title: Bakhtinian Dialogic and Vygotskian Dialectic: Compatabilities and contradictions in the classroom?

authors: White, Elizabeth Jayne

subjects: Bakhtin

abstract: This article explores two central notions of ‘dialectics’ and ‘dialogics’ based on the work of Vygotsky (drawing on philosophers such as Hegel, Spinoza, Engels and Marx) and Bakhtin (drawing on members of the Bakhtin Circle and writers such as Dostoevsky and Rabelais) respectively, as well their varying interanimations within Stalin-Marxist Russian society. It is proposed that these two positions are incommensurably located alongside one another in contemporary education. I argue that Bakhtin offers diametrically oppositional educational provocations to those of Vygotsky. The implications of these interpretations will be explored with consideration of their underlying philosophical incompatibilities and contradictions, as well as the opportunities such a consideration pose for educational practice today.

text: Bakhtinian Dialogic and Vygotskian Dialectic: Compatabilities and contradictions in the classroom? This article explores two central notions of ‘dialectics’ and ‘dialogics’ based on the work of Vygotsky (drawing on philosophers such as Hegel, Spinoza, Engels and Marx) and Bakhtin (drawing on members of the Bakhtin Circle and writers such as Dostoevsky and Rabelais) respectively, as well their varying interanimations within Stalin-Marxist Russian society. It is proposed that these two positions are incommensurably located alongside one another in contemporary education. I argue that Bakhtin offers diametrically oppositional educational provocations to those of Vygotsky. The implications of these interpretations will be explored with consideration of their underlying philosophical incompatibilities and contradictions, as well as the opportunities such a consideration pose for educational practice today.

year: 2011

title: Differentiating the temperature response of soil fungi and bacteria

authors: Ray, Seager

subjects: Soil Biochemistry

abstract: The decomposition of soil organic matter (SOM) may be accelerated under increasing temperatures from climate change, which could create feedback loops that result in the loss of soil carbon (C) stocks. Fungi and bacteria regulate the decomposition of SOM, each having their own unique adaptations that allow them to fulfill different roles in the decomposition process. However, fungi and bacteria may respond to temperature differently which could complicate soil C cycling dynamics. To date, few studies have attempted to differentiate the temperature response of fungal and bacterial respiration.

The aim of this research was to differentiate the temperature optima (Tₒₚₜ) and inflection point temperatures (Tᵢₙբ) of fungal and bacterial respiration. The Tₒₚₜ is the temperature at  which respiration is maximal whereas the Tinf is the point at which respiration is most sensitive to temperature.

Soils were collected from different locations along a geothermal temperature gradient (that had average temperatures between ~13-39 °C). The selective inhibition method was used to differentiate the temperature response of fungal and bacterial respiration by treating soils with streptomycin and cycloheximide, respectively. Soils were also treated with and without glucose to determine the non-substrate limited respiration response of fungal and bacterial respiration. Treated soils were incubated in a temperature block that allowed the incubation of soils at temperatures ranging between ~5-52 °C for five hours. Headspace samples were taken from each treatment tube and injected into an infrared gas analyser (IRGA) to measure carbon dioxide (CO₂) concentrations and respiration rates. Macromolecular rate theory (MMRT) was used to model the temperature response of the respiration curves to derive the Tₒₚₜ and Tᵢₙբ of fungal and bacterial respiration, allowing the comparison of the temperature responses of fungal and bacterial respiration.

An additional aim of this research was to measure changes in fungal and bacterial biomass along the geothermal temperature gradient using phospholipid fatty acid (PLFA) analysis. Soil samples were collected from the same sampling locations along the geothermal temperature gradient as those used in the selective inhibition experiments. A modified Bligh and Dyer method was used to extract phospholipids from soil samples, which were used as biomarkers to differentiate the biomass of different fungal and bacterial groups.

