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  • 1
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    Effects of reducing nutrient loads to surface waters within the Mississippi River Basin and the Gulf of Mexico: Topic 4 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico (2021)
    NOAA/National Centers for Coastal Ocean Science | Silver Spring, MD
    In:  http://aquaticcommons.org/id/eprint/14640 | 403 | 2014-02-23 00:20:32 | 14640 | United States National Ocean Service
    Details
    Publication Date: 2021-06-30
    Description: The overall goal of this assessment was to evaluate the effects of nutrient-source reductions that may be implemented in the Mississippi River Basin (MRB) to reduce the problem of low oxygen conditions (hypoxia) in the nearshore Gulf of Mexico. Such source reductions would affect the quality of surface waters—streams, rivers, and reservoirs—in the drainage basin itself, as well as nearshore Gulf waters. The task group’s work was divided into addressing the effects of nutrient-source reductions on: (1) surface waters in the MRB and (2) hypoxia in the Gulf of Mexico.
    Keywords: Ecology ; Environment ; Fisheries ; Management
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 130
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  • 2
    Electronic Resource
    Electronic Resource
    WATER QUALITY TRENDS IN LAKE TOHOPEKALIGA, FLORIDA, USA: RESPONSES TO WATERSHED MANAGEMENT (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 30 (1994), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Water quality in eutrophic Lake Tohopekaliga, Florida, improved markedly from 1982 to 1992 as a result of reductions in phosphorus and nitrogen loading to the lake. Annual budgets of water, chloride, phosphorus and nitrogen were constructed for the lake, and indicate it is a sink for phosphorus and a source for nitrogen. Water column concentrations of total phosphorus, soluble reactive phosphorus, total nitrogen, dissolved inorganic nitrogen, and chlorophyll a all declined as external inputs of nutrients decreased. Water column nitrogen: phosphorus ratios have increased, suggesting a probable shift from nitrogen- to phosphorus-limitation. This apparent shift in nutrient limitation status also is supported by comparisons of the mean Trophic State Indices for phosphorus, nitrogen, and chlorophyll a. These improvements in water quality are attributed to the diversion of wastewater treatment plant effluent from the lake, and the increased use of wet retention ponds for stormwater runoff.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1994.tb03311.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    PREDICTIVE MODELS FOR THE BIOMASS OF BLUE-GREEN ALGAE IN LAKES (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 21 (1985), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: In lakes which experience water quality problems due to the nuisance growth of blue-green algae, summer concentrations of chlorophyll a may not always be a meaningful measure of water quality for making management decisions. Models for the prediction of summer mean blue-green algal biomass were thus developed from data collected from five systems located in North America and Sweden. It is suggested that the model of choice is log BG =−0.142 + 0.596 log TP – 0.963 log Z, where BG is the biomass of blue-green algae (g m−3), TP is the concentration of total phosphorus (mg m−3), and Z is the mean depth of the lake (m). When coupled to current loading models, this model can potentially be used to assess the impacts of phosphorus loading reductions on threshold odor in water supplies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1985.tb00153.x
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  • 4
    Electronic Resource
    Electronic Resource
    Chlorophyll-phosphorus relations in individual lakes. Their importance to lake restoration strategies (1981)
    s.l. : American Chemical Society
    Environmental science & technology 15 (1981), S. 444-451 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es00086a009
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    A deep maximum of green sulphur bacteria (‘Chlorochromatium aggregatum’) in a strongly stratified reservoir (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Fine-scale physical and chemical gradients and deep photosynthetic microbial populations were assessed to provide an initial characterisation of a small, thermally stratified reservoir (Cross Reservoir, Kansas, U.S.A.) and its deep chlorophyll maxima (DCM). Factors were identified that may affect vertical positioning of subepilimnetic photosynthetic sulphur bacteria (PSB) in lakes.2. Results indicate that Cross Reservoir is a mesotrophic, dimictic lake with large subepilimnetic chlorophyll maxima containing dense layers of PSB. Characteristics of the deep PSB community of Cross Reservoir strongly correlate with both light and nutrient gradients.3. The deep bacterial community mostly contained single-celled and aggregating green sulphur bacteria, specifically free-living Chlorobium limicola and the conspicuous motile ectosymbiotic consortium known as ‘Chlorochromatium aggregatum’. The bacteria were within the anaerobic hypolimnion, beneath a metalimnetic plate of Cryptomonas spp. and within very low sulphide and light conditions [mean of 67 μgS L−1 and 0.05% photosynthetically active radiation (PAR)]. Pigment concentrations and fluorescence trends indicate that the bacteria made up a larger proportion of the DCM biomass than did phytoplankton in 1996.4. Cross Reservoir shares characteristics with natural lakes world-wide that also include a deep PSB community containing dense layers of ‘C. aggregatum’. Correlation analyses indicate that PSB community positioning and density are related to light, sulphide supply, redox potentials and pH. A 2-factor principal components analysis (PCA) and other data trends supported these interpretations and indicated that PSB are sensitive to the thermal stability of the water column, are nitrogen limited and regulated more by sulphide or sulphide to light ratios than local levels of light. The sensitivity of these deep photosynthetic bacteria to environmental gradients, and their significance to some aquatic systems, demonstrate their potential as indicators of environmental disturbance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01270.x
