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1.
R. Jan Stevenson Steven T. Rier Catherine M. Riseng Richard E. Schultz Michael J. Wiley 《Hydrobiologia》2006,561(1):149-165
Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability
cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass
and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities
and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams
with repeated sampling at each site over a 2−month period. Many measures of algal biomass and nutrient availability were positively
correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration
and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in
either region. Chl a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar
amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations.
Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic
algal biomass occurred in nutrient concentrations between 10 and 30 μg TP l−1 and between 400 and 1000 μg TN l−1. 相似文献
2.
Eutrophication of moderately deep Dutch lakes during the past century: flaws in the expectations of water management? 总被引:1,自引:0,他引:1
We studied the trophic development of the past 30–100 years in eight moderately deep Dutch lakes based on their sedimentary
fossil diatom assemblages. The dominant diatoms indicating meso- to eutrophic conditions were Aulacoseira subarctica, Cyclotella ocellata, C. cyclopuncta, C. meneghiniana, Puncticulata bodanica, Aulacoseira granulata, Cyclostephanos dubius, C. invisitatus, Stephanodiscus hantzschii, S. medius, and S. parvus. Ordination of diatom data separated the lakes into four groups according to their total phosphorus concentrations (TP),
water supply, water management, and origin. The first group consists of dike-breach lakes, which were in stable eutrophic
to hypertrophic conditions throughout the past century with diatom-inferred TP (DI-TP) concentrations of between 70 and 300 μg l−1. The main factors influencing these dike-breach lakes are river management, ground water supply of riverine origin, and local
land use. The second group are artificial lakes of fluctuating oligo- to mesotrophic conditions and DI-TP concentrations of
10–30 μg l−1. Only one of the artificial lakes showed a DI-TP increase due to changes in catchment agricultural practice. A third group
includes an artificial moat and an inland dike-breach lake with DI-TP concentrations of 50–100 μg l−1. The fourth group contains an individual dike-breach lake with stable mesotrophic conditions of 50 μg l−1 throughout the past century. Rather than showing a regional pattern, the studied lakes behave very individualistically with
regard to their trophic history, reflecting changes in the local hydrology and in their nutrient sources. 相似文献
3.
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
4.
Ciliate and bacterial densities and their link with eutrophication were studied in fourteen shallow lakes in northwest Spain.
Total phosphorus (TP) in these lakes varied between 30 μg l−1 and 925 μg l−1 and chlorophyll a concentration (chla) between 0.5 μg l−1 and 107 μg l−1. Bacterial abundance ranged from 1 × 106 to 14 × 106 cells ml−1, while ciliate abundance ranged from 0.6 cells ml−1 to 229 cells ml−1. Lakes were classified into three trophic types from their TP and chla concentrations. Bacterial abundance was significantly
correlated with trophic type, as well as with TP and with chla separately, whereas ciliate abundance was only correlated with
chla. No significant relationship could be established between bacterial and ciliate abundance across the trophic gradient.
A general pattern was observed in the ratios of bacterial abundance to TP and chla concentrations, of decreasing ratios with
increases in the nutrient loading. This pattern was not found for ciliates. The dominant zooplankton group in 13 of the 14
lakes studied was Rotifera, which accounted for a mean of 71% of total zooplankton abundance (41% of zooplankton biomass).
The positive correlation between bacteria and ciliates with this group, and the absence of any relationship with Cladocera
suggest that top down control by cladocerans was weaker in our lakes than previously shown in northern European shallow lakes.
Rotifers could be important predators of bacteria in the high-nutrient lakes of our study. Higher slopes of regressions on
bacterial abundance towards the hypertrophic range indicate that top-down control was weaker in our lakes than in northern
European shallow lakes. 相似文献
5.
Response of Periphytic Algae to Gradients in Nitrogen and Phosphorus in Streamside Mesocosms 总被引:2,自引:1,他引:1
In this study we manipulated both nitrogen and phosphorus concentrations in stream mesocosms to develop quantitative relationships
between periphytic algal growth rates and peak biomass with inorganic N and P concentrations. Stream water from Harts Run,
a 2nd order stream in a pristine catchment, was constantly added to 36 stream-side stream mesocosms in low volumes and then
recirculated to reduce nutrient concentrations. Clay tiles were colonized with periphyton in the mesocosms. Nutrients were
added to create P and N concentrations ranging from less than Harts Run concentrations to 128 μg SRP l−1 and 1024 μg NO3-N l−1. Algae and water were sampled every 3 days during colonization until periphyton communities reached peak biomass and then
sloughed. Nutrient depletion was substantial in the mesocosms. Algae accumulated in all streams, even streams in which no
nutrients were added. Nutrient limitation of algal growth and peak biomass accrual was observed in both low P and low N conditions.