Results from selective inhibition experiments showed that respiration rates decreased from streptomycin and cycloheximide treatment, allowing an estimation of fungal and bacterial contributions to total soil respiration, respectively. Fungal contributions to soil respiration (~55%) were greater than bacterial contributions (~21%), suggesting that fungi contribute more to soil C decomposition than bacteria. Furthermore, the Tₒₚₜ of fungal respiration was found to decrease with environmental temperature at a rate of -0.396 °C °C-1 whereas the Tₒₚₜ of bacteria and the microbial community was not correlated with environmental temperature. Additionally, the Tₒₚₜ and Tᵢₙբ of fungal respiration (38.6 °C and 22.1 °C, respectively) was not significantly different from the Tₒₚₜ and Tᵢₙբ of microbial respiration (37.0 °C and 21.7 °C, respectively) but was significantly greater than the Tₒₚₜ and Tᵢₙբ of bacterial respiration (30.4 °C and 19.0 °C, respectively). Results from PLFA analysis showed that gram-positive bacteria and general bacteria dominated total microbial biomass and biomass from identified fungal and bacterial groups peaked at ~19-21 °C. Fungal-to-bacterial (F:B) ratios decreased with increasing environmental temperature, indicating a proportional decrease in fungal biomass relative to bacteria at higher temperatures. These results suggest that fungi were excluded with increasing environmental temperature as they were unable to adapt their metabolism and growth as environmental temperatures increased.

The selective inhibition method presented a range of limitations that may have constrained interpretation of the results. First, inhibitors were not equally effective across the range of incubation temperatures. Inhibition from cycloheximide showed a clear temperature optimum where inhibition was greatest within ~45-50 °C. In contrast, inhibition from streptomycin declined at temperatures above ~30 °C. Secondly, percent inhibition of microbial respiration from streptomycin increased as total bacterial biomass increased, providing evidence that streptomycin was effective in targeting bacteria. In contrast, percent inhibition of microbial respiration from cycloheximide was not correlated with fungal biomass, indicating that cycloheximide may not have been effective in selectively targeting fungi.

Overall, these results indicate that fungi may be more at risk from increasing temperatures under climate change, though it is unknown as to how this could translate to soil C stocks. This was likely the first study that attempted to differentiate the temperature response of fungi and bacteria by selectively inhibiting fungi and bacteria and incubating them across a range of temperatures. However, caution should be taken when interpreting results as a range of methodological constraints were uncovered regarding the veracity of the selective inhibition method. While previous studies have reported some limitations of the selective inhibition method, these issues have likely been under-reported as researchers may not publish inconclusive or negative results. Therefore, this study also highlights the importance of critically assessing methods that may be ineffectual.

text: Differentiating the temperature response of soil fungi and bacteria The decomposition of soil organic matter (SOM) may be accelerated under increasing temperatures from climate change, which could create feedback loops that result in the loss of soil carbon (C) stocks. Fungi and bacteria regulate the decomposition of SOM, each having their own unique adaptations that allow them to fulfill different roles in the decomposition process. However, fungi and bacteria may respond to temperature differently which could complicate soil C cycling dynamics. To date, few studies have attempted to differentiate the temperature response of fungal and bacterial respiration.

The aim of this research was to differentiate the temperature optima (Tₒₚₜ) and inflection point temperatures (Tᵢₙբ) of fungal and bacterial respiration. The Tₒₚₜ is the temperature at  which respiration is maximal whereas the Tinf is the point at which respiration is most sensitive to temperature.

Soils were collected from different locations along a geothermal temperature gradient (that had average temperatures between ~13-39 °C). The selective inhibition method was used to differentiate the temperature response of fungal and bacterial respiration by treating soils with streptomycin and cycloheximide, respectively. Soils were also treated with and without glucose to determine the non-substrate limited respiration response of fungal and bacterial respiration. Treated soils were incubated in a temperature block that allowed the incubation of soils at temperatures ranging between ~5-52 °C for five hours. Headspace samples were taken from each treatment tube and injected into an infrared gas analyser (IRGA) to measure carbon dioxide (CO₂) concentrations and respiration rates. Macromolecular rate theory (MMRT) was used to model the temperature response of the respiration curves to derive the Tₒₚₜ and Tᵢₙբ of fungal and bacterial respiration, allowing the comparison of the temperature responses of fungal and bacterial respiration.

