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1.
Toshi Nagata 《Ecological Research》1986,1(2):207-221
The seasonal changes in the size-fractionated chlorophylla concentrations (<3 μm, 3 to 25 μm, and >25 μm) were investigated at a pelagic site of the north basin of Lake Biwa during
June to December 1985. Autofluorescing plankton cells in the <3-μm fractions were also examined using the fluorescein isothiocyanate
staining epifluorescence microscopic technique. The <3-μm phytoplankton (usually dominated by chroococcoid cyanobacteria except
for a few cases dominated by small eukaryotes) showed a clearly different pattern of seasonal change compared with the larger
fractions. That is, from August to early September, chlorophylla of the larger fractions declined considerably, while the <3-μm chlorophylla did not decrease significantly. Moreover, cyanobacterial cell density in the <3-μm fraction showed a maximum value (2–3.5×105 cells·ml−1) during this period. The relative contribution of the <3-μm chlorophylla to the total chlorophylla increased from <5% to 45% during the course of this change. No clear vertical trend in the distribution and composition of
the <3-μm phytoplankton was found, except that relatively large cyanobacteria (>4 μm3) appeared at a depth of 15m but not at 0,5 and 10 m from late July to August. These large cells were also found in November
and December. The drastic seasonal change of phytoplankton size structure occurring in this basin was discussed in relation
to grazing, nutrient depletion and sinking.
Contribution from Otsu Hydrobiological Station, Kyoto Univeristy (No. 308, foreign language series). 相似文献
2.
Picophytoplankton biomass, community structure and productivity in the Great Astrolabe Lagoon, Fiji 总被引:4,自引:0,他引:4
Phytoplankton biomass, community structure and productivity of the Great Astrolabe lagoon and surrounding ocean were studied
using measurements of chlorophyll concentration and carbon uptake. The contribution of picophytoplankton to biomass, productivity
and community structure was estimated by size fractionation, 14C-incubation and flow cytometry analysis. Picoplankton red fluorescence was demonstrated to be a proxy for chlorophyll <3 μm.
Consequently, the percentage contribution to chl a<3 μm from each picoplankton group could be calculated using regression estimated values of ψ
i
(fg chl a per unit of red fluorescence). In the lagoon, average chlorophyll concentration was 0.8 mg m-3 with 45% of phytoplankton <3 μm. Primary production reached 1.3 g C m-2 day-1 with 53% due to phytoplankton <3 μm. Synechococcus was the most abundant group at all stations, followed by Prochlorococcus and picoeukaryotes. At all stations, Prochlorococcus represented less than 4% of the chl a <3 μm, Synechococcus between 85 and 95%, and Picoeukaryotes between 5 and 10%. In the upper 40 m of surrounding oceanic waters, phytoplankton
biomass was dominated by the >3 μm size fraction. In deeper water, the <1 μm size fraction dominated. Prochlorococcus was the most abundant picoplankton group and their contributions to the chlorophyll a<3 μm were close to that of the picoeukaryotes (50% each).
Accepted: 27 May 1999 相似文献
3.
Production rates, abundance, chlorophyll a (Chl a) concentrations and pigment composition were measured for three size classes (<2 μm, 2–11 μm and >11 μm) of phytoplankton
from May to December 2000 in deep, mesotrophic, alpine lake Mondsee in Austria. The study focuses on differences among phytoplankton
size fractions characterised by their surface area to volume ratio ([mm2 l−1: mm3l−1]), pigment distribution patterns and photosynthetic rates. Particular attention was paid to autotrophic picophytoplankton
(APP, fraction <2 μm) since this size fraction differed significantly from the two larger size fractions. Among the three
fractions, APP showed the highest surface area to volume ratios and a high persistence in the pattern of lipophilic pigments
between temporarily and spatially successive samples (about 80% similarity of pigment composition between samples over seasons
and depths). The epilimnetic abundance of APP varied seasonally with an annual maximum of 180 × 103 cells ml−1 in June (at 4–9 m). The minimum (October at 12 m) was more than an order of magnitude lower (4.9 × 103 ml−1). APP peaked during autumn and contributed between 24% and 42% to the total area-integrated Chl a (10–23 mg m−2) and between 16% and 58% to total area-integrated production (5–64 mg m−2 h−1) throughout seasons. 相似文献
4.
