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1.
2.
This work constitutes the first floristic and ecological analysis of the phytoplankton community of a volcanic freshwater
lake in Deception Island (62°57′S, 60°38′W, South Shetland Islands, Antarctica). The main limnological features and phytoplankton
size fractions were analyzed. Samples were taken during the austral summer of 2002 at two opposite sites. According to ANOVA
results performed with abiotic variables, no significant differences between sites were found. The phytoplankton community
showed low algal species richness, with an important contribution of the tychoplanktonic taxa. In terms of species number,
Bacillariophyceae was the dominant class. Autotrophic picoplankton registered the highest densities from the second sampling
date onwards. Nanophytoplankton was represented by unidentified chrysophycean organisms, which showed different distribution
patterns between sites. The net phytoplankton abundance remained low during the sampling period and was strongly correlated
with chlorophyll a concentration. Both nutrient concentrations and chlorophyll a values indicated oligotrophic conditions. 相似文献
3.
The identification of the main factors driving phytoplankton community structure is essential to understand and adequately manage freshwater ecosystems. We hypothesize that differences in morphological traits reflect phytoplankton functional properties that will be selected under particular environmental conditions, namely their habitat template. We apply a morphology-based functional groups (MBFG) approach to classify phytoplankton organisms and define each group template. We use machine learning techniques to classify a large number of phytoplankton communities and environmental variables from different climate zones and continents. Random forest analysis explained well the distribution of most groups’ biovolume and the selected variables reflected ecological preferences according to morphology. By means of a classification tree it was also possible to identify thresholds of the environmental variables promoting groups dominance in different lakes. For example group III (filaments with aerotopes and high surface/volume including potentially toxic species) was dominant when light attenuation coefficient was >3.9 m−1 and total nitrogen was >2,800 μg l−1. We demonstrate that morphology captures ecological preferences of phytoplankton groups and provides empirical values to describe their habitat template. 相似文献
4.
Abundance of picophytoplankton in the halocline of a meromictic lake, Lake Suigetsu, Japan 总被引:1,自引:0,他引:1
Mari Okada Yukiko Taniuchi Akio Murakami Shinichi Takaichi Shinya Ohtake Kaori Ohki 《Limnology》2007,8(3):271-280
Numerous (0.5 to 4.8 × 105 cells/ml), small phytoplankton (smaller than 0.5–1 × 1–2 μm in cell size, picophytoplankton) were distributed in the halocline
(depth 2–12 m, 4–14 practical salinity units) of the saline meromictic lake, Lake Suigetsu (35°35′ N, 135°52′ E), located
in the central part of the coast of Wakasa Bay along the Japan Sea in Fukui Prefecture, Japan. Vertical distribution of phytoplankton
revealed that the maximum number of picophytoplankton was always observed near or a little deeper than the oxic-anoxic boundary
layer (depth 5–6 m); they were dominant phytoplankton in the water layer deeper than the oxic-anoxic boundary from July to
late September 2005. Spectral analysis of autofluorescence emitted from the particle fractions smaller than 5 μm measured
with a spectrofluorometer and from individual cells measured with a microscope photodiode array detector revealed that the
major component of picophytoplankton was phycoerythrin-rich, unicellular cyanobacteria (picocyanobacteria). Eukaryotic phytoplankton
about 2.5 μm in diameter were also found, but the numbers were low. Fluorescence intensity of chlorophyll a at 685 nm (room temperature) emitted from the particle fractions smaller than 5 μm was increased by the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea.
These observations indicated that at least some picophytoplankton had a functional photosystem II in the halocline where sulfide,
the potential inhibitor of oxygenic photosynthesis, was always present. The large abundance together with their physiological
potency suggest that picophytoplankton are one of the important primary producers in the halocline of Lake Suigetsu.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
5.
