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1.
On filament width in oceanic plankton distributions 总被引:1,自引:0,他引:1
A plankton patch deformed by diffusion, straining flow and biologicalgrowth is demonstrated to have a minimum width, /, which ispurely a function of the effective diffusivity, , and the strainrate, . 相似文献
2.
Leboulanger C.; Descolas-Gros C.; Fontugne M.R.; Bentaleb I.; Jupin H. 《Journal of plankton research》1995,17(11):2079-2091
The stable carbon isotope composition of particulate organicmatter expressed as 13C was measured in cultures of 13 speciesof marine microalgae in different phylogenetic groups. The effectsof salinity variations and changes in photoperiod were alsoassayed for three of them (i.e. Skeletonema costatum, Amphidiniumopercularum and Isochrysis galbana); the effect of nature ofnitrogen supply (nitrate. ammonium) was studied for one (S.costatum).These environmental parameters were chosen because of theirvariability in the ocean and their possible effects on 13C valuesof phytoplankton organic carbon. Batch culture conditions andsampling time after inoculum were strongly controlled in orderto provide cells in good physiological state which were comparablefrom one culture to the other. In the same way, sampling waslimited to the first 2 days of exponential growth, in orderto avoid a possible dissolved inorganic carbon (DIC) limitation.Carboxylase activities [of the enzyme ribulose 1,5-bisphosphatecarboxylase oxygenase (Rubisco), and the three ß carboxylases:phosphoenolpyruvate carboxylase (PEPC), phosphoenolpyruvatecarboxykinase (PEPCK) and pyruvate carboxylase (PC)] and totalchlorophyll a concentrations were assayed simultaneously. The13C values observed were between 30.2 and 12.7i.e. comparable to those observed in the world's oceans. Theisotopic composition of phytoplankton organic carbon was shownto be under the influence of the parameters tested but 13C variationsare specific to the species considered. The nature of ßcarboxylase found in each species, or systematic position, couldnot be linked to the isotopic composition of organic carbon.No linear or single correlation between 13C variations and environmentalmodifications were observed and there is no evidence for a simpleand universal relation between 13C of phytoplankters and theirenvironment. In monospecific cultures as in the field, 13C fractionationby Rubisco (and eventually by PEPCK) may be counterbalancedby other mechanisms. 相似文献
3.
Terazaki Makoto; Yoshimura Miwa; Kabaya Yuko; Wada Eitaro 《Journal of plankton research》1994,16(11):1589-1593
The 15N values of micronekton collected from Sagami Bay rangedfrom 9.4 to 14.2%. The 15N values of the micronekton, Gonostomagracile, increased with growth (9.4 to 12.6%) and it seems thatmales, before sex reversal, and females consume different foodorganisms. 相似文献
4.
In a series of experiments, the planktonic larvae of Marenzelleriaviridis (Verrill, 1873) were exposed to various combinationsof salinity (S = 0.6, 2.5, 5.0, 10 and 20) and temperature (T= 5, 10 and 20C) from the 1-setiger stage to the onset of metamorphosis(16- to 17-setiger stage). One-setiger larvae were unable tocomplete their development to metamorphosis at salinities below5. Metamorphosis was successful at salinities of 10 and 20,when the animals adopted a benthic life mode. Larval developmentwas more rapid at 10 than at 20, and was positively affectedby higher temperatures. Larvae exposed to a salinity of 3.5at the 4- to 5-setiger stage developed and completed metamorphosisto benthic juveniles despite the low salinity. These larvaedeveloped most rapidly at a temperature of 10C. The salinitytolerances (LC50) of M. viridis larvae (t = 48 h), juvenilesand adults (t = 72 h in each case) were determined at 10C.The results showed that all development stages can toleratesalmities <1 The importance of constraints on developmentand tolerance to low salinities for the successful colonizationof oligohaline regions is shown and discussed in connectionwith other brackish-water organisms. 相似文献
5.