In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study
was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral
spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S),
surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer).
Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted
to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September:
<0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within
spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.
Accepted: 6 September 2000 相似文献
5.
Phytoplankton biomass and primary production in the marginal ice zone of the northwestern Weddell Sea during austral summer 总被引:2,自引:0,他引:2
Myung Gil Park Sung Ryull Yang Sung-Ho Kang Kyung Ho Chung Jae Hyung Shim 《Polar Biology》1999,21(4):251-261
During the austral summer of 1995, distributions of phytoplankton biomass (as chlorophyll a), primary production, and nutrient concentrations along two north-south transects in the marginal ice zone of the northwestern
Weddell Sea were examined as part of the 8th Korean Antarctic Research Program. An extensive phytoplankton bloom, ranging
from 1.6 to 11.2 mg m−3 in surface chlorophyll a concentration, was encountered along the eastern transect and extended ca. 180 km north of the ice edge. The spatial extent
of the bloom was closely related to the density field induced by the input of meltwater from the retreating sea ice. However,
the extent (ca. 200 km) of the phytoplankton bloom along the western transect exceeded the meltwater-influenced zone (ca.
18 km). The extensive bloom along the western transect was more closely related to local hydrography than to the proximity
of the ice edge and the resulting meltwater-induced stability of the upper water column. In addition, the marginal ice zone
on the western transect was characterized by a deep, high phytoplankton biomass (up to 8 mg Chl a m−3) extending to 100-m depth, and the decreased nutrient concentration, which was probably caused by passive sinking from the
upper euphotic zone and in situ growth. Despite the low bloom intensity relative to the marginal ice zone in both of the transects,
mean primary productivity (2.6 g C m−2 day−1) in shelf waters corresponding to the northern side of the western transect was as high as in the marginal ice zone (2.1 g C m−2 day−1), and was 4.8 times greater than that in open waters, suggesting that shelf waters are as highly productive as the marginal
ice zone. A comparison between the historical productivity data and our data also shows that the most productive regions in
the Southern Ocean are shelf waters and the marginal ice zone, with emerging evidence of frontal regions as another major
productive site.
Accepted: 27 September 1998 相似文献
6.
Cyanobacteria were a major constituent of phototrophic communities in the lakes, ponds and streams of Bylot Island, in the
Canadian high Arctic. The waters spanned a range of temperatures (1.8–16.8°C in late July), pH regimes (6.2–9.2) and conductivities
(1.5–1700 μS cm−1) but nutrient concentrations were consistently low (< 1 μg dissolved reactive P l−1 at all sites; < 10 μg NO3-N l−1 at most sites). Picoplanktonic species (Synechococcus spp.) were often the numerical dominants in the plankton, and periphytic filamentous species (Oscillatoriaceae) commonly
formed thick (5–50 mm) benthic mats. Bloom-forming species of cyanobacteria were either absent or poorly represented even
in Chla-rich ponds. The total community biomass ranged from 0.1 to 29.8 μg Chla l−1 in the plankton and from 1.1 to 34.8 μg Chla cm−2 in the benthos. The in vivo absorbance characteristics of isolates from these environments indicated a genetically diverse
range of species in each group of Arctic cyanobacteria. Growth versus irradiance relationships were determined for each of
the isolates and similarly revealed large genetic differences (maximum growth rates from 0.17 to 0.61 day−1), even between morphologically identical taxa. A comparison of nutrients, pigment concentrations and species composition
underscores the strong similarities between freshwater ecosystems in the north and south polar zones.
Received: 3 June 1996 / Accepted: 3 November 1996 相似文献
7.
