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1.
Water quality experienced changes throughout the 3-year ecological engineering experiment in the drinking water source in Meiliang Bay of Lake Taihu. Average concentrations of TN, TP, NH4+, BOD5 and transparency in the drinking water source during the period of July–December 2005 were 1.85, 0.13, 0.23, 3.03 mg L−1 and 27.5 cm, respectively, decreasing by 47.9%, 21.2%, 83.3%, 54.4% and 24.2%, compared to concentrations from the same period in 2003. Concentrations of chlorophyll a and COD were 89.9 μg L−1 and 6.45 mg L−1, increasing by 27.9% and 17.7%, compared to the values in 2003. Cyanobacteria (mainly Microcystis) dominated the phytoplankton community in the ecological engineering area during July–December 2005. Densities of cyanobacteria and Microcystis were higher in 2005 than in 2004 and higher inside the engineering area than outside. Density percentages of cyanobacteria and Microcystis to total algae were above 90% and 60% during the bloom period. Average density of flagellate algae was higher during July–December 2005 than in 2004. Changes in water quality in the engineering area resulted mainly from the weakening of waves, decrease in concentrations of suspended solids, and assimilation of mass algae and periphytons. In spite of initial improvement of water quality, cyanobacterial bloom still determined the phytoplankton dynamics and variations. Additionally, nutrient concentration still remained at a high level without control of external loading. Therefore, a more holistic approach and long-term management should be adopted in Lake Taihu.  相似文献   

2.
Streptomycin and ampicillin are antibiotics commonly used to eliminate prokaryotes from the cultures of eukaryotic algae. We studied the effects of 25 mg l−1 streptomycin plus 50 mg l−1 ampicillin on the growth and photosynthesis of two broadly halotolerant algae, Picochlorum oklahomensis and Dunaliella sp. (Chlorophyceae). We measured growth rate, oxygen evolution, chlorophyll fluorescence kinetics, and pigment content in low (150 μmol photons m−2 s−1) and high (600 μmol photons m−2 s−1) light grown batch cultures. Our results show only a minor effect of the antibiotics on P. oklahomensis, and none on Dunaliella sp., so this combination of antibiotics is suitable for maintenance of stock cultures for physiological experiments. We also show that these antibiotics can be used in turbidostat cultures of P. oklahomensis, which otherwise tend to succumb to bacteria.  相似文献   

3.
Red tide blooms of Cochlodinium polykrikoides in a coastal cove   总被引:1,自引:0,他引:1  
Successive blooms of the dinoflagellate Cochlodinium polykrikoides occurred in Pettaquamscutt Cove, RI, persisting from September through December 1980 and again from April through October 1981. Cell densities varied from <100 cells L−1 at the onset of the bloom and reached a maximum density exceeding 3.4 × 106 cells L−1 during the summer of 1981. The bloom was mainly restricted to the mid to inner region of this shallow cove with greatest concentrations localized in surface waters of the southwestern region during summer/fall periods of both years. Highly motile cells consisting of single, double and multiple cell zooids were found as chains of 4 and 8 cells restricted to the late August/September periods. The highest cell densities occurred during periods when annual temperatures were between 19 and 28 °C and salinities between 25 and 30. A major nutrient source for the cove was Crying Brook, located at the innermost region at the head of the cove. Inorganic nitrogen (NH3 and NO2 + NO3) from the brook was continually detectable throughout the study with maximum values of 57.5 and 82.5 μmol L−1, respectively. Phosphate (PO4-P) was always present in the source waters and rarely <0.5 μmol L−1; silicate always exceeded 30 μmol L−1 with maximum concentrations reaching 226 μmol L−1. Chlorophyll a and ATP concentrations during the blooms varied directly with cell densities. Maximum Chl a levels were 218 mg m−3 and ATP-carbon was >20 g C m−3. Primary production by the dinoflagellate-dominated community during the bloom varied between 4.3 and 0.07 g C m−3 d−1. Percent carbon turnover calculated from primary production values and ATP-carbon varied from 6 to 129% d−1. The dinoflagellates dominated the entire summer period; other flagellates and diatoms were present in lesser amounts. A combination of low washout rate due to the cove dynamics, active growth, and life cycles involving cysts allowed C. polykrikoides to maintain recurrent bloom populations in this area.  相似文献   

