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71.
Mussels (Mytilus edulis) were exposed to the algaeAlexandrium ostenfeldii, Chrysochromulina polylepis, Gyrodinium aureolum, Gymnodinium galatheanum andHeterosigma akashiwo for 24 h; significant reductions in growth rate, as compared to the control, were observed after exposure toA. ostenfeldii, C. polylepis, G. aureolum andG. galatheanum at initial concentrations of 4.5 × 106, 110 × 106, 9 × 106 and 120 × 106 cells l–1, respectively. Exposure to high initial concentrations of the non-toxic algaeTetraselmis suecica (174 × 106 cells l–1) andIsochrysis galbana (610 × 106 cells l–1) showed no adverse effect on growth rate. When mussels with reduced growth were transferred to clean seawater, they recovered to > 90% of control growth within 2 to 4 d. Exposure to algal filtrates of the toxic algal cultures produced no reduction in growth rate. 相似文献
72.
The effect of eight polycyclic aromatic compounds (PACs) on the seed emergence and early life-stage growth of three terrestrial plants (Sinapsis alba, Trifolium pratense and Lolium perenne) were studied in a greenhouse, using a Danish agricultural soil with an organic carbon content of 1.6%. After three weeks of exposure, seed emergence and seedling weight (fresh weight and dry weight) were determined. Exposure concentrations were verified with chemical analysis. The substances tested were four polycyclic aromatic hydrocarbons (fluoranthene, pyrene, phenanthrene and fluorene), the N-, S-, and O-substituted analogues of fluorene (carbazole, dibenzothiophene and dibenzofuran, respectively), and the quinoline representative acridine. Seedling growth was a far more sensitive endpoint than seed emergence for all substances. Concentrations estimated to give a 20% reduction of seedling fresh weight (EC20-values) ranged from 36 to 290 mgkg(-1) for carbazole, 43 to 93 mgkg(-1) for dibenzofuran, 37 to 110 mgkg(-1) for dibenzothiophene, 140 to 650 mgkg(-1) for fluoranthene, 55 to 380 mgkg(-1) for fluorene, 37 to 300 mgkg(-1) for phenanthrene, and 49 to 1300 mgkg(-1) for pyrene. For acridine, no toxicity was observed within the concentration range tested (1-1000 mgkg(-1)). As illustrated by the EC20-values, there was a rather large difference in sensitivity between the species, and T. pratense was the most sensitive of the species tested. 相似文献
73.
74.
Christian Turra Carlos Eduardo de Freitas Vian Flávia Angeli Guisi Nielsen Priscilla Silva Santos Luis Fernando de Freitas Penteado 《Journal of Agricultural and Environmental Ethics》2014,27(4):663-679
This study aims to characterize the different types of certification in the Brazilian citriculture as well as analyze the major changes in the market. The paper also has the objective to discuss how social and environmental factors influence the demand for food certifications and the sustainability and ethics aspects in the field. Therefore, a literature review on the subject was carried out as well as a qualitative research using interviews with certifiers, governmental institutions, farmers, cooperatives and producer associations. The certification is becoming mandatory for those working in foreign markets and for those working nationally; it can be a competitive differential. The organic certification in citriculture shows the highest number of growers. Companies with large areas of citrus and the orange juice processing industry are adhering to this certification in order to maintain themselves competitive in the market. There is an enormous potential of Brazilian citriculture certification, because the certified area is still less than 6 % of the total area. Certification reduces the asymmetry of information and consists of an important step towards sustainability although incapable of solely guaranteeing it. 相似文献
75.
76.
The Science of Nature - 相似文献
77.
Michael Poulsen Adrianne N. Bot Mogens G. Nielsen Jacobus J. Boomsma 《Behavioral ecology and sociobiology》2002,52(2):151-157
The paired exocrine metapleural glands present in the large majority of ant species produce compounds with antibiotic properties. In the leaf-cutting ant, Acromyrmex octospinosus, the secretion consists of more than 20 different compounds and it has generally been assumed that the glands serve as a general defence against various infectious microbes of fungal and bacterial origin. We present results illuminating the direct costs and benefits of these metapleural gland defences in A. octospinosus. We show that major workers of this leaf-cutting ant experience a significant reduction in their respiration rate when the metapleural glands are experimentally closed, indicating that metapleural gland secretion incurs a substantial cost and that the production of compounds from these glands is terminated when the ants are incapable of secreting them. In another set of experiments, we show that the ability to secrete antibiotic compounds from the metapleural glands is of significant importance when ants are exposed to a general but potentially virulent insect pathogen, Metarhizium anisopliae. Infection with this fungus is lethal within a few days when ants have their metapleural glands experimentally closed, but relatively harmless when the metapleural glands are functional. These findings support experimentally the view that the metapleural glands play an important hygienic role in leaf-cutting ants. 相似文献
78.
