title: The ecological role of the suspension feeding bivalve, Austrovenus stutchburyi, in estuarine ecosystems

authors: Jones, Hannah Frances Emily

subjects: ecosystem function

abstract: Suspension feeding bivalves are described as key species in many aquatic ecosystems, where they can influence primary productivity and nutrient dynamics, are food for higher trophic levels, and may be harvested in commercial or recreational fisheries. In many areas where bivalve populations have declined, substantial changes to ecosystem structure and function have occurred. High-density beds of the infaunal suspension feeding bivalve, Austrovenus stutchburyi, are a dominant feature on intertidal flats in many New Zealand estuaries, but populations are declining in some areas, likely due to anthropogenic stressors such as overharvesting and sedimentation. This thesis examines the influence of Austrovenus on estuarine ecosystem function using laboratory, field and modelling studies.
The effects of bed density and flow speed on boundary layer dynamics and Austrovenus clearance rates (CR) were investigated in annular flumes. Bed shear stress increased with increasing bivalve density, and under certain conditions was also increased when Austrovenus were feeding, compared to when they were not. The bed roughness and siphonal currents generated by the bivalves may therefore influence food supply to the bed. Both individual and bed CR were significantly greater at the high flow speed. Bed CR did not scale proportionally with density, in part because individual CR decreased with increasing density, but also because the proportion of bivalves actively feeding decreased at high densities. Thus, scaling up individual CR obtained from animals at low densities will significantly overestimate population filtration capacity.
The effect of Austrovenus on ecosystem function was examined at two sites, one sandy, the other composed of muddy-sand, to determine whether sedimentary environment alters this key species’ role. Gross primary production (likely corresponding to microphytobenthos production) and ammonium uptake were significantly increased, and denitrification potential was also elevated, when Austrovenus was added, relative to removed, at the sandy site. In contrast, there was no effect of Austrovenus on any of these variables at the muddy-sand site. These results reveal the importance of considering sedimentary environment when examining the effect of key species on ecosystem function, and suggest that even moderate levels of sedimentation may reduce the positive effect of Austrovenus on primary productivity.
A food-web model was used to quantify the interactions between Austrovenus and other estuarine species, and to determine the effect of reducing Austrovenus biomass on ecosystem properties. The model revealed an estuarine system dominated by benthic species, characterised as a developing, rather than a mature ecosystem. Detritus production and export were high, while transfer efficiency and internal recycling were low. Decreasing Austrovenus biomass decreased system maturity, suggesting that reductions in Austrovenus populations may decrease ecosystem stability. The model also confirmed that within these estuarine systems Austrovenus and microphytobenthos are key species which impact greatly on all other trophic levels.
This thesis demonstrates that Austrovenus populations exert considerable influence on benthic communities and processes, and play a key role in the functioning of estuarine ecosystems. Reductions in Austrovenus populations will likely negatively impact on microphytobenthos and higher trophic levels, and may also reduce ecosystem maturity and stability.

text: The ecological role of the suspension feeding bivalve, Austrovenus stutchburyi, in estuarine ecosystems Suspension feeding bivalves are described as key species in many aquatic ecosystems, where they can influence primary productivity and nutrient dynamics, are food for higher trophic levels, and may be harvested in commercial or recreational fisheries. In many areas where bivalve populations have declined, substantial changes to ecosystem structure and function have occurred. High-density beds of the infaunal suspension feeding bivalve, Austrovenus stutchburyi, are a dominant feature on intertidal flats in many New Zealand estuaries, but populations are declining in some areas, likely due to anthropogenic stressors such as overharvesting and sedimentation. This thesis examines the influence of Austrovenus on estuarine ecosystem function using laboratory, field and modelling studies.
The effects of bed density and flow speed on boundary layer dynamics and Austrovenus clearance rates (CR) were investigated in annular flumes. Bed shear stress increased with increasing bivalve density, and under certain conditions was also increased when Austrovenus were feeding, compared to when they were not. The bed roughness and siphonal currents generated by the bivalves may therefore influence food supply to the bed. Both individual and bed CR were significantly greater at the high flow speed. Bed CR did not scale proportionally with density, in part because individual CR decreased with increasing density, but also because the proportion of bivalves actively feeding decreased at high densities. Thus, scaling up individual CR obtained from animals at low densities will significantly overestimate population filtration capacity.
The effect of Austrovenus on ecosystem function was examined at two sites, one sandy, the other composed of muddy-sand, to determine whether sedimentary environment alters this key species’ role. Gross primary production (likely corresponding to microphytobenthos production) and ammonium uptake were significantly increased, and denitrification potential was also elevated, when Austrovenus was added, relative to removed, at the sandy site. In contrast, there was no effect of Austrovenus on any of these variables at the muddy-sand site. These results reveal the importance of considering sedimentary environment when examining the effect of key species on ecosystem function, and suggest that even moderate levels of sedimentation may reduce the positive effect of Austrovenus on primary productivity.
A food-web model was used to quantify the interactions between Austrovenus and other estuarine species, and to determine the effect of reducing Austrovenus biomass on ecosystem properties. The model revealed an estuarine system dominated by benthic species, characterised as a developing, rather than a mature ecosystem. Detritus production and export were high, while transfer efficiency and internal recycling were low. Decreasing Austrovenus biomass decreased system maturity, suggesting that reductions in Austrovenus populations may decrease ecosystem stability. The model also confirmed that within these estuarine systems Austrovenus and microphytobenthos are key species which impact greatly on all other trophic levels.
This thesis demonstrates that Austrovenus populations exert considerable influence on benthic communities and processes, and play a key role in the functioning of estuarine ecosystems. Reductions in Austrovenus populations will likely negatively impact on microphytobenthos and higher trophic levels, and may also reduce ecosystem maturity and stability.

