10 results for Lear, Gavin, Lewis, Gillian, Conference poster

  • The use of whole community bacterial indicators to monitor ecological health, function and variability within stream biofilms

    Lear, Gavin; Boothroyd, IK; Lewis, Gillian (2009-08-30)

    Conference poster
    The University of Auckland Library

    This study describes the extent of variability in biofilm bacterial community structure across a broad range of spatial and temporal scales and assesses whether this may be used as an indicator of stream ecological health and function. A community DNA fingerprinting technique (Automated Ribosomal Intergenic Spacer Analysis - ARISA) was used to examine the structure of bacterial communities within freshwater stream biofilms. When compared with macrobenthic invertebrate community assemblages using multi-dimensional scaling techniques, similar broad-scale trends in population structure were revealed between organisms at these different trophic levels. For both communities, spatial variability in community structure was greater between streams than within each site, or compared to temporal variability measured over 1 year. Distance-based redundancy analysis of both bacterial ARISA and macroinvertebrate data estimated that the largest cause of variation in community structure was due to differences in catchment land-use, rather than any single water quality parameter (e.g. ph or ammoniacal nitrogen). Multidimensional scaling of ARISA data also revealed significant differences in community structure between urban, and less impacted stream sites, providing evidence that whole-bacterial communities could be used as an indicator of freshwater ecological health, analogous to the way that macroinvertebrate communities have been used for many years. In conclusion, we propose the analysis of whole bacterial communities as a cost-effective, high throughput alternative indicator of freshwater ecological health.

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  • Effect of light regimes on the utilisation of an exogenous carbon source by freshwater biofilm communities

    Lear, Gavin; Lewis, Gillian (2007-06-23)

    Conference poster
    The University of Auckland Library

    Biofilms are a major source of ‘in stream’ primary production, exhibiting high population density, and being an important source of carbon for microbial heterotrophs. Changing patterns of land-use within freshwater catchment areas may greatly impact on stream biofilm microbial community structure, which in turn may influence the speed and extent with which full ecosystem recovery may occur. This study reports how freshwater biofilm communities respond to additions of acetate, used as a proxy for organic matter, the primary source of carbon within shaded forests and headwater streams. The use of [ 13C] acetate and subsequent isolation of 13C-labelled nucleic acids from the metabolically active fraction of the bacterial community enabled substrate assimilating organisms to be identified. In addition, biofilms were exposed to varied levels of incident light to assess the relative contribution of phototrophic and heterotrophic nutrition.

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  • Ecosystem responses to multiple-stressor gradients: Nutrient and sediment addition to experimental stream channels

    Wagenhoff, A; Matthaei, CD; Lear, Gavin; Lewis, Gillian; Townsend, CR (2009-05-16)

    Conference poster
    The University of Auckland Library

    Agricultural land use can strongly affect stream ecosystems by increasing levels of nutrients and fine sediment cover on the streambed. Knowledge of patterns in ecological responses along gradients of these two stressors will help define thresholds of harm. Leaf breakdown rates, algal and bacterial communities are directly and/or indirectly influenced by nutrient supply and fine sediment cover. To investigate the effects of stressor gradients and their interactions on these biological response parameters, we designed a full-factorial experiment in circular stream-side channels with eight levels each of nutrients (36 to 6900 μg·l-1 DIN, 1.4 to 450 μg·l-1 DRP) and fine sediment (0 to 100 % cover). Algal biomass, bacterial diversity and leaf pack decomposition were determined after three weeks of exposure to both stressors. Algal biomass was significantly higher in channels with lower levels of fine sediment. Bacterial diversity generally increased with increasing nutrient concentrations up to an intermediate nutrient level but then decreased again with the exception of reaching the highest diversity overall at the top nutrient level. Thus, increased levels of nutrients and fine sediment caused major changes to the algal and bacterial communities. In turn, these changes affect other food-web components as well as ecosystem functioning, including decomposition.

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  • Effects of Storm water metal contaminats on microbial communities in stream biofilm revealed by Automated Ribosomal Intergenic Spacer Analysis (ARISA)

    Ancion, Pierre; Lear, Gavin; Lewis, Gillian (2008-08-17)

    Conference poster
    The University of Auckland Library

    Stormwater metal contaminants are known to be a threat to our freshwater environments but little is known about their effects on stream micro-organisms. This project investigates accumulation and release of the most common stormwater metal contaminants (zinc, copper and lead) in stream biofilms and their effects on bacterial populations.

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  • Use of whole-community bacterial indicators to monitor ecological health, function and variability within freshwater stream biofilms.