4.
The nitrogen uptake and growth capabilities of the potentially harmful, raphidophycean flagellate Heterosigma akashiwo (Hada) Sournia were examined in unialgal batch cultures (strain CCMP 1912). Growth rates as a function of three nitrogen substrates (ammonium, nitrate and urea) were determined at saturating and sub-saturating photosynthetic photon flux densities (PPFDs). At saturating PPFD (110 μE m−2 s−1), the growth rate of H. akashiwo was slightly greater for cells grown on NH4+ (0.89 d−1) compared to cells grown on NO3 or urea, which had identical growth rates (0.82 d−1). At sub-saturating PPFD (40 μE m−2 s−1), both urea- and NH4+-grown cells grew faster than NO3-grown cells (0.61, 0.57 and 0.46 d−1, respectively). The N uptake kinetic parameters were investigated using exponentially growing batch cultures of H. akashiwo and the 15N-tracer technique. Maximum specific uptake rates (Vmax) for unialgal cultures grown at 15 °C and saturating PPFD (110 μE m−2 s−1) were 28.0, 18.0 and 2.89 × 10−3 h−1 for NH4+, NO3 and urea, respectively. The traditional measure of nutrient affinity—the half saturation constants (Ks) were similar for NH4+ and NO3 (1.44 and 1.47 μg-at N L−1), but substantially lower for urea (0.42 μg-at N L−1). Whereas the α parameter (α = Vmax/Ks), which is considered a more robust indicator for substrate affinity when substrate concentrations are low (<Ks), were 19.4, 12.2 and 6.88 × 10−3 h−1/(μg-at N L−1) for NH4+, NO3 and urea, respectively. These laboratory results demonstrate that at both saturating and sub-saturating N concentrations, N uptake preference follows the order: NH4+ > NO3 > urea, and suggests that natural blooms of H. akashiwo may be initiated or maintained by any of the three nitrogen substrates examined.  相似文献   

5.
There is continuous interest in many countries in maintaining and manipulating the rich ecological value of hypersaline ecosystems for aquaculture. The Megalon Embolon solar saltworks (northern Greece) were studied in sites of increasing salinity of 60–144 ppt to evaluate Dunaliella salina abundance and microalgal composition, in relation to physical and chemical parameters. Cluster and ordination analyses were performed based on the biotic and abiotic data matrices. Using fresh aliquots from 60 and 140 ppt salinity waters, phytoplankton performance was appraised with flask cultures in the laboratory by varying the inorganic PO4-P concentration at 23 °C and 30 °C. At the saltworks, among the most abundant microalgae identified were species of the genera Dunaliella, Chlamydomonas, Amphora, Navicula, and Nitzschia. Dunaliella salina populations were predominant comprising 5–22% of the total microalgal assemblages during spring, but only 0.3–1.0% during the summer, when grazing by Artemia parthenogenetica and Fabrea salina was intense. D. salina cell density in April–July was in the range of 0.4–12.5 × 106 L−1 with typical densities of 1.5–4.5 × 106 L−1. Overall, microalgal densities were high in salinities of ≥100 ppt when inorganic-P concentrations were ≥0.20 mg L−1 within saltworks waters. Multivariate analysis of species abundance showed that algal growth responses were primarily related to variation in salinity and inorganic-P concentrations, but also to NO3-N concentration. In the laboratory, experiments indicated effective fertilization and denser microalgal growth under high inorganic PO4-P applications (4.0 and 8.0 mg L−1) at 60 ppt salinity and 23 °C. The lower PO4-P applications (0.6–2.0 mg L−1) were more effective at 60 ppt salinity and 30 °C. At 140 ppt salinity, microalgal growth response was less obvious at any of the corresponding phosphorus concentrations or temperatures. In both salinity experiments, Dunaliella salina bloomed easily and was predominant among the microalgae. Our observations indicate that Dunaliella salina populations and the overall rich microalgal profile of the saltworks, along with their performance in laboratory mono–and mixed cultures hold promise for mass cultivation within the M. Embolon saltworks basins.  相似文献   

6.
Agrobacterium tumefaciens-mediated transformation system for perilla (Perilla frutescens Britt) was developed. Agrobacterium strain EHA105 harboring binary vector pBK I containing bar and γ-tmt cassettes or pIG121Hm containing nptII, hpt, and gusA cassettes were used for transformation. Three different types of explant, hypocotyl, cotyledon and leaf, were evaluated for transformation and hypocotyl explants resulted in the highest transformation efficiency with an average of 3.1 and 2.2%, with pBK I and pIG121Hm, respectively. The Perilla spp. displayed genotype-response for transformation. The effective concentrations of selective agents were 2 mg l−1 phosphinothricin (PPT) and 150 mg l−1 kanamycin, respectively, for shoot induction and 1 mg l−1 PPT and 125 mg l−1 kanamycin, respectively, for shoot elongation. The transformation events were confirmed by herbicide Basta spray or histochemical GUS staining of T0 and T1 plants. The T-DNA integration and transgene inheritance were confirmed by PCR and Southern blot analysis of random samples of T0 and T1 transgenic plants.  相似文献   

