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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © Ecological Society of America, 2011. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Frontiers in Ecology and the Environment 9 (2011): 18–26, doi:10.1890/100008.
    Description: Nutrient fluxes to coastal areas have risen in recent decades, leading to widespread hypoxia and other ecological damage, particularly from nitrogen (N). Several factors make N more limiting in estuaries and coastal waters than in lakes: desorption (release) of phosphorus (P) bound to clay as salinity increases, lack of planktonic N fixation in most coastal ecosystems, and flux of relatively P-rich, N-poor waters from coastal oceans into estuaries. During eutrophication, biogeochemical feedbacks further increase the supply of N and P, but decrease availability of silica – conditions that can favor the formation and persistence of harmful algal blooms. Given sufficient N inputs, estuaries and coastal marine ecosystems can be driven to P limitation. This switch contributes to greater far-field N pollution; that is, the N moves further and contributes to eutrophication at greater distances. The physical oceanography (extent of stratification, residence time, and so forth) of coastal systems determines their sensitivity to hypoxia, and recent changes in physics have made some ecosystems more sensitive to hypoxia. Coastal hypoxia contributes to ocean acidification, which harms calcifying organisms such as mollusks and some crustaceans.
    Description: Funding was supplied in part by NOAA through the Coastal Hypoxia Research Program, by the NSF through the Biocomplexity Coupled Biogeochemical Cycles competition, and by DR Atkinson through an endowment given to Cornell University.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Microbial ecology 25 (1993), S. 19-33 
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterial activity was measured in the river Seine by two methods, 3H-thymidine incorporation into DNA and 3H-leucine incorporation into proteins. Both incorporation rates are characterized by low values upstream of Paris, a large increase just downstream of the outfall of the Achères treatment plant effluents, and then decreasing values further downstream. The covariation of both activities is demonstrated by the constancy of the molar ratio (leucine to thymidine incorporation rate) in the range of 6 to 8 for all the samples, except in the perturbed area where it is higher (15 to 35). These high values of molar ratio are linked to the introduction into the river of large sized bacteria (⩾1 µm) with higher incorporation rates per cell or biomass unit than the small autochthonous bacteria (〈 1 µm). Growth rates of large bacteria were on average 3.7 times higher than those of small bacteria. Bacterial production was calculated with experimentally determined conversion factors (0.5 × 1018 cells per mole of thymidine incorporated and 900 gC per mole of leucine incorporated) and by taking into account the activity of both size classes of bacteria measured through fractionation experiments (post-incubation filtration). Production estimated in the perturbed area downstream of Ach6res was very high, up to 60 µgC liter−1h−1 in the summer. Carbon consumption by bacteria in the area perturbed by the Ach6res effluents was calculated assuming a growth yield of 0.2 and compared to the load of biodegradable organic matter discharged by the treatment plant. In summer, an additional supply of organic matter is required to account for the intense bacterial activity, suggesting the importance of phytoplankton production in the carbon budget.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 25 (1991), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. Based on data for 14C-primary production and biomass changes in a small and shallow lake (Créteil Lake, France), overall phytoplankton losses were calculated through an annual cycle (November 1985-October 1986). The summer period in 1986 is compared with two other summer periods in 1985 and 1980, these two years corresponding to extreme levels of algal biomass.2. Independent from the trophic state of the lake, phytoplankton populations were dominated by small-sized species (〈20 μm); their high growth rate (maximal in May and June: 0–8 day−1) was characteristic of nanoplanktonic natural populations.3. The positive correlation between phytoplankton losses and production indicates a close coupling between growth and loss processes.4. With a high filtering rate (0.22 day−1 as an annual average), zoo-plankton impact is considerable at any time of the year but especially in late summer, when grazing losses exceeded primary production.5. Despite the uncertainty concerning the meaning of 14C-primary production, the persistence of small algae throughout the year implies that a great part of the phytoplankton production was harvested by grazers which led to a recycling of organic matter within the water column.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5117
    Keywords: Sand-pit lake ; ecological modelling ; nutrient loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A large data set (n = 154) of phytoplankton production and biomass in relation to physico-chemical environmental factors was collected from 1979 to 1986 in a recently created sand-pit lake (Paris suburbs). These data are well suited to interpret the oligotrophication observed along the 8 years period, characterized by a regular decrease in chlorophyll (from 16 to 4 µg l-1 as annual averages). A model describing the ecological functioning of the lake has been established. Biological processes related to phyto-, bacterio- and zooplankton as well as sediment-water interactions, are described within several submodels. Most of the parameters involved were determined by in situ measurements in this or similar environments The model provides a good simulation of observed data and confirms that the reduction of nutrient loading, resulting from the diversion — in 1981 — of a sewer previously discharging into the lake, was responsible for the oligotrophication of the system. The model allows to explore the response of planktonic compartments accross a gradient of nutrient loading. The role of hydrology is also tested. The systematic run of the model with and without zooplankton leads to a better understanding of top-down control.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton development in river systems is under the control of various meteorological, hydrological, chemical and biological factors. Because of the continuity of the aquatic systems which progress from headwaters to the largest rivers, the interplay of these control factors can only be understood at the scale of the entire drainage network. The RIVERSTRAHLER Model, based on the concept of stream-order, has been established for that purpose. It has been applied here on two rivers from the Seine basin: rivers Marne and Oise. It is shown that hydrological factors determine the time of onset, and the position within the drainage network, of the spring algal bloom. Phosphorus availability, when limiting, controls the intensity of the bloom. During summer, top-down control, linked to grazing and other causes of mortality, has a marked impact on algal dynamics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 207 (1990), S. 71-77 
