title: Effects of macrofauna diversity on porewater nutrient concentrations following enrichment

authors: Hines, Laura Veronica

subjects: Macrofauna diversity

abstract: Macrofauna play a key role in the functioning of soft sediment intertidal ecosystems via bioturbation and feeding habits which modify sediment biogeochemistry and influence nutrient cycling. Eutrophication is a naturally occurring phenomenon; however, enrichment due to anthropogenic inputs has increased in frequency with largely unknown consequences to benthic macrofaunal assemblages. A decline in infaunal biodiversity is thought to result in the loss of ecosystem function due to increased disturbance in the form of enhanced nutrient addition. This is increasingly important to estuarine habitats, as benthic macrofauna play an important role in controlling sediment porewater nutrient concentrations, nutrient flux to the overlying water column and ultimately ecosystem function. Sediment modification by macrofauna behaviours (e.g. bioturbation) stimulate nutrient regeneration and influence denitrification rate. Thus understanding the responses of macrofauna to enhanced nutrient levels is vital for the understanding and subsequent management of benthic assemblages to estuarine eutrophication. The aim of this thesis was to stress the intertidal sediment of the Kaipara Harbour by the addition of slow-release fertiliser in order to identify key macrofaunal diversity responses and the influence this has in the overall nutrient processing ability. I also examined whether fertiliser addition influenced primary producers, microphytobenthos biomass and the percent coverage of seagrass. 

To gain a better understanding of porewater nutrient elevation and subsequent impacts to macrofaunal diversity, 28 site locations were selected based on high and low functional macrofaunal diversity and abundance characteristics previously identified within Tapora Bank, Kaipara Harbour (Greenfield 2013). Known amounts (1400g m⁻² (high treatment) and 600g m⁻² (medium treatment)) of 70-day slow-release fertiliser (42 % N) was added to the intertidal sediment across a gradient in macrofaunal diversity. Porewater and sediment properties were measured 28 and 47 days after enrichment, with macrofaunal diversity determined on day 47.

The fertiliser enriched plots significantly elevated porewater ammonium concentrations in both treatments in upper (0-2 cm) and lower (5-7 cm) sediment depths. Lower sampling depths had greater concentrations of porewater ammonium than the upper sediments. This elevation resulted a decline in the overall macrofaunal abundance in both addition treatments however, only the decline in key functional species Macomona liliana was significant. The number of functional individuals and number of M. liliana were identified as significant factors controlling the variation in porewater ammonium concentration in ambient sediments. A switch was observed after fertiliser elevation where mud become the sole driver of porewater ammonium concentration in plots of high fertiliser addition. Normalisation treatment porewater ammonium concentration by the control plot values identified both the number of species and number of functional species as important drivers of porewater ammonium processing. No effect of fertiliser enrichment to seagrass percent coverage was observed. 

These results demonstrate that the elevation of porewater ammonium within intertidal sediments may have implications to the diversity and the subsequent functioning of intertidal benthic communities. In particularly, our study highlights the potential loss of functioning related to the decline of key species such as M. liliana; given their role as ecosystem engineers, their loss could reinforce the effects of eutrophication stress on the system and lead to further degradation.

text: Effects of macrofauna diversity on porewater nutrient concentrations following enrichment Macrofauna play a key role in the functioning of soft sediment intertidal ecosystems via bioturbation and feeding habits which modify sediment biogeochemistry and influence nutrient cycling. Eutrophication is a naturally occurring phenomenon; however, enrichment due to anthropogenic inputs has increased in frequency with largely unknown consequences to benthic macrofaunal assemblages. A decline in infaunal biodiversity is thought to result in the loss of ecosystem function due to increased disturbance in the form of enhanced nutrient addition. This is increasingly important to estuarine habitats, as benthic macrofauna play an important role in controlling sediment porewater nutrient concentrations, nutrient flux to the overlying water column and ultimately ecosystem function. Sediment modification by macrofauna behaviours (e.g. bioturbation) stimulate nutrient regeneration and influence denitrification rate. Thus understanding the responses of macrofauna to enhanced nutrient levels is vital for the understanding and subsequent management of benthic assemblages to estuarine eutrophication. The aim of this thesis was to stress the intertidal sediment of the Kaipara Harbour by the addition of slow-release fertiliser in order to identify key macrofaunal diversity responses and the influence this has in the overall nutrient processing ability. I also examined whether fertiliser addition influenced primary producers, microphytobenthos biomass and the percent coverage of seagrass. 

To gain a better understanding of porewater nutrient elevation and subsequent impacts to macrofaunal diversity, 28 site locations were selected based on high and low functional macrofaunal diversity and abundance characteristics previously identified within Tapora Bank, Kaipara Harbour (Greenfield 2013). Known amounts (1400g m⁻² (high treatment) and 600g m⁻² (medium treatment)) of 70-day slow-release fertiliser (42 % N) was added to the intertidal sediment across a gradient in macrofaunal diversity. Porewater and sediment properties were measured 28 and 47 days after enrichment, with macrofaunal diversity determined on day 47.