Temporal and spatial variations in phytoplankton carbon isotopes in a polymictic subtropical lake 总被引:2,自引:0,他引:2
Stable carbon isotopes (13C) were determined for phytoplanktonand dissolved inorganic carbon (DIC) from Lake Apopka, a shallow,polymictic and hypereutrophic lake in Florida, USA. Bulk planktondominated by pico- and nanqanobacteria were enriched in 13(13.1± 1.1%) as a result of assimilation of extremely 13C-richDIC (13C = 9.6 ± 3.0%). Diatoms (Aulacoseira spp.) hada 13C of 14.3 ± 0.6% that was slightly more negativethan that of small cyanobacteria. Meroplanktonic diatoms hada 13C (13.6 ± 1.8%), similar to their planktoniccounterparts. The 13C of a colonial cyanobacterium (Microcystisincerta) was exceptionally heavy (3.0 ± 1.0%)and attributed to localized carbon limitation. Seasonal variationin 13C of bulk plankton was small (4%) relative to reports forother lacustrine systems No difference in the 13C of bulk planktonhorn surface water between stratified and non-stratified periodswas found. No measurable changes in 13C of bulk plankton wereindicated in light and dark incubation experiments Frequentwind mixing of the water column, high DIC concentration, andconsistently high lake productivity were used to explain thetemporal and spatial isotope consistency of phytoplankton inthis lake. 相似文献
6.
The 15N of marine mesozooplankton species was measured on fouroccasions. Significant differences were found between copepodsand meroplanktonic larvae, yet not between holoplanktonic species.On average, mesozooplankton was enriched by 3.4 ± 0.9relative to selected seston size fractions. Despite suggestingsmall differences (0.5 to 1) in the 15N of different phytoplanktontaxa on one occasion, the size fractionation procedure generallyproved inadequate in separating major taxonomic groups composingseston. This circumstance, and phase-shifts in the transmissionof rapid changes (>2) in seston 15N to mesozooplankton complicatethe calculation of mesozooplankton trophic levels. 相似文献
7.
The percent of light absorbed by algae, estimated from a regressionof attenuation of downwelling photosynthetic photon flux densityon chlorophyll a concentration, was used in conjunction withmeasurements of phytoplankton photosynthesis to estimate quantumyields () of Castle Lake phytoplankton populations during the1980 ice-free season. The maximum values occurred during mid-summerin the deep hypolimnion (<1% of surface photon flux) andwere {small tilde} 78% of the theoretical maximum. However,later in the season (September) the deep-water values decreasedsignificantly to {small tilde}27% of the theoretical maximumin conjunction with a decrease in quantum flux density to thesewaters. The values for epilimnetic phytoplankton populationswere never >15% of the theoretical maximum. The presenceof relatively high concentrations of peridinin and chlorophyllc in the deep-water algae enabled these organisms to absorbthe predominantly green light in this region of the lake which(i) allowed the use of a single extinction value per unit ofchlorophyll (kc) at all depths when calculating , and (ii) increasedthe of the deep-water algae, relative to those in the near-surfacewaters. These data indicate that the deep-water algae in CastleLake were able to utilize their ambient light field, particularlyin the early summer, and suggest that the deep-chlorophyll layerin this lake is maintained primarily by in situ algal growthrather than sinking and accumulation of organisms from nearsurface waters. 相似文献
8.
Carbon isotopic composition of Trichodesmium spp. colonies off Bermuda: effects of colony mass and season 总被引:1,自引:0,他引:1
Colonies of Trichodesmium spp. are conspicuous, macroscopiccomponents of the life in tropical and subtropical oceans. Thelarge size and the morphology of the colony raise questionsregarding the mechanism of carbon supply for photosynthesis.Constraints on these mechanisms may be indicated by the stablecarbon isotopic composition (13C) that reflects the balancebetween carbon supply and speciation, as well as the growthrate and colony size. The 13C of Trichodesmium off Bermuda measuredhere revealed a strong correlation between size of individualcolonies and season. The smallest colonies, 2–7 µgC colony–1, showed the lightest 13C composition (–19),increasing to asymptotic values of –12 above 7 µgC colony–1. The average 13C of the colonies was lightestimmediately after the onset of stratification in the SargassoSea, gradually increasing by 4 to heavier values during thesummer. We propose that the mass effect is due to increaseduse of HCO3– by the larger colonies, whereas the seasonalinfluence may be related to changes in irradiance and pCO2 affectingthe internal carbon cycling. 相似文献
9.
Various kinds of measurement of tissue water status were madeseveral times during water stress and recovery in Brassica juncea(cv Canadian Black) and B napus (cv Drakkar) Unstressed plantsof the two species had similar leaf water potentials (w), solute(s) and turgor potentials (p) Values of relative water content(RWC) and the slope of the linear relationship between p andRWC (p/RWC) were greater in B napus than in B juncea Statistical correlations of pooled data for the watered andstressed treatments differentiated the relationships among RWC,w and its components in the two species The major statisticaldifference was that p/RWC was related to RWC in B napus andto w and s in B juncea A decline in p/RWC with decreasing sin B juncea may be a mechanism for maintaining p at low soilwater potentials through maintenance of more elastic cell walls. Brassica juncea, Brassica napus, osmotic adjustment, tissue elasticity, water relations 相似文献
10.
