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1.
Gelatinous zooplankton abundance and species composition were investigated at 3‐h intervals for a 48‐h period at a fringing reef in Malaysia. A total of 20 gelatinous zooplankton species were observed; the community was dominated by the calycophoran siphonophore Diphyes chamissonis (79.9%), followed by the trachymedusdae Aglaura hemistoma (5.6%) and Liriope tetraphylla (4.8%). The gelatinous zooplankton were not collected in the water column during most of the daytime hours (1200, 1500 and 1800 h) but were common during the night. However, an abrupt peak in abundance was found at 0900 h on the second day. The times of appearance at night were different depending on the species, and the number of species was also different depending on the hour of sampling. Sampling at 3‐h intervals over a 48‐h period revealed that the temporal variation (or sampling availability) was large in this study. Careful consideration should be given to the sampling variability in handling the gelatinous zooplankton samples in coral reef areas.  相似文献   

2.
Processes underlying the temporal and spatial variations observed in the distribution of jellyfish and non‐gelatinous zooplankton in the Gulf of Oman are not well understood. This information gap is clearly a major issue in controlling the harmful blooms of jellyfish and non‐gelatinous zooplankton. Samples of jellyfish and non‐gelatinous zooplankton were collected from six stations in Chabahar Bay and three stations in Pozm Bay within four seasons. At each station, environmental variables were also recorded from bottom and surface water. A total of 83 individuals of medusae representing four species of Scyphozoa (i.e., Cyanea nozakii, Chrysaora sp., Pelagia noctiluca, Catostylus tagi) and species of Hydrozoa (i.e., Diphyes sp., Rhacostoma sp., Aequorea spp.) were observed in the study area. A total of 70,727.25 individuals/m?3 of non‐gelatinous zooplankton dominated by copepods and cladocerans were collected in nine stations within the four seasons. The results of a RELATE analysis yielded no significant association between species composition for jellyfish and non‐gelatinous zooplankton. Among environmental variables, water transparency, nitrite concentration, water depth and temperature were better associated with the total variation in jellyfish species composition than with that of non‐gelatinous zooplankton. Dissolved oxygen, pH, and phosphate concentration were significant environmental variables associated with the variation in the spatial and temporal distribution patterns of non‐gelatinous zooplankton assemblages. Although some jellyfish species (i.e., Rhacostoma sp., Pelagia noctiluca, Catostylus tagi) occur independently of non‐gelatinous zooplankton assemblages, other jellyfish (i.e., Chrysaora sp., Aequorea spp., Cyanea nozakii, Diphyes sp.) are strongly correlated with non‐gelatinous zooplankton assemblages.  相似文献   

3.
Abstract. Seasonal changes in zooplankton biomass, abundance and species composition were studied at a neritic station in the Balearic Sea between April 1993 and May 1994. Sampling was carried out every 10 days in a zone influenced by the main current circulating through the Mallorca channel. Three main peaks of zooplankton biomass and abundance were observed: (1) at the beginning of summer when the thermocline developed, (2) in autumn when the thermocline broke down, and (3) in early spring. The smaller zooplankton fraction (100–250 μm) comprised on average 32 % of the total biomass and 73 % of total abundance. Copepods were the predominant group (64 % of the total abundance) with Clausocalanus, Oithona and Paracalanus being the most abundant genera. Paracalanus parvus, Clausocalanus furcatus, Acartia clausi, Oithona plumifera, Temora stylifera, Centropages typicus and Oncaea mediterranea were found to be the most important species in the area. Other abundant groups were cladocerans (15 %) and meroplankton larvae (12 %), both of which were particularly numerous during the stratified period. The copepod community was characterized by the above‐cited perennial species, which were abundant during the cycle studied. However, the influence of the hydrological conditions of the Balearic Sea, such as the Atlantic water influx and the physical structure of the water column (stratification and mixing), promoted the observed variability in zooplankton as well as the appearance of characteristic species during the annual cycle.  相似文献   

