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1.
2.
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
3.
Phytoplankton functional traits can represent particular environmental conditions in complex aquatic ecosystems. Categorizing phytoplankton species into functional groups is challenging and time‐consuming, and requires high‐level expertise in species autecology. In this study, we introduced an affinity analysis to aid the identification of candidate associations of phytoplankton from two data sets comprised of phytoplankton and environmental information. In the Huaihe River Basin with a drainage area of 270,000 km2 in China, samples were collected from 217 selected sites during the low‐water period in May 2013; monthly samples were collected during 2006–2011 in a man‐made pond, Dishui Lake. Our results indicated that the affinity analysis can be used to define some meaningful functional groups. The identified phytoplankton associations reflect the ecological preferences of phytoplankton in terms of light and nutrient acquisition. Advantages and disadvantages of applying the affinity analysis to identify phytoplankton associations are discussed with perspectives on their utility in ecological assessment. 相似文献
4.
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
5.
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
6.
Weekly dynamics of phytoplankton functional groups under high water level fluctuations in a subtropical reservoir-bay 总被引:8,自引:0,他引:8
In reservoirs, water level fluctuations strongly influence phytoplankton development. However, studies on the response of
phytoplankton in the reservoir-bay to water level fluctuations are very scarce, especially in the highly dynamic reservoir
system, for instance, the Three Gorges Reservoir (TGR) on the Yangtze River in China. Therefore, we carried out weekly monitoring
in a typical tributary bay—Xiangxi Bay of the TGR from March 2008 to March 2009, to analyze the dynamics of phytoplankton
functional groups, as well as their response to the water level fluctuations and other environmental conditions. The phytoplankton
functional groups G (short, nutrient-rich water columns with high light and without nutrient deficiency), M (dielly mixed
layers of small eutrophic, low latitude with high insolation and without flushing and low total light) and Lo (summer epilimnia
in mesotrophic lakes with segregated nutrients and without prolonged or deep mixing) were the most important in biomass, mainly
represented by Pandorina morum and Eudorina elegans, Microcystis aeruginosa, Peridiniopsis niei and Ceratium hirundinella, respectively. The dominant functional groups had close relationships with the water level fluctuations, light and nutrient,
etc. Principal components analysis and redundancy analysis indicated that phytoplankton functional groups in Xiangxi Bay were
restricted by the mixing regime and other abiotic variables under the influences of the mixing regime. In Xiangxi Bay, the
water level fluctuation showed significant correlations with many physicochemical variables, including the mixing depth (r = 0.97, p < 0.001) and the relative water column stability (r = −0.80, p < 0.001). The study implied that water level fluctuations had complex influence on environmental changes and selecting for
phytoplankton functional groups in a highly dynamic reservoir-bay. The important characteristics of the dominant phytoplankton
functional groups in Xiangxi Bay were also discussed. 相似文献
7.
Spatial and temporal variation of phytoplankton in two subtropical Brazilian reservoirs 总被引:3,自引:2,他引:1
Paula Aparecida Federiche Borges Sueli Train Luzia Cleide Rodrigues 《Hydrobiologia》2008,607(1):63-74
The purpose of this study was to verify the longitudinal distribution of phytoplankton biomass in two subtropical Brazilian
reservoirs in the State of Paraná and investigate intervening factors on changes in phytoplankton biomass according to functional
groups. In the Capivari and Segredo reservoirs, samples were obtained every 3 months during 2002, along a longitudinal axis
(fluvial, transition, and lacustrine zones) at different depths. One hundred and eighteen taxa were identified, with Chlorophyceae
as the most specious group. During the study period, both reservoirs had mostly low biomass values (less than 1 mm3 l−1). The short retention time of these reservoirs constituted the principal limiting factor to phytoplankton development. Biomass
values above 1 mm3 l−1 were observed in the Capivari fluvial zone in March and in the Segredo lacustrine zone in December, with dominance by Microcystis aeruginosa Kütz (LM) and Anabaena circinalis Rab. (H1), respectively. Vertical and horizontal gradients of analyzed abiotic variables and phytoplankton biomass were observed.
