title: Response and resilience of estuarine benthic ecosystems to anthropogenic pressures

authors: Drylie, Tarn Paige

subjects: ecosystem function

abstract: Human activities are altering coastal environments at local and global scales with largely unknown consequences. Catchment land-use changes increase the rates of delivery of fine sediments and nutrients to estuaries, resulting in increased suspended sediment concentrations (SSC) and eutrophication; this thesis investigates the response and resilience of soft-sediment intertidal ecosystems to these two anthropogenic stressors.

Increased SSC elevates water-column turbidity and reduces the light available for benthic primary producers that sustain estuarine food webs. In intertidal habitats, this turbidity stressor is removed during low tide as the water-column uncovers the seafloor. In other words, turbidity is a temporally displaced stressor in intertidal environments. Photosynthesis during low tide periods of emergence may therefore provide resilience against elevated turbidity during periods of submergence. However, the role of low tide primary production (PP) in estuarine benthic foodwebs has largely been overlooked. Emerged and submerged benthic PP was measured in adjacent seagrass and microphytobenthos-dominated (sandflat) soft-sediment habitats at three locations along a turbidity gradient. Benthic chambers were used to measure the flux of CO₂ across emerged sediments, and dissolved O₂ across submerged sediments to derive net (NPP) and gross (GPP) PP. Emerged NPP and GPP were higher (2–16 times) than submerged in all instances (p < 0.01), and when standardised by mean incident photosynthetically active radiation, the difference between emerged and submerged seagrass PP increased with site turbidity (from 2 to 26 times greater). Emerged PP may be crucial for providing resilience against benthic productivity losses in turbid environments.

Eutrophication results in the deposition of excess organic material to soft-sediments and stimulates microbial respiration; this consumes O₂, potentially leading to hypoxia, and releases CO₂, causing localised acidification. I enriched intertidal sediments with increasing quantities of organic matter to identify the effects of eutrophication-induced acidification on benthic structure and function, and assessed whether biogenic calcium carbonate (CaCO₃) would alter the response. Declines in macrofauna biodiversity (abundance and species richness), reduced benthic NPP and impaired nutrient cycling occurred along the eutrophication gradient. CaCO₃ did not alter the macrofaunal response, but significantly reduced negative effects on function (e.g. net autotrophy occurred at higher levels of organic enrichment in CaCO₃-treated plots than controls (1400 vs 950 g dw m-2)). This study represents a crucial step forward in understanding the ecological effects of coastal acidification and the role of biogenic CaCO₃ in moderating responses.

Ecological theory states that the resilience of ecosystem functions to environmental disturbance depends on the biodiversity that underpins them, but field validations of this are lacking. I explored the shifts in sandflat macrofaunal community composition following organic matter enrichment, and the consequences for the representation and composition of functional groups (FG). Taxa-specific sensitivities to enrichment resulted in significant response diversity which provided resilience to FG, but substantial declines in the abundance of dominant taxa meant they became functionally extinct nevertheless. Density compensation occurred in one FG, but overall community abundance decreased by 80 % between low and high levels of enrichment. Evidence of density-dependent relationships between ecosystem function and biodiversity were discovered, highlighting the need to conserve macrofaunal biodiversity to preserve function despite the existence of stabilising mechanisms.

This thesis demonstrates the existence of mechanisms that provide resilience against increased SSC and eutrophication in benthic ecosystems, but highlights that the structure and function of these systems remain sensitive nevertheless.

text: Response and resilience of estuarine benthic ecosystems to anthropogenic pressures Human activities are altering coastal environments at local and global scales with largely unknown consequences. Catchment land-use changes increase the rates of delivery of fine sediments and nutrients to estuaries, resulting in increased suspended sediment concentrations (SSC) and eutrophication; this thesis investigates the response and resilience of soft-sediment intertidal ecosystems to these two anthropogenic stressors.

Increased SSC elevates water-column turbidity and reduces the light available for benthic primary producers that sustain estuarine food webs. In intertidal habitats, this turbidity stressor is removed during low tide as the water-column uncovers the seafloor. In other words, turbidity is a temporally displaced stressor in intertidal environments. Photosynthesis during low tide periods of emergence may therefore provide resilience against elevated turbidity during periods of submergence. However, the role of low tide primary production (PP) in estuarine benthic foodwebs has largely been overlooked. Emerged and submerged benthic PP was measured in adjacent seagrass and microphytobenthos-dominated (sandflat) soft-sediment habitats at three locations along a turbidity gradient. Benthic chambers were used to measure the flux of CO₂ across emerged sediments, and dissolved O₂ across submerged sediments to derive net (NPP) and gross (GPP) PP. Emerged NPP and GPP were higher (2–16 times) than submerged in all instances (p < 0.01), and when standardised by mean incident photosynthetically active radiation, the difference between emerged and submerged seagrass PP increased with site turbidity (from 2 to 26 times greater). Emerged PP may be crucial for providing resilience against benthic productivity losses in turbid environments.

Eutrophication results in the deposition of excess organic material to soft-sediments and stimulates microbial respiration; this consumes O₂, potentially leading to hypoxia, and releases CO₂, causing localised acidification. I enriched intertidal sediments with increasing quantities of organic matter to identify the effects of eutrophication-induced acidification on benthic structure and function, and assessed whether biogenic calcium carbonate (CaCO₃) would alter the response. Declines in macrofauna biodiversity (abundance and species richness), reduced benthic NPP and impaired nutrient cycling occurred along the eutrophication gradient. CaCO₃ did not alter the macrofaunal response, but significantly reduced negative effects on function (e.g. net autotrophy occurred at higher levels of organic enrichment in CaCO₃-treated plots than controls (1400 vs 950 g dw m-2)). This study represents a crucial step forward in understanding the ecological effects of coastal acidification and the role of biogenic CaCO₃ in moderating responses.

