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1.
Larval feeding and survival strategies are described on a Japanese sand lance, Ammodytes personatus Girard, collected in the vicinity of a thermohaline front in the Ise Bay, in comparison with those of other predominant larvae, Hexagrammos spp. and Sebastiscus marmoratus (Cuvier). First-feeding A. personatus larvae (3.1–3.9 mm NL) fed primarily on tintinnid ciliates, subsequently switching to copepod nauplii (4.0–7.9 mm NL larvae) and post-naupliar copepods (8.0–11.3 mm NL larvae). First-feeding Hexagrammos spp. larvae (6.5–6.9 mm NL) fed primarily on post-naupliar copepods, and first-feeding S. marmoratus larvae (<4.0 mm NL), mostly on copepod nauplii. The different food preferences of these species at first-feeding were related to their different mouth widths (0.15–0.19, 0.52–0.56 and 0.32–0.40 mm, respectively) and/or body size (3.1–3.9, 6.5–6.9 and 3.2–3.9 mm NL, respectively). Ciliate-feeding by first-feeding A. personatus larvae was strongly related to the convergence of the larvae and their prey near the thermohaline front, densities of both being greater on the inshore side of the frontal zone. In conclusion, the aggregation of ciliates near the thermohaline front may have improved feeding conditions and survival of first-feeding A. personatus larvae.  相似文献   

2.
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3.
We describe the oceanographic condition as observed by hydrographic data and phytoplankton spring bloom detected by OCTS images off Sanriku, northwestern Pacific, during the spring bloom period in 1997. The relationship between the two is discussed. OCTS images detected the bloom in early April in the coastal area around the Izu ridge north of the Kuroshio and the eastern coastal area of Hokkaido to the Oyashio front. The bloom areas were seen along the offshore Kuroshio Extension from the end of April, in the upstream region of the Oyashio south of the Kurile Islands, except for a part of coastal area from the end of May, and in the Kuroshio warm-core ring 93A (KWCR 93A) from early June. The temperature difference between the surface and subsurface layer is used as a stratification index. This was large in the upstream region of the Oyashio south of the Kurile Islands and KWCR 93A from early June. Previous research has pointed out that the spring bloom usually corresponds to the development of stratification in the water column due to seasonal warming. In addition to that, we suggest that the transportation of water containing a high chlorophylla concentration by advection due to strong currents, like the Kuroshio and the Oyashio, is important for the formation of an area of high chlorophylla concentration. These results indicate that the OCTS images are useful for a knowledge of the distribution and the change of chlorophylla concentration in the northwestern Pacific region.  相似文献   

4.
Primary productivity off Enshu-nada was measured by the13C method in September 1989. Primary productivity was estimated in a cold water mass developed off Enshu-nada for the first time. The obtained value was 469 mgC·m–2·d–1 and higher than those in the pelagic area of Kuroshio, but equivalent to those in the neritic and the Oyashio areas. It was indicated that cold water mass is the place where organic matter is produced actively. Extremely high chlorophylla of more than 5g·l–1 were found in the cold water mass. The high productivity was due to high standing crop of phyoplankton. Furthermore, calculated light efficiency and quantum yield showed consistent increase with depth and showed a maximum at 10% light level. Both were larger on the coastal side than those on the oceanic side of the Kuroshio current.  相似文献   

