Press disturbance unveils different community structure, function and assembly of bacterial taxa and functional genes in mesocosm-scale bioreactors

Sustained perturbations, or press disturbances, are of interest in microbial ecology as they can drive systems to alternative stable states. Here, we tested the effect of a sustained doubling of organic carbon loading on structure, assembly and function of bacterial communities. Two sets of replicate 5-liter sequencing batch reactors were operated at two different organic carbon loading levels (323 and 629 mg COD L-1) for a period of 74 days, following 53 days of acclimation after inoculation with sludge from a full-scale treatment plant. Temporal dynamics of community taxonomic and functional gene structure were derived from metagenomics and 16S rRNA gene metabarcoding data. Assembly mechanisms were assessed through a mathematical null model on the effective bacterial turnover expressed as a proportion of total bacterial diversity. Disturbed reactors exhibited different community function, structure and assembly compared to the undisturbed reactors. Bacterial taxa and functional genes showed dissimilar alpha-diversity and community assembly patterns. Deterministic assembly mechanisms were generally stronger in disturbed reactors, associated with common taxa. Stochastic assembly was more important for functional genes and was driven by rare genes. We urge caution when assessing microbial community assembly mechanisms, as results can vary depending on the approach.

Effectiveness of Nitrification and Denitrification Processes in Biofilters Treating Wastewater from De-Icing Airport Runways

The basic factors determining the efficiency of the removal of nitrogen and carbon compounds from airport wastewater containing de-icing agents are low temperature and the C/N ratio (carbon to nitrogen ratio). Biofilm reactors (biofilters) create better conditions for nitrification and denitrification than suspended biomass reactors. The scope of the study included determination of the influence of the C/N ratio in the wastewater on nitrification, denitrification and organic compound removal in biofilm reactors depending on the temperature. The experiment was performed in 24 circular laboratory biofilters with LECA (Light Expanded Clay Aggregates) filling. The study was divided into three series differing in organic carbon loading. In each series, carried out at the same hydraulic retention time, biofilters were operated at 25, 8, 4 or 0 °C. The study showed the effective removal of nitrogen compounds across a very wide temperature range. The applied filling and properly selected operating parameters of the reactors resulted in effective simultaneous nitrification and denitrification. The highest efficiency of nitrogen removal at 0 °C (34.57 ± 4.54%) was obtained at the C/N ratio of 0.5 gC/gN. The efficiency of denitrification (the lowest at the temperature of 0 °C) increased as the temperature and C/N ratio increased in the wastewater.

APLIKASI PROSES BIOLOGI ANAEROBIK PADA PENGOLAHAN AIR LIMBAH ORGANIK BERKONSENTRASI GARAM TINGGI “STUDI KASUS INDUSTRI UME BOSHI”

Anaerobic treatment of wastewater with high organic and salt content but low pH (TOC, 14 g/l; salt, 150 g/l; pH,2.7) generated during an “ume boshi” manufacturing process was investigated. Five-fold-diluted “ume boshi” effluent was treated by a draw-and-fill method at a volumetric TOC (total organic carbon) loading rate of 3.0 g/l/d with a TOC removal efficiency of 75%. Five-fold-diluted “ome boshi” effluent was also treated in an anaerobic fluidized-bed reactor (AFBR) at a maximum volumetric TOC loading rate of 3.0 g/l/d, which gave almost the same results as the draw-and-fill method. However, ten-fold-diluted “ome boshi” effluent could be treated in the AFBR at a maximum volumetric TOC loading rate of 11 g/l/d with a TOC removal efficiency of 85%. The methane content in the evolved gas was high, being 70%. The red pigment in the “ome boshi” effluent was completely decolorized by the anaerobic treatment. Key words :, Anaerobic fluidized-bed reactor, “Ume boshi”Co2+ and Ni2+ ions, decolorization

Contribution of Terrestrial Runoff to Coral Disease Prevalence on North Bali’s Massive Porites

The widespread of coral disease may threatened Bali`s marine tourism which is the main asset for the nation prosperity. However, the disease prevalence is still unknown, in particular inshore coral reefs near to tourist spot areas. Therefore, the research aims to investigate the contribution of terrestrial runoff to coral disease prevalence and to examine the relationships between disease prevalence and environmental parameters (nitrate, phosphate, organic carbon and total suspended solids (TSS)) within the population of massive Porites on shallow north Bali reefs. Syndrome, diseases and healthy colonies of massive Porites coral were counted and noted within a 2 x 10 m belt transect at 3 sampling sites. The dominant disease observed was ulcerative white spots (UWS), while the syndromes were pigmentation response and aggressive overgrowth by macroalgae. The highest mean UWS prevalence was at site 3 which was the closest site to runoff (prevalence = 91%).This disease only affected one colony at site 1 and 2, respectively. Disease prevalence had strong relationship with TSS and nitrate, yet it showed weak relationship with phosphate and organic carbon. These results suggest that terrestrial runoff could contribute to the disease prevalence by increasing the TSS, nutrients and organic carbon loading to the inshore ecosystems. High level of organic carbon could severe the disease, particularly when combined with elevated TSS and nutrient, by reducing the coral`s immunity system. Keywords: coral disease, prevalence, terrestrial runoff, Porites, ulcerative white spot, environmental parameter, North Bali.