Increasing sulfate concentrations result in higher sulfide production and phosphorous mobilization in a shallow eutrophic freshwater lake.

Increasing sulfate input has been seen as an issue in management of aquatic ecosystems, but its influences on eutrophic freshwater lakes is not clear. In this study, it was observed that increasing sulfate concentration without additional cyanobacterial bloom biomass (CBB) addition did not have an obvious effect on element cycling during 1-year continuous flow mesocosm experiments in which water and sediments were taken from a shallow eutrophic lake with sulfate levels near 1 mM. However, following addition of CBB to mesocosms, sulfate-reducing bacteria (SRB) were observed in the water column, and increasing numbers of SRB in the water column were associated with higher sulfate input. Sulfate amendment (0-70 mg L(-1)) also resulted in a larger amount of total dissolved sulfide (peak values of 5.90 ± 0.36 to 7.60 ± 0.12 mg L(-1)) in the water column and acid volatile sulfide (1081.71 ± 69.91 to 1557.98 ± 41.72 mg kg(-1)) in 0-1 cm surface sediments due to sulfate reduction. During the period of CBB decomposition, increasing sulfate levels in the water column were positively correlated with increasing diffusive phosphate fluxes of 1.23 ± 0.32 to 2.17 ± 0.01 mg m(-2) d(-1) at the water-sediment interface. As increases in sulfide and phosphate release rates deteriorated the water quality/ecosystem and even spurred the occurrence of a black water problem in lakes, the control of sulfate input level should be considered for shallow eutrophic lake management, especially during cyanobacterial bloom periods.

To prevent the occurrence of black water agglomerate through delaying decomposition of cyanobacterial bloom biomass by sediment microbial fuel cell.

Settlement of cyanobacterial bloom biomass (CBB) into sediments in eutrophic lakes often induced the occurrence of black water agglomerate and then water quality deterioration. This study investigated the effect of sediment microbial fuel cell (SMFC) on CBB removal in sediments and related water pollution. Sediment bulking and subsequent black water from decomposition of settled CBB happened without SMFC, but were not observed over 100-day experiments with SMFC employment. While CBB in sediments improved power production from SMFC, the removal efficiency of organic matters in CBB-amended sediments with SMFC was significantly lower than that without SMFC. Pyrosequencing analysis showed higher abundances of the fermentative Clostridium and acetoclastic methanogen in CBB-amended bulk sediments without SMFC than with SMFC at the end of experiments. Obviously, SMFC operation changed the microbial community in CBB-amended sediments, and delayed the CBB degradation against sediment bulking. Thus, SMFC could be potentially applied as pollution prevention in CBB-settled and sensitive zones in shallow lakes.

Analysis of the attached microbial community on mucilaginous cyanobacterial aggregates in the eutrophic Lake Taihu reveals the importance of Planctomycetes.

The phylogenetic diversity of the microbial community assemblage of the carpet-like mucilaginous cyanobacterial blooms in the eutrophic Lake Taihu was investigated. 16S ribosomal DNA clone libraries produced from the DNA of cyanobacterial assemblages that had been washed to remove unattached bacteria contained only cyanobacteria. However, a further treatment which included grinding the freeze-dried material to physically detach cells followed by the removal of larger cells by filtration allowed us to detect a large variety of bacteria within the cyanobacterial bloom community. Interestingly, the dominant members of the microbial community were Planctomycetes followed by Cytophaga-Flavobacterium-Bacteroides (CFB), Betaproteobacteria, and Gammaproteobacteria. The analysis of the 16S ribosomal DNA clone libraries made from enrichment culture revealed much higher phylogenetic diversity of bacteria. Dominant bacterial groups in the enrichment system were identified as members of the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria subdivisions, CFB group, and Planctomycetes. In addition, the clone libraries constructed from Planctomycetes-specific 16S ribosomal RNA primers also verified that the enrichment allowed a diversity of Planctomycetes to proliferate, although the community composition was altered after enrichment.

Cellulose degradation by one mesophilic strain Caulobacter sp. FMC1 under both aerobic and anaerobic conditions.

Caulobacteria are presumed to be responsible for considerable mineralization of organic material in aquatic environments. In this study, a facultative, mesophilic and cellulolytic bacterium Caulobacter sp. FMC1 was isolated from sediments which were taken from a shallow freshwater lake and then enriched with amendment of submerged macrophyte for three months. This strain seemed to evolve a capacity to adapt redox-fluctuating environments, and could degrade cellulose both aerobically and anaerobically. Cellulose degradation percentages under aerobic and anaerobic conditions were approximately 27% and 10% after a 240-h incubation in liquid mediums containing 0.5% cellulose, respectively. Either cellulose or cellobiose alone was able to induce activities of endoglucanase, exoglucanase, and ß-1,4-glucosidase. Interestingly, ethanol was produced as the main fermentative product under anaerobic incubation on cellulose. These results could improve our understanding about cellulose-degrading process in aquatic environments, and were also useful in optimizing cellulose bioconversion process for bioethanol production.

Various voltage productions by microbial fuel cells with sedimentary inocula taken from different sites in one freshwater lake.

In this study, single-chamber microbial fuel cells (MFCs) were inoculated with sedimentary samples taken from one freshwater shallow lake. After 98 days of operation, it was found that sedimentary inocula had strong effect on MFC performances, and Fe(III) contents in sediments were significantly related to voltage values produced from MFCs. Inoculation of the sedimentary sample from the site with the highest Fe(III) content led to the production of the highest voltage with a value of 580 mV, while voltage from the MFC inoculated with sediments from the site with the lowest Fe(III) concentration was less than 30 mV at the end of the experiments. In addition, microbial communities of anode biofilms from the MFCs with the highest and lowest voltages showed significant difference. This study will help enable scientific decisions to be made regarding the selection of freshwater sediments as MFC inoculum, and survey exoelectrogenic microorganisms within sediments.