5.
核酸指标可表征桡足类营养及生长状态, 然而多物种和多指标比较研究的相对缺乏却限制了现场海区调查中对核酸标志物的广泛应用。本研究测定了系列饵料浓度(0.2~2.0μg C·mL-1)喂食的安氏伪镖水蚤Pseudodiaptomus annandalei的桡足幼体Ⅱ期个体的摄食率、生长率及成体产卵率, 并就生化组成, 包括RNA含量、DNA含量、蛋白含量(以下简写为PRO)、RNA:DNA、RNA:PRO、DNA:PRO及元素组成(N含量、P含量、C:N 和C:P比值)进行定量分析和计算。摄食率、生长率、产卵率及桡足幼体的RNA相关的核酸指标随饵料浓度的变化趋势均符合双曲线模型, 而雌性成体中仅RNA:DNA比值符合此模型。对RNA相关指标与各生理参数的相关性分析显示, 桡足幼体的RNA相关指标均与摄食率及生长率呈显著线性相关性, 显著程度的顺序为RNA:DNA>RNA:PRO>RNA含量; 雌性成体中RNA:DNA及RNA:PRO比值与产卵率显著相关, 前者的相关性远较后者显著。此结果表明, 在常用的现场浮游桡足类调查的标志比值(RNA:DNA比值或RNA含量)之外, RNA:PRO比值亦可作为指示桡足类生长状态的标志比值, 但是当指示体生长时, 桡足类必须处于同一生长阶段。RNA相关指标与饵料浓度之间稳固的双曲线相关性提示我们, RNA相关指标可帮助评估桡足类的饵料环境。  相似文献   

6.
To explore the causes of the winter shallow mixed layer and high sea surface temperature (SST) along the strong Kuroshio jet from the East China Sea to the upstream Kuroshio extension (25.5°N–150°E) during 1988–1994 when the Japanese sardine stocks collapsed, high-resolution ocean general circulation model (OGCM) hindcast data are analyzed with a bulk mixed layer model which traces particles at the mixed layer base. The shallow mixed layer and high SST along the Kuroshio jet are mainly caused by the acceleration of the Kuroshio current velocity and the reduction of the surface cooling. Because the acceleration reduces the time during which the mixed layer is exposed to wintertime cooling, deepening and cooling of the winter mixed layer are restricted. The weaker surface cooling due to less severe meteorological forcing also causes the shallow mixed layer and the high SST. The impact of the strong heat transport along the Kuroshio extends to the southern recirculation gyre of the Kuroshio/Kuroshio extension regions; previous indications that the Japanese sardine recruitment is correlated with the winter SST and the mixed layer depth (MLD) in the Kuroshio extension recirculation region could be related to the velocity, SST, and MLD near the Kuroshio axis which also could affect the variability of North Pacific subtropical water.  相似文献   

7.
Microbial biomass in seawater of Shimoda Bay was assessed using some biomass parameters, such as ATP, DNA, RNA, protein, chlorophylla, and bacterial number and every estimate is in the same order. The estimates based on the amounts of ATP, DNA and RNA showed good correlation.  相似文献   

8.
The present paper investigates the effect of environmental variability on the spawning dynamics of sardine, Sardina pilchardus, in the Eastern Mediterranean. To do so, variability in four different reproductive traits, i.e. reproductive activity, incidence of recent spawning, prevalence of early ovarian atresia and relative batch fecundity was tested along a gradient of habitat conditions like water temperature, chlorophyll a (Chl a) concentration and an index of zooplankton production. Apart from atretic prevalence all remaining traits were significantly and positively correlated with Chl a concentration which indicates that sardine in the E. Mediterranean tends to enhance egg production under conditions of increased primary productivity. On the other hand, prevalence of atresia together with spawning incidence were positively affected by water temperature whilst the only factor that correlated significantly with the index of zooplankton production was relative fecundity. These findings were interpreted as an indication of direct energy flow from phytoplankton filter-feeding to gonadal development and egg production, implying that besides capitalized energy sardine also uses current income for supporting reproduction.  相似文献   

9.
Regional and vertical distribution of the microzooplankton in the Philippine and the Celebes Seas is reported in relation to the phytoplankton distribution. The maximum concentration of chlorophylla occurred at the surface in the Celebes Sea and in subsurface layer (50–150 m depth) in the Philippine Sea. On the other hand, the maximum occurrence of the microzooplankton was observed in the subsurface layer (50–150 m) throughout these sea areas; discrepancy in the vertical positions of the chlorophylla and microzooplankton maxima was observed in the former sea area. The higher dominancy of large-sized phytoplankton such as diatoms andTrichodesmium at the surface maximum, probably because most large-sized phytoplankton were uningestible for the microzooplankton, was the main reason why the discrepancy existed in the Celebes Sea. In the Philippine Sea, where the subsurface chlorophylla maximum layer was formed mainly by small-sized phytoplankton such as coccolithophorids and small dinoflagellates, such a discrepancy was not observed. These may indicate the establishment of a close food relationship between the microzooplankton and the small-sized phytoplankton rather than to the large-sized phytoplankton.  相似文献   

