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1.
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   

2.
The mesozooplankton in both epipelagic and mesopelagic zones is essentially important for the study of ecosystem and biological carbon pump. Previous studies showed that the diel vertical migration(DVM) pattern of mesozooplankton varied among ecosystems. However, that pattern was largely unknown in the Western Pacific Warm Pool(WPWP). The vertical distribution, DVM and community structure of mesozooplankton from the surface to 1 000 m were compared at Stas JL7K(WPWP) and MA(North Pacific Subtropical Gyre, NPSG). Two sites showed similarly low biomass in both epipelagic and mesopelagic zones, which were in accordance with oligotrophic conditions of these two ecosystems. Stronger DVM(night/day ratio) was found at JL7K(1.31) than that at MA(1.09) on surface 0–100 m, and an obvious night increase of mesopelagic biomass was observed at JL7K, which was probably due to migrators from bathypelagic zone. Active carbon flux by DVM of zooplankton was estimated to be 0.23 mmol/(m2·d) at JL7K and 0.16 mmol/(m~2·d) at MA. The community structure analysis showed that calanoid copepods, cnidarians and appendicularians were the main contributors to DVM of mesozooplankton at both sites. We also compared the present result with previous studies of the two ecosystems,and suggested that the DVM of mesozooplankton was more homogeneous within the WPWP and more variable within the NPSG, though both ecosystems showed typically extremely oligotrophic conditions. The different diel vertical migration strength of mesozooplankton between NPSG and WPWP implied different efficiency of carbon pump in these two ecosystems.  相似文献   

3.
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4.
The abundance and vertical distribution pattern of a mysidMeterythrops microphthalma were investigated in the Japan Sea. Results from vertical hauls from 602–982 m depth to the surface around Yamato Rise in April 1987 indicated that the dominance (by biomass) ofM. microphthalma was third to fifth of major zooplankton taxa. Vertical distribution investigated at a single station in Toyama Bay in June, September and December 1986 showed that the most part of population of this mysid inhabited consistently below 250 m depth. No marked diurnal vertical migration was evident. Data on body composition and oxygen consumption rate ofM. microphthalma are presented. Water content of the body was 75.6–83.8% of wet weight, and ash was 11.4–20.4% of dry weight. Carbon, hydrogen and nitrogen were 37.9–47.5%, 6.2–7.4% and 9.4–10.1%, respectively, of dry weight. Oxygen consumption rates were 2.2–11.0µl O2 individual–1 hr–1 at 0.5°C, and were directly proportional to body mass. From the comparison with the published data on epipelagic and bathypelagic mysids it is revealed that both body nitrogen composition and oxygen consumption rate expressed as adjusted metabolic rate [AMR02,µl O2 (mg body N)–0.85 hr–1] ofM. microphthalma are intermediate between high epipelagic and low bathypelagic levels, indicating typical mesopelagic features.  相似文献   

5.
Diel changes in vertical distribution and gut pigment contents of Acartia clausi andPseudodiaptomus hessei were studied during several 24-h time series performed between 1993 and 1997 in four sites of the Ebrié Lagoon (Côte d'Ivoire). The sites differed by their morphology and their hydrological structure and by the vertical distribution of chlorophyll biomass. Both species showed classical diel vertical migrations (DVM). Copepodites and adult stages of P. hessei were almost benthic during the day and evenly distributed through the water column at night. The amplitude of DVM of A. clausi increased from copepodites I–III to adults. Copepodites and adults of A. clausi increased significantly their gut fluorescence at night, whereas those of P. hessei showed no clear diel feeding rhythm (DFR). These results suggest that A. clausi feed mostly at night on phytoplanktonic particles and P. hessei feed mostly on benthic algal particles during the day and on sestonic particles at night. No relationship was observed between DFR and DVM because both patterns occurred when food was either vertically homogeneous or vertically stratified. The daily average gut fluorescence of A. clausi increased with ambient chlorophyll concentration until around 12–15 μg l−1, whereas no relationship was found for P. hessei. The implication of these patterns on the adaptation capacities and the behaviour of the two species are discussed. The DVM of P. hessei should explain its rarity in the estuarine area. The comparison of our results with previous ones suggests an evolution of A. clausi DFR between 1981–1982 and 1996–1997, in relation to an intensification of eutrophication.  相似文献   

