The use of artificial biofilms to strip nutrients from an industrial smelters waste water under conditions of low temperature and high pH

The Victorian Environment Protection Authority (EPA) has identified Alcoa’s Point Henry aluminium smelter as being a major source of recognized pollutant input due to its disposal of effluent into Corio Bay. Historically, the water quality parameters that have most often exceeded Point Henry’s EPA limits have been pH and suspended solids from the smelter’s discharge points. These waste water discharges also experience high nitrogen and phosphorus concentrations which result in algal blooms that occur at the onset of warm weather. The main hypothesis of this study was that “prevention of algal blooming with the onset of warm weather by removal of nutrients during the cooler months, and continued removal thereafter, is better than curing the problems chemically”. Biofilms have been used to remove nutrients from waste waters, but not under the conditions experienced at Point Henry. The aim of this study, therefore, was to determine if significant biofilm growth would be observed on floating structures suspended in the Point Henry waste water stream during the cooler, winter months of the year. Statistically significant biofilm growth occurred on all suspended structures in all discharge ponds during the winter and early spring of 2000. The use of suspended structures, such as AquaMatTM, as an artificial substrate to attract and support periphyton and bacterial communities (biofilms), which are then able to out-compete phytoplankton communities for available nutrients, is therefore a viable option for the Point Henry smelter. However, further research on the competitive performance of biofilms in the Point Henry ponds during the summer months is required before adequate biofilm management strategies can be developed.

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences.

Isolation and phylogenetic identification of halotolerant/halophilic bacteria from the salt mines of Karak, Pakistan

Extreme environments like salt mines are inhabited by a variety of bacteria that are well-adapted to such environments. The bacterial populations provide economic benefits in terms of enzymes synthesis. The salt mines of Karak region in Pakistan are extremely saline and the microbial communities found here have not yet been explored. In the present study, 57 halotolerant/halophilic bacterial strains were isolated from the salt mines of Karak. These strains were grown in media with 0-35% NaCl concentration. The morphological and physiological characteristics of the isolated strains were studied to optimize the growth conditions and to classify the isolated bacterial strains into slightly halotolerant/halophilic, moderately halophilic and extreme halophilic. The phylogenetic analyses inferred from 16S rRNA gene sequence of the isolated strains demonstrated that the major population were closely related to species belonging to Planococcus, Jeotgalicoccus, Staphylococcus, Halobacillus, Halomonas, Brevibacterium, Gracilibacillus, Kocuria, Salinivibrio, Salinicoccus, Oceanobacillus and Bacillus genera. Results showed that the salt mines of Karak region are rich in halotolerant/halophilic bacterial population with diverse bacterial communities, which may be utilized in various industrial applications after proper screening and identification.

Impact of nest sanitation on the immune system of parents and nestlings in a passerine bird

Bacterial communities are thought to have fundamental effects on the growth and development of nestling birds. The antigen exposure hypothesis suggests that, for both nestlings and adult birds, exposure to a diverse range of bacteria would select for stronger immune defences. However, there are relatively few studies that have tested the immune/bacterial relationships outside of domestic poultry. We therefore sought to examine indices of immunity (microbial killing ability in naïve birds, which is a measure of innate immunity and the antibody response to sheep red blood cells, which measures adaptive immunity) in both adult and nestling zebra finches (Taeniopygia guttata). We did this throughout breeding and between reproductive attempts in nests that were experimentally manipulated to change the intensity of bacterial exposure. Our results suggest that nest sanitation and bacterial load affected measures of the adaptive immune system, but not the innate immune parameters tested. Adult finches breeding in clean nests had a lower primary antibody response to sheep red blood cells (SRBC), particularly males, and a greater difference between primary and secondary responses. Adult microbial killing of E.coli decreased as parents moved from incubation to nestling rearing for both nest treatments; however, killing of C.albicans remained consistent throughout. In nestlings, both innate microbial killing and the adaptive antibody response did not differ between nest environments. Together, these results suggest that the exposure to microorganisms in the environment affect the adaptive immune system in nesting birds, with exposure upregulating the antibody response in adult birds.

Riparian reforestation: are there changes in soil carbon and soil microbial communities?

Reforestation of pastures in riparian zones has the potential to decrease nutrient runoff into waterways, provide both terrestrial and aquatic habitat, and help mitigate climate change by sequestering carbon (C). Soil microbes can play an important role in the soil C cycle, but are rarely investigated in studies on C sequestration. We surveyed a chronosequence (0-23years) of mixed-species plantings in riparian zones to investigate belowground (chemical and biological) responses to reforestation. For each planting, an adjacent pasture was surveyed to account for differences in soil type and land-use history among plantings. Two remnant woodlands were included in the survey as indicators of future potential of plantings. Both remnant woodlands had significantly higher soil organic C (SOC) content compared with their adjacent pastures. However, there was no clear trend in SOC content among plantings with time since reforestation. The substantial variability in SOC sequestration among plantings was possibly driven by differences in soil moisture among plantings and the inherent variability of SOC content among reference pastures adjacent to plantings. Soil microbial phospholipid fatty acids (PLFA, an indicator of microbial biomass) and activities of decomposition enzymes (β-glucosidase and polyphenol oxidase) did not show a clear trend with increasing planting age. Despite this, there were positive correlations between total SOC concentration and microbial indicators (total PLFA, fungal PLFA, bacterial PLFA and activities of decomposition enzymes) across all sites. The soil microbial community compositions (explored using PLFA markers) of older plantings were similar to those of remnant woodlands. There was a positive correlation between the soil carbon:nitrogen (C:N) and fungal:bacterial (F:B) ratios. These data indicate that in order to maximise SOC sequestration, we need to take into account not only C inputs, but the microbial processes that regulate SOC cycling as well.

Pastures to woodlands: changes in soil microbial communities and carbon following reforestation

Reforestation of agricultural lands has the potential to sequester C, while providing other environmental benefits. It is well established that reforestation can have a profound impact on soil physicochemical properties but the associated changes to soil microbial communities are poorly understood. Therefore, the objective of this study was to quantify changes in soil physicochemical properties and microbial communities in soils collected from reforested pastures and compare then to remnant vegetation and un-reforested pastures. To address this aim, we collected soil from two locations (pasture and its adjacent reforested zone, or pasture and its adjacent remnant vegetation) on each of ten separate farms that covered the range of planting ages (0-30 years and remnant vegetation) in a temperate region of southeastern Australia. Soils were analysed for a range of physicochemical properties (including C and nutrients), and microbial biomass and community composition (PLFA profiles). Soil C:N ratios increased with age of tree planting, and soil C concentration was highest in the remnant woodlands. Reforestation had no clear impact on soil microbial biomass or fungal:bacterial ratios (based on PLFA's). Reforestation was associated with significant changes in the molecular composition of the soil microbial community at many farms but similar changes were found within a pasture. These results indicate that reforestation of pastures can result in changes in soil properties within a few decades, but that soil microbial community composition can vary as much spatially within pastures as it does after reforestation.