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1.
Growth and ingestion rates of larval fish populations in the coastal waters of Israel 总被引:1,自引:0,他引:1
Clupeoid larvae were collected on eight cruises between February1984 and February 1985 in the coastal waters of Israel. Fromanalysis of daily growth increments of otoliths, growth ratesof the abundant clupeoids, Engraulis encrasicolus, Sardina pilchardusand Sardinella aurita were found to be 0.55 mm day1,0.67 mm day1 and 0.60 mm day1, respectively, duringthe first month after hatching. Ingestion rates were estimatedusing an equation from the literature relating ingestion andgrowth of larval fish. Ingestion calculated for populationsof fish larvae in pelagic waters ranged from 0 to >23 mgC m2 day1 with maximum rates observed in April.Annual ingestion by larval fish at a pelagic station near Haifawas calculated to be 2.2 g C m2 year1, 1020%of annual primary production estimated from 14C uptake. 相似文献
2.
3.
Vertical distribution of pelagic chaetognaths and feeding of Sagitta enflata in the Central Equatorial Pacific 总被引:1,自引:0,他引:1
The vertical distribution and feeding of pelagic chaetognathsat 5°S, 160°W in the Central Equatorial Pacific wereinvestigated using a series of 0500 m vertical haulswith a VMPS net over a 24 h period between 6 and 7 October 1990.The total number of individuals per haul was between 370 and688. Fourteen species in four genera were found at this station.The most abundant species was Sagitta enflata which comprised32.461.1% of the individuals collected from the 0500m layer. Mesopelagic species made up 9.315.1% of thetotal number of individuals. Sagitta enflata and Pterosagittadraco were found in the upper part of the thermocline both byday and at night. The fraction of the population containingfood items (FCF) of S.enflata in the 050 m layer variedbetween 4.8 and 12.5% (mean 10.8%) and feeding activity washighest between sunrise and noon. The percentages of Copepoda,Foraminifera, crustacean larvae, Chaetognatha, Pteropoda, Ostracoda,fish and unidentified material in the gut of S.enflata were51.9,6.7,3.8,2.9,1.9,1.9 and 30.9%, respectively. Sagitta enflataconsumed food organisms which were mainly between 0.5 and 1.0mm in length. The daily feeding rate of S.enflata was 1.81 preyper individual, which was equivalent to 8.06 mg C m2day1. This corresponded to 相似文献
4.
Measuring the Canopy Net Photosynthesis of Glasshouse Crops 总被引:3,自引:0,他引:3
HAND D. W.; CLARK G.; HANNAH M.A; THORNLEY J. H. M.; WILSON J. WARREN 《Journal of experimental botany》1992,43(3):375-381
A null balance method is described for measuring net photosynthesisof mature canopies of cucumber and other protected crops overperiods of 10 min in a single-span glasshouse (c. 9m x 18m inarea). Accuracy of control of the CO2 concentration in the greenhouseatmosphere is within ±10 vpm of the normal ambient level(c. 350 vpm). The amounts of CO2 used in canopy net photosynthesisare measured with linear mass flowmeters accurate to within±0.80g. The total errors incurred in measuring canopynet photosynthesis at an ambient CO2 level are estimated tobe of the order of ± 1·2% in bright light (350W m2, PAR)and ±3·6% in dull light (100W m2, PAR). Measurements of the rates of net photosynthesis of a maturecanopy of a cucumber crop were made at near-ambient CO2 concentrationsover a range (0350 W m2) of natural light fluxdensities. A model of light absorption and photosynthesis applicableto row crops was used to obtain a net photosynthesis versuslight response curve for the cucumber crop. At a light fluxdensity of 350 W m2 the fitted value of canopy net photosynthesiswas 2.65 mg CO2 m2s1 (equivalent to over 95 kgCO2 ha1h1). The results are discussed in relationto the need for CO2 supplements to avoid depletion in both ventilatedand unventilated glasshouses during late spring and summer. Key words: Glasshouse crops, cucumber, measurement, canopy photosynthesis, light, CO2 相似文献
5.
