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1.
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
2.
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
3.
The Relationship between Phytoplankton Diversity and Community Function in a Coastal Lagoon 总被引:3,自引:0,他引:3
The decrease of biodiversity related to the phenomena of global climate change is stimulating the scientific community towards
a better understanding of the relationships between biodiversity and ecosystem functioning. In ecosystems where marked biodiversity
changes occur at seasonal time scales, it is easier to relate them with ecosystem functioning. The objective of this work
is to analyse the relationship between phytoplankton diversity and primary production in St. André coastal lagoon – SW Portugal.
This lagoon is artificially opened to the sea every year in early spring, exhibiting a shift from a marine dominated to a
low salinity ecosystem in winter. Data on salinity, temperature, nutrients, phytoplankton species composition, chlorophyll
a (Chl a) concentration and primary production were analysed over a year. Modelling studies based on production-irradiance curves
were also conducted. A total of 19 taxa were identified among diatoms, dinoflagellates and euglenophyceans, the less abundant
group. Lowest diversities (Shannon–Wiener index) were observed just before the opening to the sea. Results show a negative
correlation (p<0.05) between diversity and chlorophyll a (Chl a) concentration (0.2–40.3 mg Chl a m−3). Higher Chl a values corresponded to periods when the community was dominated by the dinoflagellate Prorocentrum minimum (>90% of cell abundance) and production was maximal (up to 234.8 mg C m−3 h−1). Maximal photosynthetic rates (Pmax) (2.0–22.5 mg C mg Chl a−1 h−1) were higher under lower Chl a concentrations. The results of this work suggest that decreases in diversity are associated with increases in biomass and
production, whereas increases correspond to opposite trends. It is suggested that these trends, contrary to those observed
in terrestrial and in some benthic ecosystems, may be a result of low habitat diversity in the water column and resulting
competitive pressure. The occurrence of the highest photosynthetic rates when Chl a is low, under some of the highest diversities, suggests a more efficient use of irradiance under low biomass–high diversity
conditions. Results suggest that this increased efficiency is not explained by potential reductions in nutrient limitation
and intraspecific competition under lower biomasses and may be a result of niche complementarity. 相似文献
4.
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
5.
We compared on eight dates during the ice-free period physicochemical properties and rates of phytoplankton and epipelic primary
production in six arctic lakes dominated by soft bottom substrate. Lakes were classified as shallow ( < 2.5 m), intermediate in depth (2.5 m < < 4.5 m), and deep ( > 4.5 m), with each depth category represented by two lakes. Although shallow lakes circulated freely and intermediate and
deep lakes stratified thermally for the entire summer, dissolved oxygen concentrations were always >70% of saturation values.
Soluble reactive phosphorus and dissolved inorganic nitrogen (DIN = NO3
−–N + NH4
+–N) were consistently below the detection limit (0.05 μmol l−1) in five lakes. However, one lake shallow lake (GTH 99) periodically showed elevated values of DIN (17 μmol l−1), total-P (0.29 μmol l−1), and total-N (33 μmol l−1), suggesting wind-generated sediment resuspension. Due to increased nutrient availability or entrainment of microphytobenthos,
GTH 99 showed the highest average volume-based values of phytoplankton chlorophyll a (chl a) and primary production, which for the six lakes ranged from 1.0 to 2.9 μg l−1 and 0.7–3.8 μmol C l−1 day−1. Overall, however, increased resulted in increased area-based values of phytoplankton chl a and primary production, with mean values for the three lake classes ranging from 3.6 to 6.1 mg chl a m−2 and 3.2–5.8 mmol C m−2 day−1. Average values of epipelic chl a ranged from 131 to 549 mg m−2 for the three depth classes, but levels were not significantly different due to high spatial variability. However, average
epipelic primary production was significantly higher in shallow lakes (12.2 mmol C m−2 day−1) than in intermediate and deep lakes (3.4 and 2.4 mmol C m−2 day−1). Total primary production (6.7–15.4 mmol C m−2 day−1) and percent contribution of the epipelon (31–66%) were inversely related to mean depth, such that values for both variables
were significantly higher in shallow lakes than in intermediate or deep lakes.