Toshiya Katano Shin-ichi Nakano Hiroyuki Ueno Osamu Mitamura Kaori Anbutsu Masayuki Kihira Yasuhiro Satoh Takeshi Satoh Valentin V. Drucker Yuji Tanaka Yuki Akagashi Masahito Sugiyama 《Limnology》2008,9(3):243-250
The abundance and composition of phytoplankton were investigated at six stations along a transect from the Barguzin River
inflow to the central basin of Lake Baikal in August 2002 to clarify the effect of the river inflow on the phytoplankton community
in the lake. The water temperature in the epilimnion was high near the shore at Station 1 (17.3°C), probably due to the higher
temperature of the river water, and gradually decreased offshore at Station 6 (14.5°C). Thermal stratification developed at
Stations 2–6, and a thermocline was observed at a 17–22-m depth at Stations 2–4 and an 8–12-m depth at Stations 5 and 6. The
concentrations of nitrogen and phosphorus nutrients in the epilimnion at all stations were <1.0 μmol N l−1 and <0.16 μmol P l−1, respectively. Relatively high concentrations of nutrients (0.56–7.38 μmol N l−1 and 0.03–0.28 μmol P l−1) were detected in the deeper parts of the euphotic zone. Silicate was not exhausted at all stations (>20 μmol Si l−1). The chlorophyll a (chl. a) concentration was high (>10 μg l−1) near the shore at Station 1 and low (<3 μg l−1) at five other stations. The <2 μm fraction of chl. a in Stations 2–6 ranged between 0.80 and 1.85 μg l−1, and its contribution to total chl. a was high (>60%). In this fraction, picocyanobacteria were abundant at all stations and ranged between 5 × 104 and 5 × 105 cells ml−1. In contrast, chl. a in the >2 μm fraction varied significantly (0.14–11.17 μg l−1), and the highest value was observed at Station 1. In this fraction, the dominant phytoplankton was Aulacoseira and centric diatoms at Station 1 and Cryptomonas, Ankistrodesmus, Asterionella, and Nitzschia at Stations 2–6. The present study demonstrated the dominance of picophytoplankton in the pelagic zone, while higher abundance
of phytoplankton dominated by diatoms was observed in the shallower littoral zone. These larger phytoplankters in the littoral
zone probably depend on nutrients from the Barguzin River. 相似文献
8.
The influence of brackish phytoplankton cell classes upon the response of urea decomposition was investigated in Lake Nakaumi.
The urea decomposition rate was 5 to 350 μmol urea m−3 h−1 in the light and 3 to 137 μmol urea m−3 h−1 in the dark. The urea decomposition rates in the light were obviously higher than in the dark. An extremely high rate (350
μmol urea m−3 h−1) was observed in Yonago Bay. The rate in the smaller fraction (<5 μm) exceeded that in the middle (5–25 μm) and larger fractions
(>25 μm). The chlorophyll- and photosynthesis-specific rates for urea decomposition in the light were 0.5 to 3.9 μmol urea
mg chl.a
−1 h−1 and 0.3 to 1.3 μmol urea mg photo.C−1. The specific urea decomposing activities were higher in the smaller fraction than in the other two fractions. The present
results suggest that in brackish waters urea decomposition occurred with coupling to the standing crop and photosynthetic
activity of phytoplankton.
Received: May 22, 1999 / Accepted: August 15, 1999 相似文献
9.
