985 resultados para 0.22 per mil
Resumo:
Alexandrium catenellaACDH ACDH 28.0 µM ACDH 2.5 µM ACDHACDH911 ACDH (Vm) (Ks) 0.22 pmol/cell•h 0.75 µM 34.7-88.4 fmol/cell
Resumo:
16.0-22.0 27.5-32.516.0 27.2-24.4 /33.626.0 16.0-26.027.0-42.027.0-39.012010.0 /16.3-27.0 /42.021.5 /26.1-27.0 /36.024010.0 /23.4-26.9 /42.014.2 /20.5-27.6 /38.8
Resumo:
N isotope fractionation (epsilon) was first determined during ambient NO3- depletion in a simulated diatom spring bloom. After 48 h of N-starvation, NH4+ was resupplied to the diatoms in small pulses to simulate grazer-produced N and then epsilon was determined. Large variations in epsilon values were observed: from 2.0-3.6 to 14-0 parts per thousand during NO3- and NH4+ uptake, respectively. This is the first study reporting an epsilon value as low as 0 to 2 parts per thousand for NH4+ uptake and we suggest that greater N demand after N-starvation may have drastically reduced NH3 efflux out of the cells. Thus the N status of the phytoplankton and not the ambient NH4+ concentration may be the important factor controlling epsilon, because, when N-starvation increased, epsilon values for NH4+ uptake decreased within 30 h. This study may thus have important implications for interpreting the delta(15)N of particulate N in nutrient-depleted regimes in temperate coastal oceans.
Resumo:
Fed fish farms produce large amounts of wastes, including dissolved inorganic nitrogen and phosphorus. In China, fish mariculture in coastal waters has been increasing since the last decade. However, there is no macroalgae commercially cultivated in north China in warm seasons. To exploit fish-farm nutrients as a resource input, and at the same time to reduce the risk of eutrophication, the high-temperature adapted red alga Gracilaria lemaneiformis (Bory) Dawson from south China was co-cultured with the fish Sebastodes fuscescens in north China in warm seasons. Growth and nutrient removal from fish culture water were investigated in laboratory conditions in order to evaluate the nutrient bioremediation capability of G. lemaneiformis. Feasibility of integrating the seaweed cultivation with the fed fish-cage aquaculture in coastal waters of north China was also investigated in field conditions. Laboratory seaweed/fish co-culture experiments showed that the seaweed was an efficient nutrient pump and could remove most nutrients from the system. Field cultivation trials showed that G. lemaneiformis grew very well in fish farming areas, at maximum growth rate of 11.03% day(-1). Mean C, N, and P contents in dry thalli cultured in Jiaozhou Bay were 28.9 +/- 1.1%, 4.17 +/- 0.11 % and 0.33 +/- 0.01 %, respectively. Mean N and P uptake rates of the thalli were estimated at 10.64 and 0.38 mu mol g(-1) dry weight h(-1), respectively. An extrapolation of the results showed that a 1-ha cultivation of the seaweed in coastal fish fanning waters would give an annual harvest of more than 70 t of fresh G. lemaneiformis, or 9 t dry materials; 2.5 t C would be produced, and simultaneously 0.22 t N and 0.03t P would be sequestered from the seawater by the seaweed. Results indicated that the seaweed is suitable as a good candidate for seaweed/fish integrated mariculture for bioremediation and economic diversification. The integration can benefit economy and environment in a sustainable manner in warm seasons in coastal waters of north China. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
The ciliate community structure and seasonal dynamics in a solar saltern of the Yellow Sea were studied based oil 4 sampling dates and 8 stations with salinities from 27.7 parts per thousand to 311.0 parts per thousand. The effects of the type and concentration of the fixative used (Lugol's and Bouin's) were tested at the first sampling date. Fixative type and fixative concentration had significant effects on ciliate abundance and blovolume, with 1% Lugol's giving the best results. A detailed investigation using live observations and protargol staining techniques revealed a total of 98 morphospecies from 8 sampling stations. There was obvious seasonal variation in species composition at most of the stations, but this tended to be less distinct with increasing salinity, as the dominant ciliate group shifted from oligotrichs to heterotrichs. Ciliate abundance varied from 4.40 x 10(1) to 2.11 x 10(5) cells l(-1) and biomass ranged between 2.39 and 9.87 x 10(3) mu g Cl-1 (at a salinity of 147.6 parts per thousand). Both abundance and biomass decreased abruptly when salinity exceeded 100-150 parts per thousand. Statistical analyses Suggested that the dynamics of ciliate abundance and biomass were regulated by both salinity and by season, but those of diversity and species richness were mainly controlled by salinity and both significantly decreased with increasing salinity. (C) 2009 Elsevier GmbH. All rights reserved.
