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The inorganic nitrogen transformations occurring at a municipal waste leachate treatment facility were investigated. The treatment
facility consisted of a collection well and an artificial wetland between two aeration ponds. The first aeration pond showed
a decrease in ammonium (from 3480 (± 120) to 630(± 90) mg ⋅ L−1), a reduction in inorganic nitrogen load (3480 to 1680 mg N ⋅ L−1), and an accumulation of nitrite (< 1.3 mg-N ⋅ L−1 in the collection well, to 1030 mg-N ⋅ L−1). Incomplete ammonium oxidation was presumably the result of the low concentration of carbonate alkalinity (∼2 mg ⋅ L−1), which may cause a limitation in the ammonium oxidation rate of nitrifiers. Low carbonate alkalinity levels may have been
the result of stripping of CO2 from the first aeration pond at the high aeration rates and low pH. Various chemodenitrification mechanisms are discussed
as the reason for the reduction in the inorganic nitrogen load, including; the reduction of nitrite by iron (II) (producing
various forms of gaseous nitrogen); and reactions involving nitrous acid. It is suggested that the accumulation of nitrite
may be the result of inhibition of nitrite oxidizers by nitrous acid and low temperatures. Relative to the first aeration
pond, the speciation and concentration of inorganic nitrogen was stable in the wetlands and 2nd aeration pond. The limited
denitrification in the wetlands most probably occurred due to low concentrations of organic carbon, and short retention times. 相似文献
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The association of sponges with microorganisms has been accepted to be a common feature of the phylum Porifera. Herein we describe the association between filamentous Archaea and three Mediterranean species of sponges from the family Axinellidae (Porifera: Demospongiae). Axinella damicornis, A. verrucosa and Axinella sp. harbor a high concentration of filamentous Archaea in the collagen that surrounds the siliceous spicules that form their skeleton. These Archaea have been found in every axinellid specimen studied, regardless of their environment and collection time. The morphology of the filaments has been studied using transmission electron microscopy, and they all show similar characteristics. Their nature has been determined by in situ hybridization experiments and by PCR amplification and sequencing of their 16S DNA. Each sponge species contains a single filamentous archaeal phylotype. The Archaea of the three sponges are closely related to each other and to the marine "group 1" crenarchaeotes. Our findings suggest that this newly described association could be defined as a symbiosis, where biochemical and/or metabolic relationships between the sponge hosts and their symbionts remain to be determined. 相似文献
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Summary. The capacity of benzoxazolinone metabolization of dicotyledonous species characteristic for the former vegetation classes
Secalietea (grain field weed communities) and Chenopodietea (hoed vegetable communities) was estimated by the production of
BOA-6-OH, BOA-6-β-O-glucoside, and BOA-N-glucoside. Except for Urtica urens, Galinsoga ciliata, and Polygonum aviculare (Chenopodietea), all species tested were able to synthesize BOA-6-OH, its glucoside, and BOA-N-glucoside, but effectiveness
of BOA metabolism differed highly depending on species and plant organ. There was no correlation between bacterial phenoxazinone
production and appearance of metabolites in the plants. Bioassays demonstrated that N-glucosylation is more efficient in BOA
detoxification than O-glucosylation. The intermediate BOA-6-OH, however, is more harmful than BOA itself. It is therefore
assumed that the ability to synthesize BOA-N-glucoside reduces the sensitivity to BOA strikingly. Since the detoxification
capacity did not correlate with the taxonomic position, the affiliation of the species tested with the corresponding plant
communities was taken into consideration. Evidently, the ecobiochemical potential of species to detoxify benzoxazolinone,
regarded as an essential secondary compound in rye and wheat fields, reflects their occurrence in those plant associations.
The ability to cope with the compound could be the result of co-evolutionary processes and presents a hidden aspect of allelopathic
interaction.
Received 4 January 1999; accepted 14 June 1999. 相似文献
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Estimating the amounts of resources consumed by individuals is important in many studies. For predators, allometric relationships
can be used to extrapolate the size of preys from undigested remains found in the stomach and in the faeces. However, such
equations are available for a limited number of species. Based on a large sample size gathered in New Caledonia on both predators
(sea kraits) and their preys (anguilliform fishes), we provide the first allometric relationships that allow estimating accurately
the mass and the size of various anguilliform fish species. 相似文献
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Desulfobacter sp. (Strain 3ac10), an acetate-utilizing sulphatereducing bacteria, was added to sterile marine pore water spiked with 14C-acetate, and changes in both the natural acetate pool and the added 14C-acetate were measured over time. Initially, both the added 14C-acetate and the chemically measured acetate were rapidly mineralized, but then the rate of removal decreased and a significant amount (approximately 20%) of both 14C-acetate and chemically measured acetate remained unmetabolised. In a replicate experiment, approximately 50% of the acetate was not metabolised. Kinetic analysis of the data indicated that there were two pools of acetate in the original pore water, a biologically available pool (which is rapidly metabolised) and a recalcitrant pool (which is only very slowly metabolised). Addition of 14C-acetate after the biologically available acetate had been removed resulted in rapid removal of the added acetate but no change in the recalcitrant acetate pool. The implications of this data to radiolabelled techniques of measuring in situ acetate turnover are discussed. 相似文献
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Mark R. S. Johannes Kim D. Hyatt Josie K. Cleland Leila Hanslit Margot M. Stockwell 《Journal of the American Water Resources Association》2002,38(2):555-562
ABSTRACT: Watershed stewardship activities throughout North America have evolved into a process that requires more involvement in planning and decision making by community stakeholders. Active involvement of all stakeholders in the process of watershed stewardship is dependent on effective exchange of information among participants, and active involvement of a wide range of stakeholders from “communities of place” as well as those from “communities of interest.” We developed a map‐based stream narrative tool as a means to: (a) assemble a wealth of incompletely documented, “traditional” ecological or natural history observations for rivers or streams; and (b) promote a higher level of active involvement by community stakeholders in contributing to information‐based, watershed management. Creation of stream narratives is intended for use as a tool to actively engage local stakeholders in the development of a more comprehensive information system to improve management for multiple stewardship objectives in watersheds. Completion of map‐based stream narrative atlases provides a valuable supplement to other independent efforts to assemble observations and knowledge about land‐based natural resources covering entire watersheds. We are confident that completion of stream narrative projects will make a valuable addition to the information and decision making tools that are currently available to the public and resource agencies interested in advancing the cause of community‐based approaches to watershed and ecosystem management. 相似文献