Handling editor: L. Naselli-Flores 相似文献
6.
In January 2004 the microplankton community from the coastal waters of Terre Adélie and Georges V Land (139°E–145°E) was studied.
Results showed a diatom-dominated bloom with chlorophyll a levels averaging 0.64 μg l−1 at 5 m depth (range 0.21–1.57 μg l−1). Three geographic assemblages of diatoms were identified, based on principal diatom taxa abundances. The stratified waters
near the Mertz Glacier presented highest phytoplankton biomasses (0.28–1.57 μg Chl a l−1 at 5 m) and diatom abundances (6,507–70,274 cells l−1 at 5 m), but low diversity, dominated by Fragilariopsis spp. Lower biomasses (0.38–0.94 μg Chl a l−1 at 5 m) and abundances (394–9,058 cells l−1 at 5 m) were observed in the mixed waters around the Astrolabe Glacier with a diverse diatom community characterised by larger
species Corethron pennatum and Rhizosolenia spp. Finally an intermediate zone between them over the shallower shelf waters of the Adélie Bank represented by Chaetoceros criophilus, where biomasses (0.21–0.35 μg Chl a l−1 at 5 m) and abundances (1,190–5,431 cells l−1 at 5 m) were lowest, coinciding with the presence of abundant herbivorous zooplankton. 相似文献
7.
Simon W. Wright Akira Ishikawa Harvey J. Marchant Andrew T. Davidson Rick L. van den Enden Geraldine V. Nash 《Polar Biology》2009,32(5):797-808
Filter fractionated picophytoplankton from Antarctic coastal waters (summer 2001) represented only 7–33% of total phytoplankton,
even though total stocks were low (average Chl a = 0.32 μg l−1, range = 0.13–1.03 μg l−1). Though all cells passed a 2 μm filter, electron microscopy revealed most cells were over 2 μm, principally Parmales, Phaeocystis sp., and small diatoms. CHEMTAX analysis of HPLC pigment data suggested type 8 haptophytes (e.g. Phaeocystis sp. plus Parmales and pelagophytes) contributed 7–58% of picoplanktonic chlorophyll a, type 6 haptophytes (e.g. coccolithophorids) 18–59%, diatoms 0–18% (mostly type 2 diatoms, e.g. Pseudonitzschia sp., 0–15%), prasinophytes 0–17%, with cell fragments of cryptophytes 0–40%, and dinoflagellates 0–11%. Only stocks of type
8 haptophytes and prasinophytes differed significantly due to successional changes. Zeaxanthin concentrations exceeded estimates
from previous cyanobacterial counts and may derive from non-photosynthetic bacteria. 相似文献
8.
V. I. Kolmakov O. V. Anishchenko E. A. Ivanova M. I. Gladyshev N. N. Sushchik 《Journal of applied phycology》2008,20(3):289-297
Periphyton (epilithon) gross primary production (GPP) was estimated using the DCMU-fluorescence method in the Yenisei River.
In the unshaded littoral zone, chlorophyll a concentration (Chl a) and GPP value varied from 0.83 to 973.74 mg m−2and 2–304,425 O2 m−2 day−1 (0.64–95 133 mg C m−2 day−1), respectively. Positive significant correlation (r = 0.8) between daily GPP and periphyton Chl a was found. Average ratio GPP:Chl a for periphyton was 36.36 mg C mg Chl a m−2 day−1. The obtained GPP values for the Yenisei River have a high significant correlation with values predicted by a conventional
empirical model for stream periphyton. We concluded that the DCMU-fluorescence method can be successfully used for measuring
of gross primary production of stream phytoperiphyton at least as another useful tool for such studies. 相似文献
9.
Impact of Microzooplankton and Copepods on the Growth of Phytoplankton in the Yellow Sea and East China Sea 总被引:2,自引:0,他引:2
Dilution and copepod addition incubations were conducted in the Yellow Sea (June) and the East China Sea (September) in 2003.