Elena Litchman 《Oecologia》1998,117(1-2):247-257
Light is a major resource in aquatic ecosystems and has a complex pattern of spatio-temporal variability, yet the effects
of dynamic light regimes on communities of phytoplankton are largely unexplored. I examined whether and how fluctuating light
supply affects the structure and dynamics of phytoplankton communities. The effect of light fluctuations was tested at two
average irradiances: low, 25 μmol quanta m−2 s−1 and high, 100 μmol quanta m−2 s−1 in 2- and 18-species communities of freshwater phytoplankton. Species diversity, and abundances of individual species and
higher taxa, depended significantly on both the absolute level and the degree of variability in light supply, while total
density, total biomass, and species richness responded only to light level. In the two-species assemblage, fluctuations increased
diversity at both low and high average irradiances and in the multispecies community fluctuations increased diversity at high
irradiance but decreased diversity at low average irradiance. Species richness was higher under low average irradiance and
was not affected by the presence or absence of fluctuations. Diatom abundance was increased by fluctuations, especially at
low average irradiance, where they became the dominant group, while cyanobacteria and green algae dominated low constant light
and all high light treatments. Within each taxonomic group, however, there was no uniform pattern in species responses to
light fluctuations: both the magnitude and direction of response were species-specific. The temporal regime of light supply
had a significant effect on the growth rates of individual species grown in monocultures. Species responses to the regime
of light supply in monocultures qualitatively agreed with their abundances in the community experiments. The results indicate
that the temporal regime of light supply may influence structure of phytoplankton communities by differentially affecting
growth rates and mediating species competition.
Received: 24 September 1997 / Accepted: 8 July 1998 相似文献
6.
George B. McManus Barbara A. Costas Hans G. Dam Rubens M. Lopes Salvador A. Gaeta Sylvia M. Susini Carol H. Rosetta 《Hydrobiologia》2007,575(1):69-81
We measured grazing by herbivorous zooplankton (<200 μm fraction) in coastal and slope regions of the South Brazil Bight.
Using the dilution technique, we performed nine experiments during the austral summer, when nutrient-rich South Atlantic Central
Water is present on the shelf, and five during winter. These experiments provide the first estimates of microzooplankton grazing
in the western South Atlantic Ocean. Model II regression showed a strong relationship between phytoplankton intrinsic growth
rates and grazing, with a slope of 0.64 (±0.28; 95% confidence interval) indicating that microzooplankton grazing could account
for the majority of phytoplankton mortality. Both phytoplankton growth and microzooplankton grazing were higher during the
summer upwelling season, compared to winter. For the two experiments that were conducted in oligotrophic slope water, grazing
accounted for >80% of phytoplankton production. A comparison of incubations with and without added inorganic nutrients showed
no consistent stimulation of phytoplankton growth (slope of enriched versus unenriched treatments not significantly different
from 1). Estimates from microscopic counts of heterotrophic organisms >10 μm indicated that copepod nauplii comprised the
largest share of the microzooplankton biomass (mean 62.4 ± 5.8% SE). Grazing estimates were not correlated with microzooplankton
biomass, whether or not nauplii were included, suggesting that most of the grazing was done by nano-sized zooplankton.
Electronic Supplementary Material Electronic supplementary material is available in the online version of this article at and is accessible for authorized users.
Handling editor: S. Wellekens 相似文献
7.
We conducted a 1-year survey in two humic shallow lakes from the floodplain of the Lower Paraná River, Laguna Grande Lake (LGL) and a relictual oxbow lake (ROL). We aimed to test two hypotheses: (1) the efficiency in light use of picoplankton (0.2–3 μm) is greater as light restriction increases and (2) the contribution of picoplankton to the total productivity is higher when the total photosynthetic biomass is lower. We performed P–E curves for picoplankton and nano- and microplankton (>3 μm) using the 14C assimilation technique. The light environments of the water bodies differed mainly owing to the development of free floating plants on the surface of the ROL and the dominance of phytoplankton in LGL. Primary productivity patterns in LGL were seasonality driven whilst in the ROL they were related to the coverage of floating macrophytes, which promoted light limitation and a lower productivity. In LGL, nano- and microplankton were in general more productive and the relative contribution of picoplankton to the total phytoplankton production decreased with the increase in total photosynthetic biomass. Hence, our study extends previously observed patterns to subtropical shallow lakes, where seasonality and free floating plants may influence the dynamics of phytoplankton production. 相似文献
8.