Pyrosoma atlanticum (Tunicata, Thaliacea): grazing impact on phytoplankton standing stock and role in organic carbon flux 总被引:2,自引:0,他引:2
Drits Alexander V.; Arashkevich Elena G.; Semenova Tatjana N. 《Journal of plankton research》1992,14(6):799-809
Pyrosomas are the large group of pelagic tunicates whose trophicrole in pelagic communities has not yet been sufficiently studied.We ran across a local area of high concentration of the mostwidespread and commonest species of pyrosomas, Pyrosoma atlanticum,450 miles off the Congo river mouth. The following was estimated:gut pigment content, defecation rate, organic carbon and pigmentcontent of fecal pellets, and sinking rate. Based on these dataand the measured number of pyrosomas colonies the grazing impacton phytoplankton and the fecal pellet flux were calculated.During the night swarms of 5065 mm P.atlanticum removed53% of phytoplankton standing stock in the 010 m layer;sparsely distributed pyrosomas consumed only 4%. The grazingimpact in the 050 m layer was only 12.5 and <1% respectively.The fecal pellet flux resulting from nocturnal feeding of P.atlanticumwhile swarming made up 1.41.6 x 106 pellets m210 h1 or 3051035 mg C m2 10 h1 and1.4 x 105 pellets m2 10 h1 or 87.4 mg C m210 h1 while non-swarming. Incubation experiments showedthe rapid degradation of fecal pellets at 23°C: the lossof pigment and carbon content was {small tilde}6070%after 45 h. We believe that given the sinking rate of 70 m day1the main part of fecal material does not leave the upper watercolumn and is retained in the trophic web of the epipelagiclayer. 相似文献
6.
Influence of the pycnocline on the vertical migration of chaetognaths in the northern Benguela 总被引:1,自引:0,他引:1
The vertical distribution and migration patterns of chaetognathswere studied at a sampling station off northern Namibia (18°00'S,10°30'E during a 48 h sampling cycle. The sampling areawas characterized by mixing of the Angola current with the northernmostwaters of the Benguela current in the surface region. The continuousflow of the Angola current during the study period gave riseto a thermocline and a halocline at a depth of 40 m. The samplingintervals used to study the behaviour of epipelagic chaetognathspecies under these conditions were 200100, 10060,6040, 4020 and 200 m. A total of 10 differentchaetognath species were captured. Sagitia enflata was the predominantspecies, with a mean density of 4400 individuals per 1000 m3in daytime hauls, accounting for 54.1% of all individuals collectedin the samples. Sagitia minima was the next most predominantspecies, with a mean density of 2400 individuals per 1000 m3in daytime hauls, accounting for 16.6% of the chaetognath communitysampled. Three maturity stages were considered in analysingpossible ontogenetic migrations. Nearly all the species wereaggregated above the pycnocline, and stages I and II of manyspecies carried out short migrations in the surface layers.The limited migration pattern, together with a staggered distributionof the different species and stages above the pycnocline, hasbeen interpreted as a space partitioning mechanism to preventintra- and interspecific competition. 相似文献
7.
Ion Transport in Suaeda maritima: Its Relation to Growth and Implications for the Pathway of Radial Transport of Ions across the Root 总被引:5,自引:0,他引:5
The ion relations of the halophytc Suaeda maritima are described.When plants grew in 340 mol m3 sodium chloride (176MPa) leaf solute potentials decreased, and were sustained around25 MPa Inorganic ion concentration (mostly of sodiumchloride) accounted for this. Comparable shoot ion concentrationsof potassium, nitrate and sulphate occurred when plants grewon different salinity types characterized by these ions. Netsodium transport and shoot sodium concentration increased dramaticallywith increases in external sodium chloride concentration upto 85 mol m3; thereafter, further increases in externalsodium chloride concentration had relatively little effect uponeither shoot sodium concentration or upon net transport of sodiumto the shoot. The net transport of sodium plus potassium onlydoubled when the external concentration of sodium plus potassiumincreased from 24 to 687 mol m3 Shoot ion concentrationswere remarkably constant with time, external concentration andsalinity type. The membrane flux rates and symplasmic ion concentrations neededto sustain the observed net transport of sodium (of some 10mmol g1 dry wt. of roots d1) are calculated fromanatomical and stereological data for the root system of thisspecies. The minimum net sodium chloride flux to load the symplasmwould be 260 nmol m2s1 if the whole cortical andepidermal plasmalemmal surface area were used uniformly, butthe flux rate required would be 3000 nmol m2s1if uptake took place only at the root surface. A flux rate ofat least 1000 nmol m2s1 is needed between symplasmand xylem. The symplasmic concentration of NaCl would be atleast 80 mol m3. It is argued (1), that both symplasmicand xylem loading are likely to be passive processes mediatedby ion channels rather than active carriers, (2), that net iontransport at 340 mol m3 sodium chloride is close to themaximum which is physiologically sustainable and (3), that growthof this halophyte is limited by NaCl supply from the root. Key words: Suaeda maritima, halophyte, salinity, roots, radial ion transport 相似文献
8.