year: 2011

title: Constructionism and culture in research: Understandings of the fourth Buddhist Festival, Wutaishan, China

authors: Ryan, Chris

subjects: festivals

abstract: This paper offers an interpretation of competing legitimacies at the 2007 4th Annual Wutaishan Buddhist Festival in Taihua, Shanxi Province. It suggests how spectacle, entertainment and performance spaces are condoned arenas of challenge and usage by mainstream and peripheral groups. The paper also discusses the methods employed in the framing and nature of interpretation, and possesses its own tension as the different cultural perspectives and voices are heeded. It concludes that the festival exists as a multi-layered event involving economics, politics, faith, entertainment and prestige – each of which creates its own set of interpretations contextualised in the evolving state of Chinese tourism. The paper is partially a response to the work of Hollinshead, Phillimore & Goodson and O'Dell that claim a need for a more reflexive voice in the tourism literature as a means of understanding the tourist experience. Its premises are based on thinking derived from multiple sources including symbolic interaction and Buddhist thought.

text: Constructionism and culture in research: Understandings of the fourth Buddhist Festival, Wutaishan, China This paper offers an interpretation of competing legitimacies at the 2007 4th Annual Wutaishan Buddhist Festival in Taihua, Shanxi Province. It suggests how spectacle, entertainment and performance spaces are condoned arenas of challenge and usage by mainstream and peripheral groups. The paper also discusses the methods employed in the framing and nature of interpretation, and possesses its own tension as the different cultural perspectives and voices are heeded. It concludes that the festival exists as a multi-layered event involving economics, politics, faith, entertainment and prestige – each of which creates its own set of interpretations contextualised in the evolving state of Chinese tourism. The paper is partially a response to the work of Hollinshead, Phillimore & Goodson and O'Dell that claim a need for a more reflexive voice in the tourism literature as a means of understanding the tourist experience. Its premises are based on thinking derived from multiple sources including symbolic interaction and Buddhist thought.

year: 2009

title: What does 'Ethical Research'' look like? An indigenous perspective on big data & precision medicine

authors: Hudson, Maui

abstract: Southeast Native American Health Data (SENAHD) in partnership with Native BioData Consortium will host an online symposium about the ethical use of Indigenous genetic, environmental, biological, and cultural data. SENAHD is based at UNC Chapel Hill. Our partner, Native BioData Consortium is located on the Cheyanne River Sioux Reservation in South Dakota. NativeBio is one of the most important voices advocating for Indigenous health equity, data sovereignty, and ethical research practices. NativeBio is coming to the Southeast to recognize and include our region in important conversations taking place across Indian Country

text: What does 'Ethical Research'' look like? An indigenous perspective on big data & precision medicine Southeast Native American Health Data (SENAHD) in partnership with Native BioData Consortium will host an online symposium about the ethical use of Indigenous genetic, environmental, biological, and cultural data. SENAHD is based at UNC Chapel Hill. Our partner, Native BioData Consortium is located on the Cheyanne River Sioux Reservation in South Dakota. NativeBio is one of the most important voices advocating for Indigenous health equity, data sovereignty, and ethical research practices. NativeBio is coming to the Southeast to recognize and include our region in important conversations taking place across Indian Country

year: 2022