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1.
The meridional distribution of autotrophic picoplankton groups in the central north Pacific was studied during the late northern summer of 1990. Sampling was along a section at 175°N which extended from 45°N to 8°S. The section is far from coastal regions and included subarctic, central gyre, and equatorial areas. Five autotrophic picoplankton groups, autotrophic microflagellate, red-fluorescing picoplankton,Synechococcus, prochlorophyte, and orange-fluorescing picoplankton, were identified from samples taken at stations distributed along this section. These five groups showed distinctive differences in their meridional and vertical distributions. The autotrophic microflagellates and red-fluorescing picoplankton showed distributions that were similar to that of chlorophyll a, which was dominated by the <3 μm size fraction. However, the vertical distribution of these groups was different.Synechococcus was found mostly in surface waters (PAR<10%) and was particularly abundant in the Kuroshio Extension and south of the equatorial region where the nitracline was shallow (50–75 m). Prochlorophytes were abundant in the deep euphotic layer (PAR 1-0.1%) from the south of the Kuroshio Extension to the south of the equatorial area. Orange-fluorescing picoplankton, which may be one kind of cyanobacteria but is larger than typical Synechococcus, were mostly distributed in the oligotrophic surface waters of the central gyre. The carbon biomass estimates for these organisms showed that these five groups dominated in different areas. The vertical distribution of carbon biomass did not correspond to that of chlorophyll a in the central gyre and south of the equator because of the larger carbon/ chlorophyll a ratio of Synechococcus and orange-fluorescing picoplankton relative to that of the other picoplankton.  相似文献   

2.
Abstract. Biomass and primary production rates derived from photosynthesis-light curves on picoplankton (< 1 um fraction) and total phytoplankton were compared for the Strait of Messina. Picoplankton biomass ranged between 0.063 and 0.094 mg Chi a m-5 and accounted for 56–63 % of the total. Total primary production rates were between 0.22 and 1.56 mg C-m-2-h-1 of which the picoplankton contribution ranged from 24 to 43%. In this turbulent nearshore environment, the contribution of picoplankton to total phytoplankton production is considerably less than in calmer open-ocean waters. Carbon assimilation numbers (Pmb), the initial slope (a), adaptation parameter (Ik), optimal irradiance (Im) and compensation intensity (Lm,) for the picoplankton were lower than for the > 1 μm fraction. Fitted respiration (RmB) for the picoplankton was, however, on the average higher (10.3 % of PmB) than for the > 1 μrn fraction (6.6 %). Assimilation numbers for the > 1 μm fraction in the southern stations were of higher magnitude (8.5–12.0 mg C mg Chi a-1 h-1) than in the northern station, possibly due to the impact of upwelled water flowing southward along the Sicilian coast.  相似文献   

3.
This work investigates the alkaline phosphatase activity in a littoral marine ecosystem (Toulon Bay and Le Niel Bay, France) in order to study its biochemical characteristics with respect to pH, sea water composition and phosphate sensitivity. We also characterise the active forms in sea water and determine the extent to which zooplankton generate phosphatase activity with respect to other plankton classes. In Toulon Bay, phosphatase was produced mostly by the microplankton fraction (>90 μm), accounting for more than 90% of total activity. In contrast, most of the phosphatase activity in Le Niel Bay was generated by the nanoplankton fraction (5–90 μm) and the picoplankton fraction (0.25–5 μm). The microplankton enzymes had non Michaelis-Menten kinetics suggesting the involvement of multiple enzyme processes with distinct kinetic constants. This activity is in major part secreted into the sea water and is stimulated by the ionic strength and the pH of the sea water. Cypris larvae of the genus Balanus played a special role in this release. For the nanoplankton and picoplankton, part of this activity was due to non-secreted enzymes, probably bound to membranes or occurring intracellularly. Moreover, nano and picoplankton phosphatase required higher pH than microplankton enzyme. For all plankton size classes, there was no activity at low pH, suggesting that acid phosphatases were not involved in reactions with substrates dissolved in water.  相似文献   