Microzooplankton grazing rates were in the range of 0.37–0.83 d−1 in most of the experiments (except at Station A3). Correspondingly, 31–50% of the chlorophyll a (Chl a) stock and 81–179% of the Chl a production was grazed by microzooplankton. At the end of 24 h copepod addition incubations, Chl a concentrations were higher in the copepod-added bottles than in the control bottles. The Chl a growth rate in the bottles showed good linear relationship with added copepod abundance. The presence of copepods could enhance
the Chl a growth at a rate (Z) of 0.03–0.25 (on average 0.0691) d−1 ind−1 l. This study, therefore parallels many others, which show that microzooplankton are the main grazers of primary production
in the sea, whereas copepods appear to have little direct role in controlling phytoplankton. 相似文献
10.
The Status and Characteristics of Eutrophication in the Yangtze River (Changjiang) Estuary and the Adjacent East China Sea, China 总被引:19,自引:0,他引:19
Eutrophication has become increasingly serious and noxious algal blooms have been of more frequent occurrence in the Yangtze
River Estuary and in the adjacent East China Sea. In 2003 and 2004, four cruises were undertaken in three zones in the estuary
and in the adjacent sea to investigate nitrate (NO3–N), ammonium (NH4–N), nitrite (NO2–N), soluble reactive phosphorus (SRP), dissolved reactive silica (DRSi), dissolved oxygen (DO), phytoplankton chlorophyll
a (Chl a) and suspended particulate matter (SPM). The highest concentrations of DIN (NO3–N+NH4–N+NO2–N), SRP and DRSi were 131.6, 1.2 and 155.6 μM, respectively. The maximum Chl a concentration was 19.5 mg m−3 in spring. An analysis of historical and recent data revealed that in the last 40 years, nitrate and SRP concentrations increased
from 11 to 97 μM and from 0.4 to 0.95 μM, respectively. From 1963 to 2004, N:P ratios also increased from 30–40 up to 150. In parallel with the N and P enrichment,
a significant increase of Chl a was detected, Chl a maximum being 20 mg m−3, nearly four times higher than in the 1980s. In 2004, the mean DO concentration in bottom waters was 4.35 mg l−1, much lower than in the 1980s. In comparison with other estuaries, the Yangtze River Estuary was characterized by high DIN
and DRSi concentrations, with low SRP concentrations. Despite the higher nutrient concentrations, Chl a concentrations were lower in the inner estuary (Zones 1 and 2) than in the adjacent sea (Zone 3). Based on nutrient availability,
SPM and hydrodynamics, we assumed that in Zones 1 and 2 phytoplankton growth was suppressed by high turbidity, large tidal
amplitude and short residence time. Furthermore, in Zone 3 water stratification was also an important factor that resulted
in a greater phytoplankton biomass and lower DO concentrations. Due to hydrodynamics and turbidity, the open sea was unexpectedly
more sensitive to nutrient enrichment and related eutrophication processes. 相似文献
11.
Primary production of phytoplankton and secondary production of a daphnid and a chaoborid were studied in a small eutrophic
pond. The gross primary production of phytoplankton was 290 gC m−2 per 9 months during April–December. Regression analysis showed that the gross primary production was related to the incident
solar radiation and the chlorophylla concentration and not to either total phosphorus or total inorganic nitrogen concentration. The mean chlorophylla concentration (14.2 mg m−3), however, was about half the expected value upon phosphorus loading of this pond. The mean zooplankton biomass was 1.60
g dry weight m−2, of whichDaphnia rosea and cyclopoid copepods amounted to 0.69 g dry weight m−2 and 0.61 g dry weight m−2, respectively. The production ofD. rosea was high during May–July and October and the level for the whole 9 months was 22.6 g dry weight m−2.Chaoborus flavicans produced 10 complete and one incomplete cohorts per year. Two consecutive cohorts overlapped during the growing season. The
maximum density, the mean biomass, and the production were 19,100 m−2, 0.81 g dry weight m−2, and 11.7 g dry weight m−2yr−1, respectively. As no fish was present in this pond, the emerging biomass amounted to 69% of larval production. The production
ofC. flavicans larvae was high in comparison with zooplankton production during August–September, when the larvae possibly fed not only
on zooplankton but also algae. 相似文献
12.