An additional aim of this research was to measure changes in fungal and bacterial biomass along the geothermal temperature gradient using phospholipid fatty acid (PLFA) analysis. Soil samples were collected from the same sampling locations along the geothermal temperature gradient as those used in the selective inhibition experiments. A modified Bligh and Dyer method was used to extract phospholipids from soil samples, which were used as biomarkers to differentiate the biomass of different fungal and bacterial groups.

Results from selective inhibition experiments showed that respiration rates decreased from streptomycin and cycloheximide treatment, allowing an estimation of fungal and bacterial contributions to total soil respiration, respectively. Fungal contributions to soil respiration (~55%) were greater than bacterial contributions (~21%), suggesting that fungi contribute more to soil C decomposition than bacteria. Furthermore, the Tₒₚₜ of fungal respiration was found to decrease with environmental temperature at a rate of -0.396 °C °C-1 whereas the Tₒₚₜ of bacteria and the microbial community was not correlated with environmental temperature. Additionally, the Tₒₚₜ and Tᵢₙբ of fungal respiration (38.6 °C and 22.1 °C, respectively) was not significantly different from the Tₒₚₜ and Tᵢₙբ of microbial respiration (37.0 °C and 21.7 °C, respectively) but was significantly greater than the Tₒₚₜ and Tᵢₙբ of bacterial respiration (30.4 °C and 19.0 °C, respectively). Results from PLFA analysis showed that gram-positive bacteria and general bacteria dominated total microbial biomass and biomass from identified fungal and bacterial groups peaked at ~19-21 °C. Fungal-to-bacterial (F:B) ratios decreased with increasing environmental temperature, indicating a proportional decrease in fungal biomass relative to bacteria at higher temperatures. These results suggest that fungi were excluded with increasing environmental temperature as they were unable to adapt their metabolism and growth as environmental temperatures increased.

The selective inhibition method presented a range of limitations that may have constrained interpretation of the results. First, inhibitors were not equally effective across the range of incubation temperatures. Inhibition from cycloheximide showed a clear temperature optimum where inhibition was greatest within ~45-50 °C. In contrast, inhibition from streptomycin declined at temperatures above ~30 °C. Secondly, percent inhibition of microbial respiration from streptomycin increased as total bacterial biomass increased, providing evidence that streptomycin was effective in targeting bacteria. In contrast, percent inhibition of microbial respiration from cycloheximide was not correlated with fungal biomass, indicating that cycloheximide may not have been effective in selectively targeting fungi.

Overall, these results indicate that fungi may be more at risk from increasing temperatures under climate change, though it is unknown as to how this could translate to soil C stocks. This was likely the first study that attempted to differentiate the temperature response of fungi and bacteria by selectively inhibiting fungi and bacteria and incubating them across a range of temperatures. However, caution should be taken when interpreting results as a range of methodological constraints were uncovered regarding the veracity of the selective inhibition method. While previous studies have reported some limitations of the selective inhibition method, these issues have likely been under-reported as researchers may not publish inconclusive or negative results. Therefore, this study also highlights the importance of critically assessing methods that may be ineffectual.

year: 2022

title: The modification of toheroa habitat by streams on Ripiro Beach

authors: Cope, Jane

abstract: Habitat modification and loss are key factors driving the global extinction and displacement of species. The scale and consequences of habitat loss are relatively well understood in terrestrial environments, but in marine ecosystems, and particularly soft sediment ecosystems, this is not the case. The characteristics which determine the suitability of soft sediment habitats are often subtle, due to the apparent homogeneity of sandy environments. This can make it difficult to detect habitat change in the first place let alone understand ecological consequences. Subtle differences in habitat quality are even harder to detect on dynamic surf beaches which are controlled by the interactions between the wave climate and the beach sands, and experience frequent and large changes. The exposed surf beaches of northern New Zealand, are home to toheroa (Paphies ventricosa), an endemic surf clam and New Zealand‘s most protected shell fish species. Over the course of the 20th century, toheroa were harvested to the point of collapse resulting in the closure of an important cultural, recreational and commercial fishery. Despite more than 40 years of protection, toheroa populations have failed to recover with populations in most locations continuing to decline. 

