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1.
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.
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2.
The occurrence of early larval stages of Brama brama
and Coryphaena hippurus is reported for the first time
in Adriatic waters. Two larvae of B.brama between 4.36
and 5.00 mm, and two larvae of C.hippurus between 4.75
and 4.95 mm standard length, were found in ichthyoplankton collections
taken off the River Neretva estuary (43010N,
17°250E) and station Stoncica, island Vis
(43°000N,
16°20E) (eastern middle Adriatic),
respectively. The capture of both species (B.brama) in
August 1998; C.hippurus in May 1998) is in agreement
with their proposed seasonal life cycle in the Adriatic Sea.
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3.
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.
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4.
Growth and toxin production of a highly toxic clone of the marine
dinoflagellate Alexandrium tamarense, isolated from
the lower St Lawrence estuary (Quebec) in eastern Canada, were studied in
unialgal batch cultures under different conditions. Controlled experiments
were conducted on the production of paralytic shellfish poisoning (PSP)
toxins under conditions of varying light (40, 60, 150, 230 and 470 mol m-21
s-1), salinity (10, 15, 20, 25 and 30)
and nitrate concentrations (0, 88, 364, 528 and 880 mol
l-1). The effects of variable environmental factors
on both toxin composition (% molar) and cell toxicity [pg STXeq (saxitoxin
equivalents) cell-1] were determined through the
culture cycle. The toxin profile (% molar; mean SD), determined by high-performance liquid
chromatography with fluorescence detection (HPLC-FD), remained stable and
was consistently dominated by the low-potency
N-sulfocarbamoyl toxins C1/C2 (64.0 ± 3%).
There were also substantial relative amounts of the high-toxicity carbamate
derivatives gonyautoxin 1-4 (GTX1-4) (1.7 ± 0.5%), neosaxitoxin
(NEO) (16.2 ± 2%) ans saxitoxin (STX) (17.8 ± 2%).
The cellular toxicity (mean ± SD: 58.8 ± 7 pg STXeq
cell-1) was essentially independent of light,
salinity and nitrate concentration throughout the exponential growth phase,
but varied over the growth stages in cultures. A positive correlation was
observed between cellular toxicity and salinity-dependent growth rate,
indicating that cell toxin quota may be affected by extrinsic factors, but
it is not always a direct functional response to specific environmental
stress.
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5.
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.
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6.
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.
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7.
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.
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8.
Spatial variability of the photosynthetic parameters and biomass of the Gulf of California phytoplankton 总被引:2,自引:0,他引:2
Gaxiola-Castro G; Alvarez-Borrego S; Lavin M; Zirino A; Najera-Martinez S 《Journal of plankton research》1999,21(2):231-245
Spatial variability of the central Gulf of California (CGC) phytoplankton
biomass and photosynthetic parameters in relation to physical forcing was
studied. Sampling was carried out in November, and the surface
TC range was
20-27.5°C. Strong tidal mixing in the midrift islands regions
injects relatively cool, nutrient-rich waters to the euphotic zone. Some of
this water is transported via jets and cool filaments throughout the Gulf.
In general, chlorophyll a (Chl) of small phytoplankton
(<8 m) (up to >2.5 mg
m-3) was higher than that of large phytoplankton.
Highest values of phytoplankton assimilation numbers
(PBm) [3.17 mg C (mg
Chla)-1
h-1], and photosynthetic efficiency B) [0.23 mg C (mg
Chl a)-1
h-1 (W
m-2)-1] were determined for
the large phytoplankton cells (>8 m). Our hypothesis that
PBm values increase
from cooler to warmer waters is not supported by the data. We found a
27-fold spatial difference of Chl, compared with a 10-fold difference of
PBm and a 6-fold
difference of B. Thus, in our study
area, the major source of variability for primary productivity (PP) comes
from Chl, and not from
PBm and
B. Therefore, we propose that it is
possible to estimate late-fall PP for the CGC using average photosynthetic
parameters. Average values for
PBm and
B of total phytoplankton were 0.72
mg c (mg Chl a)-1
h-1 and 0.12 mg C (mg Chl
a-1 h-1,
(W m-2)-1, with standard
errors of 0.07 and 0.03, respectively.
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9.