Neslihan Balkis 《Aquatic Ecology》2009,43(2):249-270
Seasonal changes in the microphytoplankton assemblages were examined in the coastal zone of Bozcaada Island with regard to
some major physical and chemical variables. Samples were collected from May 2000 to December 2001 at four stations. A total
of 108 dinoflagellates, 102 diatoms, 1 chrysophycean, 3 dictyochophycean, and 1 prasinophycean species were identified and
quantified during the study period. Diatoms and dinoflagellates were the most important in terms of species number and abundance.
The maximum values of total microphytoplankton were observed at 0.5 m depth (46.2 × 103 cells l−1 at st. 3) in May as this was the month when the diatom Pseudo-nitzschia pungens bloomed. Chlorophyll (chl) a concentration ranged between 0.08 (August) and 0.78 μg l−1 (February). May was another important month in which chlorophyll a increased (0.41–0.47 μg l−1). Species diversity values (H′log2) ranged from 1.66 bits (June, 20 m) to 4.11 bits (November, 0.5 m). The increase was attributed to a more balanced distribution
of abundance among species. The amounts of nitrate + nitrite (0.6−3.7 μg-at N l−1), phosphate (0.2−0.6 μg-at P l−1) and silicate (0.7−2.5 μg-at Si l−1) were recorded on each sampling occasion. Nutrient concentrations and chl a values of the research area were found to be poorer than those of the many other coastal areas in the northeastern Mediterranean.
The mean atomic ratio of nitrogen to phosphorus varied from 1.3 (June) to 12.9 (February). This ratio was lower than the Redfield
ratio of 16 for ocean phytoplankton, and phytoplankton was potentially limited by nitrogen for most of the months. The result
of this study confirms and emphasizes the oligotrophic nature of the eastern Mediterranean. 相似文献
13.
Laura Alonso-Sáez Evaristo Vázquez-Domínguez Clara Cardelús Jarone Pinhassi M. Montserrat Sala Itziar Lekunberri Vanessa Balagué Maria Vila-Costa Fernando Unrein Ramon Massana Rafel Simó Josep M. Gasol 《Ecosystems》2008,11(3):397-409
Data from several years of monthly samplings are combined with a 1-year detailed study of carbon flux through bacteria at
a NW Mediterranean coastal site to delineate the bacterial role in carbon use and to assess whether environmental factors
or bacterial assemblage composition affected the in situ rates of bacterial carbon processing. Leucine (Leu) uptake rates
[as an estimate of bacterial heterotrophic production (BHP)] showed high interannual variability but, on average, lower values
were found in winter (around 50 pM Leu−1 h−1) as compared to summer (around 150 pM Leu−1 h−1). Leu-to-carbon conversion factors ranged from 0.9 to 3.6 kgC mol Leu−1, with generally higher values in winter. Leu uptake was only weakly correlated to temperature, and over a full-year cycle
(in 2003), Leu uptake peaked concomitantly with winter chlorophyll a (Chl a) maxima, and in periods of high ectoenzyme activities in spring and summer. This suggests that both low molecular weight
dissolved organic matter (DOM) released by phytoplankton, and high molecular weight DOM in periods of low Chl a, can enhance BHP. Bacterial respiration (BR, range 7–48 μg C l−1 d−1) was not correlated to BHP or temperature, but was significantly correlated to DOC concentration. Total bacterial carbon
demand (BHP plus BR) was only met by dissolved organic carbon produced by phytoplankton during the winter period. We measured
bacterial growth efficiencies by the short-term and the long-term methods and they ranged from 3 to 42%, increasing during
the phytoplankton blooms in winter (during the Chl a peaks), and in spring. Changes in bacterioplankton assemblage structure (as depicted by denaturing gradient gel electrophoresis
fingerprinting) were not coupled to changes in ecosystem functioning, at least in bacterial carbon use. 相似文献
14.