The Monod model best explained relationships between P and N concentrations and algal growth and peak biomass. Algal growth
was 90% of maximum rates or higher in nutrient concentrations 16 μg SRP l−1 and 86 μg DIN l−1. These saturating concentrations for growth rates were 3–5 times lower than concentrations needed to produce maximum biomass.
Modified Monod models using both DIN and SRP were developed to explain algal growth rates and peak biomass, which respectively
explained 44 and 70% of the variance in algal response. 相似文献
6.
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
7.
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
8.
Phosphorus regulates stream injury by filamentous green algae,DO, and pH with thresholds in responses 总被引:1,自引:0,他引:1
Nutrient concentrations, benthic algal biomass, dissolved oxygen (DO), and pH were measured in 70 or more streams during spring and summer in the Illinois River Watershed (IRW), which crosses the Oklahoma and Arkansas (USA) border, to determine whether injury to streams occurred and if that injury was related to spreading poultry waste on fields. Definitions of injury were based on Oklahoma water quality regulations and scientific literature. Phosphorus and nitrogen concentrations were each independently related to poultry house density (PHD) in watersheds and percent urban land use in watersheds. In addition, phosphorus and nitrogen concentrations were unusually high compared to regions with similar geology and hydrology. Molar N:P ratios were high and indicated that phosphorus was the most likely limiting nutrient. Phosphorus concentrations, as well as PHD and urban land use, were related to algal biomass during spring, but were less related during summer. A threshold response in cover of stream bottoms by nuisance filamentous green algae (NFGA: Cladophora, Rhizoclonium, and Oedogonium) during spring was observed at 27 μg TP l−1 using regression tree analysis. Great increases in average NFGA cover (from 4 to 36% cover) occurred with relatively small increases in TP concentration at the 27 μg TP l−1 threshold. Average concentrations of DO, variability in DO, and pH during spring were positively related to TP, chlorophyll a, and NFGA cover. Minimum DO during spring and early morning DO during summer were negatively related to TP concentration. Spring pH and summer DO frequently violated water quality requirements for protecting biodiversity that were established by the state of Oklahoma. We conclude that poultry house operations as well as urban activities, independently and interactively, pollute IRW streams with phosphorus, which resulted in injury to aesthetic condition and the potential for injury of biodiversity. 相似文献
9.
10.
Glasgow Lake: an early-warning sentinel of lake acidification in Cape Breton Highlands National Park (Nova Scotia,Canada) 总被引:1,自引:0,他引:1
Alexandra M. Gerber Brian K. Ginn Colin J. Whitfield Peter J. Dillon Brian F. Cumming John P. Smol 《Hydrobiologia》2008,614(1):299-307
In contrast to other lakes studied in Cape Breton Highlands National Park (Nova Scotia, Canada), our paleolimnological results
indicated that Glasgow Lake has been impacted by acidic deposition starting in the early 1900s. Based on analysis of diatom
assemblages, the lake experienced a decrease in diatom-inferred lakewater pH from a pre-industrial pH of ~5.8 to a current
pH of 5.3 (2000–2002 measured mean pH = 5.0) as well as a decrease in diatom-inferred Gran-alkalinity. In this study, diatom-based
paleolimnological techniques were used in conjunction with a dynamic biogeochemical model (MAGIC) to assess both the timing
and extent of the acidification trend, as well as determine a probable explanation as to why this lake, and none of the other
15 Cape Breton Highlands lakes studied for paleolimnology thus far, acidified under a peak non-marine sulphate deposition
load of 43.6 mmolc m−2 year−1 in the mid-1970s. Steady-state models estimate that Glasgow Lake had the lowest buffering capacity of six study lakes and
estimated critical sulphate loading of <1 mmolc m−2 year−1. MAGIC also estimated a loss of charge balance alkalinity from a pre-1850 value of 38 μmolc l−1 to a low of 12 μmolc l−1. While no evidence of biological recovery has been recorded, MAGIC estimates an increase in charge balance alkalinity to
27 μmolc l−1 in 2002 in response to decreased SO2 emissions. Of the five other lakes that were modelled, all showed trends towards more acidic states and subsequent increases
in charge balance alkalinity; however, the empirical paleo-diatom approach applied to these lakes showed no evidence of acidification.
Thus, Glasgow Lake has the lowest buffering capacity among the Cape Breton Highland study lakes and serves as a sentinel of
potential acidification trends and recovery in this region.
Handling editor: J. Saros 相似文献
11.