4.
Chlorophylla concentrations (Chla) of size-fractionated phytoplankton samples were measured in the western North Pacific Ocean, the Bering Sea, and the Gulf of Alaska during the summer of 1986. Among samples collected in the upper 100 m (total of 210 samples), 207 samples were dominated by micro- (>10 m) or picoplankton (<2 m) and only three samples were represented by nanoplankton (2–10 m). These 207 samples were classified based on the total Chla content into three types: Type H (>1.0 g l–1), Type M (0.5–1.0 g l–1), and Type L (<0.5 g l–1). These types further divided into two subtypes (-p and-m), depending upon dominancy of pico (-p) and microplankton (-m). The phytoplankton community was represented by Type L-p in the Gulf of Alaska, where 80% of the samples fell into this type. It was represented by Type M-p in the western North Pacific and the Oceanic Domain in the Bering Sea, where 53 and 41% of samples were identified as this type, respectively. In the Middle Domain of the Bering Sea, 68% of samples collected below the nitracline was Type H-m, which indicates blooms of microplanton. This type was also observed in the neritic waters near the Aleutian Islands. These types described above are consistent with a general trend that an increase in phytoplankton abundance is attributed to the growth of microplankton. An unusual type occurred above the nitracline of the Middle Domain, where microplankton prevailed, although the total Chla was less (Type L-m). This type represents a feature of late phase of an ice edge bloom. Another unusual type was found mainly in the Outer Domain of the Bering Sea, where the total Chla was high and picoplankton prevailed (Type H-p). The predominance of picoplankton seems to result from the heavy grazing intensity of large calanoid copepods upon microplankton but not upon picoplankton  相似文献   

5.
为探究珠江口海域自养微微型浮游生物种群时空分布特征及其与环境之间的关系,于2013年5～11月,运用高液相色谱(HPLC)法和流式细胞术对珠江口海域表层水体中微微型浮游生物进行测定。流式细胞计数结果显示,珠江口海域自养微微型浮游生物由聚球藻(Synechococcus, Syn)和微微型真核生物(Picoeukaryotes,PEUK)组成。聚球藻始终占据总细胞丰度的主导地位。光合色素化学分类法(Chemotaxonomy,CHEMTAX)分析表明,自养微微型浮游生物群落结构具有明显的季节性变化,春季和夏季生物量以聚球藻为主,秋季生物量以青绿藻为主。CHEMTAX分析和流式细胞计数结果的相关性分析表明,在春季和夏季Syn细胞丰度与CHEMTAX生物量(即Syn贡献chla)之间呈现极显著正相关(P<0.01),PEUK细胞丰度与CHEMTAX生物量(即PEUK贡献chla)也存在显著正相关(P<0.05);然而,在秋季则无显著性相关关系(P>0.05)。冗余分析表明,温度和营养盐浓度是影响自养微微型浮游生物群落分布与组成的重要因素。另外,盐度、透明度、悬浮颗粒物对自养...  相似文献   

6.
The larval shells of Paphies ventricosa, reared to settlement in the hatchery, are similar in longitudinal profile to shells of some other mactracean larvae; the umbo‐stage larval shells are nearly round with the anterior margin less broadly curved than the posterior margin, the anterior end is longer than the posterior end, and the umbo is broadly rounded. Straight‐hinge larvae had total lengths up to 149 μm, and total heights up to 126 μm, and umbo larvae had total lengths up to 320 μm, and total heights up to 282 μm. The larvae settled in about 22 days at a size of about 270 μm. The larval hinge structure bears some similarities to those of other mactracean larvae.  相似文献   

