共查询到20条相似文献,搜索用时 31 毫秒
1.
Long-term phytoplankton studies in the Bahí Blanca estuary
showed a seasonal pattern characterized by a winter-early spring bloom of
diatoms dominated by Thalassiosira curviseriata.
Laboratory experiments were carried out to elucidate the influence of
irradiance, temperature and salinity on the growth rate of
T.curviseriata. The maximum daily growth rate was 1.93
divisions at 20C. The compensation point
(Ic) varied from approaching zero to 3.08 mol m-2
s-1, values were
-0.020-0.070 divisions mol-1, and the
calculated Ik (the irradiance at which initial slope
line reaches the maximum rate of growth) varied between 32 and 36
mol m-2 s-1. Growth
became light saturated (when max) between 70 and 80
mol m-2 s-1, and was
inhibited at -150 mol m-2
s-1 at all temperatures (5-20°C). The range
of temperatures at which T.curviseriata can grow
(5-20°C) coincides with the temperature range over which it is
found in the field. In contrast, the thermal optimum for growth,
20°C, was higher than the range of temperatures (between 5 and
10°C) characteristic of the winter-early spring bloom in
Bahí Blanca estuary. The mean specific growth rate of
T.curviseriata was not affected by salinity over the
tested range between 25 and 40 p.p.t. Field observations and experimental
data support the characterization of T.curviseriata as
a eurythermal and euryhaline species adapted to growth at relatively low
light intensity. These characteristics may explain the ability of
T.curviseriata to flourish seasonally when light
conditions are apparently limiting and its presence almost year round under
variable conditions of temperature and salinity.
相似文献
2.
The goal of this study was to provide temporal information on the
generation time of Dolioletta gegenbauri and some of
the life cycle's components. At 20C and
90 g C l-1 of
ingestible phytoplankton. D.gegenbauri's life cycle is
completed in 20.5 days. Phorozooids 5 mm produce on average 11.0
gonozooids day-1 over a period of 8-18 days.
Utilizing field data on the abundance and size distribution of an
assemblage of phorozooids and nurses, in conjunction with experimentally
obtained rates, indicates that asexual production per cubic meter by
phorozooids with that of nurses should result in rapid colonization of a
wide shelf by doliolids, as observed during July and August 1981 on the
southeastern continental shelf of the USA.
相似文献
3.
Observations on the first red tide off Kuwait, Arabian Gulf, yielded high
biomass [55.4-262.7 g chlorophyll (Chl)
a l-1] and primary production
(507.9-571.2 g C
h-1l-1), comparable with some
of the highest values reported. There were contrasting changes in the
carbon assimilation ratios, composition of the phytoplankton and the
contribution of nanoplankton (<20 m) between 11 and 12 May.
On 11 May, carbon assimilation by nanoplankton was 2.2 g C
(g Chl a)-1
h-1, but increased to 9.2 g C (g C
(g Chl a)-1
h-1 the following day. Nanoplankton contributed 56
and 9% of Chl a and production, respectively, on 11
May, while net plankton (>20 m) accounted for >65%
of the biomass and primary production on 12 May. Picoplankton (<3
m) contributed <8% of Chl a and
<3% of production. Frequent sampling will be necessary to capture
such dynamic changes and ephemeral events in these waters.
相似文献
4.
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
5.
Abundance and biogeography of tintinnids (Ciliophora) and associated microzooplankton in the Southwestern Atlantic Ocean 总被引:4,自引:1,他引:3
Absolute abundances of foraminifers, polycystine and phaeodarian
radiolarians, tintinnids, pteropods and early crustacean larvae and moults
were assessed in a collection of 57 vertically stratified (0-100 m) net
microplankton samples from 22 stations located between 34 and 58S (along 51-56°W), covered on 8-16 November
1994. Tintinnids were identified to species and measured in order to
estimate their biomass from biovolume to carbon conversions. The
distribution of the microzooplanktonic groups assessed was irregular and
patchy, both geographically and vertically, and their abundances were
characteristic of oceanic low to medium productivity environments.
Tintinnid biomass was also generally low (0.05-0.40 g Cl-1). With the exception of
the tintinnids, associations between microzooplanktonic numbers and
chlorophyll a were generally loose. Eighty-eight
tintinnid taxa were recorded, yet only five accounted for 53% of the
specimens identified. Multivariate (cluster) analysis of tintinnid specific
distribution patterns clearly showed several distinct zones. From north to
south, these are: Transition Zone (TZ), with three subzones, TZ north
(34°S-38°S), TZ central
(39°44S-44°S) and TZ south (46°S);
Subantarctic Zone (SZ; 48-55°S); Polar Front Zone
(55°30S); Antarctic Zone (AZ;
58-59°36S). Each of these was characterized by distinct
tintinnid assemblages, abundance and biomass. With few exceptions,
tintinnid cells were fairly evenly distributed throughout the upper 50 m.
