title: Proton and cadmium adsorption by the archaeon Thermococcus zilligii: Generalising the contrast between thermophiles and mesophiles as sorbents

authors: Daughney, Christopher J.

subjects: proton adsorption

abstract: Adsorption by microorganisms can play a significant role in the fate and transport of metals in natural systems. Surface complexation models (SCMs) have been applied extensively to describe metal adsorption by mesophilic bacteria, and several recent studies have extended this framework to thermophilic bacteria. We conduct acid-base titrations and batch experiments to characterise proton and Cd adsorption onto the thermophilic archaeon Thermococcus zilligii. The experimental data and the derived SCMs indicate that the archaeon displays significantly lower overall sorption site density compared to previously studied thermophilic bacteria such Anoxybacillus flavithermus, Geobacillus stearothermophilus, G. thermocatenulatus, and Thermus thermophilus. The thermophilic bacteria and archaea display lower sorption site densities than the mesophilic microorganisms that have been studied to date, which points to a general pattern of total concentration of cell wall adsorption sites per unit biomass being inversely correlated to growth temperature.

text: Proton and cadmium adsorption by the archaeon Thermococcus zilligii: Generalising the contrast between thermophiles and mesophiles as sorbents Adsorption by microorganisms can play a significant role in the fate and transport of metals in natural systems. Surface complexation models (SCMs) have been applied extensively to describe metal adsorption by mesophilic bacteria, and several recent studies have extended this framework to thermophilic bacteria. We conduct acid-base titrations and batch experiments to characterise proton and Cd adsorption onto the thermophilic archaeon Thermococcus zilligii. The experimental data and the derived SCMs indicate that the archaeon displays significantly lower overall sorption site density compared to previously studied thermophilic bacteria such Anoxybacillus flavithermus, Geobacillus stearothermophilus, G. thermocatenulatus, and Thermus thermophilus. The thermophilic bacteria and archaea display lower sorption site densities than the mesophilic microorganisms that have been studied to date, which points to a general pattern of total concentration of cell wall adsorption sites per unit biomass being inversely correlated to growth temperature.

year: 2010

title: Soil physical impacts and recovery rates following human-induced disturbances in the Ross Sea region of Antarctica

authors: O'Neill, Tanya Ann

subjects: Antarctica

abstract: With increasing visitor numbers an understanding of the impacts of human activities on Antarctic soil environments has become an important issue.  The overall objective of this thesis was to investigate soil physical impacts, and soil recovery rates, following human disturbance in the Ross Sea region of Antarctica.  Visually disturbed and nearby control sites were assessed using a combination of techniques, including field-based visual site assessments, comparative photo-records, a desert pavement recovery assessment method, soil sampling, and soil dry bulk density measurements.  An experimental soil disturbance trial was set up near Scott Base and bacterial DNA profiling was used to investigate the response of communities to removal of the top 2 cm of soil.  Infra-red track counters were installed on Ross Island walking tracks to record visitor use over a two-year period.

Five case studies, from former research stations to field campsites, were investigated to assess the accuracy of the impacts predicted in environmental impact assessments and the observed impacts.  In all cases there was a high level of consistency between predicted and observed impacts.  It was apparent that the environmental impact assessment process raised environmental awareness of visitors; motivating them to avoid, remedy, or mitigate, their environmental impacts.  

A field-based method was developed to assess desert pavement recovery and tested on 54 sites.  Eleven criteria were used: embeddedness of surface clasts; impressions of removed clasts; degree of clast surface weathering; % overturned clasts; salt on underside of clasts; development of salt coatings; armouring per m2; colour contrast; evidence of subsidence/melt out; accumulation of salt on cut surfaces; and evidence of patterned ground development.  Recovery criteria were assigned a severity rating on a scale from zero to four, and the Mean Recovery Index (MRI) of the site was calculated relative to an equivalent control.  Five recovery stages were defined as recently or highly disturbed (MRI of 0-24%), through to indistinguishable from control site (MRI = 100%).  Fifty of the 54 sites investigated were in an intermediate or higher stage of desert pavement recovery (MRI > 50%), 30 sites were in an advanced stage of recovery (MRI > 75%), and four sites were indistinguishable from adjacent control sites (MRI = 100%).  Active surfaces, such as gravel beach deposits, aeolian sand, and alluvial fan deposits, recovered relatively quickly and had higher MRIs, whereas less active sites of higher intensity disturbances, such as bulldozed tracks at Marble Point, had lower MRIs, with only intermediate recovery up to 50 years after disturbance.

