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401.
BACKGROUND: Flumioxazin is a soil-applied herbicide recommended for broadleaf weed control in soybeans and peanuts, and was recently introduced for vineyard weed management. Considering the limited information available in relation to flumioxazin field soil behaviour, the main objectives of this study were to determine the persistence, adsorption and movement of flumioxazin in soil in four Chilean vineyard production areas. RESULTS: DT(50) values ranged from 10.6 +/- 1.0 to 32.1 +/- 3.1 days between localities, being correlated with rain events, time between herbicide application and first heavy rain event, and soil pH. Flumioxazin soil residue found at 90 days after application (DAA) varied from 9.6 to 24.9% of the initial amount applied, and depended on the total rainfall amount that occurred during the first 90 DAA. Herbicide leaching below 15 cm was approximately 45% of the flumioxazin detected at 90 DAA in the whole soil profile. Flumioxazin maximum leaching soil depth was 45 cm at all locations. K(d) values varied from 2.54 to 6.51 mg L(-1), depending on localities and soil profile depth, and correlated positively with organic carbon and clay content. CONCLUSIONS: These results indicate that flumioxazin is a herbicide with low environmental risk owing to its short DT(50), reduced soil residues 3 months after application and low effective dose. 相似文献
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Marina Marrari Sergio R. Signorini Charles R. McClain Marcelo Pájaro Patricia Martos María Delia Viñas Jorge Hansen Roxana Dimauro Georgina Cepeda Claudio Buratti 《Fisheries Oceanography》2013,22(3):247-261
The mid‐shelf front (MSF) of the Buenos Aires province continental shelf in the Southwestern Atlantic Ocean plays a central role in the pelagic ecosystem of the region acting as the main spring reproductive area for the northern population of the Argentine anchovy Engraulis anchoita and supporting high concentrations of chlorophyll as well as zooplankton, the main food of anchovy. To investigate the influence of environmental variability on the reproductive success of E. anchoita, we analyzed a 13‐yr time series (1997–2009) of environmental data at MSF including chlorophyll dynamics, as well as zooplankton composition and abundance, ichthyoplankton distributions, and recruitment of E. anchoita. Spring chlorophyll concentrations showed high interannual variability and were mainly influenced by changes in water temperature and vertical stratification, which in turn control nutrient supply to the surface. Chlorophyll dynamics (magnitude, timing, and duration of the spring bloom) explained most of the variability observed in E. anchoita recruitment, most likely via fluctuations in the availability of adequate food for the larvae. Our results suggest that satellite ocean color products can be valuable tools for understanding variability in ecosystem dynamics and its effects on the recruitment of fish. 相似文献
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Álvarez‐Ruiz Píndaro Mejía‐Ruiz Claudio Humberto Magallón‐Barajas Francisco Javier Escobedo‐Bonilla César Marcial 《Aquaculture Research》2013,44(5):772-782
White spot syndrome virus (WSSV) is a major threat for farmed shrimp worldwide. RNA interference (RNAi) is the most recent tool against viral diseases. Rab7 silencing effectively inhibited virus infections in juvenile shrimp, but the antiviral effect in brooders remains unknown. This study found a homologue Penaeus monodon Rab7 gene in Litopenaeus vannamei brooders from Mexico. Sequence identity was >99% to a Thai LvRab7 sequence and >94% to Rab7 sequences from P. monodon or Marsupenaeus japonicus. Animals treated with a partial (494 bp) or a complete (618 bp) LvRab7 dsRNA sequences and challenged 48 h post treatment (hpt) with a high WSSV dose showed 80–88% mortality respectively. Shrimp treated with 4 or 20 μg LvRab7 dsRNA and challenged with a WSSV high dose had 80% mortality each, but it was reduced to 33% and 40%, respectively, with a low dose. Efficacy of dsRNA to reduce shrimp mortality was dependent on virus dose used regardless of dsRNA concentration. A significant reduction in LvRab7 mRNA levels was observed at 120 hpt. In conclusion, silencing LvRab7 in brooders showed a mild antiviral effect against a WSSV challenge at 48 hpt. 相似文献
405.