Taxonomic composition usually changed little with depth. Mean population
depths were calculated for a subset of 35 tintinnids; 29 of these dwell
preferably above 40 m. The spatial distribution of tintinnid species
richness showed a more or less gradual decrease from north to south.
Specific diversity and equitability generally increased with depth, and
were higher in antarctic waters than the southern transitional and
subantarctic ones; this trend is tentatively attributed to higher water
column vertical stability south of the Polar Front.
相似文献
6.
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
7.
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
8.
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
9.
Assimilation and release of 14C in a tropical strain of Cryptomonas obovata (Cryptophyceae) exposed to several irradiances 总被引:1,自引:0,他引:1
Carbon assimilation (14C) and dissolved organic
carbon (DO14C) release by a tropical strain of
Cryptomonas obovata was studied. Cells were exposed to
a range of irradiances (0-2000 mol
m-2 s-1) using axenic batch
cultures in the laboratory (Ek = 180 mol
m-2s-1). At up to 2000
mol m-2s-1, carbon
assimilation was not inhibited and an acclimation to low irradiances was
observed. DO14C release was dependent on carbon
fixation and no increase was detected under high irradiances. To determine
particulate organic carbon (PO14C) loss and
CO14C release cells acclimated to 350 mol
m-2 s-1 were incubated during
4 h at 35, 350, 850 and 1900 mol m-2
s-1. DO14C release was
responsible for 30% of the PO14C loss at 1900
mol m-2s-1. High-
and low-molecular-weight (HMW, LMW) compounds were released by
C.obovata under all irradiance conditions. However,
increased release with exposure time was observed only for the HMW
compounds.
相似文献
10.
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
11.
The raphidophyte flagellate Chattonella marina was
successfully cultured from Boston Bay (South Australia), coincident with
mass mortality of farmed bluefin tuna (Thunnus
maccoyii) in April 1996. Grown under laboratory conditions at
150 mol m-2
s-1 irradiance, optimal growth (>0.5
day-1) occurred at a temperature of 25C and a salinity of 30 p.s.u., but good growth
(>0.3 day-1) also occurred between a
temperature of 10 and 30°C and at a salinity of 15-45 p.s.u.
However, cultures grow much faster at an irradiance of 450 mol
m-2 s-1 (1.08
day-1). While Australian
C.marina had similar temperature and salinity
requirements as well-studied Japanese cultures from the Seto Inland Sea,
the Australian strains exhibited a light saturation level for growth four
times higher than that reported from Japan (150 mol
m-2 s-1). An adaptation to
higher light intensities was reflected in higher concentrations of
microsporine-like amino acids in the Australian strains. The different
light adaptation phenotypes were still apparent after long-term culturing
under similar physiological conditions. Potential growth habitats for this
ichthyotoxic flagellate in the Australian region and implications for
finfish aquaculture industries are discussed.
相似文献
12.
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
13.
Valérie Andersen formally began her career in oceanographywith a PhD from the Université de Pierre et Marie Curiein 1985. Her thesis (Andersen, 1985a) was centred on the developmentof numerical models of the pelagic food web. However, it wasfirmly based on her experimental studies of salps (Andersen,1985b, 1986, 1989; Andersen and Nival, 1986) and data she gatheredon cruises in the N.W. Mediterranean Sea (Andersen and 相似文献
14.
Effects of UVB radiation on freshwater autotrophic and heterotrophic picoplankton in a subalpine lake 总被引:1,自引:0,他引:1
The effects of UVB radiation on the activity of heterotrophic (HPP) and
autotrophic (APP) picoplankton (0.2-2 m) and
of autotrophic assemblages >2 m has been measured and
compared. Under natural UVB irradiance in a large, deep, oligotrophic
subalpine lake (Lago Maggiore, 4555N) with mean dissolved organic carbon
(DOC) concentrations of 1 mg Cl-1, the
microorganisms of the two size fractions were not significantly
photoinhibited in their autotrophic and heterotrophic activities. The
vertical attenuation coefficient (Kd) for irradiance
at 305 nm ranged from 1.45 to 1.67 during spring and summer. The mixing
layer extended to a greater depth than the layer affected by UVB radiation
(z1% < zmix), thus
enabling the microorganisms living there to photoadapt. As the assimilation
numbers of APP and nanoplankton were higher at 2 m depth than near the
surface, we suspected that the influence of longer wavelength (UVA,
photosynthetically active radiation) could be stronger than UVB in
affecting the photosynthetic efficiency of natural populations. The
artificial increase in UVB irradiance had a higher detrimental effect on
HPP due to their smaller size, less protection and indirect effects through
autotrophic cell inhibition. Picocyanobacteria were percentually more
affected by UVB than nanoplankton during April due to the presence of
diatoms, which are more resistant than other algal groups to solar UVB
irradiance. Furthermore, picocyanobacteria had lower assimilation numbers
with respect to larger phytoplankton in the quartz tubes during
stratification.