10.
In order to examine the applicability of remotely-sensed ocean color for the estimation of phytoplankton biomass and primary production in the Oyashio region, the western subarctic Pacific, vertical distributions of chlorophylla concentration and primary production were observed in April and May 1997. Spring bloom was observed in both April and May, and the surface concentration of chlorophylla exceeded 40 mg m−3. The relationship between the standing stocks of chlorophylla within the layer from the sea surface to one optical depth (0–1/k layer) and the surface chlorophylla concentration is expressed as a Michaelis-Menten equation. The mean ratio of the standing stock of chlorophylla in the euphotic layer to that in the 0–1/k layer was 4.41, this ratio did not significantly differ from 4.61 which was obtained at homogeneous distribution of chlorophylla within the euphotic layer. These facts suggest that the distribution of chlorophylla could be assumed to be homogeneous in the euphotic layer during the spring bloom. Results of primary production measurements by simulatedin situ method were compared with those by an algorithm with two variables; chlorphylla and non-spectral PAR. Daily primary production in the euphotic layer estimated by the algorithm varied in a range of 38–274% of that estimated by incubation, although the primary productions by the algorithm agreed with those by the incubation at a half of stations. Primary production within the euphotic layer calculated using simply the surface data was the same as that estimated using vertical distribution of chlorophylla. These results show that the primary production in the euphotic layer may be estimated from the remote sensed measurements during the spring bloom in the Oyashio region.  相似文献   

11.
The primary productivity in coastal water adjacent to the Kuroshio off Shimoda was measured as part of the International Biological Program. The total amount of chlorophylla in the euphotic zone varied widely from 20 mg/m2 to 60 mg/m2 throughout the year and the maximum values were measured in early summer. These values were higher than those in the Kuroshio but agreed with those in the Oyashio. Vertical differentiation of photosynthetic characteristics was well developed and it was strongly related to the stratification of the water column. The light-saturated photosynthetic rate of surface phytoplankton varied from 5.8 mg C/(mg chl.h) in May to 2.0 mg C/(mg chl.h) in January. These rates were higher than those in the Kuroshio. The daily primary production was estimated by the chlorophyll method. Highest value was 0.5–1.5 g C/(m2day) in early summer and the lowest was 0.2 g C/(m2day) in winter. The primary productivity in the coastal water studied accorded fairly well with that in the Oyashio.Contribution No. 239 from Shimoda Marine Biological Station. This study is part of JIBP project entitled Studies on the Dynamic Status of the Biosphere, a Special Research Project supported by the Ministry of Education.  相似文献   

12.
A field survey was undertaken to reveal the structure of the tidal front in Iyo-nada. An obvious tidal front was found between the mixed region around Hayasui Straits and the stratified region in Iyo-Nada. Its structure was typical in the eastern part and was influenced by the river discharge in the western part. An intense chlorophylla maximum was found in the subsurface layer of the eastern typical front. Analysis using TS diagram suggested that, around the eastern front, there was an intrusion from the mixed water to the middle layer of the stratified water. This intrusion was supposed to be an important process supplying nutrients from the mixed water to the subsurface of the frontal region and causing the intense chlorophylla maximum.  相似文献   

13.
Chla, protein, RNA and DNA were measured in 400 samples taken from the surface down to 5,000 m at 27 oceanographical stations in the North Pacific Ocean. Two section diagrams of these cellular constituents were given along 155°E and 155°W meridians, and several vertical profiles of the four constituents were also given at some stations near Japan. The average concentration ranges of Chla, protein, RNA and DNA obtained in this study area were 0.025–0.862, 11.4–88.1, 1.36–35.3 and 0.13–5.24g/l, respectively. Chla was distributed mostly in the photic zone as we would expect. However protein, RNA were in high concentrations within the photic zone and sometimes extremely high concentrations in the deep aphotic zone.  相似文献   