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  • 6
    Electronic Resource
    Electronic Resource
    Predator-induced phenotypic plasticity in the exotic cladoceran Daphnia lumholtzi (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The exotic cladoceran Daphnia lumholtzi has recently invaded freshwater systems throughout the United States. Daphnia lumholtzi possesses extravagant head spines that are longer than those found on any other North American Daphnia. These spines are effective at reducing predation from many of the predators that are native to newly invaded habitats; however, they are plastic both in nature and in laboratory cultures. The purpose of this experiment was to better understand what environmental cues induce and maintain these effective predator-deterrent spines. We conducted life-table experiments on individual D. lumholtzi grown in water conditioned with an invertebrate insect predator, Chaoborus punctipennis, and water conditioned with a vertebrate fish predator, Lepomis macrochirus.2. Daphnia lumholtzi exhibited morphological plasticity in response to kairomones released by both predators. However, direct exposure to predator kairomones during postembryonic development did not induce long spines in D. lumholtzi. In contrast, neonates produced from individuals exposed to Lepomis kairomones had significantly longer head and tail spines than neonates produced from control and Chaoborus individuals. These results suggest that there may be a maternal, or pre-embryonic, effect of kairomone exposure on spine development in D. lumholtzi.3. Independent of these morphological shifts, D. lumholtzi also exhibited plasticity in life history characteristics in response to predator kairomones. For example, D. lumholtzi exhibited delayed reproduction in response to Chaoborus kairomones, and significantly more individuals produced resting eggs, or ephippia, in the presence of Lepomis kairomones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01111.x
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  • 7
    Electronic Resource
    Electronic Resource
    Nitrogen deficiency, phosphorus sufficiency, and the invasion of Lake Kinneret, Israel, by the N2-fixing cyanobacterium Aphanizomenon ovalisporum (1999)
    Springer
    Aquatic sciences 61 (1999), S. 293-306 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Aphanizomenon, cyanobacteria, N-deficiency, P-sufficiency, N : P ratios, Lake Kinneret.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: Historically, the phytoplankton community of Lake Kinneret, Israel, has been dominated by the dinoflagellate Peridinium gatunense and other edible species that are important in the lake's food web. However, major changes have occurred both in external nutrient loading and in the water column chemistry of the lake since the mid-1980's. Epilimnetic particulate nitrogen: particulate phosphorous (PN : PP) ratios have declined, and measurements of seston chemistry suggest that the intensity of seasonal nitrogen limitation has increased. The phytoplankton community also was altered in 1994 and 1995 by a lake-wide summer invasion of the nitrogen-fixing cyanobacterium Aphanizomenon ovalisporum. This abrupt change in phytoplankton community structure is consistent with the development of conditions increasingly N-deficiency and P-sufficiency in the water column, which should favor cyanobacterial dominance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00001326
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems (1992)
    Springer
    Biogeochemistry 18 (1992), S. 19-35 
    Details
    ISSN: 1573-515X
    Keywords: Dinitrogen fixation ; nitrogen ; phosphorus ; competition ; legumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000424
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  • 9
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    Assessing uncertainties in crop and pasture ensemble model simulations of productivity and N2O emissions (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-10-29
    Description: Simulation models are extensively used to predict agricultural productivity and greenhouse gas (GHG) emissions. However, the uncertainties of (reduced) model ensemble simulations have not been assessed systematically for variables affecting food security and climate change mitigation, within multispecies agricultural contexts. We report an international model comparison and benchmarking exercise, showing the potential of multimodel ensembles to predict productivity and nitrous oxide (N 2 O) emissions for wheat, maize, rice and temperate grasslands. Using a multistage modelling protocol, from blind simulations (stage 1) to partial (stages 2-4) and full calibration (stage 5), 24 process-based biogeochemical models were assessed individually or as an ensemble against long-term experimental data from four temperate grassland and five arable crop rotation sites spanning four continents. Comparisons were performed by reference to the experimental uncertainties of observed yields and N 2 O emissions. Results showed that across sites and crop/grassland types, 23 to 40% of the uncalibrated individual models were within two standard deviations (s.d.) of observed yields, while 42 (rice) to 96% (grasslands) of the models were within one s.d. of observed N 2 O emissions. At stage 1, ensembles formed by the three lowest prediction model errors ( RRMSE ) predicted both yields and N 2 O emissions within experimental uncertainties for 44 and 33% of the crop and grassland growth cycles, respectively. Partial model calibration (stages 2 to 4) markedly reduced prediction errors of the full model ensemble E-median for crop grain yields (from 36% at stage 1 down to 4% on average) and grassland productivity (from 44 to 27%) and to a lesser and more variable extent for N 2 O emissions. Yield-scaled N 2 O emissions (N 2 O emissions divided by crop yields) were ranked accurately by 3-model ensembles across crop species and field sites. The potential of using process-based model ensembles to predict jointly productivity and N 2 O emissions at field scale is discussed. This article is protected by copyright. All rights reserved.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley-Blackwell
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