相似文献
15.
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
16.
In a companion paper several methods of calculating the marginal unit water
cost of plant carbon gain (E/A) were tested to determine
whether stomata were behaving optimally in relation to regulating leaf gas
exchange. In this paper one method is applied to several tropical tree
species when leaf-to-air vapour pressure difference (D), photosynthetic
photon flux density, leaf temperature, and atmospheric soil water
availability were manipulated. The response of leaves that had expanded
during the dry season were also compared to that of leaves that had
expanded in the wet season. Few differences in absolute value of
E/A, or the form of the relationship, were observed
between species or between seasons. In the majority of species,
E/A increased significantly as either leaf-to-air vapour
pressure difference increased, at a leaf temperature of either 33C or 38C, or as in
photosynthetic photon flux density increased. In contrast, as leaf
temperature increased at constant D, E/A was generally
constant. As pre-dawn water potential declined, E/A
declined. The relationship between E/A and D did not
differ whether internal or ambient carbon dioxide concentration were kept
constant. It is concluded that stomata are only behaving optimally over a
very small range of D. If a larger range of D is used, to incorporate
values that more closely reflect those experienced by tropical trees in a
savanna environment optimization is incomplete.Key
words: Stomatal optimization theory, marginal unit water cost.
相似文献
17.
Egg production of a brackish water calanoid copepod Acartia
bifilosa was measured in the laboratory in different chlorophyll
(Chl) a concentrations (0-24 mgr;
l-1) and temperatures 4-24C), and the cephalothorax length and carbon content
of females were determined. Egg production was positively correlated both
with Chl a concentration and with temperature; highest
egg production was obtained with 14-20 g Chl
a l-1 and at 13-18°C.
There was also a significant positive correlation between egg production
and female length-specific carbon content (g C
m-1). However, no correlation was observed
between egg production and cephalothorax length of females. Female carbon
content changed during the 3 day experiments; carbon content was positively
related to Chl a concentration and negatively related
to temperature. We conclude that food availability (Chl
a concentration), rather than temperature, limits the
egg production of A.bifilosa in the present study area
in the northern Baltic Sea. Further, both food concentration and
temperature affect egg production not only through the direct effect on the
numbers of eggs produced per female, but also through their effect on
female carbon content.
相似文献
18.
A karyopherin (LeKAP1) cDNA was isolated from tomato
plants. The deduced LeKAP1 protein sequence of 527 amino acids
showed similarity to other plant karyopherin proteins. When
LeKAP1 was expressed in a yeast two-hybrid
system together with the gene coding for the capsid protein (CP) of the
tomato yellow curl leaf virus (TYLCV), it interacted directly with CP.
Thus, LeKAP1 may be involved in the nuclear import of TYLCV CP
and, potentially, the TYLCV genomes during viral infection of the host
tomato cells. 相似文献
19.
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
20.
Resting egg production and oviducal cycling were investigatedfor the calanoid copepods Arctodiaptomus alpinus and Acanthodiaptomusdenticornis both in the laboratory and in a small karstic alpinelake by making a census of the number of eggs produced and theproportion of females in each of four morphologically distinguishedreproductive conditions each day in the laboratory or duringa 23 week period in lake enclosures. In the laboratory,individuals were maintained on a mixed diet of natural phytoplanktonat constant temperatures of 4, 10, 15 and 20C, respectively.Both species differed considerably in their temperature requirementsfor reproduction. Lifetime fecundity was highest at 10C in A.alpinusand at 20C in A.denticornis, with up to 327 eggs 1 spawnedin the former and up to 582 eggs 1 in the latter species.Unfavorable temperatures were further reflected in an increasein egg mortality and the allocation of time spent in a post-reproductivephase, as well as in a decrease of longevity. Increasing temperaturesenhanced egg production rates due to decreasing clutch productionperiods, although clutch size was negatively correlated withtemperature. Maximum rates reached 5.88 and 7.98 eggs 1day1 in the laboratory, and 0.73 and 0.55 eggs 1day1 in enclosures in A.alpinus and A.denticornis, respectively.Egg production rates and clutch size were clearly governed bynutritional conditions in the lake, but were less affected byfood supply in the laboratory. Here, rates of egg productionwere adapted to improving food supply by increasing the frequencyof spawning events, rather than the number of eggs per clutch.No correlation was found between female body size and reproductiveparameters in the laboratory. A very low proportion of totalclutch production resulted in clutches composed of subitaneouseggs, i.e. 0.14% in A.denticornis and 1.20% in A.alpinus. Oviducalphase duration allocations indicate that there exists a temperatureoptimum for gamete maturation. 相似文献