Productive parameters of seawater and epipelagic plankton and mesozooplankton biomass at stations of R/V Akademik Mstislav Keldysh during 1994-1998

Calculated and measured estimations of biomass of small (<3 mm), large (3-30 mm), and total zooplankton were verified (compared). These integral parameters of epipelagic communities were estimated by two methods. We used previously obtained regression equations, which correlate these parameters with water transparency. Measured values of aforesaid parameters were compared with their mean values in waters of different productivity estimated from NASA satellite maps. We compared data collected at fifteen stations in September-December in regions of different productivity in the North Atlantic. In warm regions (to the south of 40°N) measured and calculated values coincide well. In boreal regions in autumn bulk of mesozooplankton descends to deep layers due to seasonal migrations; hence correlation between measured and calculated values is disrupted. It is evident that correlation between water transparency and mesozooplankton biomass (integral index of water productivity) obtained before should be corrected for seasonal variations.

Radiolarians from ODP Leg 119, Kerguelen Plateau

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.

Late Quaternary radiolarian assemblages of ODP Site 181-1124

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.

Carbon dioxide assimilation rate, gas and ion composition in samples, and bacterial production of organic matter within and above the Broken Spur and TAG hydrothermal fields, Mid-Atlantic Ridge

Rate of CO2 assimilation was determined above the Broken Spur and TAG active hydrothermal fields for three main ecosystems: (1) hydrothermal vents; (2) 300 m near-bottom layer of plume water; and (3) bottom sediments. In water samples from warm (40-45°C) vents assimilation rates were maximal and reached 2.82-3.76 µg C/l/day. In plume waters CO2 assimilation rates ranged from 0.38 to 0.65 µg C/l/day. In bottom sediments CO2 assimilation rates varied from 0.8 to 28.0 µg C/l/day, rising up to 56 mg C/kg/day near shrimp swarms. In the most active plume zone of the long-living TAG field bacterial production of organic matter (OM) from carbonic is up to 170 mg C/m**2/day); production of autotrophic process of bacterial chemosynthesis reaches about 90% (156 mg C/m**2/day). Thus, chemosynthetic production of OM in September-October is almost equal to that of photosynthetic production in the oceanic region. Bacterial production of OM above the Broken Spur hydrothermal field is one order lower and reaches only 20 mg C/m**2/day.