In northern New Zealand toheroa distribution is strongly associated with the small streams which flow across the toheroa beaches. A reduction in the flow of fresh water to the beach via these streams has been suggested as one possible factor which may be preventing the recovery of toheroa. However, little is known about the characteristics of the habitat, and the mechanism driving this toheroa-stream relationship has not received specific attention. The objective of this research was to better understand the effect of streams on beach habitat in the hope of determining the drivers of toheroa distribution. Specifically, I investigated how sediment type, topography, water table depth and sediment temperatures varied across exposed intertidal sediments adjacent to and away from streams. Sampling took place at four sites along Ripiro Beach during the summer, the season when toheroa are most susceptible to thermal stress and streams are thought to provide some protection from dissipation and heat stress. Grainsize distributions from the sampled sediment cores were processed using a Malvern Mastersizer 3000 laser diffractometer (Malvern, UK). The surface elevation and sediment temperature profiles of the subaerial beach was measured using a theodolite CDN pro accurate waterproof thermometers (Model DTW450L). Temperatures were measured at five sediment depths (2cm, 4cm, 7.5cm, 10.5cm, 20.5cm) throughout the sampling period. 

The effect of the streams on the grain size distribution of intertidal sediments appeared to be limited to the high tide, where the proportion of fine sediments was highest in stream adjacent sediments. Greater variations in grain size occurred along the beach, but the greatest difference in sediment sizes occurred when contrasting current day beach grain size distributions with sediment data collected in 1974. Beach sediments from 2017 contained 26661% time more medium sediment indicating the beach is now much coaster than it was 44 years ago. However, as no time series is available for sediment composition at Ripiro it is uncertain whether this change in beach make up is indicative of year-to-year variation or a long term trend. Beach topography varied consistently in the vicinity of streams. The elevation and slope of the beach face was lowest in the path of streams. Along the upper beach, low elevation in the path of the stream lead to the formation of deep bowl like features. As a result of this topography, adjacent to the stream, the water table remained close to the sediment surface throughout the sampling period (< 20 cm), in contrast to point‘s away from the stream where the water table was below the sampling depth. 

The hypothesis that streams would provide a thermal refuge for toheroa was one of the key questions of this thesis. What I found was that stream driven difference in sediment temperatures were only apparent in the upper intestinal, the area occupied by juvenile toheroa when they first recruit to the beach. Temperatures away from streams were significantly higher (> 3.5 °C) than stream adjacent sediments. However, in the middle intestinal, the area occupied by adult toheroa, the seep face exerted a greater influence on sediment temperatures than the stream and temperatures were no different regardless of stream proximity. The findings of this study suggest that the toheroa-stream relationship is not a direct response to the presence of freshwater, but rather is driven by the modification of the intertidal sediments by the streams. The increased erosion in these areas reduces the distance between the sediment surface and the water table, increasing the moisture content of the sediments. Additionally, the formation of the basin like depressions in the upper intertidal may act to aggregate spat and juvenile toheroa through the effect of this topography on the beach swash regime. At mid-tide areas adjacent to streams, the depth of the water table was such that adult toheroa are likely to be either fully or partially immersed throughout the low tide. Away from streams, the water table is beyond the burrowing depth of toheroa. For both juveniles and adults, stream associated areas may provide important protection against desiccation, through increasing moisture content of the sediments and for juveniles through reduced sediment temperatures. 

Evidently, streams do modify beach habitat in a way that makes it inhabitable for toheroa. Just not in the way that was anticipated. This study has increased our knowledge of beach characteristics that provide good toheroa habitat. Further research is required to test these hypotheses and better understand the effects of climate and terrestrial land use on beach state and therefore the suitability of the beach for toheroa.

text: The modification of toheroa habitat by streams on Ripiro Beach Habitat modification and loss are key factors driving the global extinction and displacement of species. The scale and consequences of habitat loss are relatively well understood in terrestrial environments, but in marine ecosystems, and particularly soft sediment ecosystems, this is not the case. The characteristics which determine the suitability of soft sediment habitats are often subtle, due to the apparent homogeneity of sandy environments. This can make it difficult to detect habitat change in the first place let alone understand ecological consequences. Subtle differences in habitat quality are even harder to detect on dynamic surf beaches which are controlled by the interactions between the wave climate and the beach sands, and experience frequent and large changes. The exposed surf beaches of northern New Zealand, are home to toheroa (Paphies ventricosa), an endemic surf clam and New Zealand‘s most protected shell fish species. Over the course of the 20th century, toheroa were harvested to the point of collapse resulting in the closure of an important cultural, recreational and commercial fishery. Despite more than 40 years of protection, toheroa populations have failed to recover with populations in most locations continuing to decline. 