The effects of temperature and light on the growth and geosmin production of Lyngbya kuetzingii were determined. Of the three temperatures tested, 10, 25 and 35°C, the maximal geosmin concentration and geosmin productivity
were yielded at 10°C, while the highest chl a production was observed at 25°C. In the studies on light intensity, the maximal geosmin concentration and geosmin productivity
were observed at 10 μmol m−2 s−1, while the highest chl a production was at 20 μmol m−2 s−1. It was suggested that more geosmin was synthesized with lower chl a demand. Meanwhile, the relative amounts of extra- and intracellular geosmin were investigated. Under optimum growth conditions
(20 μmol m−2 s−1, 25°C; BG-11 medium), the amounts of extracellular geosmin increased as the growth progressed and reached the maximum in
the stationary phase, while the intracellular geosmin reached its maximum value in the late exponential phase, and then began
to decline. However, under the low temperature (10°C) or light (10 μmol m−2 s−1) conditions, more intracellular geosmin was synthesized and mainly accumulated in the cells. The proportions of extracellular
geosmin were high, to 33.33 and 32.27%, respectively, during the stationary phase at 35°C and 20 μmol m−2 s−1. It was indicated that low temperature or light could stimulate geosmin production and favor the accumulation of geosmin
in cells, while more intracellular geosmin may be released into the medium at higher temperatures or optimum light intensity. 相似文献
10.
Spatial changes of small nanoplankton (2–10 μm) were investigated in relation to sea-ice conditions, hydrography and receding
ice processes in the Ross Sea (Antarctica) during spring 1994. Abundance and biomass of heterotrophic and autotrophic nanoplankton,
as well as bacterioplankton, were determined along a south-north transect from the open waters polynya towards the pack ice.
Autotrophic and heterotrophic nanoplankton biomass ranged from 758 to 4570 mgC m−2 and from 3 to 387 mgC m−2, respectively. Heterotrophic nanoplankton accounted, on average, for about 9% of the total (i.e. autotrophic plus heterotrophic)
nanoplankton biomass. The size structure of both auto- and heterotrophic nanoplankton in the Ross Sea continental shelf receding
ice edge was different from that of nanoplankton associated with the shelf break and open Antarctic ice-edge area. Generally,
the highest heterotrophic biomass was found in the pack-ice zone on the continental shelf, while the highest heterotrophic
contribution to the total nanoplankton biomass (up to 25%) was encountered at the shelf break where phytoplankton was largely
dominated by 2- to 3-μm-size cells.
Accepted: 2 May 1999 相似文献
11.
12.
An investigation into the changing phytoplankton biomass and total water column production during autumn sea ice formation
in the eastern Weddell Sea, Antarctica showed reduced biomass concentrations and extremely low daily primary production. Mean
chlorophyll-a concentration for the entire study period was extremely low, 0.15±0.01 mg.m−3 with a maximum of 0.35 mg.m−3 found along the first transect to the east of the grid. Areas of low biomass were identified as those either associated with
heavy grazing or with deep mixing and corresponding low light levels. In most cases phytoplankton in the <20-μm size classes
dominated. Integrated biomass to 100 m ranged from 7.1 to 28.0 mg.m−2 and correlated positively with surface chlorophyll-a concentrations. Mean PBmax (photosynthetic capacity) and αB (initial slope of the photosynthesis-irradiance curve) were 1.25±0.19 mgC. mgChla
−1.h−1 and 0.042±0.009 mgC.mgChla
−1.h−1.(μmol.m−2.s−1)−1 respectively. The mean index of photoadaptation,I
k, was 32.2±4.0 μmol.m−2.s−1 and photoinhibition was found in all cases. Primary production was integrated to the critical depth (Z
cr) at each production station and ranged from 15.6 to 41.5 mgC.m−2.d−1. It appears that, other than grazing intensity, the relationship between the critical depth and the mixing depth (Z
mix) is an important factor as, ultimately, light availability due both to the late season and growing sea ice cover severely
limits production during the austral autumn. 相似文献
13.
