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G C L (g + c_l)
Selected AbstractsSeasonal and interannual variation of bacterial production in lowland rivers of the Orinoco basinFRESHWATER BIOLOGY, Issue 11 2004María M. Castillo Summary 1. We examined the influence of hydrologic seasonality on temporal variation of planktonic bacterial production (BP) in relatively undisturbed lowland rivers of the middle Orinoco basin, Venezuela. We sampled two clearwater and two blackwater rivers over 2 years for dissolved organic carbon (DOC), chlorophyll, phosphorus and bacterial abundance to determine their relationship to temporal variation in BP. 2. Dissolved organic carbon concentration was greater in blackwater (543,664 ,m) than in clearwater rivers (184,240 ,m), and was generally higher during periods of rising and high water compared with low water. Chlorophyll concentration peaked (3 ,g L,1) during the first year of study when discharge was lowest, particularly in blackwater rivers. Soluble reactive phosphorus (SRP) was very low in the study rivers (<3.8 ,g L,1) and concentration increased during low water. 3. Average BP was higher in clearwater (0.20,0.26 ,g C L,1 h,1) than in blackwater rivers (0.14,0.17 ,g C L,1 h,1), although mean bacterial abundance was similar among rivers (0.6,0.8 × 106 cells mL,1). 4. Periods of higher chlorophyll a concentration (low water) or flushing of terrestrial organic material (rising water) were accompanied by higher BP, while low BP was observed during the period of high water. 5. Interannual variation in BP was influenced by variations in discharge related to El Niño Southern Oscillation events. 6. Seasonal variation in BP in the study rivers and other tropical systems was relatively small compared with seasonal variation in temperate rivers and lakes. In addition to the low seasonal variation of temperature in the tropics, low overall human disturbance could result in less variation in the inputs of nutrients and carbon to the study rivers compared with more disturbed temperate systems. [source] Effect of Campsurus notatus on NH+4, DOC Fluxes, O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment-Water Interface of an Amazonian Lake Impacted by Bauxite TailingsINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2003João José Fonseca Leal Abstract The aim of this study was to evaluate the influence of Campusurus notatusEaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH4+) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment-water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment-water interface. The cores were incubated with 0 to 2,388 ind m,2 of Campsurus notatus nymphs, and the changes in NH4+, DOC, O2 concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p < 0.05, multiple regression) and oxygen uptake (F = 11.8, p < 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two-way ANOVA, p < 0.05) in bacterial production (0.44 ,g C l,1 h,1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH4+) at the sediment-water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production. [source] Leptodora kindti and Flexible Foraging Behaviour of Fish , Factors behind the Delayed Biomass Peak of Cladocerans in Lake HiidenvesiINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2003Laura Uusitalo Abstract In the eutrophic L. Hiidenvesi, the spring biomass maximum of cladoceran zooplankton is missing and the highest biomass takes place in July,August. The factors behind the delayed biomass peak were studied in four different basins of the lake with concomitant data on cladocerans assemblages, density of the predatory cladoceran Leptodora kindti and food composition of fish. In all the basins, the abundance of Leptodora peaked in June, being highest (up to 800 ind. m,3) in the two most shallow basins (max depth < 4 m). The duration of the high population density was short and in July-August Leptodora density stayed below 200 ind. m,3, although the water temperature was still favourable. The collapse of the Leptodora population coincided with the change in the feeding habits of fish. In early summer, fish predation was targeted mainly on copepods and zoobenthos, while in high summer Leptodora was one of the main preys of perch, white bream and bleak. The biomass of herbivorous cladocerans was below 10 ,g C l,1 in June, and climbed to a maximum in August in the two most shallow basins (34 and 76 ,g C l,1), in July in the deepest basin (27 ,g C l,1), and in September in the intermediate basin (55 ,g C l,1). In the two most shallow basins, the death rate of the dominating cladoceran, Daphnia cristata, closely followed the food consumption rate by the Leptodora population. In the deeper basins, the agreement was not so close, smelts (Osmerus eperlanus) and chaoborids being important predators of herbivores. The duration of the period of high Leptodora density thus depended on the predation pressure by fish, while the increased fish predation on Leptodora in July,August allowed the elevation of the biomass of herbivorous cladocerans. [source] Utilization of oligo- and polysaccharides at microgram-per-litre levels in freshwater by Flavobacterium johnsoniaeJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010E.L.W. Sack Abstract Aims:, To obtain a bacterial strain that can be used to quantify biodegradable polysaccharides at concentrations of a few micrograms per litre in freshwater. Methods and Results:,Flavobacterium johnsoniae strain A3 was isolated from tap water supplemented with laminarin, pectin or amylopectin at 100 ,g C l,1 and river Rhine water. The organism utilized 14 of 23 oligo- and polysaccharides, and 1 of 9 monosaccharides, but none of the sugar acids, sugar alcohols, carboxylic acids or aromatic acids tested at 10 ,g C l,1. Amino acids promoted growth of strain A3, but not in coculture with assimilable organic carbon (AOC) test strain Pseudomonas fluorescens P17, which utilized these compounds more rapidly than strain A3. Compounds released by strain P17 and AOC test strain Spirillum sp. NOX grown on acetate promoted the growth of strain A3 at Nmax values of , 2 × 105 CFU ml,1 of strain P17 and , 5 × 105 CFU ml,1 of strain NOX. Significant growth of strain A3 was observed in surface water and in tap water in the presence of strain P17 (Nmax P17 < 2 × 105 CFU ml,1). Conclusions:, Strain A3 utilizes oligo- and polysaccharides at microgram-per-litre levels. In surface water and in tap water, the organism was able to utilize compounds that were not utilized by strain P17. These compounds may include oligo- and/or polysaccharides. Significance and Impact of the Study:, Phytoplanktonic and bacterial polysaccharides can constitute an important biodegradable fraction of natural organic matter in water and may promote growth of heterotrophic bacteria during water treatment and drinking water distribution. Strain A3 can be used to quantify a group of compounds that includes oligo- and polysaccharides at microgram-per-litre levels in freshwater. [source] Ecological implications of biomass and morphotype variations of bacterioplankton: an example in a coastal zone of the Northern Adriatic Sea (Mediterranean)MARINE ECOLOGY, Issue 2 2005Rosabruna La Ferla Abstract This study had the objective of quantifying the variability in abundance, cell volume, morphology and C content of a natural bacterioplankton community in a coastal zone of the North Adriatic Sea during two periods (February and June) of two consequent years (1996 and 1997). We used epifluorescence microscopy with Acridine Orange staining procedures and a microphotographic technique. Low variability in bacterial abundance (range 0.3,3.1 × 105 cells ml,1) occurred between summer and winter periods. Conversely, the cell volume and the calculated carbon content changed greatly with warm and cold periods (ranges: 0.015,0.303 ,m3 and 5.83,42.17 fg C cell,1, respectively). Elongated bacteria were dominant while coccoid cells prevailed only in February 1997. Biomass showed high variability (range 0.12,10.21 ,g C l,1) whilst the abundance did not show noticeable differences among the sampling periods. As a consequence, quantification of bacterial biomass based solely on cell abundance must be considered with caution because the true biomass could depend on variability in cell volumes and morphotypes. [source] | ||||||||||