title: Scalable architecture for prefix preserving anonymization of IP addresses

authors: Blake, Anthony Martin

subjects: computer science

abstract: This paper describes a highly scalable architecture based on field-programmable gate-array (FPGA) technology for prefix-preserving anonymization of IP addresses at increasingly high network line rates. The Crypto-PAn technique, with the Advanced Encryption Standard (AES) as the underlying pseudo-random function, is fully mapped into reconfigurable hardware. A 32 Gb/s fully-pipelined AES engine was developed and used to prototype the Crypto-PAn architecture. The prototype was implemented on a Xilinx Virtex-4 device achieving a worst-case Ethernet throughput of 8 Gb/s using 141 block RAM’s and 4262 logic cells. This is considerably faster than software implementations which generally achieve much less than 100 Mb/s throughput. A technology-independent analysis is presented to explore the scalability of the architecture to higher multi-gigabit line-rates.

text: Scalable architecture for prefix preserving anonymization of IP addresses This paper describes a highly scalable architecture based on field-programmable gate-array (FPGA) technology for prefix-preserving anonymization of IP addresses at increasingly high network line rates. The Crypto-PAn technique, with the Advanced Encryption Standard (AES) as the underlying pseudo-random function, is fully mapped into reconfigurable hardware. A 32 Gb/s fully-pipelined AES engine was developed and used to prototype the Crypto-PAn architecture. The prototype was implemented on a Xilinx Virtex-4 device achieving a worst-case Ethernet throughput of 8 Gb/s using 141 block RAM’s and 4262 logic cells. This is considerably faster than software implementations which generally achieve much less than 100 Mb/s throughput. A technology-independent analysis is presented to explore the scalability of the architecture to higher multi-gigabit line-rates.

year: 2008

title: Use of genetic methods for determining patterns and processes during marine biological invasions

authors: Smith, Kirsty Fiona

subjects: Didemnum vexillum

abstract: Invasive species are widely recognised as one of the major threats to marine biodiversity worldwide. With increasingly faster and more frequent transoceanic shipping, propagule pressure in the marine environment is likely to further increase, leading to a need for effective strategies for the early detection, prevention and control of marine invasive species. However, such strategies are often difficult to implement as many marine species cannot be accurately categorised as either native or non-native. For these reasons molecular genetic methods have increasingly been utilised for the study of marine invasive species. The potential for molecular data to enhance traditional morphology-based information is recognised and there has been huge progress in the application of molecular genetic methods to the study of marine bioinvasions in the last two decades. This work aims to build on and extend current advances in the use of molecular techniques for understanding marine bioinvasions, and in particular invasive ascidians. Part One (Chapters Two and Three) contains chapters that focus on the detection and identification of marine invasive species with molecular methods. Part Two (Chapters Four, Five and Six) examines how molecular methods can aid in understanding marine invasions and the affect of genetic diversity on invasive populations.

The research in this thesis demonstrates the usefulness of molecular genetics for marine invasive species research. Chapter Two describes the development of a highly sensitive assay for rapid and accurate identification of an invasive clam from environmental samples and has the ability to enhance current marine pest surveillance methods. Chapter Three demonstrates the power of molecular methods for invasive species identification. To effectively monitor and / or control the ongoing anthropogenic spread of invasive marine species there is also a need for extensive molecular inventories of the extant marine invertebrate biodiversity.

An understanding of the genetic diversity of invasive species populations is also required and will increase understanding of the species biology and lead to more effective management strategies. Chapters Four and Five highlight the applications of molecular genetic methods for identifying the invasive species / variants present and elucidating particular populations that served as the source of an introduction. This information can contribute to effective national and international policies and management strategies.

Chapters Five and Six also show how molecular genetic data can aid in understanding why some species are invasive. The results from these two chapters add to growing evidence that, for colonial organisms, reductions in population level genetic diversity may alter colony interaction dynamics and enhance the invasive potential of newly colonising species.

