title: Effects of infaunal bivalve density and flow speed on clearance rates and near-bed hydrodynamics

authors: Jones, Hannah Frances Emily

subjects: annular flume

abstract: The influence of bed density (from 0 to 1000 ind. M⁻²) and flow speed (2, 5, and 15 cm s⁻¹, i.e. “low”, “medium” and “high”, respectively) on clearance rates (CR) of an infaunal suspension-feeding bivalve (Austrovenus stutchburyi) and boundary layer dynamics were investigated in annular flumes. Near-bed flow speeds decreased and bed shear stresses increased with bivalve density due to the bed roughness generated by the shallow burrowers. At low densities (< 500 ind. m⁻²) there was no detectable effect of feeding currents on bed shear stress, but at high densities (1000 ind. m⁻²) and at the low flow speed bed shear stress was almost 80% higher when Austrovenus were feeding (0.0016 N m⁻²), compared to when they were not feeding (0.0009 N m⁻²). These results suggest that bed roughness generated by Austrovenus and their feeding currents are capable of influencing food supply to the bed. Individual CR were significantly (p < 0.01) greater at the high flow speed (0.88 L h⁻¹ ind. ⁻¹), compared to the medium and low flow speeds (0.34 to 0.54 L h− 1 ind.− 1). With increasing bed density, individual CR was significantly (p < 0.001) reduced; at low densities CR ranged from 0.6 to 1.4 L h⁻¹ ind. ⁻¹, but at high densities they were 0.1 to 0.8 L h⁻¹ ind. ⁻¹. Bed CR (L h⁻¹ m− 2) did not scale proportionally with density, initially increasing up to 500 ind. m− 2 but remaining relatively constant thereafter. This was in part due to the negative effect of density on individual CR but also because the proportion of bivalves feeding decreased with increasing density. Our results demonstrate that recording the number of bivalves feeding is necessary to interpret the effect of density on bed CR. Moreover, if the effects of both bivalve density and flow speed are not considered, then scaling up individual CR obtained using animals at low densities will over estimate population filtration capacity. As high (but equivalent to in situ) densities reduced both the number of animals feeding and individual CR other factors may offset this negative interaction, such as protection from wave disturbance or enhanced resuspension of benthic microalgae.

text: Effects of infaunal bivalve density and flow speed on clearance rates and near-bed hydrodynamics The influence of bed density (from 0 to 1000 ind. M⁻²) and flow speed (2, 5, and 15 cm s⁻¹, i.e. “low”, “medium” and “high”, respectively) on clearance rates (CR) of an infaunal suspension-feeding bivalve (Austrovenus stutchburyi) and boundary layer dynamics were investigated in annular flumes. Near-bed flow speeds decreased and bed shear stresses increased with bivalve density due to the bed roughness generated by the shallow burrowers. At low densities (< 500 ind. m⁻²) there was no detectable effect of feeding currents on bed shear stress, but at high densities (1000 ind. m⁻²) and at the low flow speed bed shear stress was almost 80% higher when Austrovenus were feeding (0.0016 N m⁻²), compared to when they were not feeding (0.0009 N m⁻²). These results suggest that bed roughness generated by Austrovenus and their feeding currents are capable of influencing food supply to the bed. Individual CR were significantly (p < 0.01) greater at the high flow speed (0.88 L h⁻¹ ind. ⁻¹), compared to the medium and low flow speeds (0.34 to 0.54 L h− 1 ind.− 1). With increasing bed density, individual CR was significantly (p < 0.001) reduced; at low densities CR ranged from 0.6 to 1.4 L h⁻¹ ind. ⁻¹, but at high densities they were 0.1 to 0.8 L h⁻¹ ind. ⁻¹. Bed CR (L h⁻¹ m− 2) did not scale proportionally with density, initially increasing up to 500 ind. m− 2 but remaining relatively constant thereafter. This was in part due to the negative effect of density on individual CR but also because the proportion of bivalves feeding decreased with increasing density. Our results demonstrate that recording the number of bivalves feeding is necessary to interpret the effect of density on bed CR. Moreover, if the effects of both bivalve density and flow speed are not considered, then scaling up individual CR obtained using animals at low densities will over estimate population filtration capacity. As high (but equivalent to in situ) densities reduced both the number of animals feeding and individual CR other factors may offset this negative interaction, such as protection from wave disturbance or enhanced resuspension of benthic microalgae.

year: 2011

title: Transition to professional social work practice: The first three years

authors: Hunt, Sonya

subjects: Newly Qualified Social Worker

abstract: This article presents the findings of a longitudinal research project that followed the employ-ment outcomes of one cohort of Bachelor of Social Work graduates for three years. Prior to graduation, students receive professional preparation that develops their ability to critically engage with theory and practice. Following graduation, newly qualified social workers require quality induction, supervision and other workload management strategies to support the transition to social work practice. The development of this study was fuelled by political criticism of social work education. Additionally, there was a desire to track the employment outcomes of the graduates and understand what supported their transition to competent professional practice. The findings fit within a five-year longitudinal research project that follows three separate graduate cohorts each for three years to seek and compare participants’ experiences for their first three years post-qualification. An anonymous, semi-structured, on-line survey was used to provide both quantitative and qualitative data. By the second year of practice, these respond-ents were taking on the workload of an experienced social work practitioner with widely varied levels of support. By the end of their third year in practice, they reported that they had found little opportunity to apply their critical analytical academic skills to consider the wider social system in practice. Further, the graduates’ confidence in their cultural competencies also gradually decreased over the three-year period.

text: Transition to professional social work practice: The first three years This article presents the findings of a longitudinal research project that followed the employ-ment outcomes of one cohort of Bachelor of Social Work graduates for three years. Prior to graduation, students receive professional preparation that develops their ability to critically engage with theory and practice. Following graduation, newly qualified social workers require quality induction, supervision and other workload management strategies to support the transition to social work practice. The development of this study was fuelled by political criticism of social work education. Additionally, there was a desire to track the employment outcomes of the graduates and understand what supported their transition to competent professional practice. The findings fit within a five-year longitudinal research project that follows three separate graduate cohorts each for three years to seek and compare participants’ experiences for their first three years post-qualification. An anonymous, semi-structured, on-line survey was used to provide both quantitative and qualitative data. By the second year of practice, these respond-ents were taking on the workload of an experienced social work practitioner with widely varied levels of support. By the end of their third year in practice, they reported that they had found little opportunity to apply their critical analytical academic skills to consider the wider social system in practice. Further, the graduates’ confidence in their cultural competencies also gradually decreased over the three-year period.

year: 2017

title: Introduction: Recognition, redistribution and reconciliation in postcolonial settler societies

authors: van Meijl, Toon

subjects: multiculturalism

abstract: Various questions are addressed regarding recognition of special rights for indigenous minorities in postcolonial nation-states, redistributing resources to redress longstanding indigenous grievances about the history of colonial dispossession and strategy of reconciliation between the immigrant majority of settlers and their descendants against a backdrop of multiculturalism.

text: Introduction: Recognition, redistribution and reconciliation in postcolonial settler societies Various questions are addressed regarding recognition of special rights for indigenous minorities in postcolonial nation-states, redistributing resources to redress longstanding indigenous grievances about the history of colonial dispossession and strategy of reconciliation between the immigrant majority of settlers and their descendants against a backdrop of multiculturalism.

year: 2003-09-01