Water and surficial sediment samples of Lake Chascomús and its tributaries were analyzed in order to relate changes in diatom
community structure to chemical variables. Over the course of 13 months of sampling, the lake exhibited major changes in water
level (1.15–1.98 m average depth), total dissolved solids (821–1972 mg l−1), silica (0.098–8.22 mg l−1), and total algal biomass (21.4–145.9 μg Chl a l−1). However, despite these large fluctuations, the diatom species composition was relatively stable. The dominant species in
the water column was always Synedra berolinensis (68.9%–90.1% total frustules), with Fragilaria construens and F. brevistriata as subdominants. In the sediments the latter two species dominated the frustule counts. These results indicate an unusual
floristic stability of this eutrophic ecosystem, with persistent dominance by broadly tolerant, generalist species.
Received: April 24, 2001 / Accepted: January 23, 2002 相似文献
15.
Motomi Genkai-Kato Miyuki Onishi Hideyuki Doi Kentaro Nozaki Kenji Yoshino Hitoshi Miyasaka Koji Omori 《Ecological Research》2008,23(6):1025-1032
We investigated the photosynthesis–light intensity (P–I) relationships of phytoplankton collected from a sublittoral sand
bank in the Seto Inland Sea, Japan, under different temperature conditions. In spite of low chlorophyll a concentration (<3 mg m−3), phytoplankton had considerably high photosynthetic potential (>10 mg C (mg chl a)−1 h−1) in the study area. Based on the P–I relationships, we conducted numerical simulation of areal primary production using published
data on water temperature, chlorophyll a concentration, and irradiance. The areal primary production ranged between 159 and 187 g C m−2 year−1. This production was within the range of typical values reported previously in deeper areas of the Seto Inland Sea. The productivity
in the sand bank area was discussed in relation to water current, allochthonous resource input, and fisheries. 相似文献
16.
Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM),
southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29,
0.62 ± 0.33 and 0.46 ± 0.19 (× 108 cells l−1), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged
∼0.35 ± 0.14 × 108 cells l−1 in SWM and 0.39 ± 0.16 × 108 cells l−1 in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m−2 d−1 during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region
are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in
SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m−2 d−1) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m−2), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and
mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions
including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further,
rapid mineralization by bacteria will make essential nutrients available to autotrophs. 相似文献
17.
The composition and ecological role of ciliates and dinoflagellates were investigated at one station in Kongsfjorden, Svalbard,
during six consecutive field campaigns between March and December 2006. Total ciliate and dinoflagellate abundance mirrored
the seasonal progression of phytoplankton, peaking with 5.8 × 104 cells l−1 in April at an average chlorophyll a concentration of 10 μg l−1. Dinoflagellates were more abundant than ciliates, dominated by small athecates. Among ciliates, aloricate oligotrichs dominated
the assemblage. A large fraction (>60%) of ciliates and dinoflagellates contained chloroplasts in spring and summer. The biomass
of the purely heterotrophic fraction of the ciliate and dinoflagellate community (protozooplankton) was with 14 μg C l−1 highest in conjunction with the phytoplankton spring bloom in April. Growth experiments revealed similar specific growth
rates for heterotrophic ciliates and dinoflagellates (<0–0.8 d−1). Food availability may have controlled the protozooplankton assemblage in winter, while copepods may have exerted a strong
control during the post-bloom period. Calculations of the potential grazing rates of the protozooplankton indicated its ability
to control or heavily impact the phytoplankton stocks at most times. The results show that ciliates and dinoflagellates were
an important component of the pelagic food web in Kongsfjorden and need to be taken into account when discussing the fate
of phytoplankton and biogeochemical cycling in Arctic marine ecosystems. 相似文献
18.
Yasuhiro Satoh Toshiya Katano Takeshi Satoh Osamu Mitamura Kaori Anbutsu Shin-ichi Nakano Hiroyuki Ueno Masaki Kihira Valentin Drucker Yuji Tanaka Tetsuro Mimura Yasunori Watanabe Masahito Sugiyama 《Limnology》2006,7(3):225-229
Nutrient limitation of the primary production of phytoplankton at some stations in southern and central Lake Baikal was studied
by nutrient enrichment experiments in August 2002. Chlorophyll (Chl.) a concentrations ranged from 0.7 to 5.8μgl−1. Inorganic nutrient concentrations were low: soluble reactive phosphorus ranged from 0.05 to 0.20μmoll−1, ammonia from 0.21 to 0.41μmoll−1, and nitrite plus nitrate from 0.33 to 0.37μmoll−1. In the five enrichment experiments, phosphate spikes and phosphate plus nitrate spikes always stimulated primary production.
