Earth

Event Date: 
Wednesday, August 28, 2013 - 18:00 - 18:15
Institution: 
CSIRO Canberra
Title: 

Decomposer Microbial Communities Shift from Native Eucalyptus Diversity to Pine-type Diversity in Eucalypt Forests Fragmented by Pine Plantations

Abstract: 

 
The Wog Wog Fragmentation Experiment was started 29 years ago as a collaboration between CSIRO and NSW Forestry and is one of the longest running ecological experiments in the world.  It was designed to study the effects of Pinus radiata plantations on patches of old-growth Eucalyptus forest in terms of overall health as well as plant and insect species diversity.  Early work at the site showed that, in agreement with fragmentation ecology theory, predatory and generally rarer beetles decreased in eucalyptus fragments surrounded by the newly planted pines whereas decomposer and fungus-feeding beetle species increased.  These types of edge-dependant effects penetrated at least 100m into remnant eucalyptus forest fragments.
Recently, there have been a number of new studies on diverse aspects of forest diversity and health at the site.  This recent work has focused on understory plant diversity, long-term ground-dwelling beetle diversity and population dynamics, soil nutrient levels, soil bacterial and fungal diversity, skink and bird diversity, Eucalyptus growth and demographics, and understory light and temperature regimes.  Andrew King’s presentation will focus on the interaction between soil microbial communities, altered soil carbon and nitrogen cycles, and an unexpected increase in Eucalypt growth in response to fragmentation.

Event Date: 
Wednesday, May 29, 2013 - 19:00 - 19:45
Institution: 
CSIRO
Title: 

Sediment Biobarriers for Chlorinated Aliphatic Hydrocarbons in Groundwater Reaching Surface Water

Abstract: 

 
This study explored the potential of eutrophic river sediments to attenuate the infiltration of chlorinated aliphatic hydrocarbon (CAH)-polluted groundwater discharging into the Zenne River near Brussels, Belgium. Active biotic reductive dechlorination of CAHs in the riverbed was suggested by a high dechlorination activity in batch- and column biodegradation tests performed with sediment samples, and by the detection of dechlorination products in sediment pore water. Halorespiring Dehalococcoides spp. were present in large numbers in the riverbed as shown by quantification of their 16S rRNA and reductive dehalogenase genes. By using DGGE-fingerprint analysis of relevant nucleic acid markers, it was shown that the Zenne River sediments were inhabited by a metabolically diverse bacterial community. A large diversity of sulfate-reducing bacteria, Geobacteraceae and methanogens, which potentially compete with halorespiring bacteria for electron resources, was identified. The high organic carbon level in the top of the riverbed, originating from organic matter deposition from the eutrophic surface water, resulted in a homogeneous microbial community structure that differed from the microbial community structure of the sediment underneath this layer. Monitoring of CAH concentrations and stable isotope ratios of the CAHs (δ13C) and the water (δ2H and δ18O), allowed to identify different biotic and abiotic CAH attenuation processes and to delineate their spatial distribution in the riverbed. Reductive dechlorination of the CAHs was the most widespread attenuation process, followed by dilution by unpolluted groundwater discharge and by surface water-mixing. During a 21-month period, the extent of reductive dechlorination ranged from 27 to 89% and differed spatially but was remarkably stable over time, whereas the extent of abiotic CAH attenuation ranged from 6 to 94%, showed large temporal variations, and was often the main process contributing to the reduction of CAH discharge into the river. Although CAHs were never detected in the surface water, CAHs were not completely removed from the discharging groundwater at specific locations in the riverbed with high groundwater influx rates. Therefore, it was concluded that an increase in the extent of biotransformation in the riverbed is needed for acceptance of the Zenne biobarrier as a viable remedial option for attenuation of discharging CAH-polluted groundwater.

JAMS REPORT
Maria-Luisa Gutierrez-Zamora

The JAMS rendezvous this October 31st took place in the fourth floor of the Museum with a magnificent view of Sydney, and began with an ad hoc presentation featuring sulphurous scents and sexy fangs. Katherina Petrou (UTS) initiated us in the science of the sulphur cycle in the oceans and how this process is dominated by the production of dimethylsulfoniopropionate (DMSP) by microalgae and its decomposition into dimethylsulphide (DMS), a strong odorous chemoattractant for a range of marine organisms. In tackling the mystery of how harmful algal blooms disappear, Katherina discovered that DMS produced by the dinoflagellate Alexandrium minutum (causative agent of toxic algal blooms) was the chemical cue for the infection of its parasitoid Parvilucifera sinerae.  An elegant video illustrated how DMS at 300 nM was able to activate the parasitoid spores from a dormant state to leave the sporangium (an infected A. minutum cell) in transit to infect other cells and propagate. Activation only occurred in the range of 30 to 300 nM indicating that the effect was dependent on cell density. Thus, Katherina’s work showed that DMS plays an important role in the biological control of toxic algal blooms in the oceans. Her results contribute to the better understanding of marine chemical ecology.