6.
Larval fish community structure was studied in the northeastern Aegean Sea (NEA) over an area influenced by the advection of Black Sea water (BSW). Sampling was carried out in early summer during a period of 4 years (2003–2006). Taxonomic composition and abundance presented high variability in space that remained relatively constant among years. Tow depth and indicators of trophic conditions in the upper water column (i.e., zooplankton displacement volume, fluorescence) explained significantly the structure of larval assemblages during all surveys. The northern continental shelf (Thracian and Strymonikos shelf), where a large amount of enriched, low salinity BSW is retained, was dominated by larvae of epipelagic species, mainly anchovy (Engraulis encrasicolus). Interannual changes in horizontal extension of the BSW seemed to match closely observed changes in the distribution of anchovy larvae. Mesopelagic fish larvae were particularly abundant beyond the continental shelf (over the North Aegean Trough) where a strong frontal structure is created between the low salinity waters of BSW origin and the high salinity waters of the Aegean Sea. Larvae of certain mesopelagic species (e.g., Ceratoscopelus maderensis) may occasionally be transported inshore when the prevailing current meanders towards the coast or feeds anticyclonic gyres over the continental shelf.  相似文献   

7.
The biomass, abundance, and vertical distribution of micronekton, including enidarians, mysids, euphausiids, decapods, thaliaceans, and fishes, were studied on the basis of samples collected with an 8-m2 opening-closing rectangular midwater trawl (RMT-8, mesh size: 4.5 mm) at three stations in the subarctic Pacific (the western subarctic gyre, the central Subarctic, and the Gulf of Alaska) and one station in the oceanic Bering Sea. The total biomass in the 0–1000 m water column ranged from 2.9 to 5.1 gDW m–2. Except for primary consumers that showed highly variable biomass (thaliaceans and euphausiids), biomass was highest in the oceanic Bering Sea followed by the central (boundary between eastern and western gyres), western gyre, and eastern Gulf of Alaska. The biomass compositions by higher taxa were basically similar between regions: fishes were most dominant, followed by enidarians at all stations, except for the marked predominance of thaliaceans in the Gulf of Alaska. High biomasses of gelatinous animals (31% of overall dry weight), occasionally comparable to those of fishes and crustaceans, suggest their potential importance in the subarctic Pacific. Characteristics in vertical patterns of micronekton biomass common in all stations were: (1) a mesopelagic peak around 500–600 m both day and night, (2) a layer of low biomass in the cold intermediate water and/or in the upper mesopelagic zone, (3) a nighttime shift of biomass to upper layers, and (4) an highly variable biomass of epipelagic/interzonal migrants (euphausiids and thaliaceans).  相似文献   

8.
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   

9.
Correction factors based on the catch ratios of egg and larval densities in the southern waters of Korea were estimated for anchovyEngraulis japonica. This was undertaken in order to adjust ichthyoplankton data from different sampling methods, gear types and time. Samples were collected during ichthyoplankton surveys in Korean waters from 1983 to 1994. The ratios for egg densities obtained in vertical tows with a NORPAC net (ring Φ, 45 cm) compared to those obtained in oblique tows with a KOB net (ring Φ, 80 cm) were 0.86 (CV = 0.65), 1.22 (CV = 0.36), and 0.93 (CV = 0.42) for early, middle, and later developmental stages, respectively. The ratios for larval densities for vertical and oblique tows varied depending on size. For yolk-sac and small larvae (< 4 mm), the ratios were 3.08 (CV = 0.45) and 1.98 (CV = 1.34), while those of 4-6 mm, 6-8 mm, and 8-10 mm larvae were 0.44 (CV = 1.31), 0.45 (CV = 1.70), and 0.56 (CV = 2.50), respectively. Ratios of day/night densities for larvae of 4-10 mm lengths were lower (0.01-0.06) in offshore catches than values obtained in coastal areas (0.44-0.46) and similar values (0.16-0.04) for vertical and oblique tows. Our results indicated that vertical towing is more efficient for sampling early life stages (from eggs to larvae less than 4 mm long), while oblique towing is more efficient for larvae longer than 4 mm due to depth preferences for each developmental stage (e.g., changes in egg buoyancy and vertical migration of larvae).  相似文献   

