Structure, biomass distribution and trophodynamics of the pelagic ecosystem in the Oyashio region, western subarctic Pacific     

Tsutomu Ikeda  Naonobu Shiga  Atsushi Yamaguchi 《Journal of Oceanography》2008,64(3):339-354

Biomass distribution and trophodynamics in the oceanic ecosystem in the Oyashio region are presented and analyzed, combining the seasonal data for plankton and micronekton collected at Site H since 1996 with data for nekton and other animals at higher trophic levels from various sources. The total biomass of biological components including bacteria, phytoplankton, microzooplankton, mesozooplankton, micronekton, fishes/squids and marine birds/mammals was 23 g C m⁻², among which the most dominant component was mesozooplankton (34% of the total), followed by phytoplankton (28%), bacteria (15%) and microzooplankton (protozoans) (14%). The remainder (9%) was largely composed of micronekton and fish/squid. Marine mammals/birds are only a small fraction (0.14%) of the total biomass. Large/medium grazing copepods (Neocalaus spp., Eucalanus bungii and Metridia spp.) accounted for 77% of the mesozooplankton biomass. Based on information about diet composition, predators were assigned broadly into mean trophic level 3–4, and carbon flow through the grazing food chain was established based on the estimated annual production/food consumption balance of each trophic level. From the food chain scheme, ecological efficiencies as high as 24% were calculated for the primary/secondary production and 21% for the secondary/tertiary production. Biomass and production of bacteria were estimated as 1/10 of the respective values for phytoplankton at Site H, but the role of the microbial food chain remains unresolved in the present analysis. As keystone species in the oceanic Oyashio region, Neocalanus spp. are suggested as a vital link between primary production and production of pelagic fishes, mammals and birds.  相似文献   

The concentration of atmospheric carbon dioxide at the Japanese Antarctic Station, Syowa     

T. NAKAZAWA  S. AOKI  S. MURAYAMA  M. FUKABORI  T. YAMANOUCHI  H. MURAYAMA  M. SHIOBARA  G. HASHIDA  S. KAWAGUCHI  M. TANAKA 《Tellus. Series B, Chemical and physical meteorology》1991,43(2):126-135

  相似文献   

Delayed plastic model for time‐dependent behaviour of materials     

Tsutomu Namikawa 《国际地质力学数值与分析法杂志》2001,25(6):605-627

A delayed plastic model, based on the theory of plasticity, is proposed to represent the time‐dependent behaviour of materials. It is assumed in this model that the stress can lie outside the yield surface and the conjugate stress called static stress is defined on the yield surface. The stress–strain relation is calculated based on the plastic theory embedding the static stress. Thus, the stress–strain relation of the model practically corresponds to that of the inviscid elastoplastic model under fairly low rate deformation. The delayed plastic model is coupled with the Cam‐clay model for normally consolidated clays. The performance of the model is then examined by comparing the model predictions with reported time‐dependent behaviour of clays under undrained triaxial conditions. It is shown that the model is capable of predicting the effect of strain rate during undrained shear and the undrained creep behaviour including creep rupture. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Carbon dioxide variations in the stratosphere over Japan, Scandinavia and Antarctica     

S. AOKI  T. NAKAZAWA  T. MACHIDA  S. SUGAWARA  S. MORIMOTO  G. HASHIDA  T. YAMANOUCHI  K. KAWAMURA  H. HONDA 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):178-186

  相似文献   

Reconstruction of past variations of δ¹³C in atmospheric CO₂ from its vertical distribution observed in the firn at Dome Fuji, Antarctica     

S. SUGAWARA  K. KAWAMURA †  S. AOKI  T. NAKAZAWA  G. HASHIDA 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):159-169

  相似文献   

Temporal variations of the CO₂ concentration and its carbon and oxygen isotopic ratios in a temperate forest in the central part of the main island of Japan     

TAKAKIYO NAKAZAWA  SHOHEI MURAYAMA  MITSUKO TOI  MISA ISHIZAWA  KAORI OTONASHI  SHUJI AOKI  SUSUMU YAMAMOTO 《Tellus. Series B, Chemical and physical meteorology》1997,49(4):364-381

  相似文献   

Preserved paleo-oceanic plateaus in accretionary complexes: Implications for the contributions of the Pacific superplume to global environmental change   总被引：1，自引：1，他引：0  

Atsushi Utsunomiya  Norihito Suzuki  Tsutomu Ota 《Gondwana Research》2008,14(1-2):115

We have reinvestigated the mid-Cretaceous plume pulse in relation to paleo-oceanic plateaus from accretionary prisms in the circum-Pacific region, and we have correlated the Pacific superplume activity with catastrophic environmental changes since the Neoproterozoic. The Paleo-oceanic plateaus are dated at 75–150 Ma; they were generated in the Pacific superplume region and are preserved in accretionary prisms. The volcanic edifice composed of both modern and paleo-oceanic plateaus is up to 10.7 × 10⁶ km² in area and 19.1 × 10⁷ km³ in volume. The degassing rate of CO₂ (0.82 − 1.1 × 10¹⁸ mol/m.y.) suggests a significant impact on Cretaceous global warming. The synchronous occurrence of paleo-oceanic plateaus in accretionary complexes indicates that Pacific superplume pulse activities roughly coincided at the Permo-Triassic boundary and the Vendian–Cambrian boundary interval. The CO₂ expelled by the Pacific superplume probably contributed to environmental catastrophes. The initiation of the Pacific superplume contributed to the snowball Earth event near the Vendian–Cambrian boundary; this was one of the most dramatic events in Earth's history. The scale of the Pacific superplume activity roughly corresponds to the scale of drastic environmental change.  相似文献   

Atmospheric CO₂ variations over the last three glacial–interglacial climatic cycles deduced from the Dome Fuji deep ice core, Antarctica using a wet extraction technique     

KENJI KAWAMURA  TAKAKIYO NAKAZAWA  SHUJI AOKI  SATOSHI SUGAWARA  YOSHIYUKI FUJII  OKITSUGU WATANABE 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):126-137

  相似文献   

Photometric study of new southern SU UMa-type dwarf novae and candidates: V877 Ara, KK Tel and PU CMa     

Taichi Kato  Roland Santallo  Greg Bolt  Tom Richards  Peter Nelson  Berto Monard  Makoto Uemura  Seiichiro Kiyota  Rod Stubbings  rew Pearce  Tsutomu Watanabe  Patrick Schmeer  Hitoshi Yamaoka 《Monthly notices of the Royal Astronomical Society》2003,339(3):861-871

  相似文献   

Concentration variations of atmospheric CO₂ observed at Syowa Station, Antarctica from 1984 to 2000     

SHINJI MORIMOTO  TAKAKIYO NAKAZAWA  SHUJI AOKI  GEN HASHIDA  TAKASHI YAMANOUCHI 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):170-177

  相似文献