Event Date: 
Wednesday, November 28, 2012 - 07:00 - 08:00
Institution: 
University of Sydney
Title: 

Biodegradation of dichloroethane by aerobic bacteria at the Botany Industrial Park

Abstract: 

The chlorinated hydrocarbon 1,2-dichloroethane (DCA) is a common pollutant of groundwater, and poses both human and environmental health risks. The Botany Industrial Park in south Sydney is heavily contaminated with DCA and other organochlorines. The main user of the site (Orica Ltd) operates a large groundwater treatment plant (GTP) on site to contain and remediate the DCA-contaminated groundwater. At present, remediation is done by air-stripping and thermal oxidation, but this is very costly and energy-intensive. Orica is interested in alternative technologies for treating the groundwater, including bioremediation. In 2010, a pilot scale membrane bioreactor (MBR) was set up to treat a fraction of the groundwater. The aims of our study were to identify DCA-degrading bacteria and genes in the GTP and on the site at large, define the community structure and ecological successions occurring in the MBR, develop a qPCR for catabolic genes in the DCA biodegradation pathway, and field-test this qPCR assay in the MBR and in a survey of groundwater in monitoring wells on the site. We discovered that DCA-degrading bacteria using a hydrolytic pathway (dhlA/dhlB genes) were widespread and diverse at this site, and that the dhlA gene was carried on a catabolic plasmid. The community in the MBR was dominated by alpha- and beta-proteobacteria, and was highly dynamic, changing dramatically in composition as the percentage of raw groundwater in the feed was increased. By combining dhlA qPCR and 16S pyrosequencing data, we found evidence that thus-far-uncultured species of Azoarcus may play a major role in DCA bioremediation in situ in the MBR.

 
Prepared by Valentina Wong (UNSW PhD student)
On a cold Tuesday night, Adrian Low from University of New South Wales warmed the JAMS audience with his passion on bioremediation of organochlorine contaminated groundwater. Adrian described the discovery of Australia’s first 1,2-dichloroethane (DCA) degrading consortium, AusDCA. His work in the field demonstrated the efficacy and sustainability of using organochlorine respiring bacteria to remediate organochlorine contaminants in situ. He plans to isolate the bacterial species responsible for performing this unique task.

Event Date: 
Wednesday, September 28, 2011 - 18:00 - 18:15
Institution: 
University of New South Wales
Title: 

The Effects of Environmental Temperature on Biogeographic Boundaries in SAR11 Marine Bacteria.

Abstract: 

The ubiquitous SAR11 bacterial clade is the most abundant type of organism in the world's oceans, but the reasons for its success are not fully elucidated. We provide the first global characterisation of the distribution of this marine heterotrophic bacterium, from waters spanning temperatures -2ºC to 30ºC. Our data show a stable co-occurrence of paired ecotypes within both "tropical" (>20ºC) and "polar" (<10ºC) biomes, highlighting ecological niche differentiation between the major SAR11 lineages. All ecotypes display transitions in abundance that are strongly correlated to temperature. Our data demonstrates the importance of adaptive radiation in the organism's ability to proliferate throughout the world's oceans. Based on projections of sea surface temperature in 2090 we predict a redistribution of SAR11 ecotypes within a significant proportion of the ocean realm as a result of global warming.

Event Date: 
Wednesday, September 28, 2011 - 18:15 - 18:30
Institution: 
University of New South Wales
Title: 

The Polar Front is a major boundary in Southern Ocean picoplanktonic biogeography.

Abstract: 

The Polar Frontal Zone, at around 60 S, is the boundary in the SO between the cold Antarctic Zone to its south and the warmer Subantarctic Zone to the north. It is defined at its southern extent by the Polar Front (PF) and its northern by the Subantarctic Front. Across each of these fronts, the temperature decreases southward in a stepwise fashion (e.g. 1.5-2C over a distance of 30-50 km), accompanied by changes in salinity and density. In this study we performed a high-throughput metagenomic survey of Southern Ocean picoplankton during the austral summer of 2007-2008 and found that the PF was a major biogeographical boundary, separating microbial assemblages with distinct taxonomic and functional profiles. None of the physiochemical parameters measured were correlated with taxonomic or functional profile. However, we observed a strong over-representation of the oligotrophic SAR11 and SAR116 clades, the cyanobacterial genera Prochlorococcus and Synechococcus and Roseobacter spp. north of the PF. Conversely, a high abundance of the uncultured chemolithoautotrophic SUP05 clade and of ammonia oxidising archaea characterised waters south of the PF. This and other evidence suggests that mixing between deep and shallow waters shapes bacterial communities south of the PF.

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