Kwang-Hyeon Chang Masaki Sakamoto Jin-Yong Ha Yuichi Miyabara Shin-ichi Nakano Hideyuki Doi Takayuki Hanazato 《Limnology》2011,12(1):11-16
The methylthiotriazine herbicide, simetryn, is commonly used in Japan, and its concentration in surface water is often high
enough to affect natural phytoplankton. To estimate how the plankton community in eutrophic systems respond to short-term
exposure of realistic concentrations of simetryn, we collected plankton from a eutrophic lake and exposed them to low (20 μg l−1) and high (100 μg l−1) concentrations of simetryn for 12 days in microcosm tanks (50 l). High concentrations significantly lowered total phytoplankton
biomass, particularly green algal density. Consequently, the species composition was severely modified by simetryn application.
However, there was no apparent impact of simetryn on microbial food-web components, bacteria, heterotrophic nanoflagellates
(HNF), and ciliates. Despite the decreased abundance of algal food, the zooplankton community showed subtle changes with simetryn
application. The results indicate that the direct impact of simetryn on planktonic organisms other than phytoplankton, particularly
on microbial food-web components, is weak. The indirect impact of simetryn on zooplankton through the change of food quality
and quantity was also small. It has been suggested that the persistence of microorganisms, alternative food for zooplankton,
probably dilutes the indirect impact of simetryn on zooplankton by compensating for the loss of food phytoplankton. Consequently,
the plankton community in eutrophicated systems is resistant to the herbicide at a feasible concentration for a short period
of time. 相似文献
9.
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
10.
The specific inherent optical properties of three sub-tropical and tropical water reservoirs in Queensland, Australia 总被引:2,自引:0,他引:2
The underwater light climate, which is a major influence on the ecology of aquatic systems, is affected by the absorption
and scattering processes that take place within the water column. Knowledge of the specific inherent optical properties (SIOPs)
of water quality parameters and their spatial variation is essential for the modelling of underwater light fields and remote
sensing applications. We measured the SIOPs and water quality parameter concentrations of three large inland water impoundments
in Queensland, Australia. The measurements ranged from 0.9 to 42.7 μg l−1 for chlorophyll a concentration, 0.9–170.4 mg l−1 for tripton concentration, 0.36–1.59 m−1 for a
CDOM(440) and 0.15–2.5 m for Secchi depth. The SIOP measurements showed that there is sufficient intra-impoundment variation in
the specific absorption and specific scattering of phytoplankton and tripton to require a well distributed network of measurement
stations to fully characterise the SIOPs of the optical water quality parameters. While significantly different SIOP sets
were measured for each of the study sites the measurements were consistent with published values in other inland waters. The
multiple measurement stations were allocated into optical domains as a necessary step to parameterise a semi-analytical inversion
remote sensing algorithm. This article also addresses the paucity of published global inland water SIOP sets by contributing
Australian SIOP sets to allow international and national comparison. 相似文献
11.
Size-fractionated chlorophyll a (Chla)-specific productivity (μgC μgChla
−1 h−1) was measured at 11 stations off the northern coast of the South Shetland Islands during summer. The Chla-specific productivity of the 2- to 10 or 10- to 330-μm fraction was highest at 100% and 23% light depths. The Chla-specific productivity of the 2- to 10-μm fraction was generally highest, and that of the <2 or 10- to 330-μm fraction was
sometimes highest at 12% and 1% light depths. Temperature was less than 3°C within the euphotic zone at all stations. The
hypothesis of Shiomoto et al., according to which Chla-specific productivity of picophytoplankton (<2 μm) is not significantly higher than that of larger phytoplankton (>2 μm)
in water colder than 10°C, was supported on condition that light is not limited for larger phytoplankton.
Received: 16 September 1997 / Accepted: 8 December 1997 相似文献
12.
