Methanogenesis, an anaerobic microbial process in sediments, was investigated in a naturally acidic bog lake, Grosse Fuchskuhle, in northeastern Germany. The lake was artificially divided into four sub-basins: two western basins receiving humic substances from an adjacent Sphagnum bog and two eastern basins isolated from this acidic inflow with installed curtains. Within the northeast (NE) and southwest (SW) basin compartments, one of each group were studied. In the peat influenced western basins the pH-values in the water columns were kept low and increased in the others. The stratification period increased in all four compartments from some weeks to some months, from April to October, with the development of anoxic hypolimnia in all compartments after the installation of the curtains. The layer with the most active methane production moved from a sediment depth of more than 20 cm before separation to close to the surface sediments in all compartments. Methanogenic micro- Aquat. Sci. 65 (2003) 36 -46 Aquatic Sciences organisms were found in the whole sediment core -from surface sediments to a depth of 25 cm. The proportion of methanogens was approximately 15 % of total microbial cell numbers, which were approximately 2 ¥ 10 6 cells/ml sediment. Oligonucleotide probes targeting nearly all families of the phylum Euryarchaeota were tested with fluorescence in-situ hybridization (FISH). In both basins, with and without the influence from peat, oligonucleotide probe (MSMX) targeting Methanosarcinaceae could be detected only as methanogens. The finding of only acetate-using methanogens by FISH indicated acetate as a major methanogenic substrate. Concentration profiles of CH 4 as a function of sediment depth were characterized in both basins by high concentrations in the top layers. Methane bubbles were released in the late summer in the eastern sub-basin only, likely from oversaturation in the surface sediments.
Resumo -O objetivo deste trabalho foi identificar a estrutura de dependência espacial de atributos do solo e sua interferência na produção de biomassa epígea de pastagem de capim-marandu (Urochloa brizantha). Amostras de Latossolo Vermelho-Amarelo foram coletadas em rede de pontos georreferenciados, para a determinação de atributos físicos e químicos do solo e da produção de biomassa epígea da pastagem, no verão e outono de 2010/2011. Verificou-se dependência espacial das variáveis, por meio de análise geoestatística com construção e ajuste de semivariogramas, interpolação por krigagem ordinária e espacialização em mapas de isolinhas. A dependência espacial ocorreu para alguns atributos físicos e químicos do solo (areia, densidade, resistência à penetração, infiltração, pH, MO, P, K, Ca, Mg, H+Al, Al, CTC e V), e para a biomassa da pastagem medida nas estações verão e outono. A análise espacial de atributos físicos do solo permite identificar áreas degradadas da pastagem. A biomassa da pastagem é mais influenciada pelos atributos físicos do solo do que pelos químicos.Termos para indexação: Urochloa brizantha, atributos do solo, dependência espacial, espacialização. Variability of soil and pasture epigeal biomass identified by geostatisticsAbstract -The objective of this work was to identify the spatial structure dependence of soil attributes and its interference on the production of epigeal biomass of Urochloa brizantha. A Typic Hapludox was sampled at geocoded grid points in order to determine soil physical and chemical properties and the epigeal biomass production of pasture during the summer and fall seasons of 2010/2011. Spatial dependence of variables was verified by geostatistical analysis using construction and adjustment of semivariograms, ordinary kriging interpolation, and spatial maps. Spatial dependence occurred for some physical and chemical soil properties (sand, density, penetration resistance, infiltration, pH, MO, P, K, Ca, Mg, H+Al, Al, CEC, and base saturation), and for pasture biomass measured in the summer and fall seasons. Spatial analysis of soil physical attributes allows identifying areas with the highest pasture degradation. Biomass pasture is more influenced by the soil physical attributes than by the chemical ones.
About 30% of the total area of Lake Batata (Amazon) was impacted by the disposal of bauxite tailings originated from the process of washing bauxite. This effluent, composed by fine particles of clay and water, settled on top of the natural sediment, originating a new substratum with a different physical and chemical composition. This phenomenon created a new distinct habitat (impacted sediment) influencing the benthic community. The aim of this study was to evaluate the impact of bioturbation by Campsurus notatus (Ephemeroptera: Polymitarcytidae) on potential gas fluxes in the sediment of natural and impacted areas of the lake. The natural sediment had a significantly higher methane concentration when compared to the impacted one. In incubated sediment cores, the presence of C. notatus nymphs resulted in a significant increase in oxygen consumption and methane and carbon dioxide release to the water column. The effect of the presence of nymphs on methane was ambiguous. The C. notatus nymphs strongly decreased methane concentration in natural sediment samples, probably because of the enhancement of the oxic sediment area. However, this effect was not observed in impacted samples. Finally, the new substratum of Lake Batata decreased methane concentration in sediment and water column. C. notatus nymphs demonstrated to have a significant role on gas flux (methane and CO 2 ) from sediment to water column as well as on oxygen consumption in Lake Batata, consequently influencing the carbon cycle in this lake.
The purpose of this study was to measure the phytoplankton production (PP) and bacterial production (BP) simultaneously in seven lakes in the middle Rio Doce basin (southeast Brazil) during the dry and the rainy seasons. Limnological monitoring was conducted from 1999 to 2001 as well as both PP (radioactive carbon fixation) and BP ( 3 H-Leucine incorporation) in four specific depths (100%, 10%, 1% of incident radiation, and aphotic zone). Furthermore, trophic state of the lakes was analyzed, considering the index proposed by Salas and Martino (1991) and Carlson (1977). In general, some parameters increased during the rainy season such as pH, conductivity, chlorophyll and total nitrogen. In the period of 1999/2000, the rain caused PP reduction in the lakes, excepting Carioca and Á guas Claras Lake, but in the years 2000/2001, the lakes did not show a similar pattern. In contrast, the rainy season of both years caused an expressive bacterioplankton production enhancing. Using Salas and Martino index, we observed that some lakes were affected by the seasonal runoff, therefore the typologie of these lakes changed from oligotrophic to mesotrophic conditions, otherwise considering the Carlson index all lakes were classified as eutrophic in both dry and rainy seasons. Indeed, Salas and Martino index demonstrated to be more appropriate to determine the trophic status of the lakes. Finally, our data indicate that until now, in spite of the lakes location, protected and unprotected area, the lakes still maintain their natural characteristics.
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