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11.
12.
The efficacy of vegetative buffer strips (VBS) in removing herbicides deposited from surface runoff is related to the ability of plant species to promote rapid herbicide degradation. A growth chamber study was conducted to compare C-atrazine (ATR) degradation profiles in soil rhizospheres from different forage grasses and correlate ATR degradation rates and profiles with microbial activity using three soil enzymes. The plant treatments included: (i) orchardgrass ( L.), (ii) smooth bromegrass ( Leyss.), (iii) tall fescue ( Schreb.), (iv) Illinois bundle flower (), (v) perennial ryegrass ( L.), (vi) switchgrass ( L.), and (vii) eastern gamagrass (). Soil without plants was used as the control. The results suggested that all plant species significantly enhanced ATR degradation by 84 to 260% compared with the control, but eastern gamagrass showed the highest capability for promoting biodegradation of ATR in the rhizosphere. More than 90% of ATR was degraded in the eastern gamagrass rhizosphere compared with 24% in the control. Dealkylation of atrazine strongly correlated with increased enzymatic activities of β-glucosidase (GLU) ( = 0.96), dehydrogenase (DHG) ( = 0.842), and fluorescein diacetate (FDA) hydrolysis ( = 0.702). The incorporation of forage species, particularly eastern gamagrass, into VBS designs will significantly promote the degradation of ATR transported into the VBS by surface runoff. Microbial parameters widely used for assessment of soil quality, e.g., DHG and GLU activities, are promising tools for evaluating the overall degradation potential of various vegetative buffer designs for ATR remediation. 相似文献
13.
Individuals of the midwater ctenophore Bathocyroe fosteri (0.01 to 1.6 g dry weight, DW) were collected from Bahamian waters by the submersible Johnson-Sea-Link during May and September/October 1983 and October/November 1984 from 530 to 700 m depth. Metabolic rates were measured and showed oxygen consumption to be in the range of 0.01 to 0.18 mg O2 g-1 DW h-1 at temperatures ranging from 9° to 12°C. Ammonium excretion (0.01 to 0.14 g-at N g-1 DW h-1) was typically low. Energy expenditures estimated from respiration data (ca. 7% body C d-1) indicated that one to three midwater crustacean prey (ca. 150 g C d-1) could provide the daily maintenance ration required by a 40 mm ctenophore. These metabolic characteristics complemented in situ observations of poor locomotor ability and passive feeding behavior. 相似文献
14.
Measurements of the defecation rate of Salpa thompsoni were made at several stations during two cruises west of the Antarctic Peninsula in 2004 and 2006. Rates were quantified
in terms of number of pellets, pigment, carbon and nitrogen for a wide size range of both aggregate and solitary salps. Measured
defecation rates were constant over several hours when salps were held at near-surface conditions from which they had been
collected. The defecation rate per salp increased with both salp size and the ambient level of particulate organic matter
(POM) in the upper water column. The weight-specific defecation rate ranged between 0.5 and 6% day−1 of salp body carbon, depending on the concentration of available particulate matter in the water. Carbon defecation rates
were applied to biomass estimates of S. thompsoni to calculate daily carbon defecation rates for the populations sampled during the two cruises. Dense salp populations of
over 400 mg C m−2 were calculated to produce about 20 mg C m−2 day−1, comparable to other major sources of vertical flux of organic material in the Southern Ocean. Measured sinking rates for
salp fecal pellets indicated that the majority of this organic material could reach deep sediments within a few days, providing
a fast and direct pathway for carbon to the deep ocean. 相似文献
15.
B. P. Kremer 《Marine Biology》1980,59(2):95-103
The brown macroalgae Laminaria digitata (Huds.) Lamour., L. hyperborea (Gunn.) Foslie, and L. saccharina (L.) Lamour. (Laminariales, Phaeophyceae) have been investigated for carbon assimilation and assimilate biosynthesis in different tissues (meristoderm, cortex, medulla) of stipes and blades. Carboxylation via ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and phosphoenolpyruvate carboxykinase (EC 4.1.32) follows a transversal gradient from the outer to the inner tissues with maximum activity of enzymatic CO2 fixation in the meristoderm. Such transversal profiles are also recorded for photosynthetic and dark carbon assimilation as well as for kinetics of assimilate 14C-labelling in isolated tissues. Differential chemical constitution of the blade and stipe tissues examined and results from assimilate biosynthesis are discussed with regard to a transversal translocation of photosynthates from meristodermal to cortical and medullar cells. 相似文献
16.
Freshly collected pieces of the hermatypic coral Acropora cf. scandens containing dinoflagellate endosymbionts (presumably Gymnodinium microadriaticum) were allowed to assimilated 14C from H14CO
3
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in the light and in the dark. Time-dependent carbon uptake resulted in intense 14C-labelling of ethanol-soluble as well as of insoluble assimilates. About forty 14C-labelled assimilates have been identified. Polymeric (ethanol-insoluble) compounds achieve about 30% of total radiocarbon incorporation after 60 min incubation. Kinetics of 14C-labelling of single assimilates are analyzed. Percentages of typical photosynthates in the soluble fraction undergo characteristic time-dependent changes. Lipids proved to be the main accumulation products of carbon assimilation by incorporating more than 50% of 14C after 60 min photosynthesis. The data indicate that low-molecular weight photosynthates such as 14C-glycerol and 14C-glucose are rapidly converted to constituents of the polymeric fraction(s) of the coral. Besides peptides, polysaccharides, and lipophilic substances, considerable amounts of 14C are confined to skeletal CaCO3 of the coral. The results are discussed with respect to trophic and metabolic interrelationships between the autotrophic dinoflagellates and the A. cf. scandens tissues. 相似文献
17.
