title: Cross-boundary detrital subsidies: Detrital export and effects on receiving intertidal soft-sediment ecosystems

authors: Gladstone-Gallagher, Rebecca

subjects: estuary

abstract: Ecosystems are often connected by the transfer of resource ‘subsidies’ across their boundaries. In temperate estuaries, marine macrophyte leaf litter represents an obvious and visible detrital subsidy to nearby intertidal areas, where it can accumulate in temporally and spatially variable patches. This thesis investigates the ecology of macrophyte detrital subsidies, from their production and export (from the donor ecosystem), to the ecosystem effects of their decay and accumulation on recipient intertidal flats.
To quantify estuarine detrital subsidies, the fluxes of macrophyte detritus, and other sources of primary production and nutrients (dissolved and particulates), were measured at the mouth of a mixed habitat temperate estuary. This study demonstrates that the estuary (typical of a North Island, New Zealand estuary) acts as a net exporter of detritus, total nitrogen (N), and phosphorus (P) to the wider coastal environment. While macrophyte detrital subsidies contributed relatively little to the total N and P export, they were transported in large and visible quantities. This study provides empirical data on the supply of detrital subsidies in temperate estuaries, and reveals that they are transported in pulses that vary temporally, in both their source and supply. 
To explore how detrital deposition and decay in intertidal soft-sediments alters ecosystem function (benthic primary production, metabolism, and nutrient cycling), an in situ experiment manipulated the supply of three detrital sources (mangrove, macroalgae, and seagrass) to experimental plots on a sandflat.  Benthic chambers were used to measure sediment-water solute fluxes as proxies for ecosystem function. Detrital enrichment had no significant effects on nutrient cycling, benthic metabolism, or macrofaunal community structure. However, detrital addition instigated transient and source-dependent effects on benthic gross primary production (GPP), where macroalgae and mangrove detritus initially (4 d) decreased GPP, but after 17 d, GPP was slightly enhanced in these detrital treatments. 
Another field experiment aimed to determine the effects of detrital deposition on benthic ecosystem function in the presence of bioturbating crabs, as well as at different intertidal sites (characterised by different sediment properties). The presence of crabs and seagrass detritus were manipulated in cages on an intertidal sand and muddy-sand flat, and the resulting effects on ecosystem function were measured. Detrital enrichment instigated short-term negative effects on GPP in sand (regardless of the presence of crabs), and nutrient cycling in muddy-sand (but only in the presence of crabs). However, at the site characterised by muddy-sand, detrital enrichment also enhanced benthic metabolism and modified macrofaunal community structure (regardless of the presence/absence of crabs). These results emphasise that the effects of detrital subsidies on ecosystem function are context-dependent.
While detrital enrichment did not result in large shifts in benthic community structure or function, subtle and transient effects on some functions were found.  In these productive intertidal sediments, detritus is unlikely to be an important primary food source to benthic communities. However, by physically altering the structure and function of receiving sediments, seasonal pulses in the supply of detritus may add to the heterogeneous nature of intertidal flats in both time and space. As benthic ecosystem responses to detrital deposition vary with detrital species, anthropogenic changes to the supply, quality and timing of detrital subsidies (e.g. decline in seagrass, and proliferation of macroalgae blooms) could have flow-on effects to the structure and functioning of receiving soft-sediment communities.