Luz Allende Guillermo Tell Horacio Zagarese Ana Torremorell Gonzalo Pérez José Bustingorry Roberto Escaray Irina Izaguirre 《Hydrobiologia》2009,624(1):45-60
Shallow lakes often alternate between two possible states: one clear with submerged macrophytes, and another one turbid, dominated
by phytoplankton. A third type of shallow lakes, the inorganic turbid, result from high contents of suspended inorganic material,
and is characterized by low phytoplankton biomass and macrophytes absence. In our survey, the structure and photosynthetic
properties (based on 14C method) of phytoplankton were related to environmental conditions in these three types of lakes in the Pampa Plain. The
underwater light climate was characterized. Clear-vegetated lakes were more transparent (K
d 4.5–7.7 m−1), had high DOC concentrations (>45 mg l−1), low phytoplankton Chl a (1.6–2.7 μg l−1) dominated by nanoflagellates. Phytoplankton productivity and photosynthetic efficiency (α ~ 0.03 mgC mgChla
−1 h−1 W−1 m2) were relatively low. Inorganic-turbid lakes showed highest K
d values (59.8–61.4 m−1), lowest phytoplankton densities (dominated by Bacillariophyta), and Chl a ranged from 14.6 to 18.3 μg l−1. Phytoplankton-turbid lakes showed, in general, high K
d (4.9–58.5 m−1) due to their high phytoplankton abundances. These lakes exhibited the highest Chl a values (14.2–125.7 μg l−1), and the highest productivities and efficiencies (maximum 0.56 mgC mgChla
−1 h−1 W−1 m2). Autotrophic picoplankton abundance, dominated by ficocianine-rich picocyanobacteria, differed among the shallow lakes independently
of their type (0.086 × 105–41.7 × 105 cells ml−1). This article provides a complete characterization of phytoplankton structure (all size fractions), and primary production
of the three types of lakes from the Pampa Plain, one of the richest areas in shallow lakes from South America.
Handling editor: J. Padisak 相似文献
14.
During January 1989, phytoplankton biomass and species composition were studied in a north / south transect at the Weddell / Scotia
Confluence (47°W), between 57° and 61°30′S. Results showed a diatom bloom in the Scotia Sea (chlorophyll a 1.9 μg l−1, particulate organic carbon 239 μg l−1), dominated by Fragilariopsis cylindrus, Dactyliosolen antarcticus and Chaetoceros dichaeta. Low chlorophyll a / phaeopigments ratios (about 1.4) and silicate concentrations (15 μmol l−1) suggested that this was an advanced bloom phase, probably linked to high grazing pressure. Minimum chlorophyll a values of 0.1–0.2 μg l−1 and particulate organic carbon 46 μg l−1 were found at the Weddell / Scotia Front and in a subsurface layer of the Weddell Sea Water. In the southern part of the
transect (61°30′S), in the Weddell Sea, a second surface maximum was found (chlorophyll a 0.9 μg l−1, particulate organic carbon 120 μg l−1), but with a different species composition, with Cryptomonas sp. dominant. Our results show a succession within the diatom community in the Weddell / Scotia Confluence Waters when comparing
the three EPOS legs. In the Weddell Sea from spring to summer, nanoflagellates, with only a minor contribution from diatoms,
persist over a long period with little change in the community structure. We suggest that the frontal system, together with
the receding ice edge and the grazing pressure of either krill or protozooplankton, are mainly responsible for the phytoplankton
distribution patterns found.
Received: 3 July 1996 / Accepted: 3 November 1996 相似文献
15.
Temporal patterns of primary production in a large ultra-oligotrophic Antarctic freshwater lake 总被引:3,自引:1,他引:2
A large ultra-oligotrophic Antarctic freshwater lake, Crooked Lake, was investigated between January 1993 and November 1993.
The water column supported a small phytoplankton community limited by temperature, nutrient availability and, seasonally,
by low photosynthetically active radiation. Chlorophyll a concentrations were consistently low (<1 g l−1) and showed no obvious seasonal patterns. Production rates were low, ranging from non-detectable to 0.56 g C l−1 h−1, with highest rates generally occurring towards the end of the austral winter and in spring. The pattern of carbon fixation
indicated that the phytoplankton was adapted to low light levels. Chlorophyll a specific photosynthetic rates (assimilation numbers) ranged from non-detectable to 1.27 gC (g chlorophyll a)−1 h−1. Partitioning of photosynthetic products revealed carbon incorporation principally into storage products such as lipids at
high light fluxes with increasing protein synthesis at depth. With little allochthonous input the data suggest that lake dynamics
in this Antarctic system are driven by phytoplankton activity.