7.
The species composition, seasonal abundance, and vertical distribution of mesopelagic fish larvae are described based on discrete depth sampling from the surface down to 1000 m depth during four cruises at a fixed sampling station in Sagami Bay. The abundances of total mesopelagic fish larvae in April, July, September, and December were 65.7, 13.6, 118.9, and 17.2 individuals per 10 m2 sea surface, respectively. Twenty species or types of mesopelagic fish larvae belonging to 10 families were collected. Diaphus garmani, Lipolagus ochotensis, Diogenichthys atlanticus, Sigmops gracile, and Maurolicus japonicus were the five most abundant larvae and accounted for 43.1, 14.5, 7.4, 6.3, and 5.9% of the total mesopelagic fish larvae, respectively. These five species showed clear seasonal changes in abundance, i.e. L. ochotensis, D. atlanticus, and S. gracile larvae mainly occurred during winter— spring; D. garmani and M. japonicus were collected during summer—autumn. No obvious diel vertical migration was found in these larvae. The larvae of D. garmani and M. japonicus were concentrated in the 25–50 and 50–100 m depth layers, respectively. The transforming stage of L. ochotensis, S. gracile, and D. atlanticus occurred at 400–1000 m depth, while their larvae (<8 mm standard length) occurred in the upper 100 m layer, indicating that metamorphosis of these species takes place in the 400–1000 m layer. Based on the occurrence of mesopelagic fish larvae and oceanographic processes in Sagami Bay, with the exception of D. garmani and M. japonicus, most larvae are considered to originate from the Kuroshio region where their main spawning grounds are formed.  相似文献   

8.
夏季南黄海主要环境因子对微微型浮游生物分布影响   总被引：2，自引：1，他引：1  
利用流式细胞技术, 获取南黄海夏季微微型浮游生物丰度数据, 分析了其组成和分布规律, 并探讨了主要的影响因子。2011年夏季, 聚球藻、微微型真核藻、异养细菌在整个调查海区的平均丰度分别在1×104、1×103、1×106 cells/mL数量级上。在全调查海区, 聚球藻和微微型真核藻受温度和光照的限制明显, 主要集中分布在温跃层及其以上水层;而营养盐的限制较小, 它们的影响只有在沿岸流影响明显的西部海区才能较为明显的体现出来。结果表明在该海域浓度较高的营养盐能够促进微微型浮游生物的生长, 但不是其限制因素;异养细菌受环境因子限制较小, 即使在深海也保持着较高的丰度。  相似文献   

9.
北黄海冷水团对獐子岛微微型浮游生物分布的影响   总被引：3，自引：1，他引：2  
Picoplankton distribution around the Zhangzi Island(northern Yellow Sea)was investigated by monthly observation from July 2009 to June 2010.Three picoplankton populations were discriminated by flow cytometry,namely Synechococcus,picoeukaryotes and heterotrophic prokaryotes.In summer(from July to September),the edge of the northern Yellow Sea Cold Water Mass(NYSCWM)resulting from water column stratification was observed.In the NYSCWM,picoplankton(including Synechococcus,picoeukaryotes and heterotrophic prokaryotes)distributed synchronically with extremely high abundance in the thermocline(20 m)in July and August(especially in August),whereas in the bottom zone of the NYSCWM(below 30 m),picoplankton abundance was quite low.Synechococcus,picoeukaryotes and heterotrophic prokaryotes showed similar response to the NYSCWM,indicating they had similar regulating mechanism under the influence of NYSCWM.Whereas in the non-NYSCWM,Synechococcus,picoeukaryotes and heterotrophic prokaryotes exhibited different distribution patterns,suggesting they had different controlling mechanisms.Statistical analysis indicated that temperature,nutrients(NO3–and PO43–)and ciliate were important factors in regulating picoplankton distribution.The results in this study suggested that the physical event NYSCWM,had strong influence on picoplankton distribution around the Zhangzi Island in the northern Yellow Sea.  相似文献   