Behzad Ahmadi Khoshnood Alizadeh Jaime A. Teixeira da Silva 《Plant Cell, Tissue and Organ Culture》2012,109(3):525-533
The effects of three periods of incubation (10, 20 and 30 min) at different levels of bleomycin (0, 0.1, 0.2, 0.3, 0.4 and
0.5 μg ml−1), as well as three periods of exposure (12, 24 and 48 h) to different levels of the anti-auxin p-chlorophenoxyisobutyric acid (PCIB), including 1, 2, 3, 4 and 5 mg l−1, on microspore embryogenesis of rapeseed cv. ‘Amica’ were investigated. Microspore embryogenesis was significantly enhanced
following 20 min treatment with 0.2 μg ml−1 bleomycin compared with untreated cultures. Highest embryo yield (163 embryos Petri dish−1) was observed with 24 h treatment of 4 mg l−1 PCIB. The highest percentage of secondary embryogenesis was observed on B5 medium containing 0.15 mg l−1 of gibberellic acid (GA3) and 0.2 mg l−1 6-benzyladenine (BA) in 4–6 mm microspore-derived embryos (MDEs). Most callus formed on B5 medium containing 0.15 mg l−1 GA3, 0.1 mg l−1 BA and 0.1 mg l−1 indole-3-acetic acid (IAA) when 4–6 mm embryos were used. Regeneration was highest on B5 medium containing 0.05 mg l−1 GA3 or 0.1 mg l−1 BA and 0.2 mg l−1 IAA with 2–4 mm embryos. Microspore embryogenesis and plant regeneration could be improved by both bleomycin and PCIB when
the appropriate MDE length and phytohormone level were selected. 相似文献
12.
Phosphorus (P) dynamics in large shallow lakes are greatly influenced by physical processes such as wind-driven sediment resuspension,
at times scales from hours to years. Results from long-term (30 year) research on Lake Okeechobee, Florida (area 1,730 km2, mean depth 2.7 m) illustrate key features of these P dynamics. Variations in wind velocity result in changes in water column
transparency, suspended solids, and total P (TP). In summer there are diurnal changes in TP associated with afternoon winds,
and in winter, when strong winds occur for multiple days, monthly average TP remains high compared to summer. The magnitude
of daily and seasonal TP changes can exceed 100 μg l−1. Hurricanes and tropical storms also cause extreme changes in TP that are superimposed on seasonal dynamics. When a hurricane
passed 80 km south of the lake in October 1999, mean pelagic TP increased from 88 to 222 μg l−1. During large resuspension events, light attenuation is substantially increased, and this influences the biomass and spatial
extent of submerged plants, as well as water column TP. In Lake Okeechobee, TP concentrations typically are ∼20 μg l−1 when submerged plants are dense, and soluble reactive P concentrations are reduced below detection, perhaps by the periphyton
and plant uptake and by precipitation with calcium at high pH. In contrast, TP exceeds 50 μg l−1 when submerged plants and periphyton are absent due to prolonged deep water, and phytoplankton biomass and algal bloom frequency
both are increased. In Lake Okeechobee and other large shallow lakes, complex models that explicitly consider wind-wave energy,
hydrodynamics, and sediment resuspension, transport, and key biological processes are needed to accurately predict how lake
water TP will respond to different management options. 相似文献
13.
María Fernanda Adame Ruth Reef Jorge A. Herrera-Silveira Catherine E. Lovelock 《Hydrobiologia》2012,691(1):239-253
Poor water quality affects the biogeochemistry functions and the biological community structure of coastal ecosystems. In this study we investigated the effect of water quality on: (a) The exchange of dissolved organic carbon (DOC) between floodwater and mangrove forests, (b) the abundance of sediment bacteria, (c) the microbial community composition, and (d) the microbial catabolic activity. We selected six mangrove forests that were flooded by creeks with differing water qualities to test for thresholds of nutrient concentrations associated with changes in DOC dynamics and the microbial community. Our results show that in sites flooded by water high in soluble reactive phosphorus (SRP) (>20 μg l−1) and NH4 + (>30 μg l−1) the DOC concentrations in the floodwater were higher than in ebb water, suggesting DOC import by the mangroves. In contrast, in sites flooded by water low in SRP (<20 μg l−1) and NH4 + (<30 μg l−1), DOC concentrations in the floodwater were lower than in the ebb water, suggesting DOC export by the mangroves. Bacterial abundance was higher in sediments with low bulk density, high organic carbon and when flooded by water with low N:P (1–2), but the microbial composition and total catabolic activity assessed using Biolog Ecoplates™ did not differ among sites. The relationship between water quality, microbial communities and DOC exchange suggests that, at least during some periods of the year, poor water quality increases bacterial abundance and modifies DOC exchange of mangrove forests with floodwater and thus, their role in supporting near-shore productivity. 相似文献
14.