4.
Abstract. The distribution and abundance of the hyperiid amphipods collected during April–May 1986 was analysed in order to study their relationship to mesoscale features in the southern Gulf of Mexico. Hyperiids were represented by 79 species, Lestrigonus bengalensis (65% of total hyperiids), Primno abyssalis (4.3%), Anchylomera blossevillei (2.3%) and Lestrigonus schizogeneios (2.3%) being the most abundant. Several mesoscale features (two cyclonic and three anticyclonic eddies, two upwelling areas) were active in the surveyed area. Cluster analysis of density and composition produced five groups of stations that were found to be related to some of these features. Overall, the mesoscale features that most influenced the local hyperiid community were the upwelling areas; they were related both with the highest and the lowest hyperiid densities and with high and low diversity figures. Overall day/night variations were normal, with highest night‐time densities; this pattern was not consistent in the different mesoscale features studied. Reverse migrations were possibly occurring, or migration patterns were lacking, at some of these systems. The hyperiid community structure related to the anticyclonic eddies differed somewhat among the eddies; however, the oceanographic exchange with the surrounding gulf waters probably obscured sharper faunistic differences between the communities.  相似文献   

5.
根据2013年3-4月、6-7月、9月和11-12月4个航次的调查资料;分析南沙海域浮游虫戎亚目的种类组成、优势种、栖息密度和群落结构特征;并探讨季风转换对其影响及其与管水母的关系。研究海域内共鉴定浮游虫戎亚目12科26属63种。生态类群结构属于热带大洋性。优势种较少;共出现7种;其中;孟加拉蛮虫戎（Lestrigonus bengalensis）为唯一的年度优势种;优势地位显著。物种组成存在季节性变化;分为春季、夏季与秋-冬季3个群落。虫戎年均栖息密度为18.30×10-2 ind/m3;高数量区主要分布于近岸水域;数量季节变化不明显;但平面分布季节差异明显。虫戎年均丰富度、多样性、均匀度指数和多样性阈值各是1.23、1.28、0.33、0.48。虫戎物种组成随季风转换左右近岸低盐水影响程度而变化;群落结构、生物多样性和栖息密度平面分布随季风转换所驱动的表层环流结构改变而变化。虫戎群落分布与管水母间的相关性证实研究海域两类群物种间的寄宿关系。这种关系促使孟加拉蛮虫戎在沿岸低盐水影响下更易形成高优势度;而表现出类似近岸海域优势种优势地位显著的特点。  相似文献   

6.
Zooplankton diel vertical migration is evident on the mixed isothermal side of the western Irish Sea frontal system but is often influenced by large tides and persistent geostrophic currents. On the stratified side of the front, temperature acts as a controlling factor with most of the zooplankton occurring above the thermocline and carrying out pronounced vertical migration when chlorophyll a levels are low and diffuse. At higher chlorophyll levels, when discrete chlorophyll a maxima form, zooplankton vertical movement may be greatly modified with a large number of species and stages concentrating within these maxima at all times of the diel light cycle.  相似文献   

7.
In order to understand the mechanism by which zooplankters from different origins co-occur during the upwelling season within Golfo de Arauco, one of the most productive areas in central Chile, we assessed short term variations in the vertical distribution of the most abundant copepod species. Fine-scale, day and night vertical zooplankton sampling was done with a pump over 12 days in summer. The water column in the gulf consisted of three layers: Equatorial Subsurface Water of low dissolved oxygen content in the deeper part of the water column, strong temperature and oxygen gradients at mid-depth (15-25 m), and a layer of warmer, more oxygenated, less saline water at the surface. Copepods within the gulf originated from offshore, from the continental shelf, and from the coastal area. Most taxa showed distinctive vertical distributions. Three copepod groups were identified by their mean weighted depths of residence. One group included shallow residents found above the thermocline/oxycline (Acartia tonsa, Centropages brachiatus, Corycaeus sp., Paracalanus parvus, Oncaea sp.). A second group was comprised by species distributed at or below the thermocline/oxycline (Oithona sp., Oncaea conifera, Lucicutia sp., Metridia sp., Heterorhabdus papilliger). The third group was composed of vertical migrators that crossed the thermocline/oxycline (Calanus chilensis, Calanoides patagoniensis, Aetideus armatus, Pleuromamma piseki). In spite of their different vertical distribution ranges, the most abundant and frequent copepod species (P. parvus, C. chilensis, C. patagoniensis, C. brachiatus) share a common capacity to withstand wide ranges of oxygen concentration and temperature. This characteristic, along with the capacity to vary their life strategies under different environmental conditions, seems to facilitate the maintenance of large numbers of copepods in coastal waters along the Humboldt Current.  相似文献   