10.
We investigated the effect of interannual variation on the biodiversity and distribution of decapod larvae at Saint Paul's Rocks, an isolated small group of equatorial islands linked to the Atlantic Mid‐Ocean ridge. Zooplankton samples were collected between 2003 and 2005 from a range of different environments off the archipelago. Horizontal surface hauls were conducted in the inlet and at three increasing distances from the archipelago, both in the morning and at night, using a 200‐μm mesh net. Decapod larvae collected included 11 species and 37 individual taxa. Seven of them have not previously been recorded in the area. Samples taken at the shortest distance from the archipelago exhibited a significantly greater abundance than samples taken further away. No significant differences were detected between months in terms of decapod larvae abundance in the inlet. However, in the open ocean at night, the mean abundance was much higher in May and July. Decapod larvae abundance was much higher at night for both the open ocean and the inlet. Brachyuran and caridean larvae exhibited the greatest abundance and frequency in the inlet, mainly represented by the first‐stage larvae of: Grapsus grapsus, Plagusia depressa, Platypodiella spectabilis and Alpheidae. In contrast, Sergestidae holopelagic shrimps were the most abundant and the most frequent larvae in the surface waters of the open ocean. The composition, abundance and distribution of decapod larvae were very similar during the 2 years sampled. Species accumulation curves indicate that even greater diversity exists, demonstrating that long‐term research is important for acquiring accurate knowledge about the biodiversity of dynamic ecosystems such as those at Saint Paul's Rocks.  相似文献   

11.
Four enzymes and one protein were tested in starch and cellulose acetate gels as biochemical tags for the separation of flounder (Rhombosolea spp.) larvae and O‐groups. Lactate dehydrogenase phenotypes separated O‐groups and larvae (longer than about 5 mm) of R. plebeia from R. leporina and R. retiaria. General protein phenotypes separated similar specimens of R. leporina from R. plebeia and R. retiaria. Most Rhombosolea larvae and O‐groups caught in Wellington Harbour were R. plebeia.  相似文献   

12.
2009年2月(冬季)和8月(夏季)在南海北部海域(nSCS)采用流式细胞术对聚球藻、原绿球藻、超微型光合真核生物3类超微型光合浮游生物和异养浮游细菌的丰度和碳生物量的时空分布特征进行了研究,并分析了其与环境因子之间的关系。结果表明,夏季聚球藻和原绿球藻的平均丰度高于冬季,超微型光合真核生物和异养浮游细菌的丰度反之,为冬季高于夏季。聚球藻、超微型光合真核生物和异养浮游细菌在富营养的近岸陆架海域丰度较高,而原绿球藻高丰度则出现在陆坡开阔海域。在垂直分布上,聚球藻主要分布在跃层以上,跃层以下丰度迅速降低;原绿球藻高丰度主要出现在真光层底部;超微型光合真核生物在水层中的高值同样出现在真光层底部,且与Pico级份叶绿素a浓度分布一致;异养浮游细菌在水体中的分布与聚球藻类似。这些分布格局的差异,取决于环境条件的变化和4类超微型浮游生物生态生理适应性的差异。在超微型光合浮游生物群落中,各类群碳生物量的贡献因季节和海域类型的不同而发生变化:聚球藻在夏季近岸陆架区占超微型光合浮游生物总碳生物量的41%,原绿球藻在陆坡开阔海成为主要贡献者(50%),超微型光合真核生物碳生物量以冬季为高(在近岸陆架区占比68%)。冬、夏季异养浮游细菌碳生物量均高于超微型光合浮游生物碳生物量。  相似文献   

