominated by a few taxa of soft-walled saccamminids. Population density of the entire living foraminiferal community was highest at the sediment surface (mean ± SD = 279 ± 72 ind. 10 cm?3 in background and 13C-incubated cores) and decreased gradually with depth. Large differences were observed in the uptake of the algal material among species and between depth levels. During the experiment, 0.82 mg C m?2 were ingested, mainly by calcareous (~60%) and agglutinated (~40%) foraminifera. Uptake was highest at the sediment surface and 3 to 5 times less in deeper sediment horizons. Despite clear signs of vitality and a strong representation in the foraminiferal community, none of the soft-walled species showed a noticeable response to the offered algal material. We conclude that soft-walled foraminifera may not be important to the short-term phytodetrital matter cycling at the abyssal sea floor.

International audience; In Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic Event 2 (OAE-2, ca. 94 Ma), nitrogen isotopic compositions of bulk sediments are mostly in a narrow range from ?2.7 to ?0.7?. We also determined molecular distribution and nitrogen isotopic compositions of geoporphyrins extracted from the black shale. The nitrogen isotopic compositions of C32 Ni deoxophylloerythroetioporphyrin (DPEP) and total Ni porphyrins are ?3.5 and ?3.3?, respectively, leading us to the estimation that the mean nitrogen isotopic composition of photoautotrophic cells were around +1? during the formation of Bonarelli black shale. This value is suggestive of N2-fixation, a dominant process for these photoautotrophs when assimilating nitrogen. Furthermore, Ni-chelated C32 DPEP, derived mainly from chlorophyll a had the highest concentration. Based on this evidence, we conclude that diazotrophic cyanobacteria were major primary producers during that time. Cyanobacteria may be key photoautotrophs during the formation of black shale type sediments intermittently observed throughout the later half of the Earth's history, and hence may have played a crucial role in the evolution of geochemical cycles even in the later half of the Earth's history.

International audience; In Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic Event 2 (OAE-2, ca. 94 Ma), nitrogen isotopic compositions of bulk sediments are in a narrow range from ?2.7 to ?0.7. We also determined molecular distribution and nitrogen isotopic compositions of geoporphyrins extracted from the black shale. The nitrogen isotopic compositions of C32 Ni deoxophylloerythroetioporphyrin (DPEP) and total Ni porphyrins are ?3.5 and ?3.3, respectively, leading us to the estimation that the mean nitrogen isotopic composition of photoautotrophic cell was around +1 during the formation of Bonarelli black shale. This value is suggestive of N2-fixation a dominant process for these photoautotrophs when assimilating nitrogen. Furthermore, Ni-chelated C32 DPEP, derived mainly from chlorophyll a was the highest concentration. Based on these evidence, we conclude that diazotrophic cyanobacteria were major primary producers during that time. The cyanobacteria may be key photoautotrophs during the formation of black shale type sediments intermittently observed throughout the later half of the Earth's history, and hence may have played a crucial role in the evolution of geochemical cycles.

application/pdf, Porphyrins are thought to have derived from biomolecules such as chlorophylls and heme, among which eoxophylloerythroetioporphyrins (DPEP) and its analogues are structurally related to chloropigments. These compounds thus preserve stable isotopic compositions of N and C of phototrophs of the past environment. We have developed methods for precise determinations of N and C isotopic compositions of individual sedimentary porphyrins and maleimides, which include isolation and purification of individual alkylporphyrins and porphyrin acids by dual-step HPLC preparation (Kashiyama et al., 2007a). We have analyzed various alkylporphyrins and porphyrin acids from organic-rich Miocene sediments of the paleo-Japan Sea (Onnagawa Formation) as well as Cretaceous black shales (Livello Selli and Livello Bonarelli, Italy) deposited in the western Tethys during the Ocean Anoxic Events (OAEs). The N isotopic composition of DPEP, which should have derived in chlorophylls in general, ranged from -6.9 to -3.6‰ (n=7) in the Miocene shale and -6.6 to -3.9‰ (n=5) in the OAE black shales, indicating that the N2 fixation was a major process for N assimilation hence the dominance of diazotrophic cyanobacteria in primary production in these paleo-oceans. Furthermore, DPEP were relatively enriched in 13C in both environments (-17.9 to -15.6‰ in the Miocene shale and -20.5 to -17.9‰ in the OAE black shales), which suggests relatively small carbon isotopic fractionation during photosynthesis and supports significant contribution of cyanobacteria-derived chloropigments. We also determined isotopic compositions of source-specific porphyrins such as 17-nor-DPEP (derived from chlorophyll-c), 8-nor-DPEP (possibly derived from divinylchlorophylls; Kashiyama et al., 2007b) as well as DPEP with extended alkyl side chains and their equivalents among porphyrin acids (derived from bacteriochlorophyll c, d, and e; analyzed as maleimides). The latter two porphyrins had variable and rather unique isotopic compositions compared to DPEP. Such an approach should allow reconstruction of community structures of phototrophs and associated biogeochemical processes associated with the photosynthesis in the past oceans., のみ

Berichte - Reports, Geologisch-Pal��ontologisches Institut und Museum, Christian-Albrechts-Universit��t, Kiel

This paper synthesizes the geology of the Atlantic Margin off the coast of Iberia and surrounding Abyssal Plains using published thematic mapping freely downloadable from EMODNET-Geology portal at different scales. Selected information was chosen in order to highlight mineral occurrences and natural hazards overlaid on geological and morphological maps. Altogether, this information is published and interpreted here for the first time; nevertheless this exercise can be carried out by anyone interested and allows different visualizations of geological objects. Cross-correlations of geological objects and processes can easily arise. Because all of the information (each piece of data and metadata) in the EMODNET-Geology portal has bibliographic references associated, readers are able to find the original source of information. It is shown that clicking in and out of layers of information (that cannot be found all together in a single scientific paper) allows quick cross-correlation using the EMODNET Geology thematic portal. This allows a free, versatile and quick way of cross-correlating geological objects and processes in vast marine areas and their comparison with onshore geology.