Received: 21 February 1997 / Accepted: 18 May 1997 相似文献
16.
E. J. Olguín S. Galicia R. Camacho G. Mercado T. J. Pérez 《Applied microbiology and biotechnology》1997,48(2):242-247
The use of untreated sea water supplemented with anaerobic effluents from digested pig waste and sodium bicarbonate was evaluated
as a low-cost medium for semi-continuous cultivation of a mixed culture of two Spirulina strains in outdoor raceways under temperate climatic conditions (pond temperature in the range 21–26 °C and light intensity
in the range 225–957␣μE m−2 s−1). The mixed culture had a predominant population (86.6 ± 3.9%) of an atypical Spirulina strain consisting of straight filaments, which appeared spontaneously after the strain with helicoidal trichomes had been
subcultured. Morphological studies for the identification of the type and size of trichomes of the two strains (HF and SF)
were carried out. The proportions of the two strains were observed to be stable during the monitoring period (30 days). Three
different sets of semicontinuous cultures were carried out. Sets 1 and 2 were operated under regime 1 (a single addition of
anaerobic effluents at time zero and no pH control) during the same season (June and July) of different years. Set 3 was operated
under regime 2 (semi-continuous addition of anaerobic effluents and pH control) during the autumn. A minimum productivity
of 3.6 g m−2 day−1 was obtained at one of the lowest temperatures (22.1 °C) and light intensities (245 μE m−2 s−1) and a maximum productivity of 10.9 g m−2 day−1 was observed at the highest temperature (25 °C) and highest average light intensity (618 μE m−2 s−1) registered for sets 1 and 2. The protein content in the Spirulina biomass harvested from these two sets varied from 17% to 65.6%. In set 3, a maximum productivity of 9.0 g m−2 day−1 was recorded at an average temperature of 24.4 °C and at an average light intensity of 668 μE m−2 s−1. The protein content in this set under regime 2 varied within a narrower range than in set 1 and set 2 (from 34.8% to 49.1%),
apparently because of a continuous availability of ammonia nitrogen at a level of 30–50 mg l−1. However, in terms of the removal of ammonia nitrogen and chemical oxygen demand, regime 1 was more efficient than regime␣2.
Received: 3 September 1996 / Received revision: 19 February 1997 / Accepted: 7 March 1997 相似文献
17.
Phytoplankton structure and dynamics in a turbid Antarctic lake (Potter Peninsula, King George Island) 总被引:1,自引:0,他引:1
Qualitative and quantitative changes in the freshwater phytoplankton from one of the largest lakes in Potter Peninsula were
studied during the summer period of 1995/1996. The main limnological features were analysed. This research constitutes the
first study dealing with the phytoplankton structure and dynamics from lakes in Potter Peninsula. Due to the mixing of the
water column by the constant wind action during the ice-free period, neither physical, chemical nor biological parameters
showed differences between depths. Soluble reactive phosphorus remained low (26 μg l−1) while total phosphorus concentrations were up to 232 μg l−1. Suspended solids and total phosphorus differed significantly between the two basins in which the lake is divided. Sixty-five
taxa were identified. The Bacillariophyceae was the dominant class followed by Chrysophyceae. Achnanthes lanceolata var. haynaldii and Hydrurus foetidus (cysts) were the dominant species. Tychoplanktonic species were the best represented in terms of abundance and species richness.
The principal component analysis carried out with abiotic variables showed a temporal gradient characterised by the augmentation
of suspended solids, total phosphorus, conductivity, pH and NH4-N to the end of the summer period. The Principal Component Analysis performed with biotic variables also showed a temporal
trend related to a decline in phytoplankton density and an enhancement of chlorophyll-a despite a slight increase of light limitation during the study period. This inverse relation may be due to the presence of
picoplankton in chlorophyll-a samples. The potential effect of grazing on the phytoplankton structure is a subject to be tested in future studies.
Accepted: 7 February 1999 相似文献
18.