13.
Abstract

The improvement of sensors such as various high‐resolution seismic and navigational systems and side‐scan sonar, of offshore shallow‐water drilling techniques, and of laboratory analyses has allowed the marine geologist to make more accurate identifications and maps of the distribution of numerous types of marine sediment instabilities, as well as to determine the mechanisms responsible for their occurrence. A large number of data on the continental shelf and upper continental slope off the modern delta of the Mississippi river have been compiled; these data will be used to document the major types of slope instabilities. The continental shelf and slope off the modern Mississippi river delta display various types of sediment instability. High rates of sedimentation (up to 80 m per century), weak, high‐water‐content clays, and differential weighting of clay sediments characterize this region. The major types of sediment instabilities that have been documented include (a) Peripheral slumping, with dimensions of slumps ranging from 200 to 1000 m; slumping often occurring in multiple stairstep arrangement; and downslope movement as high as 700 m per year. (b) Shallow diapiric intrusions, ranging in size from a few hundred meters to 2 km in diameter; vertical displacement ranging from 200 to 500 m; rate of sediment movement several meters per year; and intrusions caused by differential sediment loading, (c) Radial graben (tensional faulting), with widths from 50 to 500 m and lengths of several kilometers; both vertical and downslope lateral movements occurring; and downslope movements of surface material as much as 5 m per year common. (d) Circular collapse depressions, with diameters of depressions ranging from 50 to 500 m; topography of depression interiors, hummocky; and depressions possibly caused by dewatering or degassing of sediments under the influence of cyclic wave loading. (e) Surface mudflows, thick (often more than 35 m) masses of surface sediment flowage; often bounded by abrupt seaward slope; mudflows often extending laterally for distances in excess of 100 km; movement sporadic and lobate and rates of movement as much as several hundred meters per year; often being associated with extremely hummocky topography and mud volcanoes; and with extrusion of sediments the possible mechanism. (f) Shelf‐edge arcuate slumps, with large arcuate slumps displacing several hundred meters of sediment; slippage planes are commonly concave. Finally, (g) Various deep‐seated faults, with faults extending from deep horizons up to modern sediment surface; commonly being associated with abrupt scarps on the seafloor; numerous contemporaneous faults; and local slumping associated with fault scarps.  相似文献   

14.
In the Wellington area (central New Zealand) Forsterygion varium (Forster, in Bloch & Schneider 1801) spawns from early June to late November, Gilloblennius decemdigitatus (Clarke, 1879) from early June to early October, and G. tripennis (Forster, in Bloch & Schneider 1801) from July to October. They deposit their eggs on firm substrates below the low tide level. Egg clusters are attended by an adult fish until hatching, which in the laboratory at 11.5–13.5°C, occurs after 18 days for F. varium and 20 days for G. decemdigitatus. Development to hatching for G. tripennis takes about 21 days at 13–15°c. The egg development of all three species is illustrated. The yolk‐sac larvae (prolarvae) of F. varium, G. decemdigitatus, and G. tripennis at hatching average 5.85, 5.03, and 5.72 mm standard length respectively. Yolk‐sac larvae of F. varium have a single row of 9–17 small, stellate melanophores along the ventral midline of the tail. The yolk‐sac larvae of G. tripennis have up to nine melanophores along the ventral midline of the tail, a medium‐sized melanophore above the optic lobes, and a further two above the medulla. The yolk‐sac larvae of G. decemdigitatus have three large mid‐dorsal melanophores interspersed with five smaller, paler pigment cells, and three large mid‐ventral melanophores interspersed with three of the smaller cells.  相似文献   

15.
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16.
This two-year study investigates the possible factors that determine spatial and temporal dynamics of picoplankton (heterotrophic bacteria, autotrophic picoplankton—Synechococcus spp., Prochlorococcus, and picoeukaryotes) and nanoflagellate abundance in the subtropical Ilan Bay, Taiwan, where the inner bay is affected by freshwater run-off from the Lanyang River and the eastern outer bay by the Kuroshio Current. In the inner bay, there was more rain and freshwater discharge in 2005 than in 2004 during the warm season (>24° C, June–September). The abundance of bacteria, Synechococcus spp., Prochlorococcus, and picoeukaryotes and the percentage contributions of pigmented nanoflagellate (PNF %) were two- to eight-fold greater during this period (July in 2005) than for other sampling periods. Relatively low abundance of heterotrophic nanoflagellates (HNF) in the presence of abundant picoplankton prey suggests that top-down control determined HNF abundance in the Ilan Bay, Taiwan.  相似文献   