8.
南沙群岛西南大陆斜坡海域浮游动物的垂直分布   总被引：4，自引：0，他引：4  
浮游动物是海洋生态系统物质和能量转移的关键环节,也是渔业资源的重要饵料,其种类组成和数量分布均有明显的垂直分层现象。利用2011年4月在南沙群岛西南大陆斜坡海域开展的18个站点90份样品的调查数据,对该海域浮游动物的垂直分布进行了研究,表明:(1)该海域浮游动物种类组成丰富,共出现18个类群580种(类);(2)浮游动物种类组成垂直变化明显,特定水层出现的种类数占总种数的43.6%,各水层均出现的种类仅占总种数的15.8%;(3)优势种组成复杂,垂直变化明显,单一种类的优势度不高;(4)浮游动物平均密度和湿重生物量分别为206.27ind/m3、94.03mg/m3,密度和生物量均以0~2m层和30~75m层较高,沿水深梯度的变化呈明显的双峰型;(5)浮游动物数量的垂直变化主要受温跃层影响,温跃层内浮游动物数量最高,温跃层上方和下方的水层内数量较低;(6)南沙西南大陆斜坡区浮游动物生产力水平较高,表明该海域渔业资源有一定的开发潜力。  相似文献   

9.
Horizontal and vertical distributions of δ~(18)O and δ~(13)C were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ~(18)O and δ~(13)C of these four species were linked to freshwater input. In the Bali Sea,however, depleted δ~(18)O and δ~(13)C for these species may be due to different reasons. Depleted δ~(18)O was a result of freshwater input and as well influenced by along-shore currents while depleted δ~(13)C was more likely due to the Java-Sumatra upwelling. Comparison of shell δ~(18)O records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0–50 m and 20–75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75–125 m water depth. N.dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ~(13)C values of both G.ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.  相似文献   

10.
基于2013年8月琼东海域两个连续站的观测资料,对比分析了近岸站位和陆架站位的营养盐和叶绿素a浓度周日变化特征及其影响因素。结果表明:在垂直分布上,近岸站位S1与陆架站位S2的温跃层减弱了营养盐的向上输运;在时间变化上,S1站底层硅酸盐、硝酸盐和磷酸盐浓度具有半日波动的特点,而S2站的营养盐则不具有周日波动的现象,这说明近岸站位的营养盐受到潮汐作用的影响更显著。S1站的叶绿素a分层不明显,夜间的低值可能体现浮游动物的摄食作用,S2站位的叶绿素a分层明显,夜间没体现浮游动物的摄食作用。总体上,琼东海域近岸站位S1和陆架区站位S2叶绿素a和营养盐周日波动都受到温跃层、潮汐、生物作用和光照的影响,但S1站受潮汐作用影响更显著,且S1站叶绿素a浓度还受到浮游动物摄食作用影响。由于叶绿素a和营养盐受到多种环境要素的影响,使得两者相关性不显著。  相似文献   

11.
The goal of studies described here was to determine the responses of zooplankton taxa to phytoplankton patches which develop in and near intrusions of cold, nutrient-rich Gulf Stream water. To achieve this goal we determined the horizontal and vertical distributions of abundant mesozooplankton taxa on the south-eastern continental shelf of the USA between 29°30′ and 31°N. The study period was from June 23 to August 16, 1981. Highest concentrations of zooplankton usually occurred in and near patches of phytoplankton. Increased phytoplankton appeared to trigger the formation of patches of the calanoid copepod Temora turbinata and the cyclopoid copepods Oithona spp. and Oncaea spp. The patches of zooplankton had greater alongshore than cross-shelf dimensions. T. turbinata responded rapidly to increased concentrations of phytoplankton by reproducing and aggregating in and above intruded waters. Oithonidae which were often, but not always, abundant in phytoplankton patches eventually attained high concentrations over most of the middle and part of the inner shelf. Their concentration and that of Oncaeidae increased steadily. Oncaeidae were not abundant in recently upwelled waters, as was T. turbinata but reached high concentrations in older intrusions when the abundance of T. turbinata remained level or decreased slowly. Both cyclopoid taxa are thought to reproduce slowly (egg sacs) compared to T. turbinata. Another taxon, the doliolids, became abundant far more rapidly in intruded waters (by asexual reproduction) than did the other three taxa. Doliolids were the most opportunistic intrusion zooplankton form. They do not regularly occur in low abundance on the shelf, as do the three copepod taxa, but develop in pulses in regions where T. turbinata and Oncaea are not abundant. Of the four taxa studied the abundance of doliolids increased and decreased most rapidly, whereas Oithona and Oncaea increased slowly and did not decrease during the study period. T. turbinata and Oncaea were most abundant at 60% of all stations in the intruding water. Doliolids and Oithona on the other hand, were mostly in the thermocline and intrusion. Whereas phytoplankton patches, which developed in intrusions, were physically induced (PAFFENHÖFER and LEE, 1988), patches of zooplankton were biologically induced.  相似文献   