Considering the phytoplankton biomass values, both reservoirs were oligotrophic for the duration of the study. The Canonical
Correspondence Analysis (CCA) evidenced temporal and spatial gradients of phytoplankton biomass; nevertheless, it did not
follow the classic model proposed for deep reservoirs, since higher biomass was registered in the lacustrine zone during some
months and in fluvial zones during other months. Distinct functional groups of phytoplankton characterized both studied reservoirs.
Capivari Reservoir was best characterized by LM and Y groups, indicative of its greater water column stability and higher phosphorus concentration, whereas Segredo Reservoir
was principally characterized by the MP functional group, indicative of its greater mixing zone extension and higher nitrate
concentration. The obtained results also evidenced the influence of morphometric conditions and watershed purposes as important
structuring factors of phytoplankton biomass in these reservoirs.
Handling editor: L. Naselli-Flores 相似文献
8.
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
9.
Research was carried out to determine aquatic oligochaete habitat preferences in the Rokytná River (Thaya River basin), a
sixth order highland stream in the Czech Republic during the period of April 1999–April 2001. Quantitative samples were collected
and current velocity and basic physico-chemical variables were measured monthly in four typical habitats in the Rokytná River.
During this study, 28, 842 individuals representing 44 oligochaete species or higher taxa were collected. Temporal variability
of proportional occurrence of trophic groups found on selected habitats (gathering collectors and grazers) was analysed. Habitat
preferences of oligochaete species were evaluated by Canonical Correspondence Analysis (CANOCO). Biochemical oxygen demand
(BOD) and nitrate (NO3−) ion concentration were the most important variables explaining the distribution of Oligochaeta along the first axis. Current
velocity (at 40% of the depth) and presence of oligochaetes associated with the habitat where gravel bars never formed were
the most important variables along the second axis. Both axes were correlated with the temperature, reflecting the sampling
in summer along the first axis and sampling in late spring along the second axis. The amount of organic matter (BOD) and concentrations
of NO3− ions represented both oligochaete food source and decomposition products contributing to the growth of algae. Current velocity
and preferred habitat explained the spatial pattern of oligochaete distributions. 相似文献
10.
Xiuyun Cao Chunlei Song Yiyong Zhou Alena Štrojsová Petr Znachor Eliška Zapomělová Jaroslav Vrba 《Limnology》2009,10(2):95-104
Extracellular phosphatases are an important part of the phosphorus cycle in aquatic environments. Phosphatase activity (PA)
in plankton was studied in seven subtropical shallow lakes of different exploitation management and trophic status in the
urban area of Wuhan City. Bulk PA was rather high (range 1.1–11 μmol l−1 h−1), although concentrations of soluble reactive phosphorus (SRP) were also high (range 27 μg P l−1 to ~1.5 mg P l−1) in all lakes. Cell-associated extracellular PA in phytoplankton was detected using the fluorescence-labelled enzyme activity
technique. Phytoplankton species partly contributed to the bulk PA. We found explicit differences in the presence of cell-associated
phosphatase within the main phytoplankton groups; species belonging to Chlorophyta and Dinophyta were regularly phosphatase-positive,
while Cyanophyta and Bacillariophyceae were phosphatase-negative in all but one case. Furthermore, there is a certain potential
of extracellular phosphatases produced by heterotrophic nanoflagellates in most of the lakes. This new finding compromises
the ‘traditional’ interpretation of bulk phosphatase data as being due to overall phytoplankton or bacterial P regeneration. 相似文献
11.
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
12.