Kremer AR 《Disasters》1992,16(3):207-216
Between 1985 and 1988 large-scale spray campaigns were carried out against migratory crop pests in the Sahel. The Malian government and its donors subsequently adopted this emergency response to a natural disaster as a long-term strategy for crop protection in Sahelian Mali. This is financially unsustainable, probably economically wasteful and stunts the development of other plant protection strategies. A similar process has occurred in Burkina Faso, Niger and Senegal. Donors should therefore exercise critical, collective control over the release of pesticide aid and should subject it to economic evaluation. 相似文献
18.
James N. Kremer Jamie M.P. Vaudrey Deanna L. Bergondo Chris Kincaid Mark J. Brush 《Ecological modelling》2010,221(7):1080-314
A computational scheme has been developed and tested to simulate property exchange by advection and dispersion in estuaries at time and space scales that are well suited to ecological and management simulations, but are coarse relative to the demands of physical hydrodynamic models. An implementation of the Regional Ocean Model System (ROMS) for the Providence River and Narragansett Bay (RI, USA) was used to determine property exchanges between the spatial elements of an ecological box model. The basis for the method is the statistical tabulation of numerical dye experiments done with the full ROMS physical model. The ROMS model domain was subdivided into fifteen coarse boxes, each with two vertical layers, defining 30 elements that were used for the box model simulations. Dye concentrations were set to arbitrary initial concentrations for all ROMS grids in the large elements, and the ROMS model was run for 24 h. The final distribution of the dye among the elements was used as a tracer for property exchange over that day and was used to develop an exchange matrix. Box model predictions of salinity over 77 days in each element compared favorably with ROMS simulated salinity averaged over the same spatial elements, although the disparity was greater in areas where large river inflows caused strong gradients in ROMS within elements assumed to be homogeneous in the box model. The 77-day simulation included periods of high and low river flow. Despite the large size of the spatial elements, dispersion artifacts were small, much less than the modeled daily exchanges. While others have taken a similar approach, we found a number of theoretical and practical considerations deserved careful attention for this approach to perform satisfactorily. Whereas the full ROMS model takes 9 days on a powerful computing cluster to compute the physics simulation for 77 days, the box model simulates physics and biology for the same interval in 5 s on a personal computer, and a full year in under 1 min. The exchange matrix mixing model is a fast, cost effective, and convenient way to simulate daily variation of complex estuarine physics in ecological modeling at appropriate scales of space and time. 相似文献
19.
Enrico Di Minin Christoph Fink Anna Hausmann Jens Kremer Ritwik Kulkarni 《Conservation biology》2021,35(2):437-446
Social media data are being increasingly used in conservation science to study human–nature interactions. User-generated content, such as images, video, text, and audio, and the associated metadata can be used to assess such interactions. A number of social media platforms provide free access to user-generated social media content. However, similar to any research involving people, scientific investigations based on social media data require compliance with highest standards of data privacy and data protection, even when data are publicly available. Should social media data be misused, the risks to individual users' privacy and well-being can be substantial. We investigated the legal basis for using social media data while ensuring data subjects’ rights through a case study based on the European Union's General Data Protection Regulation. The risks associated with using social media data in research include accidental and purposeful misidentification that has the potential to cause psychological or physical harm to an identified person. To collect, store, protect, share, and manage social media data in a way that prevents potential risks to users involved, one should minimize data, anonymize data, and follow strict data management procedure. Risk-based approaches, such as a data privacy impact assessment, can be used to identify and minimize privacy risks to social media users, to demonstrate accountability and to comply with data protection legislation. We recommend that conservation scientists carefully consider our recommendations in devising their research objectives so as to facilitate responsible use of social media data in conservation science research, for example, in conservation culturomics and investigations of illegal wildlife trade online. 相似文献
20.
Impact of genetically modified crops and their management on soil microbially mediated plant nutrient transformations 总被引:1,自引:0,他引:1
One of the potential environmental effects of the recent rapid increase in the global agricultural area cultivated with transgenic crops is a change in soil microbially mediated processes and functions. Among the many essential functions of soil biota are soil organic matter decomposition, nutrient mineralization and immobilization, oxidation-reduction reactions, biological N fixation, and solubilization. However, relatively little research has examined the direct and indirect effects of transgenic crops and their management on microbially mediated nutrient transformations in soils. The objectives of this paper are to review the available literature related to the environmental effects of transgenic crops and their management on soil microbially mediated nutrient transformations, and to consider soil properties and climatic factors that may affect the impact of transgenic crops on these processes. Targeted genetic traits for improved plant nutrition include greater plant tolerance to low Fe availability in alkaline soils, enhanced acquisition of soil inorganic and organic P, and increased assimilation of soil N. Among the potential direct effects of transgenic crops and their management are changes in soil microbial activity due to differences in the amount and composition of root exudates, changes in microbial functions resulting from gene transfer from the transgenic crop, and alteration in microbial populations because of the effects of management practices for transgenic crops, such as pesticide applications, tillage, and application of inorganic and organic fertilizer sources. Possible indirect effects of transgenic crops, including changes in the fate of transgenic crop residues and alterations in land use and rates of soil erosion, deserve further study. Despite widespread public concern, no conclusive evidence has yet been presented that currently released transgenic crops, including both herbicide and pest resistant crops, are causing significant direct effects on stimulating or suppressing soil nutrient transformations in field environments. Further consideration of the effects of a wide range of soil properties, including the amount of clay and its mineralogy, pH, soil structure, and soil organic matter, and variations in climatic conditions, under which transgenic crops may be grown, is needed in evaluating the impact of transgenic crops on soil nutrient transformations. Future environmental evaluation of the impact of the diverse transgenic crops under development could lead to an improved understanding of soil biological functions and processes. 相似文献