Residues of enrofloxacin, furazolidone and their metabolites in Nile tilapia (Oreochromis niloticus)
Resumo:
The residues of enrofloxacin and its metabolite in Nile tilapia (Oreochromis niloticus) were studied after oral dose of 50 mg/kg for 7 days. To find the differences between Nile tilapia and Chinese shrimp (Penaeus chinensis), the residues of enrofloxacin in P chinensis were also studied under the same conditions. The results showed that enrofloxacin metabolized into ciprofloxacin in both Nile tilapia and P chinensis, the maximal concentration of enrofloxacin in muscle, liver and plasma of Nile tilapia were 3.61 mu g/g, 5.96 mu g/g, 1.25 mu g/ml respectively, and ciprofloxacin in muscle was 0.22 mu g/g. The maximal concentration of enrofloxacin and ciprofloxacin in P chinensis were 1.68 mu g/g and 0.07 mu g/g respectively. The predicted withdrawal time for Nile tilapia was 22 days, and P. chinensis was 12 days under our experiment conditions. The residues of fitrazolidone [3-(5-nitrofurfurylidenamino)-2-oxazolidinone] and its main metabolite 3-amina-2-oxazolidinone (AOZ) in Nile tilapia were first determined by HPLC/MS. Results showed that after oral dose of 30 mg/kg for 7 days, the maximum concentration of farazolidone in Nile tilapia was 413 mu g/kg after 6 h, whereas AOZ residue reached its maximum (31 mu g/kg) right after stopping treatment. In contrast to the high metabolic rate of furazolidone, AOZ was very difficult to eliminate in vivo, thus the withdrawal time of furazolidone in Nile tilapia was 22 days at least. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
The hyphenated technique of high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was applied to the simultaneous determination of five organotin compounds (trimethyltin, dibutyltin, tributyltin, diphenyltin and triphenyltin) in seawater samples. Agilent TC-C18 column was used for the separation, the mobile phase of HPLC was CH3CN : H2O: CH3COOH=65 : 23 : 12 (phi), 0.05% TEA, and pH value was adjusted to 3.0 by diluent ammonia. The flow rate was 0.6 mL . min(-1). Five mixed organotin compounds in a mix standard solution from 100 to 0.5 mu g . L-1 were applied for the method assessment. The experimental results indicate that the correlation coefficient of calibration curves (R-2) for each organotin compound was over 0.998 and the detection limits of the five organotin compounds were lower than 3 ng . L-1. Different mixed organic solvents including dichloromethane or toluene were used for extraction of organotin and the extraction condition of organotin from seawater was optimized. The 100 mL seawater acidized by hydrochloric acid was extracted by 10 mL carbon dichloride (CH2Cl2) with 2% tropolone for 10 min twice. Extracted organic solvents were mixed And blown to one drop by nitrogen with the rate of 1.7 mL . min(-1), then 1 mL acetonitrile was added to the drop for redissolving the organotin compounds. Finally, the mixed redissolution was filtered by 0.22 mu m organic filter membrane before analysis. it was found that the only organotin compound in seawater was triphenyltin (TPHT) and the content was 53.2 ng . L-1. The recoveries test from the standard addition for diphenyltin (DPHT), dibutyltin (DBT), tributyltin (TBT) and triphenyltin (TPHT) were over 80%. However, the recovery for trimethyltin (TMT) was relatively low and the value was 50%. The reason might be attributed to the decomposition or adsorption of those compounds during the extraction procedure. Further study on this subject is in progress.