R. C. Wilson J. Vives i Batlle S. J. Watts P. McDonald S. R. Jones A. Craze 《Radiation and environmental biophysics》2010,49(1):87-95
A conceptual model of the effects of chronic radiation on a population of phytoplankton and zooplankton in an oceanic nutrient
layer is presented. The model shows that there are distinct threshold dose rates at which the different plankton populations
become unsustainable. These are 10,400 μGy h−1 for phytoplankton and 125 μGy h−1 for zooplankton. Both these values are considerably greater than the current screening values for protection of 10 μGy h−1. The model highlights the effects of predator–prey dynamics in predicting that when the zooplankton is affected by the radiation
dose, the phytoplankton population can increase. In addition, the model was altered to replicate the dose rates to the plankton
of a previous ERICA Irish Sea assessment (24 μGy h−1 for zooplankton and 430 μGy h−1 to phytoplankton). The results showed only a 10% decrease in the zooplankton population and a 15% increase in the phytoplankton
population. Therefore, at this level of dose, the model predicts that although the dose rate exceeds the guideline value,
populations are not significantly affected. This result highlights the limitations of a single screening value for different
groups of organisms. 相似文献
13.
The objective of this study is to describe the biogeochemical characteristics in the waters of Mongolian lakes, particularly
those related to parameters limiting phytoplankton growth and the trophic state. Investigations into the distribution of chemical
and biological parameters were carried out in the following 18 lakes: Har Us, Har, Hovsgol, Achit, Dalai, Bayan, Tolbo, Holboo,
Bust, Sangiyn Dalai, Tunamal, Dorgon, Uureg, Telmen, Hyargas, Uvs, Erkhel and Oygon, all of which showed a wide range of salinity
between 0.16 and 24.9 g l−1. Lake water was classified into four types: six fresh (less than 0.5 g l−1 salinity), three subsaline (0.5–3 g l−1), seven hyposaline (3–20 g l−1) and two mesosaline (20–50 g l−1) lakes. Predominant cations and anions in the order of dominance were Ca, Mg > Na > K and HCO3 > SO4, Cl in freshwater lakes, Na > Mg > Ca, K and HCO3, Cl > SO4 in subsaline lakes, and Na > Mg > K, Ca and Cl, SO4 > HCO3 in hyposaline and mesosaline lakes. Nitrogenous and phosphorus nutrients in the waters were low, seemingly caused by the
low loads from their watersheds, where the ground was free of vegetation with an extremely low level of human activity. The
present investigations revealed some 234 taxa of phytoplankton and 38 of zooplankton. The PC:PN:PP stoichiometric ratio by
weight was (22–202):(3–27):1. Phosphorus was assessed as the potential limiting parameter in eight lakes, nitrogen in six
and both nutrients in four others. Twelve lakes showed an oligotrophic character, while six were mesotrophic type. The six
oligotrophic lakes seemed to be subject to phosphorus limiting phytoplankton growth, four to nitrogen and two to both limitations.
In the mesotrophic lakes, on the other hand, phosphorus limitation was verified in two lakes, nitrogen in two others and both
in two lakes. 相似文献
14.
Tolerance of environmental variables differs between corals and their dinoflagellate symbionts (Symbiodinium spp.), controlling the holobiont’s (host and symbiont combined) resilience to environmental stress. However, the ecological
role that environmental variables play in holobiont distribution remains poorly understood. We compared the drivers of symbiont
and coral species distributions at Palmyra Atoll, a location with a range of reef environments from low to high sediment concentrations
(1–52 g dry weight m−2 day−1). We observed uniform holobiont partnerships across the atoll (e.g. Montipora spp. with Symbiodinium type C15 at all sites). Multivariate analysis revealed that field-based estimates of settling sediment predominantly explained
the spatial variation of coral species among sites (P < 0.01). However, none of the environmental variables measured (sedimentation, temperature, chlorophyll concentration, salinity)
affected symbiont distribution. The discord between environmental variables and symbiont distributions suggests that the symbionts
are physiologically tolerant of the variable environmental regime across this location and that the distribution of different
host–symbiont combinations present is largely dependent on coral rather than Symbiodinium physiology. The data highlight the importance of host tolerance to environmental stressors, which should be considered simultaneously
with symbiont sensitivity when considering the impact of variations in environmental conditions on coral communities. 相似文献
15.