Summer nutrient dynamics in the Middle Atlantic Bight: primary production and utilization of phytoplankton carbon 总被引:2,自引:0,他引:2
Falkowski P.G.; Vidal J.; Hopkins T.S.; Rowe G.T.; Whitledge T.E.; Harrison W.G. 《Journal of plankton research》1983,5(4):515-537
In late summer, production and utilization of carbon in thestratified water of the Middle Atlantic Bight appears to approachsteady-state conditions. In the euphotic zone there is a paniculateorganic carbon (POC) pool of {small tilde}6000 mg Cm2.Primary production adds {small tilde}350 mg C m2 d1,while zooplankton ingestion removes {small tilde}450 mg C m2d1, of which {small tilde}135 mg C m2 d1are returned to the POC pool as feces. Sinking of POC averages{small tilde}240 mg C m 2 d1. Thus, there is anet loss from the euphotic zone of {small tilde}200 mg C m2d1, which represents a removal rate from the POC poolof {small tilde}3%d1. However, sinking losses of phytoplanktoncarbon from the POC pool were small ({small tilde}12 mg C m2d1), which suggests that most of the primary productionenters the pelagic food chain. This is in sharp contrast tothe conditions in early spring, when the POC pool increasessubstantially, and the main loss is sinking rather than heterotrophicconsumption.
*This research was supported by the U.S. Department of Energyunder Contract No. DE-AC02-76CH000I6. 相似文献
9.
Zoea I larvae of the brown shrimp Crangon crangon (Decapoda)were exposed to varying levels of UV radiation in a sunshinesimulator. Short-term exposures (08 h)were used to determine the highest UV dose with no significanteffect (NOEC; defined by limit of detection) and the lethaldose of 10 and 50% mortality (LD10 and LD50). Crangon crangonshowed a relatively high sensitivity to UVB radiation (NOEC= 10 kJ m2, LD10 = 15 kJ m2, LD50 = 24 kJ m2)compared to other crust-acean species. LD values (19971998)showed no adaptation to seasonal light regimes. Long-termexposures (010 days) were carried out to assessthe range where the law of reciprocity is valid.The larvae were exposed to UV levels of 0.2, 0.4 and 0.7 J m2for appropriate time intervals, always cumulating in a sublethaldose of 5 kJ m2 day1. Results reflect a possiblethreshold (0.20.4 J m2 UVB) in the effect of thedifferent UVB doses used; thus, a proportional relationshipof intensity and exposure time can only be shown at UVB levelsabove this threshold intensity. 相似文献
10.
Daytime surface swarms of Meganyctiphanes norvegica in the Bayof Fundy were examined using a variety of techniques to providemeasurements of their shapes, sizes and densities. Shapes andsizes were determined from two aerial photographs: swarms werespherical, ribbon-like or amorphous. were up to 28 6 m longand ranged in area from 0.4111 7 m2. Densities were measuredby a bag-sampling device which gave figures of up to 41 000animals m3 by photographic methods which gave figuresof up to 770 000 animals m3 and by a plankton net whichgave maximum values of six animals m3 Using the photographicmethod the maximum euphausud biomass was estimated to be 154kg m3 within swarms and the largest swarm measured wasestimated to contain up to 2 1 tonnes of M. norvegica. Meanpatch biomass estimates for the two aerial photographs rangedfrom 77.8778 g m3 and 15 6155.6 g m3which are similar to figures obtained by other authors usingintegrating sampling techniques at depth. 相似文献
11.