To understand the characteristics of the ecosystem in Japanese lowland marsh, we investigated chlorophyll-a (Chl. a), photosynthesis and respiration of a phytoplankton community in a brownish-colored pond in Naka-ikemi marsh, Tsuruga, Fukui
Prefecture. Chl. a concentrations and volumetric gross primary production rates ranged between 1.3–57.0 μg Chl. a l−1 and 148–1619 μg C l−1 day−1 during the study period. Higher values of Chl. a and primary production rates were clearly observed from June to September, when the dominant algae were the phytoflagellates,
Peridinium (Dinophyceae) and Cryptomonas (Cryptophyceae), with swimming ability. The trophic status of the pond water of Naka-ikemi marsh was defined as being in
eutrophic condition based on the biomass and productivity of phytoplankton. However, depths of Z
1% showing the productive layer in this study site were relatively narrower than those observed in the hyper-eutrophic Lake
Suwa with frequent cyanobacterial water bloom. Factor-attenuating underwater light intensity in Naka-ikemi marsh was presumed
to be colored dissolved organic matter. Thus, not only phytoplankton primary production, but also allochthonous organic matter
supplied from the catchment area seems to be the dominant factor in the whole energy budget of the pond. In conclusion, we
regarded the pond ecosystem in Naka-ikemi marsh to be in a eutrophic–dystrophic condition. 相似文献
19.
L. Guglielmo G. C. Carrada G. Catalano A. Dell'Anno M. Fabiano L. Lazzara O. Mangoni A. Pusceddu V. Saggiomo 《Polar Biology》2000,23(2):137-146
Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S,
164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes
of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were
studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition,
microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in
relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values
of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to
35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations
in the intact sea ice ranged from 0.5 to 2.3 mg l−1 and 0.2 to 2.0 mg l−1, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic
activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l−1 h−1 ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By
contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was
converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom
layer was high, increasing during the sampling period from 680 to 2480 μg l−1. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities.
The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P
B
max
of 0.12 mgC mg Chl−1 and low photoadaptation index (E
k=18 μE m−2 s−1, E
m=65 μE m−2 s−1). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m−2 s−1. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms.
Accepted: 4 August 1999 相似文献
20.
The spring mesozooplankton community at South Georgia: a comparison of shelf and oceanic sites 总被引:3,自引:3,他引:0
Mesozooplankton (predominantly 200–2000 μm) were sampled at a shelf and an oceanic station close to South Georgia, South
Atlantic, during austral spring (October/November) 1997. Onshelf zooplankton biomass was extremely high at 10–16 g dry mass
m−2 (0–150 m), 70% comprising the small neritic clausocalaniid copepod Drepanopus forcipatus. Large calanoid species, principally Calanoides acutus and Rhincalanus gigas, contributed only 8–10%. At the oceanic station, biomass in the sampled water column (0–1000 m) was ∼6.5 g dry mass m−2 and 4–6 g dry mass m−2 in the top 200 m. Here, large calanoids composed 40–50% of the standing stock. Antarctic krill (Euphausia superba) occurred in low abundances at both stations. Vertical profiles obtained with a Longhurst Hardy Plankton Recorder indicated
that populations of C. acutus and R. gigas, which overwinter at depth, had completed their spring ascent and were resident in surface waters. Dry mass, carbon and lipid
values were lower than found in summer but were consistent with overwintered populations. Phytoplankton concentrations were
considerably higher at the oceanic station (2–3 mg chlorophyll a m−3) and increased over the time on station. In response to this, egg production of both large calanoid species and growth rates
of R. gigas approached those measured in summer. Onshelf phytoplankton concentrations were lower (<1 mg m−3), and low egg production rates suggested food limitation. Here phytoplankton rations equivalent to 6% zooplankton body C
would have been sufficient to clear primary production whereas at the oceanic station daily carbon fixation was broadly equivalent
to zooplankton carbon biomass.
Accepted: 25 April 1999 相似文献