Abstract
Seasonal variation in bacterioplankton abundance, biomass, and bacterioplankton production was studied over eight years in
hypertrophic Lake S?byg?rd. Biologically, the lake is highly variable; this is due mainly to large interannual variation in
fish recruitment. Bacterioplankton production was low during winter, typically 1–3 × 107 cells l−1 h−1, and high during summer, albeit greatly fluctuating with maximum rates typically ranging from 60 to 90 × 107 cells l−1 h−1 (or 0.4 to 0.6 mg C l−1 day−1). Less pronounced variations were found in bacterioplankton abundance, which typically ranged from 3–8 × 109 cells l−1 in winter to 15–30 × 109 cells l−1 during summer. The specific growth rate of bacterioplankton varied from 0.02–0.2 d−1 in winter to 0.5–2.3 day−1 during summer. Interpolated mean bacterioplankton production, in terms of carbon, ranged from 0.08 to 0.16 mg C l−1 day−1, corresponding to 1.6–5.5% of the phytoplankton production, while biomass ranged from 0.28 to 0.36 mg C l−1, corresponding to 1.9–4.6% of the phytoplankton biomass. We conducted regression analysis, relating the bacterioplankton
variables to a number of environmental variables, and evaluated the interannual parameter variability. Chlorophyll a and phytoplankton production contributed less to the variation in the bacterioplankton variables than in most previous analyses
using data from less eutrophic systems. We suggest that the proportion of phytoplankton production that is channelized through
bacterioplankton in lakes decreases with increasing trophic state and decreasing mean depth. This probably reflects a concurrent
increase in fish predation on macrozooplankton and loss by sedimentation. An important part of the residual variation in the
equations hitherto proposed in the literature could be explained by variation in macrozooplankton biomass and pH > 10.2. A
negative effect of high pH on bacterioplankton production was confirmed by laboratory experiments. The impact of different
zooplankton varies considerably, with Daphnia seeming to have a negative impact on bacterioplankton abundance and, thereby, indirectly on bacterioplankton production,
while Bosmina, rotifers, and cyclopoid copepods seem to stimulate both abundance and production. Bosmina apparently also stimulate the bacterioplankton specific growth rate.
Received: 8 February 1996; Accepted: 16 July 1996 相似文献
16.
Phytoplankton biomass is mainly controlled by hydrology and phosphorus concentrations in tropical hydroelectric reservoirs 总被引:5,自引:0,他引:5
Luciana M. Rangel Lúcia H. S. Silva Priscila Rosa Fábio Roland Vera L. M. Huszar 《Hydrobiologia》2012,693(1):13-28
Phytoplankton is widely recognized as being regulated mainly by resources (nutrients and light) and predation by higher trophic levels. In reservoirs, these controls also can be modulated by hydrology, for example through the influence of flow pulses generated by the operation of the dam. In this study, we tested the influence of light, nutrients, and zooplankton grazing pressure, and also hydrology (as water residence time) on the phytoplankton biomass in eight tropical hydroelectric reservoirs, which differ in size, morphometry, location, trophic state, and water residence time. Our hypothesis was that, as these reservoirs are used for hydroelectric purposes, the control that would otherwise be exerted on phytoplankton biomass primarily by resource availability and grazing will also be modulated by hydrology. Low phytoplankton biomass (range of system medians = 12–299 μg C l−1) occurred in most systems, except for one highly eutrophic reservoir (median = 1331 μg C l−1). Our data showed that phosphorus was more often likely to be the limiting nutrient in these systems, as assessed through nutrient limitation indexes (nitrogen and phosphorus), based on concentrations and ratios. For most reservoirs, excluding the eutrophic system with high cyanobacteria biomass, seasonal water residence time was the variable that best explained phytoplankton variation among the several environmental variables analyzed in this study (P < 0.0001; adjusted r 2 = 0.38). Hydrology was an important and additional factor modulating phytoplankton in these tropical reservoirs, directly removing phytoplankton populations and their potential zooplankton grazers by washout, and also affecting nutrient availability. 相似文献
17.