14.
Phytoplankton chlorophyll stocks in the Antarctic Ocean   总被引：5，自引：0，他引：5  
Phytoplankton chlorophyll stocks in the Indian sector of the Antarctic Ocean were estimated on the basis of published data collected from nine cruises of the Icebreaker,Fuji in 1965–1976, during routine observations of the Japanese Antarctic Research Expedition (JARE). Surface chlorophylla concentration, measured at 631 stations in waters south of 35°S, ranged from 0.01 to 3.01 mg m–3, At about half of the stations the values were less than 0.24 mg and at only 29 stations were high values more than 1.00 mg m–3 recorded. The levels of surface chlorophylla stocks were estimated in three groups; (1) data obtained on the southward leg through the eastern Indian sector (middle-late December), (2) those on the northward leg through the western Indian sector (late February–early March) and (3) those on the northward leg through the eastern Atlantic sector (late February–early March). Furthermore, mean values and standard deviations were calculated for each of six different water masses from north to south,i. e., subtropical water between 35°S and the Subtropical Convergence (STC) zone, water within the STC zone, Subantarctic Upper Water, water within the Antarctic Convergence (AC) zone, Antarctic Surface Water between the AC zone and 63°S, and Antarctic Surface Water south of 63°S. Mean values of surface chlorophylla concentrations for each of the six water masses on the three legs ranged from 0.15 to 0.58 mg m–3 and were comparable to those reported by other workers previously. Seasonal periodicity of phytoplankton chlorophyll stock is discussed. The surface chlorophyll stock in the oceanic water of the Antarctic Ocean does not seem to be so high as previously believed.  相似文献   

15.
Phyllosoma larvae collected to date in Japanese and Taiwanese waters have been classified into two genera (Linuparus, Panulirus) of the Palinuridae, four genera (Ibacus, Parribacus, Scyllarides, Scyllarus) of the Scyllaridae, and one genus (Palinurellus) of the Synaxidae. However, phyllosoma larvae of three Scyllarus species (S. bicuspidatus, S. cultrifer, S. kitanoviriosus) are absolutely dominant among the larvae collected in the waters. Scyllarus larvae are abundant in coastal waters while those of Panulirus are often collected in offshore/oceanic waters. Based on previous and ongoing studies dealing with spatial distributions of phyllosoma larvae in Japanese and Taiwanese waters, it appears that phyllosoma and nisto larvae of the Scyllarus are retained within coastal waters north of the Kuroshio Current. On the other hand, the life history of the Panulirus (particularly P. japonicus) may be completed within the Kuroshio Subgyre: their phyllosoma larvae may be flushed out from coastal waters into the Kuroshio, then transported through the Counter Current south of the Kuroshio into the water east of Ryukyu Archipelago and Taiwan where they attain the subfinal/final phyllosoma or puerulus stages, once again entering the Kuroshio and dispersing into coastal waters. This revised version was published online in July 2006 with corrections to the Cover Date. An erratum to this article is available at .  相似文献   

16.
We have determined chlorophyll a (Chla) concentration, primary productivity, cell density and species composition of diatoms, and the number of microzooplankton at the surface in the subarctic North Pacific in January 1996. The wet weight of copepods obtained by vertical tows from 150 m to the surface was also measured during the cruise. Chla concentration and primary productivity tended to be higher in the region west of 180°, the western subarctic North Pacific (WSNP), than east of 180°, the eastern subarctic North Pacific (ESNP). The same results were observed for the total diatom cell densities and for the genera Thalassiosira and Denticulopsis. Significant linear relationships were observed between the Thalassiosira cell density and Chla concentration and primary productivity, indicating that Thalassiosira contributes to the high-WSNP and low-ESNP distribution patterns of Chla concentration and primary productivity. Moreover, naked ciliate abundance tended to be lower in the WSNP than in the ESNP, whereas copepod biomass showed an inverse trend. Significantly negative Spearman rank correlations were found between the Thalassiosira cell density and the number of naked ciliates and between the number of naked ciliates and the wet weight of copepods. These results indicate that copepod grazing indirectly controls Thalassiosira cell density via predation on the naked ciliates. We conclude that the high copepod biomass in the WSNP is a factor controlling the high-WSNP and low-ESNP Thalassiosira abundance and hence Chla concentration and primary productivity patterns.  相似文献   

