917 resultados para A. glacialis


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Zooplankton samples were taken in five depth strata using a Multinet type Midi, with 50 µm nets. The samples were taken during the second leg only, three times at station 1, two times at station 2 and once at station 3. Zooplankton were identified to species / genus and life-stage, and at least 300 individuals were counted per sample. 10 individuals of each stage / species were measured and the numbers of eggs counted.

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Radiolarians are abundant and well preserved in the Neogene of the Kerguelen Plateau. They are common and moderately to well preserved in the Oligocene sequences of Site 738, where the Eocene/Oligocene boundary was observed for the first time in subantarctic sediments, and Site 744. Radiolarians are absent from all glacial sediments from Prydz Bay. Classical Neogene stratigraphic markers were tabulated at all sites. Correlations with paleomagnetic ages were made at Sites 745 and 746 for 26 Pliocene-Pleistocene radiolarian events. Many Miocene to Holocene species are missing from Sites 736 and 737, which were drilled in shallow water (less than 800 m). The missing species are considered to be deepliving forms. Occurrences and relative abundances of morphotypes at six sites are reported. Two new genera (Eurystomoskevos and Cymaetron) and 17 new species (Actinomma kerguelenensis, A. campilacantha, Prunopyle trypopyrena, Stylodictya tainemplekta, Lithomelissa cheni, L. dupliphysa, Lophophaena(?) thaumasia, Pseudodictyophimus galeatus, Lamprocyclas inexpectata, L. prionotocodon, Botryostrobus kerguelensis, B. rednosus, Dictyoprora physothorax, Eucyrtidium antiquum, E.(?) mariae, Eurystomoskevos petrushevskaae, and Cymaetron sinolampas) are described from the middle Eocene to Oligocene sediments at Sites 738 and 744. Twenty-seven stratigraphic events are recorded in the middle to late Eocene of Site 738, and 27 additional stratigraphic datums are recorded, and correlated to paleomagnetic stratigraphy, in the early Oligocene at Sites 738 and 744. Eight radiolarian events are recorded in the late Oligocene at Site 744. New evolutionary lineages are proposed for Calocyclas semipolita and Prunopyle trypopyrena.

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Abundant and diverse polycystine radiolarian faunas from ODP Leg 181, Site 1123 (0-1.2 Ma at ~21 kyr resolution) and Site 1124 (0-0.6 Ma, ~5 kyr resolution, with a disconformity between 0.42-0.22 Ma) have been used to infer Pleistocene-Holocene paleoceanographic changes north of the Subtropical Front (STF), offshore eastern New Zealand, southwest Pacific. The abundance of warm-water taxa relative to cool-water taxa was used to determine a radiolarian paleotemperature index, the Subtropical (ST) Index. ST Index variations show strong covariance with benthic foraminifera oxygen isotope records from Site 1123 and exhibit similar patterns through Glacial-Interglacial (G-I) cycles of marine isotope stages (MIS) 15-1. At Site 1123, warm-water taxa peak in abundance during Interglacials (reaching ~8% of the total fauna). Within Glacials cool-water taxa increase to ~15% (MIS2) of the fauna. Changes in radiolarian assemblages at Site 1124 indicate similar but much better resolved trends through MIS15-12 and 7-1. Pronounced increases in warm-water taxa occur at the onset of Interglacials (reaching ~15% of the fauna), whereas the abundance of cool-water taxa increases in Glacials peaking in MIS2 (~17% of the fauna). Overall warmer conditions at Site 1124 during the last 600 kyrs indicate sustained influence of the subtropical, warm East Cape Current (ECC). During Interglacials radiolarian assemblages suggest an increase in marine productivity at both sites which might be due to predominance of micronutrient-rich Subtropical Water. At Site 1123, an increased abundance of deep-dwelling taxa in MIS 13 and 9 suggests enhanced vertical mixing. During Glacials, reduced vigour of ECC flow combined with northward expansion of cool, micronutrient-poor Subantarctic Water occurs. Only at Site 1123 there is evidence of a longitudinal shift of the STF, reaching as far north as 41°S.

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Radiolarians are present in samples from six of the seven Deep Sea Drilling Project Leg 96 sites examined. The age of the siliceous fauna in these samples ranges from late Pleistocene through Holocene, with some Cretaceous radiolarians redeposited in Pleistocene sequences. Radiolarian preservation is discontinuous at these sites except for intraslope basin Site 618, where the sediments throughout the first five cores contain radiolarians.

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Presented are physical and biological data for the region extending from the Barents Sea to the Kara Sea during 158 scientific cruises for the period 1913-1999. Maps with the temporal distribution of physical and biological variables of the Barents and Kara Seas are presented, with proposed quality control criteria for phytoplankton and zooplankton data. Changes in the plankton community structure between the 1930s, 1950s, and 1990s are discussed. Multiple tables of Arctic Seas phytoplankton and zooplankton species are presented, containing ecological and geographic characteristics for each species, and images of live cells for the dominant phytoplankton species.

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The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.