12.
The copepods Neocalanus plumchrus, N. flemingeri, N. cristatus, and Eucalanus bungii dominate the net zooplankton throughout the subarctic Pacific Ocean. All four species have an extensive seasonal ontogenetic vertical migration, completing most or all of their feeding and somatic growth in spring and early summer. We used stratified tows with MOCNESS and BIONESS instrumented net systems to resolve their upper ocean vertical distributions in May and June of 1984, 1987 and 1988. In each year the feeding copepodite stages of all four species were concentrated above the permanent halocline (roughly from 0 to 150m). However, the four species showed strong vertical species zonation and segregation within this layer. We consistently found a near-surface pair (N. plumchrus and N. flemingeri) and a subsurface pair (N. cristatus and E. bungii). The boundary between these groups shifts vertically, but was sharply defined and was very often coincident with a weak and transient thermocline marking the base of the layer actively mixed by surface wind and wave energy. Diel vertical migration was very limited during our sampling periods.The data suggest that the vertical distribution patterns of the copepods could be set by responses to the local intensity of turbulent mixing in the watercolumn. N. plumchrus and N. flemingeri occupied a stratum characterized by strong turbulence. N. cristatus and E. bungii occupied a stratum that was a local minimum in turbulence profiles. The depth of the boundary between the species pairs was deeper when winds and surface energy inputs were strong. The vertical partition pattern may also be determined by a difference in feeding strategy between the species pairs. N. plumchrus and N. flemingeri may feed on the enhanced protozoan population of the mixed layer, while N. cristatus and E. bungii feed on particle aggregates settling from above.  相似文献   

13.
During the 1990s many studies on zooplankton in the Japan Sea have been carried out. In this review, I have synthesized the study of horizontal distribution, seasonal and annual variations of zooplankton biomass, and ecological characteristics of major component species in the southern Japan Sea, which area is influenced by the warm Tsushima Current. The zooplankton biomass (annual mean) in the southern Japan Sea was lower than in the subarctic Pacific, including the northern Japan Sea, and similar to biomass levels in Kuroshio waters. Temporal variations in zooplankton biomass showed both seasonal and year-to-year components. Seasonal biomass increases to a maximum in spring with a weak secondary peak in autumn. As for long-term changes, 3–6 year cycles were identified, with the dynamics of the surface warm Tsushima Current and the subsurface cold water playing important roles in determining the yearly zooplankton community structure and biomass. Cold water species in the southern Japan Sea had extensive diel vertical migrations whose range is restricted in summer by the development of a thermocline. Among these species, the herbivores Euphausia pacifica and Metridia pacifica encounter a lower food supply, resulting in lower growth rates. The vertical dispersal of epipelagic carnivorous zooplankton such as Sagitta elegans and Themisto japonica to the deep-sea is probably facilitated by reduced interspecific competition. Their interaction with Japan Sea Proper Water, characterized by near-zero temperatures in the meso- and bathypelagic zones suppresses growth rates of the mesopelagic zooplankton. The lack of micronektonic predators in the mesopelagic zone may allow the persistence of slow growing populations.  相似文献   

