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31.
Nutrient-enrichment bottle experiments in the northwestern Indian Ocean surface waters were conducted to investigate phytoplankton growth following enrichments with either NH4+, NO3−, Fe or Fe + NO3−. Stimulation of phytoplankton growth could be achieved by the addition of either NH4+ or NO3− under the ambient Fe concentrations, but the most significant increases in Chl a, POC, and cell densities were observed in the Fe + NO3−-amended culture. Iron addition caused more rapid responses of phytoplankton growth in the Fe + NO3− treatment than those in the NO3− and NH4− treatment. However, the Fe-enrichment treatment revealed minimal growth of phytoplankton because of severe major nutrient deficiency and was similar to the control treatment. Increases in the cell density of diatoms and spherical phytoplankton cells (< 10 μm) were significant in the NH4+-enriched samples, whereas NO3− enrichment alone had little effect on the diatoms. Simultaneous addition of Fe and NO3− stimulated maximal growth of phytoplankton, in particular in diatoms, coccolithophorids and Phaeocystis type colonies. However, the dominance of coccolithophorids and Phaeocystis type colonies in the Fe + NO3− treatment may be interpreted as resulting from Si-limitation. The high N/P ratio for phytoplankton nutrient uptake in the N-amended culture indicates the possibility of some P-limited growth. From these results, we conclude that in the northwestern Indian Ocean, Fe and major nutrients are co-limiting phytoplankton production during the northeast monsoon. Iron appeared to affect the ability of phytoplankton to respond quickly to transient nutrient inputs. 相似文献
32.
Hiroshi Takeda 《Journal of Oceanography》1984,40(6):410-415
Waves which propagate along a vertical wall lying in an arbitrary direction on aβ-plane are derived as a generalization of Haurwitz waves (Haurwitz, 1940) whose direction of propagation is restricted to
the east-west direction. The waves are classified into two types. One consists of neutral waves, which correspond to a generalization
of Haurwitz waves. The other consists of waves with complex wavenumber and without energy flux. The phase of the waves also
propagates in the direction normal to the coast in an envelope except for the case in which the coast lies in the east-west
direction. 相似文献
33.
Hiroshi Takeda 《Journal of Oceanography》1984,40(6):432-436
Topographically trapped (subinertia) waves that propagate along a coast lying in an arbitrary direction on aβ-plane are studied. It is found that the waves also propagate in the direction normal to the coast within an envelope due
to theβ-effect. The dispersion relation is hardly affected by theβ-effect except in a long wavelength or long period range in which generalized Haurwitz waves (Takeda, 1984b) exist. In the
long wavelength or long period range, two types of waves exist: topographically trapped type waves and generalized Haurwitz
type waves. 相似文献
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Aoshio-hypoxic water which can be distinguished from surrounding coastal water by its milky blue-green color-is often observed at
the head of Tokyo Bay when coastal upwelling of sulfidic bottom water occurs during summer and early autumn. Optical properties
and the biological-chemical composition of suspended matter in theaoshio water were investigated using nearby “normal” coastal water as a reference.
Suspended matter in theaoshio water contributed to the large beam-attenuation coefficient and also to the strong upward radiance with maximal intensity
around 550 nm as a result of the scattering process. No significant difference in bacterial density was observed between samples
ofaoshio water and reference coastal water. The low chlorophylls concentration inaoshio water samples indicates that biological pigments may not play a dominant role in the color of theaoshio events.
The suspended particles inaoshio water samples had much higher contents of sulfur and manganese and a lower silicon content than those in reference coastal
water samples. The colloidal elemental sulfur and manganese-rich particles identified in theaoshio water appear to be oxidation products of dissolved sulfide and manganese (II) in the anoxic water.
On the basis of these findings, it may be concluded that there is a high probability that elemental sulfur and manganese-rich
particles are responsible for the color and turbidity inaoshio. 相似文献
37.
Daisuke Tsumune Jun Nishioka Akifumi Shimamoto Shigenobu Takeda Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):111
The first iron (Fe) – fertilization experiment in the western North Pacific was carried out using SF6 to trace the Fe-fertilized water mass. A solution in 10,800 liters of seawater of 350 kg of Fe and 0.48 M of SF6 tracer was released into the mixed layer over a 8 × 10 km area. On the first underway transects through the patch after the Fe release, we observed a significant increase of dissolved Fe (ave. 2.89 nM). The fertilized patch was traced for 14 days by on-board SF6 analysis. A Lagrangian frame of reference was maintained by the use of a drogued GPS buoy released at the center of the patch. The patch moved westward at a rate of 6.8 km d−1. Mixed layer depth increased from 8.5 to 15 m during the experiment. Horizontal diffusivity was determined by the change of SF6 concentration in the patch. The horizontal diffusivity increased during the experiment. We evaluate here the fate of Fe in a Fe-fertilized patch using the dilution rate determined from sulphur hexafluoride (SF6) concentration. Dissolved Fe concentrations subsequently decreased rapidly to 0.15 nM on Day 13. However, the dissolved Fe half-life of 43 h was relatively longer than in previous Fe-enrichment studies, and we observed a larger increase of the centric diatom standing stock and corresponding drawdown of macro-nutrients and carbon dioxide than in the previous studies. The most important reason for the larger response was the phytoplankton species in the western North Pacific. In addition, the smaller diffusivity and shallower mixed layer were effective to sustain the higher dissolved Fe concentration compared to previous experiments. This might be one reason for the larger response of diatoms in SEEDS. 相似文献
38.
The effects of long-term preservation on flow cytometric parameters of natural oceanic populations of pico-and nanophytoplankton
have been examined. Populations collected at oligotrophic subtropical and subarctic locations in the North Pacific were fixed
with glutaraldehyde and frozen in liquid nitrogen, according to Vaulot et al. (1989). During six months’ storage, chlorophyll red fluorescence declined in all the groups examined, while forward light
scatter was enhanced in Synechococcus and Prochlorococcus, and weakened in nanoeucaryotes. Cell loss was not significant except for Synechococcus. Caution is required when analyzing flow cytometric data of samples stored for more than a month. 相似文献
39.
40.
Bengt G. Martinsson Göran Frank SvenInge Cederfelt Olle H. Berg Besim Mentes Giorgos Papaspiropoulos Erik Swietlicki Jingchuan Zhou Michael Flynn Keith N. Bower Tom W. Choularton Jyrki Mäkelä Aki Virkkula Rita Van Dingenen 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):801-814
The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE‐2). Very high cloud droplet number concentrations (almost 3000 cm−3 ) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios between the measurements, three criteria of typically 30% in maximum deviation were applied to the measurements to test their validity. Agreement was found for 88% of the cases. The validated data set spans droplet number concentrations of 150–3000 cm−3 . The updraught velocity during the cloud formation was estimated to 2.2 m s−1 by model calculations, which is typical of cumuliform clouds. The results of the present study are discussed in relation to cloud droplet number concentrations previously reported in the literature. The importance of promoting the mechanistic understanding of the aerosol/cloud interaction and the use of validation procedures of cloud microphysical parameters is stressed in relation to the assessment of the indirect climatic effect of aerosols. 相似文献