    Lear, Gavin; Smith, Joanna; Roberts, Kelly; Boothroyd, Ian; Lewis, Gillian (2008-08-17)

    Conference poster
    The University of Auckland Library

    This study describes the extent of variability in biofilm bacterial community structure across a broad range of spatial and temporal scales and assesses whether this may be used as an indicator of stream ecological health and function. A community DNA fingerprinting technique (Automated Ribosomal Intergenic Spacer Analysis - ARISA) was used to examine the structure of bacterial communities within freshwater stream biofilms. When compared with macrobenthic invertebrate community assemblages using multi-dimensional scaling techniques, similar broad-scale trends in population structure were revealed between organisms at these different trophic levels. For both communities, spatial variability in community structure was greater between streams than within each site, or compared to temporal variability measured over 1 year. Distance-based redundancy analysis of both bacterial ARISA and macroinvertebrate data estimated that the largest cause of variation in community structure was due to differences in catchment land-use, rather than any single water quality parameter (e.g. ph or ammoniacal nitrogen). Multidimensional scaling of ARISA data also revealed significant differences in community structure between urban, and less impacted stream sites, providing evidence that whole-bacterial communities could be used as an indicator of freshwater ecological health, analogous to the way that macroinvertebrate communities have been used for many years. In conclusion, we propose the analysis of whole bacterial communities as a cost-effective, high throughput alternative indicator of freshwater ecological health.

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  • Human Activities Modify Bacterial Diversity in Stream Benthic Biofilm Communities

    Lewis, Gillian; Roberts, Kelly; Turner, Susan; Lear, Gavin (2008-06-01)

    Conference poster
    The University of Auckland Library

    This study tests the hypothesis that human impact is an important driver of stream biofilm bacterial population diversity. The seasonal bacterial composition of biofilm in 4 streams with different levels of human impact was determined over 2 years. Bacterial diversity derived from 16S rDNA clone libraries, shows both between stream differences and seasonal transitions in bacterial occurrence and population dominance at a class and genus level. Diversity analysis calculated on pooled seasonal data (class level identification) shows that while composition of the populations are different there is a similar level of both bacterial richness and bacterial diversity in each stream. Trends in bacterial occurrence suggest that the most degraded stream were dominated by cyanobacteria, the mid range impact streams by aeromonads and gamma proteobacteria, while the unimpacted stream showed both high diversity and no dominance by any particular class.

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  • What drives bacterial community structure in stream biofilms?

    Roberts, Kelly; Lear, Gavin; Turner, Susan; Lewis, Gillian (2008-08-17)

    Conference poster
    The University of Auckland Library

    BACKGROUND The microorganisms within biofilms are the key basal trophic level within most freshwater systems. However, microbial structure, function and succession in natural stream systems remain poorly understood. This research characterises the biofilm community structure of stream biofilms experiencing different anthropogenic impacts and how they change over time. Our aim is describe the changes in bacterial biofilm communities over time and to investigate what drives these changes.

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  • Stream Restoration: Getting the microbial ecology right.

    Lewis, Gillian; Lear, Gavin; Turner, Susan; Boothroyd, Ian; Stott, Rebecca; Roberts, Kelly; Ancion, Pierre; Dopheide, Andrew; Washington, Vidya; Knight, Duane; Smith, Joanna (2008-08-17)

    Conference poster
    The University of Auckland Library

    A comprehensive program to re-establish the structure and function of an ecosystem, including its natural diversity and aquatic habitats.

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  • Ciliate Diversity in Stream Biofilms revealed by group-specific PCR primers.

    Dopheide, Andrew; Lear, Gavin; Stott, R; Lewis, Gillian (2008-08-17)

    Conference poster
    The University of Auckland Library

    The ciliates are a diverse protozoan phylum, thought to be of considerable ecological importance in stream ecosystems, including organisms which are abundant and important consumers of bacteria, algae and other protozoa. Understanding of ciliate diversity and ecology is limited, however, particularly in benthic habitats such as stream biofilms. In this study, phylum-specific PCR primers were used in combination with cloning, sequencing and terminal restriction fragment length polymorphism (T-RFLP) analysis to investigate ciliate communities in stream biofilms.

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  • Molecular investigation of protozoan diversity in stream biofilms

    Dopheide, AJ; Lear, Gavin; Lewis, Gillian (2006-11-21)

    Conference poster
    The University of Auckland Library

    This research aims to test the following hypothesis: that molecular biological methods will allow description of protozoan diversity and ecology in streams.

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