José Juan Barrera-Alba Sônia Maria Flores Gianesella Gleyci Aparecida Oliveira Moser Flávia Marisa Prado Saldanha-Corrêa 《Hydrobiologia》2008,598(1):229-246
Heterotrophic bacterial and phytoplankton biomass, production, specific growth rates and growth efficiencies were studied
in July 2001 and January 2002 during both spring and neap tides, along a tidal cycle, at three sites in a subtropical estuary.
Major freshwater inputs located in the Northern region led to differences in both phytoplankton and bacterioplankton biomass
and activity along the estuary. While in the Northern region phytoplankton is light-limited, with mean phytoplankton production
(PP) between 1.1 and 1.9 μg C l−1 h−1 and mean specific growth rates (PSG) between 0.14 and 0.16 d−1, the Southern region registered values as high as 24.7 μg C l−1 h−1 for PP and 2.45 d−1 (mean PP between 3.4 and 7.3 μg C l−1 h−1; mean PSG between 0.28 and 0.57 d−1). On the other hand, maximum bacterial production (BP: 63.8 μg C l−1 h−1) and specific growth rate (BSG: 32.26 d−1) were observed in the Northern region (mean BP between 3.4 and 12.8 μg C l−1 h−1; mean BSG between 1.98 and 6.67 day−1). These bacterial activity rates are among the highest recorded rates in estuarine and coastal waters, indicating that this
system can be highly heterotrophic, due to high loads of allochthonous carbon (mainly derived from mangrove forest). Our results
also showed that, despite that BP rates usually exceeded PP, in the Southern region BP may be partially supported (∼45%) by
PP, since a significant regression was observed between BP and PP (r = 0.455, P < 0.001).
Handling editor: P. Viaroli 相似文献
13.
The principal environmental factors influencing the seasonal dynamics of phytoplankton were examined from September 1997 to
July 1998 in three stations along a 26-km stretch of the lowland course of River Adige (northeast Italy). Nutrient concentrations
did not appear to be limiting for the phytoplankton growth. Annual minimum concentrations of reactive and total phosphorus,
and dissolved inorganic nitrogen were 22 μg P l−1, 63 μg P l−1 and 0.9 mg N l−1, respectively. The most critical forcing factors were physical variables, mainly water discharge and other variables related
to hydrology, i.e. suspended solids and turbidity, which acted negatively and synchronously by diluting phytoplankton cells
and decreasing light availability. Higher algal biomass was recorded in early spring, in conditions of lower flow velocity
and increasing water temperature. In late spring and summer, higher water discharge caused a decrease in phytoplankton biomass.
Conversely, low algal biomass in late autumn and winter, during low discharge, was mainly related to low water temperatures
and shorter photoperiod. Physical constraints had a significant and measurable effect not only on the development of total
biomass, but also on the temporal dynamics of the phytoplankton community. Abiotic and biotic variables showed a comparable
temporal development in the three sampling stations. The small number of instances of spatial differences in phytoplankton
abundance during the period of lower flow velocity were related to the increasing importance of biological processes and accumulation
of phytoplankton biomass. 相似文献
14.
The use of higher plants as the basis for a biological life support system that regenerates the atmosphere, purifies water, and produces food has been proposed for long duration space missions. The objective of these experiments was to determine what effects microgravity (μg) had on chloroplast development, carbohydrate metabolism and gene expression in developing leaves of Triticum aestivum L. cv. USU Apogee. Gravity naive wheat plants were sampled from a series of seven 21-day experiments conducted during Increment IV of the International Space Station. These samples were fixed in either 3% glutaraldehyde or RNAlater™ or frozen at −25°C for subsequent analysis. In addition, leaf samples were collected from 24- and 14-day-old plants during the mission that were returned to Earth for analysis. Plants grown under identical light, temperature, relative humidity, photoperiod, CO2, and planting density were used as ground controls. At the morphological level, there was little difference in the development of cells of wheat under μg conditions. Leaves developed in μg have thinner cross-sectional area than the 1 g grown plants. Ultrastructurally, the chloroplasts of μg grown plants were more ovoid than those developed at 1 g, and the thylakoid membranes had a trend to greater packing density. No differences were observed in the starch, soluble sugar, or lignin content of the leaves grown in μg or 1 g conditions. Furthermore, no differences in gene expression were detected leaf samples collected at μg from 24-day-old leaves, suggesting that the spaceflight environment had minimal impact on wheat metabolism.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
15.