PRANGE ROBERT K.; ORMROD DOUGLAS P.; PROCTOR JOHN T. A. 《Journal of experimental botany》1983,34(9):1108-1116
Experiments were conducted in a gas exchange system to examinethe effect of a water stress, induced by 200 kPa polyethyleneglycol (PEG), on carbon dioxide and water vapour flux, fronddiffusive resistance, intercellular carbon dioxide concentration,carbon dioxide residual resistance and frond water potentialin the ostrich fern (Matteuccia struthiopteris (L.) Todaro).Measurements were taken 1 d after the application of PEG. Themeasurements were made on young fronds (8 d old) and maturefronds (2024 d old) at PPFD's (Photosynthetic PhotonFlux Density) from 01400 µmol m22 s1.Water stress decreased the net photosynthesis rate in maturefronds at PPFD's of 210 µmol m2 s1 or greaterand increased the net photosynthesis rate below 210 µmolm2 s1 in young fronds. The increase in net photosynthesisin stressed young fronds was associated with a significant reductionin the dark respiration rate. Water stress and decreasing PPFD'sincreased frond diffusive resistance. Carbon dioxide concentrationin the intercellular spaces decreased with increasing frondage and PPFD's up to 200 µmol m2 s1. Theresidual resistance to carbon dioxide flux was not significantlyaffected by either frond age or water stress. Frond water potentialwas significantly lower in mature fronds than in young fronds. Key words: Matteuccia struthiopteris, Water relations, Photosynthesis, Dark respiration 相似文献
12.
Changes in the spatial distribution of Baltic herring larvaethrough time were investigated in the waters off Helsinki, thenorthern Baltic Sea. The average larval densities were comparableto the relatively low levels (mean around 2 larvae m2)found in other studies in the Gulf of Finland. In shallow baysvirtually no herring larvae were found in early June. In lateJune and early July the densities of larvae longer than 10 mmincreased to 14 larvae m2 in shallow areas (depth<2 m), i.e. to levels higher than those recorded in deeperwaters. In combination with data on the size distributions ofthe larvae, these observations suggest that a significant proportionof the herring larvae are found in shallow water after the yolksac stage. We conclude that shallow coastal waters are potentiallyimportant nursery areas for herring larvae and that this featureof herring larval biology should be taken into account in planningsampling programs for larval herring. 相似文献
13.
Excised seed-coat halves and cotyledons of developing seedsof Pisum sativum L. were incubated in a bathing medium (pH 5·5),in order to measure the release or uptake of sucrose and aminoacids. Net efflux of sucrose and amino acids was reduced bya 250 mol m 3 mannitol solution and a 400 mol m 3solution, in comparison with a 100 mol m3 control. Thiseffect could not be observed in the case of the amino acid analogue-aminoisobutyric acid (AIB). Net uptake of labelled sucroseor valine by cotyledons and seed coats was enhanced by a highosmolality of the bathing medium. The data on AIB and the datafrom uptake experiments support the view that net efflux ofassimilates is reduced by a high solute concentration in theapoplast (e.g. 400 mol m3 mannitol), via a stimulationof carrier-mediated sucrose and amino acid uptake into cotyledonaryand seed coat tissues. In experiments with attached empty ovulesof pea in a very early stage of development, sugar release fromthe seed coat was enhanced by a low osmolality of the apoplastsolution (e.g. 100 mol m3 mannitol, in comparison witha 400 mol m 3 control). This paradoxical effect may beobserved when the stimulatory effect on net assimilate effluxfrom seed coat tissues is exceeding the inhibitory effect onassimilate import into the seed coat. Key words: Seed development, turgor-sensitive transport, assimilate transport 相似文献
14.
