title: Bayesian tools for tephrochronology

authors: Buck, Caitlin E.

subjects: radiocarbon dating

abstract: It is suggested that Bayesian statistical methods for radiocarbon data interpretation, already widely used in archaeology, also have potential to improve the dating of tephra layers and hence enhance their use for tephrochronology. By re-analysing data from a recently published paper in which the authors sought to identify the calendar date of the eruption of fourteenth-century AD Kaharoa Tephra, a key marker in New Zealand prehistory, it is shown that Bayesian methods can be used to draw together a coherent collection of radiocarbon data, undertake formal outlier detection, and include prior information. Regardless of the calibration curve adopted, the distribution of likely dates for the Kaharoa eruption is multimodal. By including prior information from wiggle-matched dendrochronology, the uncertainty on the estimate of the calendar date is reduced from a range of about 100 years to about 25 years (i.e., 648-623 cal. BP, with modes at 638 and 632 cal. BP). Using sensitivity analysis, however, it is shown that such estimates are affected by the quality and nature of the prior information available. As a result, we urge tephrochronologists to seek fastidiously both high-quality radiocarbon data and reliable stratigraphic sequences that might inform future geochronological model building.

text: Bayesian tools for tephrochronology It is suggested that Bayesian statistical methods for radiocarbon data interpretation, already widely used in archaeology, also have potential to improve the dating of tephra layers and hence enhance their use for tephrochronology. By re-analysing data from a recently published paper in which the authors sought to identify the calendar date of the eruption of fourteenth-century AD Kaharoa Tephra, a key marker in New Zealand prehistory, it is shown that Bayesian methods can be used to draw together a coherent collection of radiocarbon data, undertake formal outlier detection, and include prior information. Regardless of the calibration curve adopted, the distribution of likely dates for the Kaharoa eruption is multimodal. By including prior information from wiggle-matched dendrochronology, the uncertainty on the estimate of the calendar date is reduced from a range of about 100 years to about 25 years (i.e., 648-623 cal. BP, with modes at 638 and 632 cal. BP). Using sensitivity analysis, however, it is shown that such estimates are affected by the quality and nature of the prior information available. As a result, we urge tephrochronologists to seek fastidiously both high-quality radiocarbon data and reliable stratigraphic sequences that might inform future geochronological model building.

year: 2003

title: A genus in the bacterial phylum Aquificota appears to be endemic to Aotearoa-New Zealand.

authors: Power, Jean F.

subjects: New Zealand

abstract: Allopatric speciation has been difficult to examine among microorganisms, with prior reports of endemism restricted to sub-genus level taxa. Previous microbial community analysis via 16S rRNA gene sequencing of 925 geothermal springs from the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand, revealed widespread distribution and abundance of a single bacterial genus across 686 of these ecosystems (pH 1.2-9.6 and 17.4-99.8 °C). Here, we present evidence to suggest that this genus, Venenivibrio (phylum Aquificota), is endemic to Aotearoa-New Zealand. A specific environmental niche that increases habitat isolation was identified, with maximal read abundance of Venenivibrio occurring at pH 4-6, 50-70 °C, and low oxidation-reduction potentials. This was further highlighted by genomic and culture-based analyses of the only characterised species for the genus, Venenivibrio stagnispumantis CP.B2T, which confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between Venenivibrio populations illustrated that dispersal is not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of global microbial communities from DNA sequence databases indicates Venenivibrio is geographically restricted to the Aotearoa-New Zealand archipelago. We conclude that geographic isolation, complemented by physicochemical constraints, has resulted in the establishment of an endemic bacterial genus.

text: A genus in the bacterial phylum Aquificota appears to be endemic to Aotearoa-New Zealand. Allopatric speciation has been difficult to examine among microorganisms, with prior reports of endemism restricted to sub-genus level taxa. Previous microbial community analysis via 16S rRNA gene sequencing of 925 geothermal springs from the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand, revealed widespread distribution and abundance of a single bacterial genus across 686 of these ecosystems (pH 1.2-9.6 and 17.4-99.8 °C). Here, we present evidence to suggest that this genus, Venenivibrio (phylum Aquificota), is endemic to Aotearoa-New Zealand. A specific environmental niche that increases habitat isolation was identified, with maximal read abundance of Venenivibrio occurring at pH 4-6, 50-70 °C, and low oxidation-reduction potentials. This was further highlighted by genomic and culture-based analyses of the only characterised species for the genus, Venenivibrio stagnispumantis CP.B2T, which confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between Venenivibrio populations illustrated that dispersal is not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of global microbial communities from DNA sequence databases indicates Venenivibrio is geographically restricted to the Aotearoa-New Zealand archipelago. We conclude that geographic isolation, complemented by physicochemical constraints, has resulted in the establishment of an endemic bacterial genus.

year: 2024-01-02

title: Boat electrofishing survey of fish populations in the Ohau Channel in December 2010

authors: Hicks, Brendan J.

abstract: The original purpose of this series of surveys was to apply an independent method to estimate the densities of common smelt and bullies in the Ohau Channel at fixed points along the bank which coincided with trap netting sites used by the National Institute of Water and Atmospheric Research (NIWA). Since the low number of smelt captured by a single day’s boat electrofishing became apparent compared to the numbers captured by seasonal trapping, the aim of the survey has been modified to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura).

text: Boat electrofishing survey of fish populations in the Ohau Channel in December 2010 The original purpose of this series of surveys was to apply an independent method to estimate the densities of common smelt and bullies in the Ohau Channel at fixed points along the bank which coincided with trap netting sites used by the National Institute of Water and Atmospheric Research (NIWA). Since the low number of smelt captured by a single day’s boat electrofishing became apparent compared to the numbers captured by seasonal trapping, the aim of the survey has been modified to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura).

year: 2011-11-15