In the Schelde continuum, a succession in the phytoplankton community is observed along the transition from the river to the freshwater tidal reaches of the estuary and from the freshwater to brackish reaches of the estuary. The goal of this study was to experimentally evaluate the contribution of changes in salinity and light climate to this succession. In summer 2000 and in spring 2001, phytoplankton communities from the river, the freshwater tidal reaches and the brackish reaches of the estuary were incubated under high or low light intensities and exposed to a change in salinity. HPLC analysis was used to evaluate the response of different algal groups to changes in light intensity and salinity. When incubated at a light intensity corresponding to the mean underwater light intensity of the freshwater tidal reaches, growth of phytoplankton from the river as well as from freshwater tidal reaches was significantly lower than when incubated at a light intensity corresponding to the mean underwater light intensity of the river. The phytoplankton community from the freshwater tidal reaches did not appear to be better adapted to low light intensities than the phytoplankton community from the river. Although diatoms were expected to be less sensitive to a reduction in light intensity than green algae, the opposite response was observed. Freshwater and brackish water phytoplankton were negatively affected by respectively an increase or decrease in salinity. However, the effect of salinity was not strong enough to explain the disappearance of freshwater and brackish water phytoplankton between a salinity of 0.5 and 10 psu, suggesting that other factors also play a role. In the freshwater phytoplankton communities from the river and the freshwater tidal reaches, green algae and diatoms responded in a similar way to an increase in salinity. In the brackish water phytoplankton community, fucoxanthin displayed a different response to salinity than lutein and chlorophyll a. 相似文献
16.
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
17.
Contribution of Picocyanobacteria to total primary production and community respiratory losses in a backwater system 总被引:2,自引:0,他引:2
The contribution of autotrophic picoplankton (APP) to phytoplanktonicprimary production, investigated during the phytoplankton growingseason (MarchSeptember) in a macrophyte-dominated backwatersystem near Vienna, showed that APP mainly consisted of rod-shapedand coccoid cyanobacteria. Two stations were examined, exhibitingsimilar seasonal patterns in the development of picocyanobacteria,although the two sites differed in picocyanobacterial cell numbersand biomass by a factor of 1.5. Cell numbers determined by epifluorescencemicroscopy varied between 0.29 x 104 and 34.5 x 104 cells ml1at Station 1, and between 0.23 x 104 and 19.1 x 104 cells ml1at Station 2. At both sites, the mean cell volume of picocyanobacteriawas 0.5 µm3. Carbon fixation in the planktonic communityof the Kühwörter Wasser was dominated primarily bylarger phytoplankton, although the picoplankton community sometimessupplied up to 74% (mean: 35%) of total primary production.Distinct differences in chlorophyll a concentrations and primaryproduction between the two sites refer to a greater competitionbetween phytoplankton and macrophytes at Station 2. Communityrespiration deviated greatly in time and in level at the twostations, showing a higher dynamic in community metabolism atStation 1. At this site, community respiration losses rangedbetween 12 and 100% of gross production. Hence, community metabolismcomprised net autotrophic, balanced, and net heterotrophic situationsover the investigation period, whereas at Station 2, only netautotrophic situations could be determined. 相似文献
18.
