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Freshwater Reservoir (freshwater + reservoir)
Selected AbstractsMaximum growth rates and possible life strategies of different bacterioplankton groups in relation to phosphorus availability in a freshwater reservoirENVIRONMENTAL MICROBIOLOGY, Issue 9 2006Karel, imek Summary We investigated net growth rates of distinct bacterioplankton groups and heterotrophic nanoflagellate (HNF) communities in relation to phosphorus availability by analysing eight in situ manipulation experiments, conducted between 1997 and 2003, in the canyon-shaped ,ímov reservoir (Czech Republic). Water samples were size-fractionated and incubated in dialysis bags at the sampling site or transplanted into an area of the reservoir, which differed in phosphorus limitation (range of soluble reactive phosphorus concentrations , SRP, 0.7,96 µg l,1). Using five different rRNA-targeted oligonucleotide probes, net growth rates of the probe-defined bacterial groups and HNF assemblages were estimated and related to SRP using Monod kinetics, yielding growth rate constants specific for each bacterial group. We found highly significant differences among their maximum growth rates while insignificant differences were detected in the saturation constants. However, the latter constants represent only tentative estimates mainly due to insufficient sensitivity of the method used at low in situ SRP concentrations. Interestingly, in these same experiments HNF assemblages grew significantly faster than any bacterial group studied except for a small, but abundant cluster of Betaproteobacteria (targeted by the R-BT065 probe). Potential ecological implications of different growth capabilities for possible life strategies of different bacterial phylogenetic lineages are discussed. [source] PRODUCTION OF PARALYTIC SHELLFISH TOXINS BY APHANIZOMENON SP.JOURNAL OF PHYCOLOGY, Issue 4 2002LMECYA 31 (CYANOBACTERIA) We examined intracellular and extracellular paralytic shellfish toxins (PST) in a strain of Aphanizomenon sp. (LMECYA31) isolated from a Portuguese freshwater reservoir throughout the growth cycle and under different conditions affected by temperature and nitrate and phosphate availability. PST concentrations and compositions were greatly influenced by cell density, growth stage, and temperature and nutrients conditions. On a per-cell basis results showed (1) the enhancement of PST cell quota after the end of exponential growth phase in nutrient replete batch cultures, (2) the absence of a PST increment at late growth stages under phosphate limitation, (3) a rise in PST maximum cell quota under nitrate depletion, and (4) the enhancement of toxin production at higher temperatures. The relative proportion of the four toxins detected, neoSTX, dcSTX, STX and GTX5, also changed within and between culture settings. While growing under phosphate rich media cells produced mainly GTX5 and neoSTX, whereas under phosphate limitation the proportion of STX and dcSTX increased substantially with culture age. Large amounts of extracellular toxins were found in the culture medium, increasing during culture time. Extracellular toxin composition in each culture was fairly constant and always similar to the intracellular composition found at late stages of growth. This further supported other research that indicates that PSTs are released to the water through cell lysis, and a significant concentration of PST may be expected to remain in the water upon the collapse of a toxic bloom or after cells removal by water treatment. [source] INDIVIDUAL-BASED MODELS AND THE MANAGEMENT OF SHOREBIRD POPULATIONSNATURAL RESOURCE MODELING, Issue 1 2008JOHN D. GOSS-CUSTARD Abstract Individual-based models (IBMs) predict how animal populations will be affected by changes in their environment by modeling the responses of fitness-maximizing individuals to environmental change and by calculating how their aggregate responses change the average fitness of individuals and thus the demographic rates, and therefore size of the population. This paper describes how the need to develop a new approach to make such predictions was identified in the mid-1970s following work done to predict the effect of building a freshwater reservoir on part of the intertidal feeding areas of the shorebirds Charadrii that overwinter on the Wash, a large embayment on the east coast of England. The paper describes how the approach was developed and tested over 20 years (1976,1995) on a population of European oystercatchers Haematopus ostralegus eating mussels Mytilus edulis on the Exe estuary in Devon, England. The paper goes on to describe how individual-based modeling has been applied over the last 10 years to a wide range of environmental issues and to many species of shorebirds and wildfowl in a number of European countries. Although it took 20 years to develop the approach for 1 bird species on 1 estuary, ways have been found by which it can now be applied quite rapidly to a wide range of species, at spatial scales ranging from 1 estuary to the whole continent of Europe. This can now be done within the time period typically allotted to environmental impact assessments involving coastal bird populations in Europe. The models are being used routinely to predict the impact on the fitness of coastal shorebirds and wildfowl of habitat loss from (i) development, such as building a port over intertidal flats; (ii) disturbance from people, raptors, and aircraft; (iii) harvesting shellfish; and (iv) climate change and any associated rise in sea level. The model has also been used to evaluate the probable effectiveness of mitigation measures aimed at ameliorating the impact of such environmental changes on the birds. The first steps are now