In the future, invasive species research will increasingly utilise metagenomics / next-generation sequencing (NGS) technologies. Such applications will provide the ability to not only detect specific invasive species but also the native species present in a sample to assess environmental health. Studies of invasive species are increasingly using functional markers to identify physiologically and ecologically important traits. Future gene expression experiments can utilise NGS technology to identify the genes involved in producing invasive phenotypes and species. Such studies may provide findings which could be of both evolutionary and importantly, practical interest for guiding invasive species management decisions. The application of molecular genetic methods to understanding the biology of invasive species is an extremely promising area of research and such knowledge should be utilised to guide and inform management decisions.

text: Use of genetic methods for determining patterns and processes during marine biological invasions Invasive species are widely recognised as one of the major threats to marine biodiversity worldwide. With increasingly faster and more frequent transoceanic shipping, propagule pressure in the marine environment is likely to further increase, leading to a need for effective strategies for the early detection, prevention and control of marine invasive species. However, such strategies are often difficult to implement as many marine species cannot be accurately categorised as either native or non-native. For these reasons molecular genetic methods have increasingly been utilised for the study of marine invasive species. The potential for molecular data to enhance traditional morphology-based information is recognised and there has been huge progress in the application of molecular genetic methods to the study of marine bioinvasions in the last two decades. This work aims to build on and extend current advances in the use of molecular techniques for understanding marine bioinvasions, and in particular invasive ascidians. Part One (Chapters Two and Three) contains chapters that focus on the detection and identification of marine invasive species with molecular methods. Part Two (Chapters Four, Five and Six) examines how molecular methods can aid in understanding marine invasions and the affect of genetic diversity on invasive populations.

The research in this thesis demonstrates the usefulness of molecular genetics for marine invasive species research. Chapter Two describes the development of a highly sensitive assay for rapid and accurate identification of an invasive clam from environmental samples and has the ability to enhance current marine pest surveillance methods. Chapter Three demonstrates the power of molecular methods for invasive species identification. To effectively monitor and / or control the ongoing anthropogenic spread of invasive marine species there is also a need for extensive molecular inventories of the extant marine invertebrate biodiversity.

An understanding of the genetic diversity of invasive species populations is also required and will increase understanding of the species biology and lead to more effective management strategies. Chapters Four and Five highlight the applications of molecular genetic methods for identifying the invasive species / variants present and elucidating particular populations that served as the source of an introduction. This information can contribute to effective national and international policies and management strategies.

Chapters Five and Six also show how molecular genetic data can aid in understanding why some species are invasive. The results from these two chapters add to growing evidence that, for colonial organisms, reductions in population level genetic diversity may alter colony interaction dynamics and enhance the invasive potential of newly colonising species.

In the future, invasive species research will increasingly utilise metagenomics / next-generation sequencing (NGS) technologies. Such applications will provide the ability to not only detect specific invasive species but also the native species present in a sample to assess environmental health. Studies of invasive species are increasingly using functional markers to identify physiologically and ecologically important traits. Future gene expression experiments can utilise NGS technology to identify the genes involved in producing invasive phenotypes and species. Such studies may provide findings which could be of both evolutionary and importantly, practical interest for guiding invasive species management decisions. The application of molecular genetic methods to understanding the biology of invasive species is an extremely promising area of research and such knowledge should be utilised to guide and inform management decisions.