Physical Factors Control Phytoplankton Production and Nitrogen Fixation in Eight Texas Reservoirs 总被引:1,自引:0,他引:1
Margaret G. Forbes Robert D. Doyle J. Thad Scott Jacob K. Stanley Hui Huang Bryan W. Brooks 《Ecosystems》2008,11(7):1181-1197
We compared regression tree analyses and multiple linear regression models to explore the relative importance of physical
factors, land use, and water quality in predicting phytoplankton production and N2 fixation potentials at 85 locations along riverine to lacustrine gradients within eight southern reservoirs. The regression
tree model (r
2 = 0.73) revealed that differences in phytoplankton production were primarily a function of water depth. The highest rates
of production (mg C m−3 h−1) occurred at shallow sites (<0.9 m), where rates were also related to total phosphorus (TP) levels. At deeper sites, production
rates were higher at sites with relative drainage area (RDA, ratio of drainage area to water surface area) below 45, potentially
due to longer hydraulic residence times. In contrast, multiple linear regression selected TP, RDA, dissolved phosphorus, and
percent developed land as significant model variables (r
2 = 0.63). The regression tree model (r
2 = 0.67) revealed that N2 fixation potentials (mg N m−3 h−1) were substantially higher at sites with relatively smaller drainage areas (RDA < 45). Within this subgroup, fixation rates
were additionally related to TP values (threshold = 41 μg l−1). The multiple linear regression model (r
2 = 0.67) also selected RDA as the primary predictor of N2 fixation. Regression tree models suggest that nutrient controls (phosphorus) were subordinate to physical factors such as
depth and RDA. We concluded that regression tree analysis was well suited to revealing nonlinear trends in data (for example,
depth), but yielded large uncertainty estimates when applied to linear data (for example, phosphorus). 相似文献
18.
Tsuyoshi Kobayashi Darren S. Ryder Geoff Gordon Ian Shannon Timothy Ingleton Max Carpenter Stephen J. Jacobs 《Aquatic Ecology》2009,43(4):843-858
Environmental flows were released to the Macquarie Marshes (~210,000 ha) in north-west NSW of Australia between October and
December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains
would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the
overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with
a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black roly-poly.
At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a
6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed
in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results
from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7–14.8 mg l−1, followed by more gradual increases in total phosphorus (mean concentrations 0.6–0.8 mg l−1) and DOC (26.1–50.2 mg l−1) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations
of nutrients and DOC, attaining mean densities of (6.0–6.9) × 106 cells ml−1 of planktonic bacteria and (80.7–81.4) × 103 cells ml−1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes,
over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain
sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying
flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord
with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely
to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain
sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses
including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton. 相似文献
19.
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
20.
F. Witte G. M. Silsbe R. E. Hecky P. C. Goudswaard S. J. Guildford M. A. Kishe-Machumu J. H. Wanink 《Hydrobiologia》2012,679(1):283-296
Possible causes of the increased algal blooms in Lake Victoria in the 1980s have been disputed by several authors; some suggested
a top-down effect by the introduced Nile perch, whereas others suggested a bottom-up effect due to eutrophication. In this
article the potential impact is established of grazing by fish on phytoplankton densities, before the Nile perch upsurge and
the concomitant algal blooms in the Mwanza Gulf. The biomass and trophic composition of fish in the sublittoral area of the
Mwanza Gulf were calculated based on catch data from bottom trawls, and from gill nets covering the whole water column. Estimates
of phytoplankton production in the same area were made from Secchi values and chlorophyll concentrations. The total phytoplankton
intake by fish was estimated at 230 mg DW m−2 day−1. The daily gross production ranged from 6,200 to 7,100 mg DW m−2 day−1 and the net production from 1,900 to 2,200 mg DW m−2 day−1. Thus, losses of phytoplankton through grazing by fish were about 3–4% of daily gross and 10–12% of daily net phytoplankton
production. As a consequence it is unlikely that the phytoplankton blooms in the second half of the 1980s were due to a top-down
effect caused by a strong decline in phytoplankton grazing by fish. 相似文献