Investigations at former dry cleaning sites in Denmark show that sewer systems often are a major vapor intrusion pathway for chlorinated solvents to indoor air. In more than 20 percent of the contaminated drycleaner sites in Central Denmark Region, sewer systems were determined to be a major vapor intrusion pathway. Sewer systems can be a major intrusion pathway if contaminated groundwater intrudes into the sewer and contamination is transported within the sewer pipe by water flow in either free phase or dissolved states. Additionally, the contamination can volatilize from the water phase or soil gas can intrude the sewer system directly. In the sewer, the gas phase can migrate in any direction by convective transport or diffusion. Indications of the sewer as a major intrusion pathway are:
- higher concentrations in the upper floors in buildings,
- higher concentrations in indoor air than expected from soil gas measurements,
- higher concentrations in bathrooms/kitchen than in living rooms,
- chlorinated solvents in the sewer system, and
- a pressure gradient from the sewer system to indoor air.
- prevention of the contaminants from intruding into the sewer system or
- prevention of the contaminated gas in the sewer system from intruding into the indoor air.
- lining of the sewer piping to prevent the contamination from intruding into the sewer;
- sealing the sewer system in the building to prevent the contamination from the sewer system to intrude the indoor air;
- venting of manholes; and
- depressurizing the sewer system.
79.
Particle trajectories of 6.4m Latex spheres were recorded by video, both near an isolated blue mussel, Mytilus edulis, gill filament and, in place of an intact interfilamentary canal, in a model canal of width 200, 100 or 70m, formed by a transparent plate positioned next to a gill filament. Each arrangement was placed in a 2 x 10 x 10 cm test vessel filled with seawater. Serotonin (nerve-transmitter) stimulation was used to activate lateral cilia and to either lock latero-frontal cirri at the end of an active stroke (10-5
M), or to activate them (10-6
M), yielding lateral cilia beat frequencies of 19 and 16 Hz, respectively. With latero-frontal cirri locked, image analysis of particle tracks gave maximum velocities of ca. 2.9±0.2mm s-1 close to the tips of lateral cilia, for both isolated filament and model canal cases. Experimental velocity profiles along the 200-m wide model canal were recorded and used as good approximations to the fluid velocity because of the low Reynolds number. A two-dimensional steady model was proposed for the gill pump, assumed to only comprise lateral cilia. This model was solved numerically for the experimental model, canal in the vessel and the results showed satisfactory agreement with experimental volocity profiles from particle tracks. The numerical approach was also applied to a model of a single interfilamentary canal in the vessel. The resulting mean velocity in the canal was 1.70 mm s-1, but the resistance to flow in the model was less than that in an intact mussel gill. Video graphs of particle tracks indicated that active latero-frontal cirri play a role in the transfer of particles from through current to frontal current, probably by means of a strong interaction through the motion of intervening fluid rather than through a direct physical contact. M. edulis specimens used in the present study were collected in 1990 at Helsingør and in 1991 at Kerteminde, Denmark. 相似文献
80.
Jessica R. Frost Anneke Denda Clive J. Fox Charles A. Jacoby Rolf Koppelmann Morten Holtegaard Nielsen Marsh J. Youngbluth 《Marine Biology》2012,159(2):239-253
The ecology of small, gelatinous zooplankton is not integrated into management of Dogger Bank (54° 00′ N, 3° 25′ E to 55°
35′ N, 2° 20′ E). In pursuit of this goal, gelatinous zooplankton and their potential prey were sampled along a transect across
the bank on June 10–16, 2007. Eleven species of small medusae and ctenophores were collected, with six abundant taxa occurring
in greater numbers below the thermocline and in the shallower, southeastern portion of the bank. There were no statistically
significant diel changes in distribution. In contrast, potential prey were distributed more evenly across the bank and throughout
the water column. Isotopic analyses revealed that gelatinous zooplankton fed on both smaller (100–300 μm) and larger (>300 μm)
mesozooplankton, but also potentially on each other. These ecological insights suggest that small medusae and ctenophores
should be integrated into sustainable management of Dogger Bank. 相似文献