14.
Seasonality of Plankton Assemblages in a Temperate Estuary   总被引：3，自引：0，他引：3  
Abstract. Synoptic measurements of temperature, salinity, nutrients, primary productivity, chlorophyll a, and abundance and composition of phytoplankton, zooplankton, and ichthyoplank-ton were made over an annual cycle on the Peconic Bay estuary (Long Island, New York, USA). There were pronounced seasonal fluctuations in all variables measured. During the warmer season, the plankton was dominated by nanophytoplankton (athecate microflagellates and chlorophytes, short chains of diatoms), small zooplankton (copepod nauplii, copepodites, and adults of small copepod species) and gelatinous carnivores (ctenophores and medusae). During the colder season, the plankton was dominated (in terms of primary productivity and chlorophyll a) by netplankton, larger zooplankton (adult copepods) and fish larvae. The winter bloom of apparent netplankton (> 20 μm fraction) was largely an artifact of the screening method employed, in that long chains of a diatom with small individual cell size (Skeletonema costatum) comprised 84.4–97.8% of the phytoplankton present. There was a significant negative relationship over the year between length of diatom chains and number of smaller zooplankton. For this reason, as well as initiation of the winter bloom during a period of declining levels of both light and zooplankton, inception of the bloom appeared more related to release of zooplankton grazing pressure than to illumination. Temporally offset pulses of ctenophores and other zooplankton during the warmer season suggest substantial predation by ctenophores. Apparent decimation of copepod populations by ctenophore predation in late summer and fall immediately preceeded inception of the winter diatom bloom. Larval Ammodytes americanus were the dominant ichthyoplankton, and these co-occurred in winter with increased abundances of larger adult copepods of species upon which A. americanus is known to feed. With certain modifications the patterns recorded for Peconic Bay corresponded to both of two generalized trophic pathways proposed by Greve & Parsons (1977) for temperate waters: nanoplankton → small zooplankton → gelatinous zooplankton carnivores or netplankton → larger zooplankton → young fish. The former pattern characterized the warmer season, and the latter the colder season. Comparison of patterns in Peconic Bay with those in some other temperate estuarine and coastal waters suggests similarity, particularly for estuaries of the northeastern United States.  相似文献   

15.
Turbulence and zooplankton production: insights from PROVESS   总被引：1，自引：0，他引：1  
Zooplankton are directly influenced by turbulence in both a passive and an active manner. Passively, zooplankton are at the mercy of turbulence in how it affects their vertical mixing, encounter rate, detection abilities and feeding current efficiency. Many zooplankton species, however, are actively able to mitigate the effects of turbulence by modifying their behaviour, e.g. vertical migration, prey switching and habituation to hydromechanical stimuli. Both theoretical treatments of these processes and field observations from the northern North Sea are examined. Field observations show that some copepod species actively migrate to avoid high turbulence levels in surface waters. Furthermore, observations show a negative relationship between turbulence and zooplankton ingestion rates. This supports the paradigm of a dome-shaped response for zooplankton production with environmental turbulence. A theoretical treatment shows that the reaction distance, R, for an ambush-feeding copepod feeding on swimming organisms follows R ∝ −1/6 where is the turbulent dissipation rate, a result that shows close agreement with previously reported experimental results.  相似文献   

16.
Carnivorous zooplankton in the Benguela system have tended to be ignored by all but early taxonomists and a handful of recent researchers. An attempt is made here to address the importance of carnivores in this system but, because the database is poor, it was necessary to apply material from outside the region. The taxa covered include ctenophores, cnidarians (Scyphozoa and Hydrozoa, including Siphonophora), chaetognaths and hyperiid amphipods as well as such minor groups as pelagic gastropods and decapods. Most groups of carnivores within the Benguela are represented by only one or two "common" species. These tend to be epiplanktonic and generally concentrated inshore of the shelf-break, where their distributions are influenced by changes in local hydrography. Their densities frequently exceed those of herbivores. The dominant carnivores share a number of attributes: wide-ranging diets, high assimilation and growth efficiencies and mostly a Type I functional response to food concentration. They fall into two categories. The first is the gelatinous species, which have short lifespans and exhibit rapid growth and often massive reproductive response to high concentrations of food. They are patchily distributed and some appear to have behavioural traits that enable them to stay within localized patches of prey on which they may be dependent because of high metabolic costs. In the second category are crustacean predators and chaetognaths which have slower response times to the food environment but may have longer lifespans, lower daily maintenance needs and an ability to store lipids. They are less dependent on high densities of food organisms and can survive throughout winter, when gelatinous predators are rare. The effect of predation on abundance of copepods is estimated on the basis of both published and unpublished data. Should swarms of predators coincide with a critical gateway of zooplankton or larvae, then there may be total depletion. This applies especially to the nearshore zone of the West Coast and to semi-enclosed bays. The role of carnivorous zooplankton in the diets of commercially important fish species is stressed, but their importance in the regeneration of nutrients may be insignificant.  相似文献   