    ISSN: 1573-5117
    Keywords: phytoplankton ; bacterioplankton ; biomass ; activity ; seasonal coupling ; shallow lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phyto- and bacterioplankton biomass and activity were simultaneously measured during the course of one year in the shallow Créteil Lake (France). Phytoplankton was dominated, during the whole year, by small-sized organisms (10 to 25 µm). Bacteria were in a majority small coccoids (〈0.3 µm). Phyto -and bacterioplankton abundances averaged respectively 3.3 × 106 cells l−1 and 6 × 109 cells l−1. The phasing of the activity and biomass periods suggest a close coupling between phyto- and bacterioplankton. There were two distinct periods of high activity and biomass. Maximal values were observed in summer but an early increase occurred also in winter. Low or undetectable phytoplankton excretion rates, when heterotrophic activity was maximum, indicated a bacterial uptake of up to 100% of the released algal products during the incubation period. Heterotrophic uptake measurements with both glucose and amino acids revealed a seasonal change of the substrates in the lake, glucose uptake being associated more with the maximum activity of the algae, while the amino acids uptake was relatively higher during their decline. The maximal photosynthetic rate averaged 21.5 mgC m−3 h−1 and mean Vmax values were 0.056 and 0.050 mgC m−3 h−1 respectively for glucose and amino acids uptake.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5117
    Keywords: Seine river ; ecological modelling ; validation ; anthropic impacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Seine river crosses the most densely populated and industrialized area of France, Paris (16 million inhabitants), surrounded by fertile land with intensive agriculture. In the framework of a CNRS (Scientific Research National Center) research project, computer programs have been designed to tackle problems related to eutrophication, non-point pollution and the impact of sewage during dry or wet periods (urban runof and sewage network overflow). The PROSE software has been specially designed to simulate the behaviour of the most disturbed stretches of the Seine ecosystem on the last 300 kilometers of the river, upstream of the estuarine area. The 1-D hydraulic sub-model of PROSE is based on a finite difference solution of Saint-Venant equations solved with the Preissman scheme. It simulates steady state situations as well as highly transient situations such as fast changes in river discharge during rainy periods or dam motions. The biological sub-model is based on the RIVE model, describing the major processes in a river ecosystem: primary production, heterotrophic bacterial activity and organic matter decomposition, major nutrients species (nitrogen, phosphorus), nitrifying activity and oxygen balance. Water column and sediment variables are simulated. Most of the parameters have been estimated during laboratory experiments or field studies. Different situations observed between 1989 and 1991 allowed a detailed validation of the model. The model was then used to explore the reaction of the ecosystem (particularly its oxygen status) to changes in physical constrains (discharge, reoxygenation at dams) or in biological processes (release of microorganisms accompanying waste water discharge).
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5117
    Keywords: Microbial activity ; organic substrates ; sandpit lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biomass and activity of planktonic bacteria were investigated during a one year study in a shallow sandpit lake. The shallowness of the lake helped keep the water column homogeneous regarding bacterioplankton. Small free-living bacteria (0.03 µm3 cell−1) dominated the populations throughout the period studied. Bacterial abundances varied from 1 to 11 × 106 cells ml−1. Kinetic parameters (V max, K + S and T) were determined with 14C labelled compounds (glucose and amino acids mixture). V max values were high and averaged 0.056 and 0.050 µgCl−1 h−1 for glucose and amino acids respectively. Maximal V max values were observed in summer at the highest temperatures, but also in early spring. T values were much greater in winter. K + S values were significantly higher for amino acids (3 µg Cl−1) than for glucose (1 µg Cl−1). A low percentage of mineralization (about 25% for both tracers) could be the expression of the high growth efficiency expected when bacteria are growing at the expense of low molecular weight compounds as phytoplankton exudates.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-5117
    Keywords: river Mosel ; ecological modelling ; oxygen budget ; P vs R ratio ; phytoplankton decline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The oxygen budget in the transboundary river Mosel was analyzed with the help of the RIVERSTRAHLER model. The model, developed for the river Seine, was used after minor modifications of the kinetics of microbial processes. The impact of benthic filter feeders (Dreissena polymorpha) was introduced into the model to better explain phytoplankton decline in the canalized sector of the river. Hydro-geomorphology, meteorology and point and non-point sources of nutrients were analyzed as required by the model, according to the stream order concept at the scale of the whole drainage network of the main tributaries and along the main branch of the river Mosel, from Millery to Koblenz. The model was validated on water quality data (phytoplankton biomass -Chl a-, nutrients, oxygen) collected at half-monthly intervals during the period 1993–1995. A reasonable agreement was found at both the seasonal and spatial scales. The validated model was used to calculate the oxygen budget that shows variations in the contributions of biological processes (net primary production, bacterial and benthic respiration, nitrification) along successive stretches of the main river branch. Bacterial respiration dominates in sectors particularly affected by effluent inputs. Benthic filter feeders colonising these canalized sectors contribute to increases in respiration and oxygen deficit through their own respiration and their impact on phytoplankton. Several possible management scenarios, aimed at improving oxygenation, were tested with the model. An 80% reduction of both phosphates (to reduce eutrophication) and organic matter (to decrease bacterial activity) restores autotrophic conditions in the 7th order sector.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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