title: Volcanic hazards in Auckland, New Zealand: a preliminary assessment of the threat posed by central North Island silicic volcanism based on the Quaternary tephrostratigraphical record

authors: Alloway, Brent V.

abstract: The City of Auckland (population c. 1 million), built on a basaltic volcanic field active as recently as c. AD 1400, faces an additional volcanic threat: that from several large and productive rhyolitic and andesitic eruptive centres of the central North Island, 140-280 km to the south and southeast. Non-basaltic tephra fallout layers originating from these distal eruptive centres are numerous and widespread in the Auckland region and have primary thicknesses ranging from c. 1 mm to  = 0.6 m; ignimbrites up to 9 m thick are also documented but are uncommon. The assessment of volcanic hazards in Auckland is made problematical by the different types of volcanic threat posed by these two spatially distinct source areas, and by the lack of recognition hitherto given to the threat from the distal sources. This paper reviews the Quaternary records of distal volcanism affecting Auckland and outlines current investigations into the assessment of environmental impacts of past eruptions. Our preliminary results indicate that the potential threat to Auckland from the distal volcanic sources has been underestimated and that further research into the impacts of Quaternary volcanism on Auckland's environment and infrastructure is essential. The importance of this threat was underscored in mid-1996 when a small magnitude eruption of Mt Ruapehu necessitated closure of Auckland International Airport for three nights.

text: Volcanic hazards in Auckland, New Zealand: a preliminary assessment of the threat posed by central North Island silicic volcanism based on the Quaternary tephrostratigraphical record The City of Auckland (population c. 1 million), built on a basaltic volcanic field active as recently as c. AD 1400, faces an additional volcanic threat: that from several large and productive rhyolitic and andesitic eruptive centres of the central North Island, 140-280 km to the south and southeast. Non-basaltic tephra fallout layers originating from these distal eruptive centres are numerous and widespread in the Auckland region and have primary thicknesses ranging from c. 1 mm to  = 0.6 m; ignimbrites up to 9 m thick are also documented but are uncommon. The assessment of volcanic hazards in Auckland is made problematical by the different types of volcanic threat posed by these two spatially distinct source areas, and by the lack of recognition hitherto given to the threat from the distal sources. This paper reviews the Quaternary records of distal volcanism affecting Auckland and outlines current investigations into the assessment of environmental impacts of past eruptions. Our preliminary results indicate that the potential threat to Auckland from the distal volcanic sources has been underestimated and that further research into the impacts of Quaternary volcanism on Auckland's environment and infrastructure is essential. The importance of this threat was underscored in mid-1996 when a small magnitude eruption of Mt Ruapehu necessitated closure of Auckland International Airport for three nights.

year: 1999-01-01

title: Field and laboratory investigations of Echyridella menziesii (Unionida: Hyriidae) interactions with host fishes

authors: Hanrahan, Nicole Joy

subjects: freshwater mussel

abstract: Globally, the study of freshwater mussels has increased markedly in recent years, spurred on by recognition that many mussel populations are declining or are already extinct. The New Zealand freshwater mussel Echyridella menziesii (Unionida: Hyriidae) has a current threat classification of ‘At Risk, Declining’, in part reflecting disruption of recruitment on host fish. The life cycle of E. menziesii includes a parasitic stage in which the larvae (glochidia) must attach to a host fish to transform into the juvenile stage. However, no research has been conducted to understand whether fish develop immunity that limits infestation rates, and little is known about the spatial and temporal variations of mussel-host interactions in natural environments in New Zealand. This study therefore aimed to: i) determine whether multiple infestations of E. menziesii glochidia influenced the suitability of common bully (Gobiomorphus cotidianus) as a host; and ii) quantify fish host associations over the glochidial release period in three contrasting Waikato streams.

Common bully considered naïve to E. menziesii were infested with glochidia in the laboratory, and placed in individual, flow-through tanks (22oC) which were flushed every second day to measure glochidia detachment and juvenile excystment. Fishes were infested either one, two or three times, with ‘control’ fish infested for the first time in the second and third rounds. There were no differences in cumulative detachment rates of glochidia and no major reductions in metamorphosis success across multiple infestations. 

Metamorphosis success rate across all infestation rounds was ≤30%, and was highest when initial glochidia viability was also high. The lack of detectable immunity in common bully, at least after three sequential infestations, is promising for the future conservation of E. menziesii as host-fish are likely to be repetitively infested with glochidia over the mussel spawning season in a natural setting.

Infestation by glochidia was determined on the associated fish community, caught using a combination of electrofishing and minnow trapping. In parallel with these evaluations, mussel brood pouch development was assessed fortnightly from October 2018 to February 2019 at three Waikato stream sites. Peak glochidia release occurred in February when average monthly water temperatures were >18.8oC. A field method was developed to quantify glochidial attachment on external surfaces of fish, while internal attachment (gills, mouth) was quantified by laboratory dissection. While a range of fish hosts were identified, 86% of recorded glochidia were attached to Gobiomorphus species, including redfin bully (G. huttoni) and common/Crans bully (G. cotidianus/G. basalis). Most externally-attached glochidia (73%) occurred on caudal, pelvic and pectoral fins. Host associations appeared to favour benthic rather than pelagic species, and did not change throughout the mussel reproductive season despite seasonal change in fish communities.