being taken to extend the approach to diving sea ducks and farmland birds during the nonbreeding season. The models have been successful in predicting the observed behavior and mortality rates in winter of shorebirds on a number of European estuaries, and some of the most important of these tests are described. These successful tests of model predictions raise confidence that the model can be used to advise policy makers concerned with the management of the coast and its important bird populations. [source] Effects of tidal flat reclamation on sediment quality and hypoxia in Isahaya BayAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2006Yoshikuni Hodoki Abstract 1.Ariake Bay, which is located in western Japan, has a large tidal range (>6 m) and a vast tidal flat (200 km2). In the early 1990s, the government-managed Isahaya Reclamation Project began in the western part of Ariake Bay. A 16-km2 area of tidal flat in the inner part of Isahaya Bay was destroyed through reclamation and separated from the sea by a dyke, which created land and a freshwater reservoir. 2.Since the initiation of the project, fishery yields around Isahaya Bay have dramatically decreased. The objective of this study was to clarify the relationship between the work associated with the Isahaya Reclamation Project and the recent environmental deterioration in Ariake Bay, with references to present sediment thickness and organic matter content, and hypoxic water distributions in Isahaya Bay. 3.The organic matter load from the reservoir has increased since the initiation of the reclamation project and has been associated with a thick layer of fine sediment at the bottom of Isahaya Bay. The thickness of fine sediment and the total organic carbon content were higher in Isahaya Bay than in the freshwater reservoir. 4.Based on measurements in August 2001, hypoxic water spread widely in and around Isahaya Bay; the lowest dissolved oxygen (DO) concentration (0.53 mg L,1) was observed just outside the dyke. An analysis based on a two-layered box model using data obtained in August 2001 showed that the DO consumption rate in the bottom layer was high (0.61 mg O2 L,1 day,1), and that 22,41% of the total organic carbon load needed to induce the hypoxic water was derived from the reclamation area. 5.Our findings strongly suggest that enclosed seas may suffer from eutrophic and hypoxic conditions because of their low seawater-exchange rate. A comprehensive conservation programme and environmental assessment including physical and material transport processes in the system is needed to manage the environment of the enclosed sea. Copyright © 2005 John Wiley & Sons, Ltd. [source] Particulate fatty acids in two small Siberian reservoirs dominated by different groups of phytoplanktonFRESHWATER BIOLOGY, Issue 3 2003Nadezhda N. Sushchik SUMMARY 1. We studied the composition of fatty acids (FAs) in the seston from two small freshwater reservoirs (Bugach and Lesnoi) with distinct periodicity of domination by cyanobacteria and eukaryotic algae during the growth season. 2. The diatoms in the both reservoirs were characterised by a high content of 14:0 and C16 unsaturated acids, whereas that of the essential FA 20:5,3 [eicosapentanoic acid (EPA)] was low. The correlation between this polyunsaturated FA (PUFA) and diatom biomass was not significant in either reservoir. The percentage of 20:5,3 in seston significantly correlated with the biomass of euglenophyta in Bugach and dinophyta in Lesnoi. Hence the diatoms, usually referred as a valuable food for zooplankton, were not an important source of the essential PUFA in these systems. 3. The dominant cyanobacteria in Bugach, and the green algae in Lesnoi, both contained the same marker acids: 18:3,3 and 18:2,6. Hence, a discrimination between these two phytoplanktonic groups on the basis of FA biomarkers may be difficult in some cases. 4. We found no significant correlation between the content of 20:5,3 in seston and the biomass of the dominant daphniids in either reservoir. This is contrary to expectations, based on the literature, that EPA is generally important. Rather, the biomass of the two dominant Daphnia species in Bugach correlated strongly with the content of 18:3,3 in the seston. The cyanobacteria were a probable source of this ,3 FA for Daphnia. We conclude that EPA is not always important for Daphnia populations although, in such cases, some other PUFA (e.g. 18:3,3) might be related to their growth. [source] EXTRACELLULAR ENZYMES OF THE MICROCYSTIS AERUGINOSA PCC 7813 STRAIN ARE INHIBITED IN THE PRESENCE OF HYDROQUINONE AND PYROGALLOL, ALLELOCHEMICALS PRODUCED BY AQUATIC PLANTS,JOURNAL OF PHYCOLOGY, Issue 6 2009Dariusz Dziga Several cyanobacterial species have a high potential to dominate in marine environments and freshwater reservoirs, and the ecological and physiological reasons for this phenomenon are not understood comprehensively. In this study, the ability of a Microcystis aeruginosa Kütz. strain to produce free dissolved enzymes was documented. We have observed that this highly toxic strain releases alkaline phosphatase, leucine aminopeptidase, and ,-glucosidase into the ambient environment. Additionally, the inhibitory activity of selected phenols produced by aquatic plants on the activity of these enzymes was analyzed. The investigated compounds, pyrogallol and, to a lesser degree, hydroquinone, decreased the activity of extracellular enzymes produced by M. aeruginosa, with leucine aminopeptidase being the most sensitive to the inhibitors. The noncompetitive character of enzymatic inhibition suggests that the polyphenols produced by aquatic plants are able to influence the activity of different extracellular or membrane-bound enzymes. [source] | ||||||||||