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  • 1
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    ISSN: 1365-2486
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Energietechnik , Geographie
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 52 (1982), S. 181-186 
    ISSN: 1432-1939
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The demography of shoots of eight populations of a herbaceous perennial exhibiting clonal growth, is presented. The study was done along an elevational gradient, from a more open secondary mixed forest to a denser, more mature stand. Most shoots lived one to three years on the average, but shoots as old as twelve years were found. Large variation in formation and mortality of shoots was observed among plots and years. Yearly trends in the mortality rates of site replicates showed a higher correlation than rates of shoot formation. Although the density of shoots was highest in the drier sites, the turnover of shoots was highly variable and apparently uncorrelated with site location. Age structures revealed a tendency of longer-lived and higher reproductive activities among shoots from more mesic sites. It is hypothesized that environmental rather than density controls are primary causes of the population dynamics observed in this species.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    ISSN: 1573-5125
    Schlagwort(e): denitrification ; eutrophication ; estuary ; nitrogen ; sediment-water exchange
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In this review of sediment denitrification in estuaries and coastal ecosystems, we examine current denitrification measurement methodologies and the dominant biogeochemical controls on denitrification rates in coastal sediments. Integrated estimates of denitrification in coastal ecosystems are confounded by methodological difficulties, a lack of systematic understanding of the effects of changing environmental conditions, and inadequate attention to spatial and temporal variability to provide both seasonal and annual rates. Recent improvements in measurement techniques involving 15 N techniques and direct N2 concentration changes appear to provide realistic rates of sediment denitrification. Controlling factors in coastal systems include concentrations of water column NO 3 − , overall rates of sediment carbon metabolism, overlying water oxygen concentrations, the depth of oxygen penetration, and the presence/absence of aquatic vegetation and macrofauna. In systems experiencing environmental change, either degradation or improvement, the importance of denitrification can change. With the eutrophication of the Chesapeake Bay, the overall rates of denitrification relative to N loading terms have decreased, with factors such as loss of benthic habitat via anoxia and loss of submerged aquatic vegetation driving such effects.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 16 (2006): 2091–2122, doi:10.1890/1051-0761(2006)016[2091:MFMDDA]2.0.CO;2.
    Beschreibung: Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3-) and nitrite (NO2-), to the gases nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2), is important to primary production, water quality and the chemistry and physics of the atmosphere at ecosystem, landscape, regional and global scales. Unfortunately, this process is very difficult to measure, and existing methods are problematic for different reasons in different places at different times. In this paper, we review the major approaches that have been taken to measure denitrification in terrestrial and aquatic environments and discuss the strengths, weaknesses and future prospects for the different methods. Methodological approaches covered include; 1) acetylene-based methods, 2) 15N tracers, 3) direct N2 quantification, 4) N2/Ar ratio quantification, 5) mass balance approaches, 6) stoichiometric approaches, 7) methods based on stable isotopes, 8) in situ gradients with atmospheric environmental tracers and 9) molecular approaches. Our review makes it clear that the prospects for improved quantification of denitrification vary greatly in different environments and at different scales. While current methodology allows for the production of accurate estimates of denitrification at scales relevant to water and air quality and ecosystem fertility questions in some systems (e.g., aquatic sediments, well defined aquifers), methodology for other systems, especially upland terrestrial areas, still needs development. Comparison of mass balance and stoichiometric approaches that constrain estimates of denitrification at large scales with point measurements (made using multiple methods), in multiple systems, is likely to propel more improvement in denitrification methods over the next few years.
    Schlagwort(e): Denitrification ; Greenhouse effect ; Nitrate ; Nitric oxide nitrogen ; Nitrous oxide ; Stable isotopes ; Water quality
    Repository-Name: Woods Hole Open Access Server
    Materialart: Preprint
    Format: 822728 bytes
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Pollution Bulletin 56 (2008): 1049-1056, doi:10.1016/j.marpolbul.2008.03.010.
    Beschreibung: The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.
    Beschreibung: This paper was developed under the Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB) core research project on HABs and Eutrophication and the GEOHAB regional focus on HABs in Asia. GEOHAB is supported by the International Oceanographic Commission (IOC) of UNESCO and by the Scientific Committee on Oceanic Research (SCOR), which are, in turn, supported by multiple agencies, including NSF and NOAA of the USA.
    Schlagwort(e): Urea dumping ; Ocean fertilization ; Carbon credits ; Sulu Sea ; Carbon sequestration ; Harmful algae ; Toxic dinoflagellates ; Cyanobacteria ; Hypoxia
    Repository-Name: Woods Hole Open Access Server
    Materialart: Preprint
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Publikationsdatum: 2022-05-26
    Beschreibung: From 1967 to 1984 the Matamek Research Station, located near Sept-Iles, Quebec, was the focus of a research program on salmonid production in boreal river ecosystems. Research was conducted under the auspices of Woods Hole Oceanographic Institution and in cooperation with the Ministere du Loisir, de la Chasse et de la Peche du Quebec and representatives of several universities in Canada and the United States. One of the central activities throughout the history of the Station was monitoring of Atlantic salmon (Salmo salar) in the Matamek River. All salmon life history stages were involved, although the greatest effort was spent in estimates of parr population size at select sites and in estimates of population size, age and sex ratios of sea-run adults entering the river to spawn. Effort and methods were not consistent from year to year due to changes in program focus and improvements in techniques. Nonetheless, we believe the data represent the only long-term record for an Atlantic salmon population on the North Shore of the St. Lawrence. Heretofore, information on Atlantic salmon from the Matamek River was available only in published works or in the Matamek Annual Reports published by Woods Hole Oceanographic Institution. Because of the potential value for analyses of salmon population dynamics and life history, we have assembled the raw data, with neither analysis nor interpretation, in this report. During the period of 1980-1984, considerable effort was exerted in collecting data from original sources (field notebooks, scale envelopes, etc.) and in correcting errors in the data. We cannot, of course, guarantee complete accuracy. Nonetheless, this collection of information is the most complete and accurate compilation possible at this time. The data are presented as records for individual fish, and are ordered by date and by life history stage. We include a key to the designations of columns and to conventions used in coding data. All entries are raw data as initially recorded and coded; no analyses are available beyond those used by various individual authors in their preparation of reports or publications. While these data are made available for general use through this compilation, we request that proper acknowledgment be given the Matamek Research Program of Woods Hole Oceanographic Institution, under whose directorship this compilation was accomplished.
    Beschreibung: Funding was provided by the Department of Commerce, NOAA National Sea Grant College Program under contract Number NABO-AA-D-00077.
    Schlagwort(e): Atlantic salmon ; Fish populations
    Repository-Name: Woods Hole Open Access Server
    Materialart: Technical Report
    Standort Signatur Einschränkungen Verfügbarkeit
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