Ethrel treatment enhanced isoflavonoids accumulation in cell suspension cultures of Pueraria tuberosa, a woody legume 总被引:1,自引:0,他引:1
The cell cultures of Pueraria tuberosa, a perennial leguminous lianas, were maintained in modified MS medium (KNO3 475 mg l−1, thiamine 1 mg l−1, biotin 1 mg l−1, calcium pantothenate 1 mg l−1) containing 0.1 mg l−1 2,4,5-trichloroacetic acid and 0.1 mg l−1 kinetin. Isoflavonoids (puerarin, genistin, daidzein, genistein) accumulation in cell suspension cultures was increased by
14-fold to ~12 mg l−1 after 48 h of adding 100 μM ethrel. Ethrel inhibitors (silver nitrate and silver thiosulfate) completely inhibited this effect
in the presence of ethrel and isoflavonoids were not detected in the spent medium. The increase was dose dependent and can
be explored to trigger high yield of isoflavonoids production. 相似文献
15.
Effect of ice melting on bacterial carbon fluxes channelled by viruses and protists in the Arctic Ocean 总被引:1,自引:0,他引:1
Julia A. Boras M. Montserrat Sala Jesus M. Arrieta Elisabet L. Sà Jorge Felipe Susana Agustí Carlos M. Duarte Dolors Vaqué 《Polar Biology》2010,33(12):1695-1707
During the last few years, extensive sea ice melting in the Arctic due to climate change has been detected, which could potentially
modify the organic carbon fluxes in these waters. In this study, the effect of sea ice melting on bacterial carbon channelling
by phages and protists has been evaluated in the northern Greenland Sea and Arctic Ocean. Grazing on bacteria by protists
was evaluated using the FLB disappearance method. Lysis of bacteria due to viral infections was measured using the virus reduction
approach. Losses of bacterial production caused by protists (PMMBP) dominated losses caused by viruses (VMMBP) throughout the study. Lysogenic viral production was detected in 7 out of 21 measurements and constituted from 33.9 to 100.0%
of the total viral production. Significantly higher PMMBP and lower VMMBP were detected in waters affected by ice melting compared with unaffected waters. Consequently, significantly more bacterial
carbon was channelled to the higher trophic levels in affected waters (13.05 ± 5.98 μgC l−1 day−1) than in unaffected waters (8.91 ± 8.33 μgC l−1 day−1). Viruses channelled 2.63 ± 2.45 μgC l−1 day−1 in affected waters and 4.27 ± 5.54 μgC l−1 day−1 in unaffected waters. We conclude that sea ice melting in the Arctic could modify the carbon flow through the microbial food
web. This process may be especially important in the case of massive sea ice melting due to climate change. 相似文献
16.
The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and
in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates
dominated the algal biomass (226 ± 154 μg ww l−1) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l−1). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25
and 21 ± 14 μg ww l−1, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical
cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest
chlorophyll-a concentrations (6.6–22.2 μg l−1) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional
peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a
−1 h−1) (μE m−2 s−1)−1] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a
−1 h−1)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced
the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients
and possibly habitable space, which seemed to have favored centric diatoms in our study. 相似文献
17.
Luis Arigita Ma Jesús Cañal Ricardo Sánchez Tamés Aida González 《In vitro cellular & developmental biology. Plant》2010,46(3):312-322
In traditional in vitro culture, the low CO2 concentration inside the vessels restricts photosynthesis and necessitates the addition of sucrose to the culture medium
as the main energy source, thus bringing about changes in the absorption of mineral elements from the culture medium. In this
study, we investigated macronutrient absorption and sugar consumption in Actinidia deliciosa Chevalier Liang and Ferguson cv. Hayward (kiwi), cultured on medium supplemented with varying amounts of sucrose (0, 10,
and 20 g l−1) under both heterotrophy and autotrophy, flushed with different concentrations of CO2 (non-ventilation, 300, 600, and 2,000 μl l−1). In ventilated systems with 20 g l−1 of sucrose, sucrose absorption was less than under non-ventilation. The lowest rate of sucrose absorption was recorded when
the explants were cultured on medium supplemented with 20 g l−1 of sucrose and flushed with 600 μl l−1 CO2. Absorption of NO3
−, PO4
3−, and Mg2+ were high (maximum) at the end of the culture period (40 d) in explants flushed with 600 μl l−1 CO2 that have been cultured 20 d in the presence of sucrose and then transferred to a sucrose-free medium. These autotrophic
conditions promoted maximum plant growth in terms of both fresh and dry mass as well as the length and number of shoots and
leaves. The study shows that to maintain an optimum regime of mineral nutrition for prolonged culture of kiwi in vitro, an increased amount of these three ions should be supplemented in Murashige and Skoog’s medium. 相似文献
18.