Simulated annual plankton production in the northeastern Pacific Coastal Upwelling Domain 总被引:1,自引:0,他引:1
Robinson Clifford L.K.; Ware Daniel M.; Parsons Timothy R. 《Journal of plankton research》1993,15(2):161-183
A microcomputer simulation model is presented that describesthe generalized plankton production dynamics, in the surfacemixed layer, of the Juan de Fuca Eddy located on the southwesternBritish Columbia continental shelf. The Juan de Fuca Eddy simulationmodel evaluates how the annual biomass production of diatoms,copepods and euphausiids is forced by plankton feeding interactions,seasonal variability in upwelling, water temperature and solarradiation, and generalized fish predation. The model estimatesannual primary production of 345 g C m2 year1and secondary production of 19.4 g C m2 year1for copepods and 6 g C m2 year1 for euphausiids,during 198589; -90% of the annual plankton productionwas generated during the April-October upwelling season. Perturbationsof 22 abiotic and biotic parameters, one at a time by ±10%of nominal values, indicated that oceanic variability (e.g.upwelling rate) most strongly affected primary production. Conversely,zooplankton production was most sensitive to variability inbiological parameters describing zooplankton grazing potentialand growth (e.g. gross growth efficiency). Simulated seasonalbiomass patterns of diatoms, copepods and euphausiids were foundto closely match empirical data. However, euphausiid biomassproduction in the Juan de Fuca Eddy alone was unable to meetthe demands of estimated pelagic fish consumption. Local Eddyeuphausiid populations had to be supplemented, from regionaleuphausiids. by a mechanism that is proposed to be linked tothe seasonal pattern and intensity of positive Ekman transport(upwelling). 相似文献
15.
Distribution pattern of decapod larvae off the north-western Iberian Peninsula coast (NE Atlantic) 总被引:3,自引:0,他引:3
In October 1977 the model of general circulation of the watermasses off the coast of Galicia, and the presence of a coastalupwelling, led to a high primary productivity. This high productivityin turn favoured the development of a rich population of decapodlarvae. The abundance and distribution pattern of these organismswere closely linked (i) to the abundant presence of the correspondingadult species in the area, (ii) with the spatial distributionof phytoplanktonic populations concurrently studied by Estrada[J. Plankton Res ., 6, 417434 (1984)] and (iii) withthe hydrodynamic pattern in the area. Fifty-two decapod larvaetaxa were identified and Solenocera membranacea, Pisidia longicornis,Pilumnushirtellus and Goneplax rhomboides were the most representativespecies It was observed that the greatest concentrations oflarvae (3387 larvae 102 m3) were to be found nearthe mouth of the Rfas Baixas (situated in the south-west ofthe coastal area) and in some zones further out to sea (863larvae 102 m3) (due to a process of hydrodynamictransport) 相似文献
16.
The contribution of ammonia excreted by zooplankton to phytoplankton production in Narragansett Bay 总被引:1,自引:0,他引:1
Ammonia excreted by mixed zooplankton populations over an annual(19721973) cycle in Narragansett Bay varied from 0.04to 3.21 µg at NH3-N dry wt1 day1, exclusiveof two exceptional rates measured one year apart: 11.74 and18.39 µg at NH3-N mg dry wt1 day1. Grossphytoplankton production integrated over the year (19721973)averaged 151 mg C m3 day1 for an 8 m water column;peaks of 332 and 905 mg C m3 day1 occurred duringthe winter-spring and summer blooms, respectively. Excretedammonia, integrated seasonally and annually, contributed only0.2% and 4.9% of the nitrogen required for observed gross productionduring the winter-spring and summer blooms, respectively, and4.4% annually. However, excreted ammonia may be an importantsource of the nitrogen required by Skeletonema costatum, thedominant diatom in Narragansett Bay, during the post-bloom periodwhen 186% of the nitrogen required for its net production wasmet by ammonia excretion. A combination of zooplankton ammoniaexcretion and benthic ammonia flux contributed 22% of the nitrogenrequired for the annual gross production (440 g C m2)while 51% of the nitrogen required for the net production ofSkeletonema was accounted for by regenerated nitrogen.
1This research was supported by NSF grant GA 31319X awardedto Dr.T.J.Smayda. 相似文献
17.