Nitrate spikes also stimulated primary production in four of the experiments. Significant differences were detected between
the controls and phosphate spikes and between the controls and phosphate plus nitrate spikes. Thus, the first limiting nutrient
is thought to be phosphorus, but once phosphorus is supplied to the surface water, the limiting nutrient will quickly shift
from phosphorus to nitrogen. 相似文献
19.
This study has two main objectives, the first being the determination of net phytoplankton primary production to explain the
phytoplankton’s function in a wetland carbon cycle, while the second objective is to relate this function with the phytoplankton
assemblage composition. The annual variation in the phytoplankton production was monitored monthly for more than a year (2007–2008)
in the semiarid eutrophic, hydrologically-perturbed “Tablas de Daimiel” National Park wetland. The phytoplankton fraction
considered in this study comprised all organisms between the size 3 and 100 μm. The total biomass of phytoplankton was obtained
by counting algae and calculating their volume, while net primary production and respiration were quantified by in situ incubations
with the Winkler method. The respiration ranged from undetectable to 0.07 mgO2 l−1 h−1; net photosynthesis reached 0.20 mgO2 l−1 h−1. Net primary production was maximum at the end of the warm period (October 2007), and other peaks occurred at the start of
summer (July 2007) or spring (March 2008). When maximum production took place, phytoplankton was mainly composed of small
fast-growing chlorophytes (Tetraselmis cf. fontiana or Chlamydomonas sp.), in addition to some of the large, S-strategist algae (Peridinium
umbonatum, Microcystis flos-aquae, Euglena sp.). The phytoplankton metabolism in “Tablas de Daimiel” was autotrophic as a whole due to changing contributions of algal
groups. Only chlorophyte biomass was statistically related to net primary production. The conclusion reached is that this
shallow eutrophic semiarid wetland possessed an annual net autotrophic production of phytoplankton fraction resulting from
the small, fast-growing algae enhanced by hydrological perturbations that interrupted the autogenic course of S strategists. 相似文献
20.
Optical fractionation of chlorophyll and primary production for coastal waters of the Southern Ocean 总被引:1,自引:1,他引:0
Our objective was to quantify the potential variability in remotely sensed chlorophyll a (Chl a) and primary productivity in coastal waters of the Southern Ocean. From data collected throughout the springs/summers of
1991–1994, we calculated the proportion of water column Chl a and primary productivity within the upper optical attenuation length (K −1
par) and the satellite-weighted depth. The temporal variability was resolved every 2–3 days and was observed to be greater within
years than between years. Three-year averages (n=223) revealed that 10.2 ± 3.6% of total Chl a and 14.8 ± 6.5% of production occurred within satellite-weighted depth in predominantly Case I waters. The average values
were twice as high within K −1
par, 24.1 ± 8% of total Chl a and 34 ± 9% of production respectively. Masked in these long-term averages are very large changes occurring on short time
scales of seasonal blooms. We observed that the patterns of Chl a vertical distribution within blooms are also subject to taxonomic influence and dependent upon the physiological state of
the phytoplankton. Highest proportions of water column Chl a in the first optical depth were measured during the rapid onset of surface cryptophyte blooms each year, i.e. 50% within
K −1
par and 30% above the satellite-weighted depth. Lowest fractions, 6% and 2% of biomass within K −1
par and satellite-weighted depth respectively, were associated with peak bloom conditions independent of taxonomy. Our analyses
suggest that satellite-dependent models of Chl a and subsequent chlorophyll-dependent primary production will be challenging to develop for the near-shore Southern Ocean,
especially given the potentially high natural variability in the vertical distribution of Chl a driven by physical forcing, the photoadaptive abilities of polar phytoplankton, and taxonomic influences.
Accepted: 27 August 1999 相似文献