We describe the occurrence of phycocyanin and phycoerythrocyanin-likepigment in natural Microcystis colonies collected in Lake Kasumigaura.For differentiating pigments, the combination of simultaneousdetermination of molecular weights of and ß and subunitsby electrospray ionization mass spectrometry with HPLC separationand fluorescence measurements was used. It was suggested thatthe natural Microcystis colonies may contain the phycoerythrocyanin-likepigment, judged from the excitation and emission spectra. Measuredpigments consisted of different molecular weights of and ßsubunits, but the molecular weights of and ß subunitsin both phycocyanin and phycoerythrocyanin-like pigments werenot always identical. 相似文献
11.
Occurrence of mycosporine-like amino acids in the red-tide dinoflagellate Alexandrium excavatum: UV-photoprotective compounds? 总被引:1,自引:0,他引:1
Carreto J.I.; Carignan M.O.; Daleo G.; Marco S.G.De 《Journal of plankton research》1990,12(5):909-921
Water extracts of the red-tide dinoflagellate Alexandrium excavatumgrown at high light intensity (200 µE m2s1) show a broad absorbance maximum in the UV regionof the spectrum (310360 nm). Using TLC and reverse-phaseHPLC a series of mycosporine-like amino acids have been characterized:mycosporine-glycine (max = 310 nm), palythine (max = 320 nm),asterina-330 (max = 330 nm), shinorine (max = 334 nm), porphyra-334(max= 334 nm), palythenic acid (max = 337 nm) and the isomericmixture of usujirene and palythene (max = 359 nm). From theobserved spectral changes during transference from low(20 µE m2 s1) to high (200µE m2 s1) light intensities and vice versa,the series of compounds are supposed to be biogenically relatedto one another. The presence of these compounds in A.excavatumis discussed in relation to their possible role in the photoprotectionto deleterious UV radiation. 相似文献
12.
Integrated likelihood functions for non-Bayesian inference 总被引:1,自引:0,他引:1
Consider a model with parameter = (, ), where is the parameterof interest, and let L(, ) denote the likelihood function. Oneapproach to likelihood inference for is to use an integratedlikelihood function, in which is eliminated from L(, ) by integratingwith respect to a density function (|). The goal of this paperis to consider the problem of selecting (|) so that the resultingintegrated likelihood function is useful for non-Bayesian likelihoodinference. The desirable properties of an integrated likelihoodfunction are analyzed and these suggest that (|) should be chosenby finding a nuisance parameter that is unrelated to and thentaking the prior density for to be independent of . Such anunrelated parameter is constructed and the resulting integratedlikelihood is shown to be closely related to the modified profilelikelihood. 相似文献
13.
nAlkyl - and -lactosides, galactosides and glucosides with differentalkyl chain lengths (C2, C8, C14, and C20) were synthesizedand used as acceptors for sialyltransferases from rat liverGolgi vesicles. The -galactosides, -glucosides, and both - and-lactosides, were sialylated. Keeping the acceptor concentrationconstant, sialylation rates reached a maximum for the n-octyl- and -lactosides, n-Octyl -galactoside and noctyl -glucoside,respectively. noctyl -glucoside, respectivwly. n-Octyl -galactosideand n-octyl -glucoside were not sialylated. The reaction productswere characterized by TLC. With n-octyl lactoside and galactosideas acceptors, two major sialylation products were formed. Thjeycould be separated by preparative TLC, and their structureswere identified as 23 and 26 sialylated acceptors,respectively, by a combination of periodated oxidation, NaBD4reduction,permethylation and subsequent analysis by fast atombombardment mass spectrometry (FAB-MS). The structure of thesingle product obtained from n-ictyl -glucoside was determinedto be the 26 sialylated glucoside. Competition experimentswith n-octyl lactoside and lactosylceramide and gangliosideGal1-3GalNAc1-4(NeuAc23)Gal14Glcbeeta11Cer(GM1) as acceptors for sialyltransferases suggested that SAT-I[NeuAc23Gal14Glc1-1Cer (GM3) synthase] was atleast in least in part responsible for the 23 sialylationof n-octyl lactoside. alkylgalactosides alkylglucosides alkyllactosides neoglycolipids sialytransferases 相似文献
14.