10.
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11.
Mesoscale eddies are important suppliers of nutrients to the surface waters of oligotrophic gyres, but little is known about the biological response, particularly that of higher trophic levels, to these physical perturbations. During the summers of 2004 and 2005, we followed the development of a cyclonic eddy and an anti-cyclonic mode-water eddy in the Sargasso Sea. Zooplankton (>150 μm) were collected across both eddies in 9 discrete depth intervals between 0 and 700 m. Comparison of the abundance of major taxa of mesozooplankton in the upper 150 m at eddy center and outside the eddies (day and night) indicated that the cyclone and mode-water eddy supported similar mesozooplankton communities, with several taxa significantly higher in abundance inside than outside the eddies, when compared with the Bermuda Atlantic Time-series Study site as representative of mean conditions. In both eddies copepod peak abundance occurred in the 50-100 m depth interval, coincident with the chlorophyll a maximum, suggesting elevated food concentration in the eddies may have influenced zooplankton vertical distribution. The two eddies differed in the strength of diel vertical migration of zooplankton, as indicated by the ratio of night:day abundance in the epipelagic zone, which was higher at the center of the mode-water eddy for most taxa. Over the sampling interval of 1-2 months, abundance of the three most common taxa (copepods, chaetognaths, and ostracods) decreased in the cyclone and increased in the mode-water eddy. This further supports previous findings that over the sampling period the cyclone was in a decay phase, while the mode-water eddy was sustaining nutrient fluxes and high phytoplankton concentrations. A more detailed analysis of community structure in the mode-water eddy indicated the 0-700 m integrated abundance of doliolids was significantly higher inside the mode-water eddy than outside. The presence of a mesopelagic (200-700 m) layer of lepadid barnacle cyprids in this eddy highlights the potential of eddies to transport and disperse biota. We conclude that when compared with average ambient conditions (as measured at BATS), mesoscale eddies can influence zooplankton behavior and alter zooplankton community structure which can affect food-web interactions and biogeochemical cycling in the open ocean.  相似文献   

12.
Seasonal changes in mesozooplankton biomass and their community structures were observed at time-series stations K2 (subarctic) and S1 (subtropical) in the western North Pacific Ocean. At K2, the maximum biomass was observed during the spring when primary productivity was still low. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 1.39 (day) and 2.49 (night) g C m?2 and 4.00 (day) and 3.63 (night) g C m?2, respectively. Mesozooplankton vertical distribution was bimodal and mesopelagic peak was observed in a 200- to 300-m layer; it mainly comprised dormant copepods. Copepods predominated in most sampling layers, but euphausiids were dominant at the surface during the night. At S1, the maximum biomass was observed during the spring and the peak timing of biomass followed those of chlorophyll a and primary productivity. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 0.10 (day) and 0.21 (night) g C m?2 and 0.47 (day) and 0.26 (night) g C m?2, respectively. Copepods were dominant in most sampling layers, but their mean proportion was lower than that in K2. Mesozooplankton community characteristics at both sites were compared with those at other time-series stations in the North Pacific and with each other. The annual mean primary productivities and sinking POC fluxes were equivalent at both sites; however, mesozooplankton biomasses were higher at K2 than at S1. The difference of biomasses was probably caused by differences of individual carbon losses, population turnover rates, and trophic structures of communities between the two sites.  相似文献   

13.
Using the hydroacoustic method with a 200 kHz scientific echo sounding system,the diel vertical migration(DVM) of the sound-scattering layer(SSL) in the Yellow Sea Bottom Cold Water(YSBCW) of the southeastern Yellow Sea was studied in April(spring) and August(summer) of 2010 and 2011.For each survey,13–27 hours of acoustic data were continuously collected at a stationary station.The acoustic volume scattering strength(Sv) data were analyzed with temperature profile data.In the spring of both 2010 and 2011,the SSL clearly showed the vertical migration throughout the entire water column,moving from the surface layer at night to near the bottom during the day.Conductivity,temperature,and depth data indicated that the entire water column was well mixed with low temperature of about 8 C.However,the SSL showed different patterns in the summers of 2010 and 2011.In the summer of 2010(28 C at the surface),the SSL migrated to near the bottom during the day,but there were two SSLs above and below the thermocline at depth of 10–30 m at night.In the summer of 2011(20 C at the surface),the SSL extended throughout the entire water column at night,possibly owing to an abrupt change in sea weather conditions caused by the passage of a Typhoon Muifa over the study area.It was concluded that the DVM patterns in summer in the YSBCW area may be greatly influenced by a strengthened or weakened thermocline.  相似文献   