7.
A strain of Nannochloropsis isolated originally from the East China Sea and obtained from Institute of Hydrobiology, Chinese Academy of Sciences was shown to utilize glucose or ethanol for mixotrophic and heterotrophic growth. The highest cell density, 550 mg L− 1 dry weight after culture for 8 days, was obtained during mixotrophic culture with 30 mM glucose. The organic carbon sources had no effect on the net photosynthetic rate, but enhanced the respiratory rate. The addition of an organic carbon source led to an increase in the cell lipid content and a decrease in their eicosapentaenoic acid (EPA) content. The EPA yield was 21.9 mg L− 1 using photoautotrophic culture, and 23.4 mg L− 1 and 23.0 mg L− 1, respectively, in mixotrophic cultivation with glucose or ethanol as the carbon source.  相似文献   

8.
Biofilm formation and growth on equipment surfaces is detrimental to papermaking processes. However, a fundamental understanding leading to an optimal control strategy is yet to be found. Quaternary ammonium compounds (QAC) are being increasingly applied in the papermaking processes. Among them, the most frequently applied, N-alkyl-benzyl-dimethyl ammonium chloride, was employed in this study. To foster fundamental understanding of QAC efficacy towards biofilm control, two of the highest QAC-resistant strains of bacteria were isolated from the papermaking processing water and employed as model organisms. By the 16S rRNA gene sequencing technique, two Gram-negative rods with QAC resistance were identified as Morganella morganii (HB22) and the biofilm-forming Pseudomonas putida (HB45). The minimal inhibition concentration (MIC) values were 8 mg L−1 for HB22 and 16 mg L−1 for HB45, respectively, against QAC in basal medium (BM). However, both strains could grow under more than 150 mg L−1 QAC in basal medium at neutral pH. As observed by crystal violet assay and fluorescent confocal microscopy, HB45 formed biofilm more slowly on stainless steel coupon which is the prime material of papermachine than on the surface of polystyrene, the most common material for food packaging and semi-finished/finished products. HB45 formed biofilm more slowly on stainless steel coupons than on polystyrene Petri dish surfaces, as observed by crystal violet assay and fluorescent confocal microscopy. For HB45, there was a marginal increase of inhibition of biofilm formation by increasing QAC concentration from 50 to 75 mg L−1. By comparison of inhibition concentration in liquid state and in biofilm formation, the results implicate that the current practice in papermaking processes of adding biocide to qualitatively control planktonic bacterial communities does not ensure control of biofilm formation.  相似文献   

9.
The biological control of water hyacinth is affected by water nitrogen and phosphorus content and this was investigated experimentally at five levels of nutrient supply by measuring plant photosynthetic and growth responses, and mirid reproduction and herbivory of nutrient treated plants. Low nitrogen (2–0.2 mg L−1) and phosphorus (0.2–0.01 mg L−1) supply decreased hyacinth photosynthesis, growth and biomass accumulation relative to plants supplied 200 mg L−1 N and 20 mg L−1 P. This effect depended more on nitrogen supply than phosphorus supply. Chlorophyll fluorescence showed that the photosynthetic light reactions of low nutrient plants were affected and leaves had decreased chlorophyll content, density of functional photosystems II and dissipated a greater proportion of absorbed energy as heat. Gas exchange parameters showed reduced carboxylation efficiency, rates of RuBP regeneration and light saturated photosynthetic rates, but not quantum yields. Effects on photosynthesis translated into lower plant dry biomass. Mirid herbivory exacerbated the effects of low nutrients noted for chlorophyll fluorescence, gas exchange parameters and biomass accumulation, however, these effects were not always significant and there was no obvious correlation between the level of nutrients supplied and the effect of mirid herbivory. Low nutrient supply did, however, affect mirid performance reducing the number of adult insects, nymphs and herbivory intensity suggesting that in the long-term mirid populations would be significantly affected by water nutrient status.  相似文献   

10.
EU regulations recommend effluent treatment and nutrient recycling for aquaculture sustainability, so a study was undertaken to provide base-line data for the integration of commercial fish-farm effluents with the production of microalgae. The project relates to a specific bivalve consumer (Tapes decussatus) and biofiltration. Effluent inorganic nutrient composition was assessed and evaluated as culture media for Phaeodactylum tricornutum, Tetraselmis suecica and Tetraselmis sp. Optimization of the microalgal compartment included studies on preparation of a simple medium, nutrient or dilution rate manipulation and nutrient removal. Cell harvest was increased chiefly by N correction (6-fold for Tetraselmis sp.) and semi-continuous or continuous operation (by a factor of 3 to 11). Nutrient removal efficiency was high for ammonium and nitrite-nitrogen (80–100%), depending on species, nutrient ratio (Si correction for P. tricornutum) and culture regime for nitrate (41–100%) or phosphorus (21–99%). Data obtained under cyclostat cultivation (yields of 1.38 and 0.50×106 P. tricornutum or Tetraselmis sp. cells mL−1 d−1 and nutrient uptake rates of 2.32 mg N L−1 d−1 and 0.96 mg P L−1 d−1) were used to show clam production and simultaneous wastewater treatment possibilities through the proposed fish-microalgae-clam integrated aquaculture system.  相似文献   

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