Temperature and salinity effect on growth and chemical composition of Gyrodinium aureolum Hulburt in culture 总被引:1,自引:0,他引:1
A factorial experiment shows highly significant effects of temperature(12 522.5°C) and salinity (17.834 S) on thegrowth rate of Gyrodinium aureolum, with a significant temperature-salinityinteraction. The maximum growth rate of G aureolum is measuredto 0.61 div. day1 at 20°C and 22.3 S. Gyrodiniumaureolum does not grow at temperatures :10 °C or 25°Cand at salinities 12 S. The cellular content of carbon (C) andnitrogen (N) and the elemental ratios N/C, P/C and N/P are significantlyaffected by the temperature The cellular content of phosphorus(P) and the elemental ratios P/C and N/P vary significantlywith salinity Significant temperature-salinity interactionsare found for the cellular content of carbon, nitrogen and phosphorus.Variations in the N/P ratio indicate that G.aureolum has a largestorage capacity for phosphorus It is suggested that temperatureis one important limiting factor in the initiation of bloomsof G.aureolum in north European waters. 相似文献
15.
Effects of Priming and Endosperm Integrity on Seed Germination Rates of Tomato Genotypes: II. GERMINATION AT REDUCED WATER POTENTIAL 总被引:3,自引:0,他引:3
Seed germination rates (GR =inverse of time to germination)are sensitive to genetic, environmental, and physiological factors.We have compared the GR of tomato (Lycopersicon esculentum Mill.)seeds of cultivar T5 to those of rapidly germinating L. esculentumgenotypes PI 341988 and PI 120256 over a range of water potential(). The influence of seed priming treatments and removal ofthe endosperm/testa cap enclosing the radicle tip on germinationat reduced were also assessed. Germination time-courses atdifferent 's were analysed according to a model that identifieda base, or minimum, allowing germination of a specific percentage(g) of the seed population (b(g)), and a hydrotime constant(H) indicating the rate of progress toward germination per MPa.h.The distribution of b(g) determined by probit analysis was characterizedby a mean base (b) and the standard deviation in b among seeds(b). The three derived parameters, b, b) and H, were sufficientto predict the time-courses of germination of intact seeds atany . A normalized time-scale for comparing germination responsesto reduced is introduced. The time to germination at any (tg())can be normalized to be equivalent to that observed in water(tg(0)) according to the equation tg(0)=[l(/b(g))]tg().PI 341988 seeds were more tolerant of reduced and had a morerapid GR than T5 seeds due to both a lower b and a smaller H.The rapid germination of PI 120256, on the other hand, couldbe attributed entirely to a smaller H. Seed priming (6 d in1.2 MPa polyethylene glycol 8000 solution at 20 ?C followedby drying) increased GR at all >b(g), but did not lower theminimum allowing germination; i.e. priming reduced H withoutlowering b. Removing the endosperm/testa cap (cut seeds) markedlyincreased GR and lowered the mean required to inhibit germinationby 0.7 to 0.9 MPa. However, this resulted primarily from downwardadjustment in b during the incubation of cut seeds at low inthe test solutions. The difference in b between intact and cutseeds incubated at high was much less (0.l MPa), indicatingthat at the time of radicle protrusion, the endosperm had weakenedto the point where it constituted only a small mechanical barrier.In the intact seed, endosperm weakening and the downward adjustmentin embryo b ceased at < 0.6 MPa, while the reductionin H associated with priming proceeded down to at least 1.2MPa. Based on these data and on the pressure required to pushthe embryos from the seeds at various times after imbibition,it appears that the primary effect of priming was to shortenthe time required for final endosperm weakening to occur. However,as priming increased GR even in cut seeds, priming effects onthe embryo may control the rate of endosperm weakening. Key words: tomato, Lycopersicon esculentum Mill., water potential, germination rate, seed priming, genetic variation 相似文献
16.
Response of Gonyaulax tamarensis to the presence of a pycnocline in an artificial water column 总被引:1,自引:0,他引:1
In nature, large concentrations of the toxic bloom-forming dinoflagellate,Gonyaulax tamarensis, are frequently observed in the vicinityof the pycnocline. In the absence of a pycnocline the organismis usually recorded near the surface, where light levels aremore advantageous for photosynthesis. In this paper we examinethe swimming behaviour of G.tamarensis when exposed to varyingdegrees of stratification and investigate whether the maintenanceof a subsurface (pycnocline) population is the result of retentionof the algae by a physical barrier or active accumulation ofthe organisms at a density interface. The study indicates thatG.tamarensis cells presented with a halocline of S<{smalltilde}67 (occurring over a few centimeters) cross thissalinity barrier and accumulate at the highest available photonflux density ({small tilde}100 µmol m2 s1).Cells exposed to a gradient of S>{small tilde}7remain atthe halocline (pfd={small tilde}40 µmol m2 s1).However, when light above the pycnocline is attenuated by theaddition of food colour to the medium, the cells cross a haloclineof S=10 and accumulate at the highest available photon fluxdensity. In the absence of added nutrients (inorganic N andP) the organism fails to exhibit a phototactic response. Thus,the presence of a strong halocline does not represent an inpenetrablephysical barrier for G.tamarensis and the development of pycnoclinepopulations of this organism is a function of density, lightand nutrient climate. 相似文献
17.