Population structure and production of Eudiaptomus gracilis(G.O. Sars) have been calculated from daily measurements inLake Balaton for one month during each summer in 1975 and 1977.Fecundity was different in the two years 6.98 ? 1.16 and 10.68? 1.42 in 1975 and 1977, respectively. A total of 80% and 64%of the population were made up of larvae in 1975 and 1977, respectively.The ratio of males to females was 1:1.63 and 1:1.1, respectively.In 1975 it was possible to follow the development of cohorts,19 20 days in the former year, 17 20 days in thelatter. In both years of examination 80 83% of naupliiand 1215% of copepodites were eliminated. Daily net biomassproduction was 6.88 mg (dry wt.)/m3 in 1975 and 1.94 mg (drywt.)/m3 in 1977. Ratios of eggs, nauplii and copepodites indaily production was 1:2.4:1.4 in 1975 and 1:1.0:1.0 in 1977.The daily potential biomass production were 34.40 mg (dry wt.)/m3 and 10.28 mg (dry wt.)/m3 and the elimination were 80 and81 wt.%, respectively. P/B ratio allowing for net productionvalues was nearly the same in both periods of investigation(0.12 and 0.099 respectively). 相似文献
18.
Pseudobalanion plancioracum was the most abundant ciliate speciesin the pelagic zone of Lake Constance, FRG, over a 3 year period.Annual averages accounted for 30, 35 and 43% of total ciliatenumbers in the uppermost 20 m of the water column in 1987, 1988and 1989 respectively. Highest cell numbers were observed inearly spring, simultaneously with the first phytoplankton maximum.The small ciliate (mean length 15 µm, mean cell volume1300 µm3) is a raptorial feeder and predominantly consumesphytoplankton. In laboratory cultures, P planctonicum grew wellon a diet of Rhodomonas sp. (Cryptophyceae). Maximum growthrates increased from 0.46 day1 at 5 5°C to 1.52 day1at 18.5° C, while temperatures above 21°C were lethal.Depending on food concentration, 0.24.4 Rhodomonas cellswere ingested per ciliate and hour. 相似文献
19.
Apparatus is described for exposing plants to low concentrationsof SO2 (50500µg m3 in air) and for measuringeffects on photosynthesis, dark respiration, and transpiration.Temperature, humidity, and irradiance in the chambers were controlledindependently, and fans ensured that leaf boundary layer resistanceswere low. Experiments with plants of Vicia faba in clean andpolluted air showed that: (i) a depression of net photosynthesisby 50 µg m3 SO2 depended on boundary layer resistanceand on irradiance; (ii) stomatal resistance was increased ordecreased by 50 µg m3 SO2 when relative humidityin the chambers was low (35% r.h., 22 °C) or high (50% r.h.,22 °C) respectively. 相似文献
20.
Autotrophic picoplankton in southern Lake Baikal: abundance, growth and grazing mortality during summer 总被引:5,自引:0,他引:5
Nagata Toshi; Takai Kenji; Kawanobe Kyoko; Kim Dong-Sup; Nakazato Ryoji; Guselnikova Nina; Bondarenko Nina; Mologawaya Oliga; Kostrnova Tatyana; Drucker Valentine; Satoh Yasuhiro; Watanabe Yasunori 《Journal of plankton research》1994,16(8):945-959
Autotrophic picoplankton were highly abundant during the thermalstratification period in late July in the pelagic area (waterdepth 5001300 m) of southern Lake Baikal; maximum numberswere 2 x 106 cells ml1 in the euphotic zone ({small tilde}15m). Unicellular cyanobacteria generally dominated the picoplanktoncommunity, although unidentified picoplankton that fluorescedred under blue excitation were also abundant (maximum numbers4 x 105 cells ml1) and contributed up to {small tilde}40%of the total autotrophic picoplankton on occasions. Carbon andnitrogen biomasses of autotrophic picoplankton estimated byconversion from biovolumes were 1484 µg C l1and 3.621 µg N l1. These were comparableto or exceeded the biomass of heterotrophic bacteria. Autotropicpicoplankton and bacteria accounted for as much as 33% of paniculateorganic carbon and 81% of nitrogen in the euphotic zone. Measurementsof the photosynthetic uptake of [l4C]bicarbonate and the growthof picoplankton in diluted or size-fractionated waters revealedthat 80% of total primary production was due to picoplankton,and that much of this production was consumed by grazers inthe <20 µ.m cell-size category. These results suggestthat picoplankton-protozoan trophic coupling is important inthe pelagic food web and biogeochemical cycling of Lake Baikalduring summer. 相似文献