text: Cross-boundary detrital subsidies: Detrital export and effects on receiving intertidal soft-sediment ecosystems Ecosystems are often connected by the transfer of resource ‘subsidies’ across their boundaries. In temperate estuaries, marine macrophyte leaf litter represents an obvious and visible detrital subsidy to nearby intertidal areas, where it can accumulate in temporally and spatially variable patches. This thesis investigates the ecology of macrophyte detrital subsidies, from their production and export (from the donor ecosystem), to the ecosystem effects of their decay and accumulation on recipient intertidal flats.
To quantify estuarine detrital subsidies, the fluxes of macrophyte detritus, and other sources of primary production and nutrients (dissolved and particulates), were measured at the mouth of a mixed habitat temperate estuary. This study demonstrates that the estuary (typical of a North Island, New Zealand estuary) acts as a net exporter of detritus, total nitrogen (N), and phosphorus (P) to the wider coastal environment. While macrophyte detrital subsidies contributed relatively little to the total N and P export, they were transported in large and visible quantities. This study provides empirical data on the supply of detrital subsidies in temperate estuaries, and reveals that they are transported in pulses that vary temporally, in both their source and supply. 
To explore how detrital deposition and decay in intertidal soft-sediments alters ecosystem function (benthic primary production, metabolism, and nutrient cycling), an in situ experiment manipulated the supply of three detrital sources (mangrove, macroalgae, and seagrass) to experimental plots on a sandflat.  Benthic chambers were used to measure sediment-water solute fluxes as proxies for ecosystem function. Detrital enrichment had no significant effects on nutrient cycling, benthic metabolism, or macrofaunal community structure. However, detrital addition instigated transient and source-dependent effects on benthic gross primary production (GPP), where macroalgae and mangrove detritus initially (4 d) decreased GPP, but after 17 d, GPP was slightly enhanced in these detrital treatments. 
Another field experiment aimed to determine the effects of detrital deposition on benthic ecosystem function in the presence of bioturbating crabs, as well as at different intertidal sites (characterised by different sediment properties). The presence of crabs and seagrass detritus were manipulated in cages on an intertidal sand and muddy-sand flat, and the resulting effects on ecosystem function were measured. Detrital enrichment instigated short-term negative effects on GPP in sand (regardless of the presence of crabs), and nutrient cycling in muddy-sand (but only in the presence of crabs). However, at the site characterised by muddy-sand, detrital enrichment also enhanced benthic metabolism and modified macrofaunal community structure (regardless of the presence/absence of crabs). These results emphasise that the effects of detrital subsidies on ecosystem function are context-dependent.
While detrital enrichment did not result in large shifts in benthic community structure or function, subtle and transient effects on some functions were found.  In these productive intertidal sediments, detritus is unlikely to be an important primary food source to benthic communities. However, by physically altering the structure and function of receiving sediments, seasonal pulses in the supply of detritus may add to the heterogeneous nature of intertidal flats in both time and space. As benthic ecosystem responses to detrital deposition vary with detrital species, anthropogenic changes to the supply, quality and timing of detrital subsidies (e.g. decline in seagrass, and proliferation of macroalgae blooms) could have flow-on effects to the structure and functioning of receiving soft-sediment communities.

year: 2017

title: Knowledge through a collaborative network: a cross-cultural partnership

authors: Alcorn, Noeline

subjects: knowledge mobilisation

abstract: A recurring issue for researchers, policy-makers and practitioners is how new knowledge can be disseminated, critiqued, assessed and incorporated into policy development and practice. Campbell and Fulford examined strategies in a Canadian Education Ministry which was striving to incorporate research findings into policy debate. They evolved a useful framework indentifying six forms and stages of knowledge development related to research use in this context: generation of new knowledge, mobilisation, contextualisation, adaptation, application and integration. This paper uses their framework to explore links between research and practice in a collaborative cross-cultural partnership designed to develop greater capacity in teacher education in a Pacific country, and based on action, co-construction and reflection. It argues that there are blurred boundaries between knowledge production and its practical implementation, use and testing, that contextualisation and relationship building are crucial to knowledge mobilisation, and that knowledge is generated across all stages in the process.

text: Knowledge through a collaborative network: a cross-cultural partnership A recurring issue for researchers, policy-makers and practitioners is how new knowledge can be disseminated, critiqued, assessed and incorporated into policy development and practice. Campbell and Fulford examined strategies in a Canadian Education Ministry which was striving to incorporate research findings into policy debate. They evolved a useful framework indentifying six forms and stages of knowledge development related to research use in this context: generation of new knowledge, mobilisation, contextualisation, adaptation, application and integration. This paper uses their framework to explore links between research and practice in a collaborative cross-cultural partnership designed to develop greater capacity in teacher education in a Pacific country, and based on action, co-construction and reflection. It argues that there are blurred boundaries between knowledge production and its practical implementation, use and testing, that contextualisation and relationship building are crucial to knowledge mobilisation, and that knowledge is generated across all stages in the process.

year: 2010

title: “BODY-SNATCHING”: Changes to coroners legislation and possible Māori responses

authors: Mika, Carl Te Hira

subjects: body-snatcher

abstract: The term body-snatcher has enjoyed a renaissance in the media recently, as various Māori have moved to reclaim their deceased relations. From a Māori perspective, the claiming of bodies has nothing to do with body-snatching, a term that referred to episodes in the West. Indeed, Māori may see some laws themselves as instruments that snatch the body, in contravention of Māori customs. One of these laws, the Coroners Act 2006, may have made some progress by quietly acknowledging these customs in many ways, but that is merely the start of a greater dialogue between Māori and the Crown in relation to proper Māori respect of the dead body.

text: “BODY-SNATCHING”: Changes to coroners legislation and possible Māori responses The term body-snatcher has enjoyed a renaissance in the media recently, as various Māori have moved to reclaim their deceased relations. From a Māori perspective, the claiming of bodies has nothing to do with body-snatching, a term that referred to episodes in the West. Indeed, Māori may see some laws themselves as instruments that snatch the body, in contravention of Māori customs. One of these laws, the Coroners Act 2006, may have made some progress by quietly acknowledging these customs in many ways, but that is merely the start of a greater dialogue between Māori and the Crown in relation to proper Māori respect of the dead body.

year: 2009