Microcosm studies for neutralization of hypolimnic acid mine pit lake water (pH 2.6).

Ten microcosms of 0.088 m3 water volume (0.3 m i.d. and 1.20 m height) were designed for neutralization studies representing hypolimnic ecosystem models for acid mine pit lakes. Sediment and water were collected from an acid lignite mine pit lake (Brandenburg, Germany) and filled into the microcosms. To determine the efficacy of controlled in situ organic carbon amendments as a possible neutralization method, sediment and water were treated with ethanol and Carbokalk with and without wheat straw. The water chemistry was monitored for 1 yr. At start-up and end of the experiments, the sedimentwas characterized. Iron and sulfate were removed with varying intensity from the water phase as a result of microbial iron and sulfate reduction together with a subsequent precipitation of unsoluble sulfide minerals to the sediment. The pH rose, and alkalinity generation and bacterial growth were observed. Neutralization rates were calculated using equivalents of accumulated total reduced inorganic sulfur together with the nonsulfidic reactive ferrous iron in the sediment. In the treated microcosms, the neutralization rates were between 6 and 15 equiv m(-2) a(-1). Carbokalk was most effective in stimulating growth of sulfate-reducing bacteria and probably also served as inoculum. With Carbokalk together with wheat straw, the pH increased from 2.6 to around 6.5 within the whole microcosm. The critical revision of the results indicates that the application of Carbokalk (approximately 3.9 kg m(-2)) together with the application of wheat straw (approximately 9.3 kg m(-2)) is most suitable for further experiments in outdoor enclosures (mesocosms). For that case, the prediction of the water quality for a lake water column after multiple lake turnover events is presented based on batch reaction simulation using the geochemical model PHREEQC.

Phylogenetic Composition, Spatial Structure, and Dynamics of Lotic Bacterial Biofilms Investigated by Fluorescent in Situ Hybridization and Confocal Laser Scanning Microscopy.

> Abstract The phylogenetic composition, three-dimensional structure and dynamics of bacterial communities in river biofilms generated in a rotating annular reactor system were studied by fluorescent in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM). Biofilms grew on independently removable polycarbonate slides exposed in the reactor system with natural river water as inoculum and sole nutrient and carbon source. The microbial biofilm community developed from attached single cells and distinct microcolonies via a more confluent structure characterized by various filamentous bacteria to a mature biofilm rich in polymeric material with fewer cells on a per-area basis after 56 days. During the different stages of biofilm development, characteristic microcolonies and cell morphotypes could be identified as typical features of the investigated lotic biofilms. In situ analysis using a comprehensive suite of rRNA-targeted probes visualized individual cells within the alpha-, beta-, and gamma-Proteobacteria as well as the Cytophaga-Flavobacterium group as major parts of the attached community. The relative abundance of these major groups was determined by using digital image analysis to measure specific cell numbers as well as specific cell area after in situ probing. Within the lotic biofilm community, 87% of the whole bacterial cell area and 79% of the total cell counts hybridized with a Bacteria specific probe. During initial biofilm development, beta-Proteobacteria dominated the bacterial population. This was followed by a rapid increase of alpha-Proteobacteria and bacteria affiliated to the Cytophaga-Flavobacterium group. In mature biofilms, alpha-Proteobacteria and Cytophaga-Flavobacteria continued to be the prevalent bacterial groups. Beta-Proteobacteria constituted the morphologically most diverse group within the biofilm communities, and more narrow phylogenetic staining revealed the importance of distinct phylotypes within the beta1-Proteobacteria for the composition of the microbial community. The presence of sulfate-reducing bacteria affiliated to the Desulfovibrionaceae and Desulfobacteriaceae confirmed the range of metabolic potential within the lotic biofilms.http://link.springer-ny.com/link/service/journals/00248/bibs/37n4p225.html