Part of the Larsen A Ice Shelf (64°15′S to 74°15′S) collapsed during January 1995. A first oceanographic and biological data
set from the newly free waters was obtained during December 1996. Typical shelf waters with temperatures near and below the
freezing point were found. A nutrient-rich water mass (max: PO4
3− 1.80 μmol L−1 and NO3
− 27.64 μmol L−1) was found between 70 and 200 m depth. Chlorophyll-a (Chl-a) values (max 14.24 μg L−1) were high; surface oxygen saturation ranged between 86 and 148%. Diatoms of the genera Nitzschia and Navicula and the prymnesiophyte Phaeocystis sp. were the most abundant taxa found. Mean daily primary production (Pc) estimated from nutrient consumption was 14.80 ± 0.17 mgC m−3 day−1. Pc was significantly correlated with total diatom abundance and Chl-a. Calculated ΔpCO2 (difference of the CO2 partial pressure between surface seawater and the atmosphere) was –30.5 μatm, which could have contributed to a net CO2 flux from the atmosphere to the sea and suggests the area has been a CO2 sink during the studied period. High phytoplankton biomass and production values were found in this freshly open area, suggesting
its importance for biological CO2 pumping. 相似文献
19.
Alchichica is a warm-monomictic, oligotrophic lake whose phytoplanktonic biomass is dominated by large size (average ca. 55 μm) diatoms. The fast sinking phytoplankton leads to silica, and other nutrient exportation out of the productive zone
of the lake. The aim of the present study was to identify and measure the sedimentation fluxes of the diatom species and their
temporal dynamics to better understand the magnitude of silica and carbon fluxes. Sediment-traps were exposed at three different
depths and collected monthly. A total of 13 diatom species were observed in the traps. The maximum diatom flux was in February
(304 × 106 cells m−2 day−1) related to the winter diatom bloom. The diatom silica (DSi) fluxes varied from 2.2 to 2,997 mg m−2 day−1 and the diatom carbon (DC) fluxes from 1.2 to 2,918 mg m−2 d−1. Cyclotella alchichicana was the main contributor (>98%) to the total DSi and DC fluxes. The annual diatom (15 × 109 cells m−2 year−1), DSi (147 g m−2 year−1) and DC (92 g m−2 year−1) fluxes are higher than in other aquatic ecosystems of similar or even higher trophic conditions. Our findings in Alchichica
are indicative of the relevance of the phytoplankton type and size in understanding the role tropical and oligotrophic lakes
play regarding silica and carbon fluxes. In addition, our results support previous findings suggesting that inland aquatic
ecosystems are more important than formerly thought in processing carbon, and can, therefore, affect regional carbon balances. 相似文献
20.
Sou Nagasoe Tomoyuki Shikata Yasuhiro Yamasaki Tadashi Matsubara Yohei Shimasaki Yuji Oshima Tsuneo Honjo 《Hydrobiologia》2010,651(1):225-238
We investigated the impact of different nitrogen (N) and phosphorus (P) compounds and concentrations on the growth of Gyrodinium instriatum Freudenthal et Lee in laboratory experiments, and possible links to blooms of this species at Hakozaki Fishing Port, Fukuoka,
Japan. G. instriatum utilized only inorganic N compounds as N sources for growth. In contrast, G. instriatum utilized many inorganic and organic phosphorus compounds. We used the Monod equation to describe the growth rate of G. instriatum in N- or P-limited batch cultures as a function of ambient nutrient concentrations. Kinetic growth parameters for maximum
specific growth rate (μmax) and half-saturation nutrient concentration (K
S) were 0.57 divisions d−1 and 14.2 μmol l−1, respectively, under N-limitation and 0.65 divisions d−1 and 1.75 μmol l−1, respectively, under P-limitation. Compared with these K
S values, all in situ average dissolved inorganic nitrogen (DIN) concentrations in Hakozaki Fishing Port were higher than K
S for N, but all in situ average dissolved inorganic phosphorus (DIP) concentrations were lower than K
S for P, whether a red tide occurred or not bloom. Moreover, average DIP concentration in April (a month critical to red-tide
genesis) of 2004 (a non-red-tide year) was less than half those in 2002 and 2003 (red-tide years). Thus, differences in DIP
concentrations may be an important factor controlling blooms of G. instriatum in Hakozaki Fishing Port. 相似文献