14.
The feeding habits of the gonostomatid fish,Vinciguerria nimbaria (Jordan andWilliams), from off southern Japan were studied in relation to its food organisms, process of digestion, and diel vertical migration. Food organisms were composed mainly of small- to moderate-sized copepods which live almost entirely in the 0–200 m epipelagic zone.V. nimbaria appears to feed twice a day; after having migrated to the epipelagic zone in the evening, all individuals fed intensively from 6 to 8 p.m. They then spent the remainder of the night in digestion. Many, but not all, of the individuals foraged again in the morning.  相似文献   

15.
The food habits of five species of eels and one species of spiny eel collected from the upper continental slope off the Cape west coast and Agulhas Bank, South Africa, are described. All a re embers of a defined demersal micro- or mesocarnivore feeding guild except Simenchelys parasitica, a scavenger. Two congrids, Bassanago albescens and Gnathophis capensis and the spiny eel Notacanthus sexspinis usually employ the demersal grazer feeding method and infrequently switch to picking nekton in the water column. Two synaphobranchids, Diastobranchus capensis and Synaphobranchus kaupii, are chiefly demersal mesocarnivores that stalk prey, but also pick nekton and scavenge. A significant amount of the prey ofthe three large eels, B. albescens and the two synaphobranchids, consisted mainly of mesopelagic stomiiform, myctophid and juvenile gadiform fish, penaeid and caridean shrimps and various squid taken at the bathyal/deep-pelagic interface, as was found previously with some grnadiers (Macrouridae. Five categories of fleshy remains are documented for the scavenging Simenchelys parasitica for the first time.  相似文献   

16.
Seasonal change in the downward carbon transport due to respiration and mortality through diel vertical migration (DVM) of the calanoid copepods Metridia pacifica and Metridia okhotensis was estimated in the Oyashio region, western subarctic Pacific during six cruises from June 2001 to June 2002. M. pacifica (C4, C5 and adult females) was an active migratory species throughout the year though its DVM amplitude varied among seasons and stages. The mean distribution depths of adult females during the daytime were positively related with the illumination level in the water column, being shallowest in April and deepest in January. M. okhotensis generally showed less-extensive migrations than M. pacifica. Therefore, together with their lower abundance, this species is considered to be a less-important mechanism of downward transport of carbon except for April when their DVM was more active and descended deeper than M. pacifica, which remained in the upper 150 m even during the daytime. The mean migrating biomass of the two Metridia species was 558 mg C m−2 d−1 and was high during summer to winter (263–1676 mg C m−2 d−1) and low during spring (59–63 mg C m−2 d−1). Total downward flux through DVM fluctuated between 1.0 and 20.0 mg C m−2 d−1 with an annual mean of 8.0 mg C m−2 d−1. Contribution of the respiratory flux was greater than the mortality flux and accounted for 64–98% of total migratory flux throughout the year except for January when contribution of both fluxes was equal. Overall the annual carbon transport by DVM of Metridia spp. was estimated as 3.0 g C m−2 year−1, corresponding to 15% of the annual total POC flux at 150 m at the study site, suggesting that DVM is a significant process for carbon export in the subarctic region as well as that in tropical and subtropical oceanic regions. Since DVM in M. pacifica is more active during the non-bloom season when the gravitational flux of particulate matter is low, this species plays an important role in driving the biological pump in the subarctic Pacific during summer to winter.  相似文献   

17.
The bathymetric distribution, abundance and diel vertical migrations (DVM) of zooplankton were investigated along the axis of the Cap-Ferret Canyon (Bay of Biscay, French Atlantic coast) by a consecutive series of synchronous net hauls that sampled the whole water column (0–2000 m in depth) during a diel cycle. The distribution of appendicularians (maximum 189 individuals m−3), cladocerans (maximum 287 individuals m−3), copepods (copepods<4 mm, maximum 773 individuals m−3, copepods>4 mm, maximum 13 individuals m−3), ostracods (maximum 8 individuals m−3), siphonophores (maximum >2 individuals m−3) and peracarids (maximum >600 individuals 1000 m−3) were analysed and represented by isoline diagrams. The biomass of total zooplankton (maximum 18419 μg C m−3, 3780 μg N m−3) and large copepods (>4 mm maximum 2256 μg C m−3, 425 μg N m−3) also were determined. Vertical migration was absent or affected only the epipelagic zone for appendicularians, cladocerans, small copepods and siphonophores. Average amplitude of vertical migration was about 400–500 m for ostracods, some hyperiids and mysids, and large copepods, which were often present in the epipelagic, mesopelagic, and bathypelagic zones. Large copepods can constitute more than 80% of the biomass corresponding to total zooplankton. They may play an important role in the active vertical transfer of carbon and nitrogen.  相似文献   