17.
Tautog, Tautoga onitis, is an abundant species of fish in estuaries of the northeastern United States. Planktonic tautog larvae are abundant in summer in these estuaries, but there is little information on rates of growth of tautog larvae feeding on natural assemblages of food in the plankton. We examined abundance and growth of larval tautog and environmental factors during weekly sampling at three sites along a nearshore‐to‐offshore transect in Buzzards Bay, Massachusetts, USA during summer 1994. This is the first study of a robust sample size (336 larvae) to estimate growth rates of field‐caught planktonic tautog larvae feeding on natural diets, using the otolith daily‐growth‐increment method. The study was over the entire summer period when tautog larvae were in the plankton. The sampling sites contrasted in several environmental variables including temperature, dissolved oxygen (DO), and chlorophyll a concentration. There was a temporal progression in the abundance of tautog larvae over the summer, in relation to location and temperature. Tautog larvae were first present nearshore, with a pronounced peak in abundance occurring at the nearshore sites during the last 2 weeks in June. Larvae were absent at this time further offshore. From late June through August, larval abundance progressively decreased nearshore, but increased offshore although never approaching the abundance levels observed at the nearshore sites. The distribution and abundance of tautog larvae appeared to be related to a nearshore‐to‐offshore seasonal warming trend and a nearshore decrease in DO. Otoliths from 336 larvae ranging from 2.3 to 7.7 mm standard length had otolith increment counts ranging from 0 to 19 increments. Growth of larval tautog was estimated at 0.23 mm·day?1, and length of larvae prior to first increment formation was estimated at 2.8 mm indicating that first increment formation occurs 3–4 days after hatching at 2.2 mm. Despite spatial and temporal differences in environmental factors, there were no significant differences in growth rates at any of three given sites over time, or between sites. Because larval presence only occurred at a narrow range of temperature (17–23.5 °C) and DO (6.5–9.3 mg·l?1), in situ differences in growth did not appear to be because of differences in larval distribution and abundance patterns relative to these parameters.  相似文献   

18.
In a laboratory study of the ingestion and assimilation efficiency of larvae of Aeshna brevistyla Rambur and Hemicordulia australiae Rambur, ingestion was determined using Cerenkov radiation techniques and assimilation efficiency by a double‐labelled isotope technique. Of each prey item (Daphnia carinata), 30% was not ingested but lost as body fluids and as material within the alimentary canal of the prey. Assimilation efficiency was greater than 70% for both dragonfly species, which appears to be typical for most other invertebrate predators. The efficiency with which 12th‐15th‐instar Aeshna assimilated 14C did not increase with feeding rate, but Hemicordulia increased its efficiency through instars 12–14. When dragonfly larvae were pre‐fed before experimentation, assimilation efficiency decreased in both species.  相似文献   

19.
The annual distribution and dispersal of early‐stage phyllosoma of the Japanese spiny lobster Panulirus japonicus were examined in the East China Sea and the Sea of Japan off western Japan. Early‐stage larvae were sampled mainly in summer and relatively near the coast off western Kyusyu Island. Few larvae were found in the other three seasons in the East China Sea and the Sea of Japan. This finding suggests that P. japonicus larvae are retained in coastal areas for a few months after hatching until stage V and are transported offshore until autumn, before they grow to stage VI. Examination of archival drifter data off western Kyusyu Island during the spawning season of P. japonicus supported the relatively rapid dispersal of the larvae from the East China Sea near Japan to the Pacific Ocean or the Sea of Japan. Larval transport from the East China Sea to the Pacific Ocean, which is considered to be a main distribution area of middle‐ and late‐stage larvae, would occur in the south at approximately 32–33°N in the East China Sea near western Kyusyu Island.  相似文献   

20.
Detailed comparisons of the larvae of four species of New Zealand oyster (Saccostrea glomer‐ata, Crassostrea gigas, Ostrea lutaria, and a new species of Ostrea) and one Chilean oyster (Ostrea chilensis) showed that larvae of species other than O. lutaria and O. chilensis share certain features. One conspicuous feature is a distinct tract, termed here the posterior dorsal sulcus, which runs from the posterior margin of prodissoconch I to the valve margin of prodissoconch II; other characteristic features are an umbonate, inequivalve shell and a provinculum bearing distinct teeth. The larvae of O. lutaria and O. chilensis, in contrast, lack the posterior dorsal sulcus, are nonumbonate, and have nearly equal valves with an edentulous provinculum. These distinctive features, together with other adult features, suggest that the two species are more appropriately included in a separate genus. The name Tiostrea is proposed for the new genus. Certain supraspecific groupings within the Ostreinae need to be re‐examined in the light of breeding experiments.  相似文献   

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