The administration of antimicrobials to control bacterial pathologies in Chilean scallop hatcheries is a frequent practice, but their effects on these cultures remained unknown. This study was undertaken to obtain information on the effect of the administration of florfenicol and oxytetracycline on the growth, survival and bacterial content of scallop larvae under farming conditions. Florfenicol‐treated cultures exhibited high survival rates (44% after 17 days of culture), whereas cultures not treated or treated with oxytetracycline collapsed after 11 days of culture. Surprisingly, no significant differences in the heterotrophic (Tukey test; P = 0.226) and Vibrio (Tukey test; P = 0.666) concentrations between the oxytetracycline‐treated and untreated larval cultures were observed. Otherwise, florfenicol administered directly into rearing tanks produced significantly higher larval growth (Tukey test; P = 0.0001) and survival (Tukey test; P = 0.011) than bath treatment. When 2 and 4 mg L?1 of florfenicol were compared, no significant differences in growth (t‐test; P = 0.4596) and survival (Tukey test; P = 0.057) were observed, suggesting that a concentration of 2 mg L?1 is sufficient to ensure larval production. The present results demonstrate the efficacy of florfenicol‐based therapy to increase larval survival and growth at commercial scale and prompt the necessity to standardize its use in Chilean scallop hatcheries. 相似文献
406.
Effects of stocking density and natural food availability on the extensive cage culture of pejerrey (Odontesthes bonariensis) in a shallow Pampean lake in Argentina
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Javier Ricardo Garcia de Souza Patricio José Solimano Tomás Maiztegui Claudio Rafael Mariano Baigún Darío César Colautti 《Aquaculture Research》2015,46(6):1332-1344
An experiment was conducted for 80 days at La Salada de Monasterio Lake (Buenos Aires, Argentina) to assess the effect of stocking density and natural food availability on the growth and production of zooplanktivorous juveniles of pejerrey (Odontesthes bonariensis) in extensive cage culture. Ten cages were installed and stocked with 33‐day‐old fish, at three density treatments: 25, 50 and 75 ind. m?3. Zooplankton was analysed in terms of abundance, biomass and diversity considering three size classes. Caged pejerrey diet was assessed regularly. The pejerrey gut contents composition was clearly different from cage zooplankton, showing a trend to contain bigger components. Reared fish exhibited a tendency to diversification of the diet and to change the mean prey size depending on fish length and stocking density. Regression models showed a positive and direct effect of the bigger zooplankton biomass on fish growth rates, which were also inversely affected by the availability of smaller zooplankton. The results demonstrate that stocking density and available zooplankton, in both quantity and quality, are key factors in regulating extensive cage culture of pejerrey. Handling stocking densities in a dynamic way it is possible to maximize fish growth, biomass harvest or fish number according to the goals of production. 相似文献
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Gagliardi G Salza M Avino S Ferraro P De Natale P 《Science (New York, N.Y.)》2010,330(6007):1081-1084
The measurement of relative displacements and deformations is important in many fields such as structural engineering, aerospace, geophysics, and nanotechnology. Optical-fiber sensors have become key tools for strain measurements, with sensitivity limits ranging between 10(-9) and 10(-6)ε hertz (Hz)(-1/2) (where ε is the fractional length change). We report on strain measurements at the 10(-13)ε-Hz(-1/2) level using a fiber Bragg-grating resonator with a diode-laser source that is stabilized against a quartz-disciplined optical frequency comb, thus approaching detection limits set by thermodynamic phase fluctuations in the fiber. This scheme may provide a route to a new generation of strain sensors that is entirely based on fiber-optic systems, which are aimed at measuring fundamental physical quantities; for example, in gyroscopes, accelerometers, and gravity experiments. 相似文献