Ecological theory states that the resilience of ecosystem functions to environmental disturbance depends on the biodiversity that underpins them, but field validations of this are lacking. I explored the shifts in sandflat macrofaunal community composition following organic matter enrichment, and the consequences for the representation and composition of functional groups (FG). Taxa-specific sensitivities to enrichment resulted in significant response diversity which provided resilience to FG, but substantial declines in the abundance of dominant taxa meant they became functionally extinct nevertheless. Density compensation occurred in one FG, but overall community abundance decreased by 80 % between low and high levels of enrichment. Evidence of density-dependent relationships between ecosystem function and biodiversity were discovered, highlighting the need to conserve macrofaunal biodiversity to preserve function despite the existence of stabilising mechanisms.

This thesis demonstrates the existence of mechanisms that provide resilience against increased SSC and eutrophication in benthic ecosystems, but highlights that the structure and function of these systems remain sensitive nevertheless.

year: 2020

title: Living a useful life: Physically disabled children in New Zealand 1935 - 1980s

authors: Pooley, Emma

abstract: This dissertation examines the history of physically disabled children in New Zealand between 1935 and the mid 1980s. It is designed to provide an insight into a dimension of history that has been missing from mainstream histories. It examines official and popular attitudes towards disabled people and the changes to these over the period discussed here.
Using a range of primary and secondary materials, this study indicates the ways the notion of 'social utility' has given way to discussions about equality with regards to the role of disabled children in New Zealand society. The dissertation introduces ideas and theories about the study of disability in a general sense and applies them in a New Zealand context. It also introduces ideas about childhood and applies these to disabled children in New Zealand. This dissertation explores events that have been pivotal in the study of disability, for example, the emergence of the Crippled Children Society (later CCS) and changes in the fields of rehabilitation and special education. Events such as the beginning of Social Security are discussed in the light of their impact upon childhood disability.
Other developments in the health sector such as the increase in orthopaedic practice have had an impact upon the lives of disabled children. This dissertation explores the relationship between the field of Orthopaedics and the Crippled Children Society which was the main agency providing for the needs of disabled children. A further area that is explored is the influence of visiting specialist Dr Earl Carlson as well as parental guides upon the treatment of disabled children. The final section looks at the changes in special education including ideas about inclusion and mainstreaming. It discusses the notion that education changed from a focus on utility to one of equality. It also explores the role of the family with regards to education.

text: Living a useful life: Physically disabled children in New Zealand 1935 - 1980s This dissertation examines the history of physically disabled children in New Zealand between 1935 and the mid 1980s. It is designed to provide an insight into a dimension of history that has been missing from mainstream histories. It examines official and popular attitudes towards disabled people and the changes to these over the period discussed here.
Using a range of primary and secondary materials, this study indicates the ways the notion of 'social utility' has given way to discussions about equality with regards to the role of disabled children in New Zealand society. The dissertation introduces ideas and theories about the study of disability in a general sense and applies them in a New Zealand context. It also introduces ideas about childhood and applies these to disabled children in New Zealand. This dissertation explores events that have been pivotal in the study of disability, for example, the emergence of the Crippled Children Society (later CCS) and changes in the fields of rehabilitation and special education. Events such as the beginning of Social Security are discussed in the light of their impact upon childhood disability.
Other developments in the health sector such as the increase in orthopaedic practice have had an impact upon the lives of disabled children. This dissertation explores the relationship between the field of Orthopaedics and the Crippled Children Society which was the main agency providing for the needs of disabled children. A further area that is explored is the influence of visiting specialist Dr Earl Carlson as well as parental guides upon the treatment of disabled children. The final section looks at the changes in special education including ideas about inclusion and mainstreaming. It discusses the notion that education changed from a focus on utility to one of equality. It also explores the role of the family with regards to education.

year: 2001

title: Street health: Practitioner service provision for Maori homeless people in Auckland

authors: Nikora, Linda Waimarie

abstract: Drawing insights from interviews with Maori homeless people, health professionals, and relevant local and international literatures, this chapter focuses on the provision of medical care to homeless people. In particular, we propose that health services orientate to accommodate the worldviews and circumstances of Maori homeless people. Below we consider colonialism and societal developments that have led to homelessness among Maori today. We then present a case study of ‘Grant’, which was compiled from common aspects of various Maori homeless people who access health services at the Auckland City Mission (ACM); an organisation with a long history of catering to the needs and hopes of dispossessed groups, providing food, clothing, advocacy, social and health services. The relational orientation of healthcare at the ACM is discussed, and leads to an exploration of ‘judgement-free service space’ for meeting client needs (cf., Trussell & Mair, 2010). Lastly, we focus on how health professionals can respond to the multiple healthcare needs of Maori homeless people, in partnership with social services.

text: Street health: Practitioner service provision for Maori homeless people in Auckland Drawing insights from interviews with Maori homeless people, health professionals, and relevant local and international literatures, this chapter focuses on the provision of medical care to homeless people. In particular, we propose that health services orientate to accommodate the worldviews and circumstances of Maori homeless people. Below we consider colonialism and societal developments that have led to homelessness among Maori today. We then present a case study of ‘Grant’, which was compiled from common aspects of various Maori homeless people who access health services at the Auckland City Mission (ACM); an organisation with a long history of catering to the needs and hopes of dispossessed groups, providing food, clothing, advocacy, social and health services. The relational orientation of healthcare at the ACM is discussed, and leads to an exploration of ‘judgement-free service space’ for meeting client needs (cf., Trussell & Mair, 2010). Lastly, we focus on how health professionals can respond to the multiple healthcare needs of Maori homeless people, in partnership with social services.

year: 2012-09