Resumo:
,,CO_2,-,10,40.0%22.7%17.5%9.0%5.7%,62.7%
Resumo:
120004104227.049Wm~(-1)4100.23590.22256%69428.6%68.0%3.4%37001900
Resumo:
1999200268pelletsfood remains736281391424224114.26%40.79%17.39%26.99%0.22%0.35%33017774418322511.83%30.87%7.36%16.00%0.15%0.62%33.17%
Resumo:
: (1) 14:00 (,) 1061 Wm-2 , 670218380 168 Wm-2 , 58 %20 %36 %14 % , 6 0. 22 ; (2) 91274 362 Wm-2 , 20 %38 %42 %; (3) , 20 :00 11 :00 , 01 :00 ; (4),
Resumo:
, , 1314 h -158 499Wm- 2, 8 9 h 18 h , , 18 h 8 h , 13 h 49, 0.200.22, 0.24 0.49, 3d 0.25, 11h 15h 0.21
Resumo:
We used an eddy covariance technique to measure evapotranspiration and carbon flux over two very different growing seasons for a typical steppe on the Inner Mongolia Plateau, China. The rainfall during the 2004 growing season (344.7 mm) was close to the annual average (350.43 mm). In contrast, precipitation during the 2005 growing season was significantly lower than average (only 126 mm). The wet 2004 growing season had a higher peak evapotranspiration (4 mm day(-1)) than did the dry 2005 growing season (3.3 mm day(-1)). In 2004, latent heat flux was mainly a consumption resource for net radiation, accounting for similar to 46% of net radiation. However, sensible heat flux dominated the energy budget over the whole growing season in 2005, accounting for 60% of net radiation. The evaporative rate (LE/R-n) dropped by a factor of four from the non-soil stress to soil water limiting conditions. Maximum half-hourly CO2 uptake was -0.68 mg m(-2) s(-1) and maximum ecosystem exchange was 4.3 g CO2 m(-2) day(-1) in 2004. The 2005 drought growing stage had a maximum CO2 exchange value of only -0.22 mg m(-2) s(-1) and a continuous positive integrated-daily CO2 flux over the entire growing season, i.e. the ecosystem became a net carbon source. Soil respiration was temperature dependent when the soil was under non-limiting soil moisture conditions, but this response declined with soil water stress. Water availability and a high vapor pressure deficit severely limited carbon fixing of this ecosystem; thus, during the growing season, the capacity to fix CO2 was closely related to both timing and frequency of rainfall events. (c) 2007 Published by Elsevier Masson SAS.
Resumo:
Stable nitrogen isotope signatures of major sources of mineral nitrogen ( mineralization of soil organic nitrogen, biological N-2 fixation by legumes, annual precipitation and plant litter decomposition) were measured to relatively define their individual contribution to grass assimilation at the Haibei Alpine Meadow Ecosystem, Qinghai, China. The results indicated that delta N-15 values (- 2.40 parts per thousand to 0.97 parts per thousand) of all grasses were much lower than those of soil organic matter (3.4 +/- 0.18 parts per thousand) and mineral nitrogen ( ammonium and nitrate together,7.8 +/- 0.57 parts per thousand). Based on the patterns of stable nitrogen isotopes, soil organic matter (3.4 +/- 0.18 parts per thousand), biological N-2 fixation (0 parts per thousand), and precipitation (- 6.34 +/- 0.24 parts per thousand) only contributed to a small fraction of nitrogen requirements of grasses, but plant litter decomposition (- 1.31 +/- 1.01 parts per thousand) accounted for 67%.
Resumo:
[1] The alpine meadow ecosystem on the Qinghai-Tibetan Plateau may play a significant role in the regional carbon cycle. To assess the CO2 flux and its relationship to environmental controls in the ecosystem, eddy covariance of CO2, H2O, and energy fluxes was measured with an open-path system in an alpine meadow on the plateau at an elevation of 3,250 m. Net ecosystem CO2 influx (Fc) averaged 8.8 g m(-2) day(-1) during the period from August 9 to 31, 2001, with a maximum of 15.9 g m(-2) day(-1) and a minimum of 2.3 g m(-2) day(-1). Daytime Fc averaged 16.7 g m(-2) day(-1) and ranged from 10.4 g m(-2) day(-1) to 21.7 g m(-2) day(-1) during the study period. For the same photosynthetic photon flux density (PPFD), gross CO2 uptake (Gc) was significantly higher on cloudy days than on clear days. However, mean daily Gc was higher on clear days than on cloudy days. With high PPFD, Fc decreased as air temperature increased from 10degreesC to 23degreesC. The greater the difference between daytime and nighttime air temperatures, the more the sink was strengthened. Daytime average water use efficiency of the ecosystem (WUEe) was 8.7 mg (CO2)(g H2O)(-1); WUEe values ranged from 5.8 to 15.3 mg (CO2)(g H2O)(-1). WUEe increased with the decrease in vapor pressure deficit. Daily albedo averaged 0.20, ranging from 0.19 to 0.22 during the study period, and was negatively correlated with daily Fc. Our measurements provided some of the first evidence on CO2 exchange for a temperate alpine meadow ecosystem on the Qinghai-Tibetan Plateau, which is necessary for assessing the carbon budget and carbon cycle processes for temperate grassland ecosystems.