Following physical impacts such as foot and vehicle traffic the surface recovery recorded here was often greater than that predicted by previous researchers.  At one-off campsites, footprints from dispersed trampling were undetectable within five years.  At some sites walking tracks remained visible in the landscape 17 years after they were formed (due to surface recontouring and larger clasts concentrating along track margins).  For steep slopes and sites where repeated visits occur, use of a single track is recommended.  At sites where visually obvious impacts were remediated by replacing larger stones back in their original positions, ensuring that surface stones are placed with the weathered side up, and raking of gravel sand-sized displaced materials, visible evidence of former occupation was almost undetectable.  Concentrating activity on young, active, and readily recoverable surfaces, or resilient bedrock, is recommended.

There were no significant changes in bacterial community structure in response to experimental removal of the top 2 cm of soil over a 35 day sampling period.  Differences in bacterial community structure between samples correlated with differences in soil electricity conductivity (R2 = 0.55) and soil pH (R2 = 0.67), reflecting small scale (< 2 m) soil heterogeneity.

Infrared track counters recorded: 5084 passes on the Scott Base to McMurdo Station walking track, 2842 on the Wind Vane Hill walking track, 3561 on the Round Observation Hill walking track, and 10936 on the Up Observation Hill track between January 2009 and January 2011.  On the Crater Hill summit walking track there were 693 passes in 2009.  Higher counts were recorded on all tracks in the 2010/2011 summer season, compared with the 2009/2010 summer, and the highest frequency of visitors occurred on Sundays in the summer months.  Peak daily counts at the Wind Vane Hill track coincided with the arrival of tourist ships.  There was no relationship between the number of passes on the track and the measured impacts, indicating that higher usage of a formed track had little cumulative impact.  Track width and track incision were related to the slope of the terrain, with tracks traversing flatter areas generally wider (R² = 0.85) and less incised (R² = 0.96) than those traversing steeper hillsides.  Soil dry bulk density was higher in the walking tracks compared with the adjacent control areas (p <0.05).

text: Soil physical impacts and recovery rates following human-induced disturbances in the Ross Sea region of Antarctica With increasing visitor numbers an understanding of the impacts of human activities on Antarctic soil environments has become an important issue.  The overall objective of this thesis was to investigate soil physical impacts, and soil recovery rates, following human disturbance in the Ross Sea region of Antarctica.  Visually disturbed and nearby control sites were assessed using a combination of techniques, including field-based visual site assessments, comparative photo-records, a desert pavement recovery assessment method, soil sampling, and soil dry bulk density measurements.  An experimental soil disturbance trial was set up near Scott Base and bacterial DNA profiling was used to investigate the response of communities to removal of the top 2 cm of soil.  Infra-red track counters were installed on Ross Island walking tracks to record visitor use over a two-year period.

Five case studies, from former research stations to field campsites, were investigated to assess the accuracy of the impacts predicted in environmental impact assessments and the observed impacts.  In all cases there was a high level of consistency between predicted and observed impacts.  It was apparent that the environmental impact assessment process raised environmental awareness of visitors; motivating them to avoid, remedy, or mitigate, their environmental impacts.  