17.
Myctophids are among the most abundant fishes in the world׳s ocean and occupy a key position in marine pelagic food webs. Through their significant diel vertical migrations and metabolism they also have the potential to be a significant contributor to carbon export. We investigated the feeding ecology and contribution to organic carbon export by three myctophid species, Benthosema glaciale, Protomyctophum arcticum, and Hygophum hygomii, from a structurally and ecologically unique ecosystem- the Mid-Atlantic Ridge (MAR). Similar to the results of previous studies, the diet of these fishes was primarily copepods and euphausiids, however, gelatinous zooplankton was identified in the diet of B. glaciale for the first time. Ridge section and time of day were significant explanatory variables in the diet of B. glaciale as determined by canonical correspondence analysis, while depth was the only significant explanatory variable in the diet of P. arcticum. Daily consumption by MAR myctophids was less than 1% of dry body weight per day and resulted in the removal of less than 1% of zooplankton biomass daily. Although lower than previous estimates of carbon transport by myctophids and zooplankton in other areas, MAR myctophid active transport by diel vertical migration was equivalent to up to 8% of sinking particulate organic carbon in the North Atlantic. While highly abundant, myctophids do not impart significant predation pressure on MAR zooplankton, and play a modest role in the active transport of carbon from surface waters.  相似文献   

18.
We investigated the fouling community on the Fisheries Vessel (F/V) Khronometer during a 3‐year period, from its sinking, by means of video transects. The results demonstrate that the shipwreck presented high macroinvertebrate coverage from the first survey (100 days after sinking). The most conspicuous organisms were cnidarians, followed by amphipods and serpulids (tubes). The hydroid Ectopleura crocea was the most abundant colonizer in the early stages; the sea anemone Anthothoe chilensis and the azooxanthellate soft coral Tripalea clavaria were abundant 2 years after the vessel sank. Interestingly, shipwreck coverage and species composition at the end of the sampling period (940 days after sinking) were similar to those of the wood vessel Cristo Rey, which sank 36 years before the Khronometer. Besides, some different taxa from that seen on video transects were identified from samples taken during dives, corresponding to isolated organisms with scarce abundance or cryptic habits. Moreover, four reef fish species were recorded. Shipwrecks represent interesting places for recreational activities such as diving and fishing. This is the only study about the early development of an invertebrate community on artificial reefs in Buenos Aires coast, Argentina. Monitoring natural and artificial substrata could help to understand the ecological patterns occurring around them and provide information to help manage artificial reefs in sustainable ways.  相似文献   

19.
Vertical distributions of phyllosoma larvae were examined in waters east of the Philippines or west of the Mariana Islands (18°56′ N to 19°04′ N; 129°10′ E to 129°35′ E) based on zooplankton samples collected with an Isaacs-Kidd Midwater Trawl on September 22–24, 1986. Phyllosoma larvae belonged to the two families Scyllaridae and Palinuridae comprising 4 genera and 9 species. Of the collected phyllosoma larvae, those of Scyllarus cultrifer and Panulirus longipes were most abundant and showed similar vertical distributions: (1) both species were collected from the mixed layer at night but not in the day, (2) their vertical distributions did not change with their stages, and (3) the upper limit of their vertical distributions during the day accorded with the base of mixed layer. Furthermore, their vertical distributions were similar to those of lepthocephalus larvae which were collected using the same sampling stations and gear in the present study. Vertical distributions of phyllosoma larvae were discussed in relation to their horizontal distributions. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

20.
Continuous sampling of the plankton with a pump sampler was carried out along a 960 m straight-line course in Maizuru Bay. The 25 collections of plankton were successively obtained at a depth of 1.5 m along the course, each of the collections covering a horizontal distance of 38 m. Vertical samplings of the plankton were done at five different depths (90, 120, 150, 180 and 210 cm) at 13 stations along the course. In both kinds of samplings temperature and chlorinity were measured.In the horizontal distribution ofF. taraikaensis, it was demonstrated that the counts of plankton had no correlation with the temperature and chlorinityin situ. There was a correlation between the counts and the differences of temperature and chlorinity between two successive sampling stations. It seemed thatF. taraikaensis was most abundant in the locations where the temperature difference was greater than +0.2C and the chlorinity difference was greater than +0.04 . This species was more abundant around the steep thermocline and the steep halocline. When the vertical profiles of temperature and chlorinity did not show steep gradients, this species was more abundant near the surface.  相似文献   

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