In northern New Zealand toheroa distribution is strongly associated with the small streams which flow across the toheroa beaches. A reduction in the flow of fresh water to the beach via these streams has been suggested as one possible factor which may be preventing the recovery of toheroa. However, little is known about the characteristics of the habitat, and the mechanism driving this toheroa-stream relationship has not received specific attention. The objective of this research was to better understand the effect of streams on beach habitat in the hope of determining the drivers of toheroa distribution. Specifically, I investigated how sediment type, topography, water table depth and sediment temperatures varied across exposed intertidal sediments adjacent to and away from streams. Sampling took place at four sites along Ripiro Beach during the summer, the season when toheroa are most susceptible to thermal stress and streams are thought to provide some protection from dissipation and heat stress. Grainsize distributions from the sampled sediment cores were processed using a Malvern Mastersizer 3000 laser diffractometer (Malvern, UK). The surface elevation and sediment temperature profiles of the subaerial beach was measured using a theodolite CDN pro accurate waterproof thermometers (Model DTW450L). Temperatures were measured at five sediment depths (2cm, 4cm, 7.5cm, 10.5cm, 20.5cm) throughout the sampling period. 

The effect of the streams on the grain size distribution of intertidal sediments appeared to be limited to the high tide, where the proportion of fine sediments was highest in stream adjacent sediments. Greater variations in grain size occurred along the beach, but the greatest difference in sediment sizes occurred when contrasting current day beach grain size distributions with sediment data collected in 1974. Beach sediments from 2017 contained 26661% time more medium sediment indicating the beach is now much coaster than it was 44 years ago. However, as no time series is available for sediment composition at Ripiro it is uncertain whether this change in beach make up is indicative of year-to-year variation or a long term trend. Beach topography varied consistently in the vicinity of streams. The elevation and slope of the beach face was lowest in the path of streams. Along the upper beach, low elevation in the path of the stream lead to the formation of deep bowl like features. As a result of this topography, adjacent to the stream, the water table remained close to the sediment surface throughout the sampling period (< 20 cm), in contrast to point‘s away from the stream where the water table was below the sampling depth. 

The hypothesis that streams would provide a thermal refuge for toheroa was one of the key questions of this thesis. What I found was that stream driven difference in sediment temperatures were only apparent in the upper intestinal, the area occupied by juvenile toheroa when they first recruit to the beach. Temperatures away from streams were significantly higher (> 3.5 °C) than stream adjacent sediments. However, in the middle intestinal, the area occupied by adult toheroa, the seep face exerted a greater influence on sediment temperatures than the stream and temperatures were no different regardless of stream proximity. The findings of this study suggest that the toheroa-stream relationship is not a direct response to the presence of freshwater, but rather is driven by the modification of the intertidal sediments by the streams. The increased erosion in these areas reduces the distance between the sediment surface and the water table, increasing the moisture content of the sediments. Additionally, the formation of the basin like depressions in the upper intertidal may act to aggregate spat and juvenile toheroa through the effect of this topography on the beach swash regime. At mid-tide areas adjacent to streams, the depth of the water table was such that adult toheroa are likely to be either fully or partially immersed throughout the low tide. Away from streams, the water table is beyond the burrowing depth of toheroa. For both juveniles and adults, stream associated areas may provide important protection against desiccation, through increasing moisture content of the sediments and for juveniles through reduced sediment temperatures. 

Evidently, streams do modify beach habitat in a way that makes it inhabitable for toheroa. Just not in the way that was anticipated. This study has increased our knowledge of beach characteristics that provide good toheroa habitat. Further research is required to test these hypotheses and better understand the effects of climate and terrestrial land use on beach state and therefore the suitability of the beach for toheroa.

year: 2018