A field-based method was developed to assess desert pavement recovery and tested on 54 sites.  Eleven criteria were used: embeddedness of surface clasts; impressions of removed clasts; degree of clast surface weathering; % overturned clasts; salt on underside of clasts; development of salt coatings; armouring per m2; colour contrast; evidence of subsidence/melt out; accumulation of salt on cut surfaces; and evidence of patterned ground development.  Recovery criteria were assigned a severity rating on a scale from zero to four, and the Mean Recovery Index (MRI) of the site was calculated relative to an equivalent control.  Five recovery stages were defined as recently or highly disturbed (MRI of 0-24%), through to indistinguishable from control site (MRI = 100%).  Fifty of the 54 sites investigated were in an intermediate or higher stage of desert pavement recovery (MRI > 50%), 30 sites were in an advanced stage of recovery (MRI > 75%), and four sites were indistinguishable from adjacent control sites (MRI = 100%).  Active surfaces, such as gravel beach deposits, aeolian sand, and alluvial fan deposits, recovered relatively quickly and had higher MRIs, whereas less active sites of higher intensity disturbances, such as bulldozed tracks at Marble Point, had lower MRIs, with only intermediate recovery up to 50 years after disturbance.

Following physical impacts such as foot and vehicle traffic the surface recovery recorded here was often greater than that predicted by previous researchers.  At one-off campsites, footprints from dispersed trampling were undetectable within five years.  At some sites walking tracks remained visible in the landscape 17 years after they were formed (due to surface recontouring and larger clasts concentrating along track margins).  For steep slopes and sites where repeated visits occur, use of a single track is recommended.  At sites where visually obvious impacts were remediated by replacing larger stones back in their original positions, ensuring that surface stones are placed with the weathered side up, and raking of gravel sand-sized displaced materials, visible evidence of former occupation was almost undetectable.  Concentrating activity on young, active, and readily recoverable surfaces, or resilient bedrock, is recommended.

There were no significant changes in bacterial community structure in response to experimental removal of the top 2 cm of soil over a 35 day sampling period.  Differences in bacterial community structure between samples correlated with differences in soil electricity conductivity (R2 = 0.55) and soil pH (R2 = 0.67), reflecting small scale (< 2 m) soil heterogeneity.

Infrared track counters recorded: 5084 passes on the Scott Base to McMurdo Station walking track, 2842 on the Wind Vane Hill walking track, 3561 on the Round Observation Hill walking track, and 10936 on the Up Observation Hill track between January 2009 and January 2011.  On the Crater Hill summit walking track there were 693 passes in 2009.  Higher counts were recorded on all tracks in the 2010/2011 summer season, compared with the 2009/2010 summer, and the highest frequency of visitors occurred on Sundays in the summer months.  Peak daily counts at the Wind Vane Hill track coincided with the arrival of tourist ships.  There was no relationship between the number of passes on the track and the measured impacts, indicating that higher usage of a formed track had little cumulative impact.  Track width and track incision were related to the slope of the terrain, with tracks traversing flatter areas generally wider (R² = 0.85) and less incised (R² = 0.96) than those traversing steeper hillsides.  Soil dry bulk density was higher in the walking tracks compared with the adjacent control areas (p <0.05).

year: 2013

title: "Kia Mauri Tau!" Narratives of recovery from disabling mental health problems

authors: Lapsley, Hilary

subjects: Maori

abstract: A bicultural research team at the University of Waikato successfully applied for funding from the Health Research Council to do a qualitative research project in the area of ‘pathways to wellness’. The Mental Health Narratives Project set out to gather forty narratives of mental ill health, recovery and life after recovery by interviewing Maori and non-Maori women and men who once had a disabling mental health problem. We aimed to describe journeys to mental health, identify key themes in accounts of the recovery process and describe the impact of the experience of mental ill health on life after recovery.

text: "Kia Mauri Tau!" Narratives of recovery from disabling mental health problems A bicultural research team at the University of Waikato successfully applied for funding from the Health Research Council to do a qualitative research project in the area of ‘pathways to wellness’. The Mental Health Narratives Project set out to gather forty narratives of mental ill health, recovery and life after recovery by interviewing Maori and non-Maori women and men who once had a disabling mental health problem. We aimed to describe journeys to mental health, identify key themes in accounts of the recovery process and describe the impact of the experience of mental ill health on life after recovery.

year: 2002