Molly A. Palmer Kevin R. Arrigo C. J. Mundy Jens K. Ehn Michel Gosselin David G. Barber Johannie Martin Eva Alou Suzanne Roy Jean-��ric Tremblay 《Polar Biology》2011,34(12):1915-1928
During summer 2008, as part of the Circumpolar Flaw Lead system study, we measured phytoplankton photosynthetic parameters
to understand regional patterns in primary productivity, including the degree and timescale of photoacclimation and how variability
in environmental conditions influences this response. Photosynthesis–irradiance measurements were taken at 15 sites primarily
from the depth of the subsurface chlorophyll a (Chl a) maximum (SCM) within the Beaufort Sea flaw lead polynya. The physiological response of phytoplankton to a range of light
levels was used to assess maximum rates of carbon (C) fixation (P
m*), photosynthetic efficiency (α
*), photoacclimation (E
k), and photoinhibition (β
*). SCM samples taken along a transect from under ice into open water exhibited a >3-fold increase in α
* and P
m*, showing these parameters can vary substantially over relatively small spatial scales, primarily in response to changes in
the ambient light field. Algae were able to maintain relatively high rates of C fixation despite low light at the SCM, particularly
in the large (>5 μm) size fraction at open water sites. This may substantially impact biogenic C drawdown if species composition
shifts in response to future climate change. Our results suggest that phytoplankton in this region are well acclimated to
existing environmental conditions, including sea ice cover, low light, and nutrient pulses. Furthermore, this photoacclimatory
response can be rapid and keep pace with a developing SCM, as phytoplankton maintain photosynthetic rates and efficiencies
in a narrow “shade-acclimated” range. 相似文献
19.
Miguel Alvarez Cobelas 《International Review of Hydrobiology》1991,76(2):213-223
The underwater light field has been studied in a hypertrophic, gravel-pit lake close to Madrid (Spain) during a one year cycle. Both the inherent and the apparent properties of the underwater light field have been weekly surveyed. As theoretically expected, there is a link between inherent and apparent properties in this lake. Evidence is given suggesting that a seasonal trend in the underwater light field seems to occur. The main factor attenuating light in the vertical column is phytoplankton chlorophyll “a” but humic substances also appear to play an importtant role in light attenuation. 相似文献
20.
Norbert Kemka Serge Hubert Zébazé Togouet Robert Patrick Djogo Kinfack Moïse Nola Samuel Foto Menbohan Thomas Njiné 《Hydrobiologia》2009,625(1):91-103
This study carried out within the framework of a multi-disciplinary project, aimed at highlighting the fundamental processes
governing the functioning of the hypertrophic Yaoundé Municipal Lake. It was based on the hypothesis that, even within a small
range of lake trophic status, important variations can occur in the species composition, biomass and photosynthetic activity
of the phytoplankton size-fractions. For this purpose, samples were taken at weekly intervals from November 1996 to December
1997 at a fixed set of depths in the water column. Spatial-temporal fluctuations of some physical–chemical variables, associated
with biological variables such as phytoplankton size-class species composition, phytoplankton size-class biomass, phytoplankton
primary production and chlorophyll-a were analysed. The water transparency was low and rarely exceeded 100 cm. Conductivity values relatively higher increased
generally from the top to the lake bottom. The oxygen deficiency, and sometimes anoxia, recorded from 2.5 m depth resulted
in high quantities of ammonium nitrogen. Total phosphorus and total Kjeldahl nitrogen concentrations were characteristics
of hypertrophic lakes. The fertility of this biotope favoured the development of a high phytoplanktonic community with remarkable
physiological adaptations to the variations of the nutritive potentials of the lake, characterized by the size-structure of
these organisms. Cells of small size (<12 μm) contributed up to 11.42% of the total phytoplanktonic biomass. Species with
average size (12–45 μm), dominated by Chlamydomonas spp., represented a more significant contribution reaching up to 69.85%, whereas the cells of big size (>45 μm), mainly Euglenophyta,
maintained the relatively most important biomass, accounting for up to 89.85% of the total phytoplanktonic biomass. Chlorophyll-a concentrations are among the highest reported for both fresh water and sea water, being a consequence of high proportions
of Chlorophyta and Euglenophyta. This led to intense phytoplanktonic photosynthetic activity which continued throughout the
year, even though it was confined to the upmost first meter of the water column. Analyses pointed out the allogenic nature
of the functioning of this urban lake ecosystem, due to a poor waste management on the surrounding landscape.
Handling editor: J. Padisak 相似文献