The fertiliser enriched plots significantly elevated porewater ammonium concentrations in both treatments in upper (0-2 cm) and lower (5-7 cm) sediment depths. Lower sampling depths had greater concentrations of porewater ammonium than the upper sediments. This elevation resulted a decline in the overall macrofaunal abundance in both addition treatments however, only the decline in key functional species Macomona liliana was significant. The number of functional individuals and number of M. liliana were identified as significant factors controlling the variation in porewater ammonium concentration in ambient sediments. A switch was observed after fertiliser elevation where mud become the sole driver of porewater ammonium concentration in plots of high fertiliser addition. Normalisation treatment porewater ammonium concentration by the control plot values identified both the number of species and number of functional species as important drivers of porewater ammonium processing. No effect of fertiliser enrichment to seagrass percent coverage was observed. 

These results demonstrate that the elevation of porewater ammonium within intertidal sediments may have implications to the diversity and the subsequent functioning of intertidal benthic communities. In particularly, our study highlights the potential loss of functioning related to the decline of key species such as M. liliana; given their role as ecosystem engineers, their loss could reinforce the effects of eutrophication stress on the system and lead to further degradation.

year: 2015

title: Relationship between meteoric ¹⁰Be and NO₃⁻ concentrations in soils along Shackleton Glacier, Antarctica

authors: Diaz, Melisa A.

abstract: Outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced changes in ice thickness greater than other coastal regions of Antarctica during glacial maxima. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, complicating our understanding of ecological succession in TAM soils. Our knowledge of glacial extent on small spatial scales is limited for the TAM, and studies of soil exposure duration and disturbance, in particular, are rare. We collected surface soil samples and, in some places, depth profiles every 5 cm to refusal (up to 30 cm) from 11 ice-free areas along Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. We explored the relationship between meteoric ¹⁰Be and NO₃⁻ in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric ¹⁰Be spanned more than an order of magnitude across the region (2.9×10⁸ to 73×10⁸ atoms g⁻¹) and are among the highest measured in polar regions. The concentrations of NO₃⁻ were similarly variable and ranged from ∼ μg g⁻¹ to 15 mg g⁻¹. In examining differences and similarities in the concentrations of ¹⁰Be and NO₃⁻ with depth, we suggest that much of the southern portion of the Shackleton Glacier region has likely developed under a hyper-arid climate regime with minimal disturbance. Finally, we inferred exposure time using ¹⁰Be concentrations. This analysis indicates that the soils we analyzed likely range from recent exposure (following the Last Glacial Maximum) to possibly >6 Myr. We suggest that further testing and interrogation of meteoric ¹⁰Be and NO₃⁻ concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.

text: Relationship between meteoric ¹⁰Be and NO₃⁻ concentrations in soils along Shackleton Glacier, Antarctica Outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced changes in ice thickness greater than other coastal regions of Antarctica during glacial maxima. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, complicating our understanding of ecological succession in TAM soils. Our knowledge of glacial extent on small spatial scales is limited for the TAM, and studies of soil exposure duration and disturbance, in particular, are rare. We collected surface soil samples and, in some places, depth profiles every 5 cm to refusal (up to 30 cm) from 11 ice-free areas along Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. We explored the relationship between meteoric ¹⁰Be and NO₃⁻ in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric ¹⁰Be spanned more than an order of magnitude across the region (2.9×10⁸ to 73×10⁸ atoms g⁻¹) and are among the highest measured in polar regions. The concentrations of NO₃⁻ were similarly variable and ranged from ∼ μg g⁻¹ to 15 mg g⁻¹. In examining differences and similarities in the concentrations of ¹⁰Be and NO₃⁻ with depth, we suggest that much of the southern portion of the Shackleton Glacier region has likely developed under a hyper-arid climate regime with minimal disturbance. Finally, we inferred exposure time using ¹⁰Be concentrations. This analysis indicates that the soils we analyzed likely range from recent exposure (following the Last Glacial Maximum) to possibly >6 Myr. We suggest that further testing and interrogation of meteoric ¹⁰Be and NO₃⁻ concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.

year: 2021

title: Exploring the nature of intimate relationships: A Māori perspective

authors: King, Pita

subjects: Maori

abstract: The 2002 World Report on Violence states that violence occurs in about 70 percent of intimate relationships (Krug, Dahlberg, Mercy, Zwi, & Lozano, 2002). New Zealand research indicates that more than a quarter of relationships have experienced intimate partner violence (IPV), with Māori (Indigenous people of New Zealand) women three times more likely to experience IPV in their lifetime. Utilising Kaupapa Māori (Māori-centred approach) and narrative methodologies, this paper explores the nature of intimate relationships from a Māori perspective, investigating how Māori initiate intimate relationships, attempt to maintain positive intimate relationships and when applicable, exit intimate relationships. The findings from two case studies reveal that intimate relationships involve identity negotiation and an incorporation of cultural values. Communication processes are highlighted as a facilitating factor of intimate relationships.

text: Exploring the nature of intimate relationships: A Māori perspective The 2002 World Report on Violence states that violence occurs in about 70 percent of intimate relationships (Krug, Dahlberg, Mercy, Zwi, & Lozano, 2002). New Zealand research indicates that more than a quarter of relationships have experienced intimate partner violence (IPV), with Māori (Indigenous people of New Zealand) women three times more likely to experience IPV in their lifetime. Utilising Kaupapa Māori (Māori-centred approach) and narrative methodologies, this paper explores the nature of intimate relationships from a Māori perspective, investigating how Māori initiate intimate relationships, attempt to maintain positive intimate relationships and when applicable, exit intimate relationships. The findings from two case studies reveal that intimate relationships involve identity negotiation and an incorporation of cultural values. Communication processes are highlighted as a facilitating factor of intimate relationships.

year: 2012