Among the benthic ostracods Asterope mariae and
Philomedes interpuncta, the adult males emerge at dusk
from the benthos and swim straight up to the surface, where they soon
concentrate in the neustonic realm. The migration starts when the
irradiance is almost 1 W
cm-2 and the maximal density occurs at the surface
when the light has reached 0.005 W cm-2,
before it is completely dark. The migration ends <1 h later and very
few animals are observed in the water column later in the night. Upward
migration does not result from a positive phototaxis to dim light, but
rather from a strong negative geotaxis and an increase in kinesis or
swimming activity which occur at around 1 W
cm-2. This activity is induced both by the end of
the diurnal period of photoinhibition and by an endogenous circadian
rhythm. This rhythm could be clearly observed in both species from the
recordings made during up to 2 weeks in constant darkness. The length of
the period was roughly 24 h (24 h 3 min in Asterope,
23 h 10 min i Philomedes). The timing of the activity
phase in total darkness varied depending on the post-capture history of the
experimental animals, especially on the time of onset of the experiment.
The adaptive advantage of this rapid diel vertical migration may be a
question of feeding, but this may also increase the nocturnal dispersal of
the reproductive males, and thus promote the reproduction of the species.
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10.
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
11.
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
12.
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
13.
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
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.
Influence of nutrient ratios on the in vitro extracellular polysaccharide production by marine diatoms from the Adriatic Sea 总被引:4,自引:0,他引:4
Three different species of marine diatoms, Nitzschia
closterium (Ehr) Smith, Chaetoceros sp.
(Ehr) and Skeletonema costatum (Grev) Cleve, were
isolated from the Adriatic sea and studied in vitro
for the production of extracellular carbohydrates. Variations of the
nitrogen (N)/phosphorus (P)/silicon (Si) ratios in the growth medium affect
the accumulation and release of carbohydrates. In the
N.closterium cultures at high N/P ratio, the rate of
extracellular polysaccharide release was higher both in rapidly growing
cells (2.14 g per 106
cells day-1 and in stationary phase (1.0 g
per 106 cells day-1) compared
to S.costatum and Chaetoceros sp.
Instead, at low N/P ratios, S.costatum and
Chaetoceros sp. produced large amounts of
extracellular polysaccharides during the logarithmic phase, compared to
N.closterium, with values of 10 g per
106 cells day-1 for
S.costatum and 2.8 g per
106 cells day-1 for
Chaetoceros sp., respectively; in particular, only
S.costatum was able to produce extracellular
carbohydrates (1.2 g per 106 cells
day-1) during the stationary phase of growth. Under
Si limitation, any of the three diatom species produce extracellular
polysaccharides both in the logarithmic and stationary phase of growth. The
potential ecological significance of these findings is discussed.
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16.
Short communication. Carbon:nitrogen ratios of Baltic Sea copepods-indication of mineral limitation?
The carbon (C) and nitrogen (N) content and the C:N ratio of two common
calanoid copepods, Eurytemora affinis and
Acartia bifilosa were measured during spring and
summer at the SW coast of Finland, northern Baltic Sea. The C:N ratio of
both copepod species was slow and stable (4-4.5), irrespective of sampling
time, which implies N limitation at least during intermediate to high food
concentrations in spring and early summer. In addition, experiments were
conducted to reveal whether the diet of copepods affects their C and N
content. Adding green algae Brachiomonas submarina in
concentrations of 50-500 g C
l-1 to <100-m-filtered sea water did
not significantly increase copepod C or N content in 3 day experiments.
However, the C and N contents of E.affinis eggs were
2 times higher in high food concentration, which may increase
survival of eggs and nauplii.
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17.
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.
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18.
Tintinnid diversity in surface waters was investigated in the Bay of
Villefranche in March, before the formation of the seasonal thermocline,
and in May, following water column stratification. Tintinnid abundance was
much greater in March (500 cells l-1), corresponding
to a bloom of Stensomella nivalis compared to May (30
cells l-1). Nonetheless, high numbers of species
were encountered on both dates: 32 in March and 39 in May, respectively.
Diversity was higher (H2.5) for the May
date with low tintinnid concentrations. We examined taxonomic diversity and
morphological diversity. Variance of lorica length was correlated with
taxonomic diversity, in contrast to variance of lorica diameter, which was
nearly invariant. We suggest that either species with similar lorica
diameters exploit different prey items or competition for prey items is not
the dominant factor in structuring tintinnid communities.
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19.
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
20.