In recent years alternative ways have been proposed to transformmeasurements of leaf water potential, , and relative water content,R*, in order to derive values of osmotic pressure at full turgidityin leaves and shoots, o(when 0). Two types of transformationsare usually considered: 1/ versus R* and versus 1/R*, and linearregression is used to fit the data in the region where turgoris thought to be zero. It appears that when o is estimated bylinear extrapolation of 1/Psi; versus R* then apoplastic watermight not influence the accuracy of o but when the versus \/R*transformation is used apoplastic water causes an underestimateof o. We examine the accuracy of the estimate of o obtainedfrom the two transformations when there are random errors in, systematic errors in , and when the osmotic solutions arenon-ideal. The 1/ versus R* transformation generally producesthe best estimate of 0 by linear extrapolation. 相似文献
18.
Water-relations parameters were measured on sections of secondaryphloem from red oak (Quercus borealis michx. f.) and white ash(Fraxinus americana var. biltmoreana [Beadle] J. Wright) usinga linear displacement transducer. Changes in tissue thicknessin response to changes in the osmotic pressure of the bathingsolution were used to calculate the volumetric elastic modulusplus osmotic pressure (v + ) of the tissue, and an applied forcemethod was used to estimate the time constant for water equilibration(T). The hydraulic conductivity of the cell membranes (Lp) wascalculated utilizing v + and r values. The time-dependent behaviour of the tissue was much more complexthan originally expected. A correction for a time-dependentprocess that we call drift was required to obtainnumbers for v + . Furthermore, v + was calculated on two assumptionsin order to relate changes in tissue dimensions to sieve elementparameters. In the first case, a lower limit for v + of thesieve elements was determined by attributing all changes intissue dimensions to these cells. For red oak the average v+ on this assumption is 72 bars. Assuming that all cell typeswere equally responsible for the changes in tissue dimensionsresulted in an v + value of 192 bars for oak. If v + and rare the same for all cells in the tissue, Lp for the sieve elementsof oak is 9.6 x 108 cm s1 bar1. Exudationfrom the sieve elements of white ash during excision of thephloem led to artificially high values of v + for that species. Quercus borealis michx. f., Fraxinus americana var, biltmoreana (Beadle) J. Wright, red oak, white ash, water relations, phloem, volumetric elastic modulus, membrane hydraulic conductivity 相似文献
19.
Light-limited photosynthetic carbon incorportion is expectedto be directly proportional to the scalar quantum irradiance.The proportionality constant is , where mis the maximum quantum yield (mol C Einstein1 absorbed)and $$\stackrel{\¯}{{\hbox{ k }}_{\hbox{ c }}}$$ isthe mean spectral absorption coefficient (m2 mg1 chla). Recent efforts to evaluate of in situphytoplankton photosynthesis are variously flawed. Lack of evidenceof proportionality and lack of correction of cosine to scalarirradiance are common deficiencies. Most data, as we interpretthem, indicate values in the range 0.0003 0.0006 mol C m2 Einstein1 abs mg1 chl a. New determinationsin lrondequoit Bay, New York, lie in this range. Most estimatesof at depth have been about 0.010 m2 mg1chl a. Similar values are being obtained for total particulatesfrom lrondequoit Bay; whether detritus contributes significantlyis not yet known. Published data, in our view, all point tovalues of m in situ in the range 0.030.07 mol C Einstein1abs. Published values >0.10 are almost certainly due to imprecisionor systematic error.
*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP) First International Workshop heldat the Limnological Institute, University of Konstanz, in April1982. 相似文献
20.
An error occurs in the calibration of xylem pressure potential() against leaf-water potential () when the calibration is madeusing plant material in which the water stress has been inducedartificially after excision. The impostion of water stress afterexcision affects the determination more than it affects , consequentlythe relationship between these two indices of water stress isaltered. Care should be exercised to ensure that identical proceduresare adopted during . calibrations and during susbsequent fieldmeasurements of with the pressure-chamber apparatus. 相似文献