18.
李琦  陈朝晖 《海洋与湖沼》2022,53(2):305-319
利用深海潜标所搭载的声学多普勒流速剖面仪(acoustic doppler current profiler,ADCP)得到的后向散射强度Sv,研究了黑潮-亲潮混合区浮游动物的垂向分布、其昼夜垂直迁移(diel vertical migration;DVM)的基本特征、多时间尺度变化及对反气旋式中尺度暖涡的响应.结果表...  相似文献   

19.
Studies in epipelagic waters report higher heterotrophic microbial biomass in the productive high latitudes than in the oligotrophic low latitudes; however, biogeographical data are scarce in the deep ocean. To examine the hypothesis that the observed latitudinal differences in heterotrophic microbial biomass in the epipelagic zone also occur at depth, abundance and biomass of heterotrophic prokaryotes, nanoflagellates (HNF), and ciliates were determined at depths of 5–5000 m in the central Pacific between August and September of 2005. Heterotrophic microbial biomass increased from the tropical to the subarctic region over the full water column, with latitudinal differences in prokaryotic biomass increasing from 2.3-fold in the epipelagic zone to 4.4-fold in the bathypelagic zone. However, the latitudinal difference in HNF and ciliate biomass decreased with depth. In the mesopelagic zone, the vertical attenuation rate of prokaryotic abundance, which was calculated as the linear regression slope of log-log plot of abundance versus depth, ranged from –0.55 to –1.26 and was more pronounced (steeper slope) in the lower latitudes. In contrast, the vertical attenuation rate of HNF in the mesopelagic zone (–1.06 to –1.27) did not differ with latitude. In the subarctic, the attenuation rate of HNF was 1.7 times steeper than for prokaryotes. These results suggest the accumulation of prokaryotes in the deep subarctic Pacific, possibly due to low grazing pressure. Although the vertical attenuation rate of ciliates was steepest in the bathypelagic zone, HNF abundance did not further decrease at depths below 1000 m, except for at 2000 m where HNF was lowest across the study area. Ciliate abundance ranged 0.3–0.8 cells l–1 at 4000 m, and were below the detection limit (<0.1 cells l –1) at 5000 m. To our knowledge, this study presents the first data for ciliates below 2000 m.  相似文献   

20.
Vertical and seasonal characteristics of biogenic silica (BSi) dissolution in seawater were investigated by multiple dissolution experiments using seawater collected from surface and mesopelagic layers in Suruga Bay during the period 2002–2004. The dissolution rate coefficients calculated based on temporal changes of BSi concentration varied with the season of sample collection. They ranged from 0.023–0.057 day− 1 for surface samples and 0.0018–0.0025 day− 1 for mesopelagic samples for temperatures approaching in situ conditions. Experiments at various temperatures confirmed that BSi dissolution depends on temperature in natural seawater. Dissolution rate coefficient (day− 1) of BSi correlated significantly with temperature (°C), and Q10 was 2.6. Addition of bioavailable organic matter to low-bioactivity seawater enhanced the protease activity and abundance of bacteria, and increased BSi dissolution rate by a factor of 1.4–2.0. There is clear evidence that BSi dissolution is accelerated by bacterial activity and potentially limited by bioavailable organic matter in natural seawater. Dissolution rates and total decreases of BSi concentration were lower during experiments using mesopelagic samples than in those using surface samples. This suggests that dissolution of BSi varies with depth and that BSi in the mesopelagic water is more resistant to the dissolution than that in the surface water. This lower dissolution rate was caused by lower temperature and lower bacterial activity due to less bioavailable organic matter in mesopelagic water. Our results provide a mechanistic understanding of variations in silica cycling within the seasonally and vertically differing marine environment.  相似文献   

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