17.
Hypotheses regarding temperature, food abundance and food size were tested to explore niche separation between Calanoides carinatus, an abundant copepod in the cool and food-rich southern Benguela upwelling system, and Calanus agulhensis, the dominant copepod on the warmer, relatively food-poor Agulhas Bank off the south coast of South Africa. Under non-limiting food conditions, egg production by both species increased linearly with temperatures between 9°C and 18°C. Egg production by C. carinatus was relatively faster at 21°C, but was offset by greater mortality. Both species showed similar functional responses to food concentration in the field, reaching satiation at ～15mg Chl a m?3, or ～3–4ppm. Food abundance was the most important predictor of egg production, whether measured as Chl a or as particle volume. Both species preferred larger particles that dominated the biomass peak, but particle size appeared more important for C. carinatus, with increasingly faster rates of egg production as the proportion of large cells (>10μm) exceeded 50%, and slower ingestion of small (<10μm) cells. Omnivory may be more important to C. agulhensis. Niche separation between the two species appears unrelated to temperature, food abundance or diel vertical migratory behaviour, and is more likely a function of variability in food availability, although food size may also play a role.  相似文献   

18.
By using existing data obtained in the offshore area from the Boso Peninsula to the Joban Coast, it was shown that the double structure of the Kuroshio Front — which is usually found along the northern edge of the Kuroshio Extension to the east 143°E (Nagataet al., 1986 ; Shinet al., 1988) — is hardly found at the edge of the Kuroshio when it is flowing along the Japanese coast or in the area to the west of 142°E. It was suggested that the cold and fresh water core beneath the density front of the double structure originates from the fresh and cold Oyashio Water which is captured beneath the Kuroshio Front just off the Kashima Coast. The double structure of the Kuroshio Front would be generated and developed very rapidly in the region between 142°E and 143°E just after the Kuroshio leaves the Japanese coast.  相似文献   

19.
An algorithm was evaluated for estimating primary production in the Kuroshio front of the East China Sea. The algorithm involves three principal inputs: chlorophyll-a (Chl-a) vertical profile, water column photosynthetic parameter and underwater irradiance parameter. We construct empirical models for estimating those three inputs from sea surface variables accessible by means of satellite remote sensing. Types of Chl-a vertical profile were closely associated with water mass features, and sea surface temperature seemed to be a potential variable to distinguish profile types. The consequence of the deep Chl-a maximum (DCM) presence was investigated by comparing the vertically non-uniform Chl-a profile against the uniform Chl-a profile in terms of the integrated biomass and primary production estimates. Since the DCM in the frontal region occurred in a relatively shallow layer with relatively high light level, allowing intensive photosynthetic processes to take place in the DCM layer. In contrast, as the DCM in the Kuroshio region occurred in the low-light, deep layer, it contributed less to the integrated primary production. We inferred that the DCM formation is more important in the frontal region than in the Kuroshio region, as they potentially contributed within 30.9% (±9.1%) and 20.9% (±5.4%) to the integrated primary production in the frontal and the Kuroshio regions, respectively. Such different degrees in the DCM contribution was then revealed by the higher integrated primary production in the frontal region than in the Kuroshio region.  相似文献   

20.
Primary production in the Kuroshio current flowing around Taiwan Island was measured by using the radiocarbon method. High values of the daily primary production were found in both the aquacultural area at the western coast and the polluted area with raw rubbish heaps at the Keelung-Patoutzu coast. In the upwelling region of southeastern coast, low values of the primary production were observed. In the eastern coast, the rate of photosynthesis for an unit amount of chlorophylla under the saturated light was in the range of 1.2±0.2 mg C/mg chlorophylla/hr. Some discussions are made on the observed results.  相似文献   

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