This research demonstrates that common bully, and more broadly Gobiomorphus species, are important hosts for glochidia and do not develop immunity to repeated infestations. Gobiomorphus species have the potential to be very useful ‘tools’ to assist in restoring E. menziesii populations, and therefore conservation management must consider these host fish populations as well as other habitat and water quality factors affecting E. menziesii.

text: Field and laboratory investigations of Echyridella menziesii (Unionida: Hyriidae) interactions with host fishes Globally, the study of freshwater mussels has increased markedly in recent years, spurred on by recognition that many mussel populations are declining or are already extinct. The New Zealand freshwater mussel Echyridella menziesii (Unionida: Hyriidae) has a current threat classification of ‘At Risk, Declining’, in part reflecting disruption of recruitment on host fish. The life cycle of E. menziesii includes a parasitic stage in which the larvae (glochidia) must attach to a host fish to transform into the juvenile stage. However, no research has been conducted to understand whether fish develop immunity that limits infestation rates, and little is known about the spatial and temporal variations of mussel-host interactions in natural environments in New Zealand. This study therefore aimed to: i) determine whether multiple infestations of E. menziesii glochidia influenced the suitability of common bully (Gobiomorphus cotidianus) as a host; and ii) quantify fish host associations over the glochidial release period in three contrasting Waikato streams.

Common bully considered naïve to E. menziesii were infested with glochidia in the laboratory, and placed in individual, flow-through tanks (22oC) which were flushed every second day to measure glochidia detachment and juvenile excystment. Fishes were infested either one, two or three times, with ‘control’ fish infested for the first time in the second and third rounds. There were no differences in cumulative detachment rates of glochidia and no major reductions in metamorphosis success across multiple infestations. 

Metamorphosis success rate across all infestation rounds was ≤30%, and was highest when initial glochidia viability was also high. The lack of detectable immunity in common bully, at least after three sequential infestations, is promising for the future conservation of E. menziesii as host-fish are likely to be repetitively infested with glochidia over the mussel spawning season in a natural setting.

Infestation by glochidia was determined on the associated fish community, caught using a combination of electrofishing and minnow trapping. In parallel with these evaluations, mussel brood pouch development was assessed fortnightly from October 2018 to February 2019 at three Waikato stream sites. Peak glochidia release occurred in February when average monthly water temperatures were >18.8oC. A field method was developed to quantify glochidial attachment on external surfaces of fish, while internal attachment (gills, mouth) was quantified by laboratory dissection. While a range of fish hosts were identified, 86% of recorded glochidia were attached to Gobiomorphus species, including redfin bully (G. huttoni) and common/Crans bully (G. cotidianus/G. basalis). Most externally-attached glochidia (73%) occurred on caudal, pelvic and pectoral fins. Host associations appeared to favour benthic rather than pelagic species, and did not change throughout the mussel reproductive season despite seasonal change in fish communities.

This research demonstrates that common bully, and more broadly Gobiomorphus species, are important hosts for glochidia and do not develop immunity to repeated infestations. Gobiomorphus species have the potential to be very useful ‘tools’ to assist in restoring E. menziesii populations, and therefore conservation management must consider these host fish populations as well as other habitat and water quality factors affecting E. menziesii.

year: 2019

title: Mates at the school gates:Investigating peer relationships among rangatahi Māori

authors: Knowles, Anthea Heather

subjects: school attendance

abstract: As a teacher, I have found that while some rangatahi feel connected to school, many others do not. In an attempt to reduce the gap between Māori and non-Māori educational achievement, there have been significant nationwide initiatives implemented into schools across New Zealand. These programmes have been centred mostly around improving school engagement. Despite these efforts, school attendance rates among Māori continue to decline. This thesis explores the role of peer relationships among rangatahi Māori, including how these relationships may influence various domains of engagement at school, such as participation, belonging and orientation to learning. 

This research involves focus group interviews with six rangatahi Māori aged 17-18, and in Years 12 and 13 in a small-town New Zealand High School. The wāhine Māori who contributed to the study, had been identified by the school as successfully engaged through regular attendance and participation of school activites. The findings from this study identify some critical aspects to building strong peer relationships, including: having a social space to gather, practicing manaakitanga, recognising equity, maintaining connection with each other, and welcoming humour. The rangatahi in this study value their peers and social relationships and they freely access these resources as needed. In doing so they are able to collectively critique experiences of marginalisation and acquire a collective source of resilience. The participants in this study then draw on this collective resilience during challenging situations.

text: Mates at the school gates:Investigating peer relationships among rangatahi Māori As a teacher, I have found that while some rangatahi feel connected to school, many others do not. In an attempt to reduce the gap between Māori and non-Māori educational achievement, there have been significant nationwide initiatives implemented into schools across New Zealand. These programmes have been centred mostly around improving school engagement. Despite these efforts, school attendance rates among Māori continue to decline. This thesis explores the role of peer relationships among rangatahi Māori, including how these relationships may influence various domains of engagement at school, such as participation, belonging and orientation to learning. 

This research involves focus group interviews with six rangatahi Māori aged 17-18, and in Years 12 and 13 in a small-town New Zealand High School. The wāhine Māori who contributed to the study, had been identified by the school as successfully engaged through regular attendance and participation of school activites. The findings from this study identify some critical aspects to building strong peer relationships, including: having a social space to gather, practicing manaakitanga, recognising equity, maintaining connection with each other, and welcoming humour. The rangatahi in this study value their peers and social relationships and they freely access these resources as needed. In doing so they are able to collectively critique experiences of marginalisation and acquire a collective source of resilience. The participants in this study then draw on this collective resilience during challenging situations.

year: 2019