year: 2012

title: Phytoplankton nutrient limitation in Lake Rotorua

authors: Tempero, Grant Wayne

abstract: Lake Rotorua is one of 12 lakes jointly managed by the Rotorua Lakes Council, Te Arawa Lakes Trust and the Bay of Plenty Regional Council under the Rotorua Te Arawa Lakes Programme. The lake is currently classified as eutrophic and a Trophic Lake Index (TLI) value of 4.2 has been set as an integrated target for lake water quality. A number of catchment and lake management strategies have been implemented to achieve the targeted TLI including land use changes, wetland enhancement, lake weed harvesting, sediment detainment bunds, sewage reticulation and alum dosing. Alum (aluminium sulphate) is commonly applied to freshwater and wastewater systems to remove phosphorus, reducing its availability for phytoplankton growth. The initiation of alum dosing to the Utuhina Stream in 2006 and the Puarenga Stream in 2010 was associated with a significant decline in water column dissolved reactive phosphorus (DRP) and improvements in water quality of Lake Rotorua. 
The use of alum to control external and internal phosphorus loading has been identified as key component in the restoration of Lake Rotorua and recently observed improvements in water quality suggest that the lake could be transitioning to a more phosphorus limited state. Determination of phytoplankton nutrient limitation in Lake Rotorua was identified as a priority through the 2017 Plan Change 10 Science Review. An initial seasonal nutrient limitation study was carried out in 2019 with nutrient limitation assays conducted at 3-monthly intervals over the course of the year. Nitrogen limitation was indicated for the March assay and nutrient co-limitation for the December period, but results for the winter and spring periods were inconclusive. There has also been increasing recognition that nutrient availability in limnetic systems may vary in response to seasonal changes in external and external loading and even to isolated storm events. 
The University of Waikato was contracted to investigate potential changes in nutrient limitation within Lake Rotorua at sub-monthly time-scales, and to determine if alum dose rates could be optimised to take advantage of periods of phosphorus limitation. Phytoplankton nutrient limitation growth assays were conducted on a fortnightly basis from mid-October 2020 to May 2021. In addition to determination of lake surface nutrient and chlorophyll a concentrations, triplicate 1 L phytoplankton samples were spiked with either phosphorus (0.1 mg-P L⁻¹), nitrogen (1 mg-N L⁻¹) or phosphorus (0.1 mg-P L⁻¹) and nitrogen (1 mg-N L⁻¹) and incubated for 5-days under a single light intensity of 100 μmol m⁻²s⁻¹ PAR at lake surface temperature and photoperiod. Phytoplankton growth responses were measured as comparative chlorophyll a, comparative biomass and net biomass growth. Summarised results from the 16 assays along with the predicted nutrient state from the stoichiometric mass ratio of TN:TP are presented in the table below. 
Under the test conditions nitrogen limitation was indicated for most of the summer months (December–March) and nutrient co-limitation during the spring and late autumn. Only short (~2 weeks) periods of P-limitation were observed, one of which was associated with an intensive storm event at the end of March. These seasonal fluctuations in nitrogen and phosphorus supply are similar to those observed in other temperate limnetic systems. In the spring, external nitrogen and phosphorus loading is high, then decline in the summer as rainfall and associated inflows wane. During the summer, internal loading becomes more important in polymictic lakes due to repeated internal nutrient cycling from stratification and mixing events. This results in phosphorus limitation in the spring, transitioning to nitrogen limitation or colimitation (primarily nitrogen) in the summer, and then returning to phosphorus/colimitation during the winter due to increased nitrogen-loading from the catchment from increased catchment discharge. 
Due to the modest periods of phosphorus limitation indicated by the assays, there appears to be little potential for optimisation of alum dose rates in order capitalise on natural periods of phosphorus limitation. Further, changes in phytoplankton community composition and abundance appear to be more strongly driven by physical environmental factors such as temperature, light and wind speed, than nutrient availability. Although alum dosing is effective in removing DRP from the Utuhina and Puarenga inflows, its assumed effectiveness in reducing internal phosphorus loading in Lake Rotorua requires further evaluation.

text: Phytoplankton nutrient limitation in Lake Rotorua Lake Rotorua is one of 12 lakes jointly managed by the Rotorua Lakes Council, Te Arawa Lakes Trust and the Bay of Plenty Regional Council under the Rotorua Te Arawa Lakes Programme. The lake is currently classified as eutrophic and a Trophic Lake Index (TLI) value of 4.2 has been set as an integrated target for lake water quality. A number of catchment and lake management strategies have been implemented to achieve the targeted TLI including land use changes, wetland enhancement, lake weed harvesting, sediment detainment bunds, sewage reticulation and alum dosing. Alum (aluminium sulphate) is commonly applied to freshwater and wastewater systems to remove phosphorus, reducing its availability for phytoplankton growth. The initiation of alum dosing to the Utuhina Stream in 2006 and the Puarenga Stream in 2010 was associated with a significant decline in water column dissolved reactive phosphorus (DRP) and improvements in water quality of Lake Rotorua. 
The use of alum to control external and internal phosphorus loading has been identified as key component in the restoration of Lake Rotorua and recently observed improvements in water quality suggest that the lake could be transitioning to a more phosphorus limited state. Determination of phytoplankton nutrient limitation in Lake Rotorua was identified as a priority through the 2017 Plan Change 10 Science Review. An initial seasonal nutrient limitation study was carried out in 2019 with nutrient limitation assays conducted at 3-monthly intervals over the course of the year. Nitrogen limitation was indicated for the March assay and nutrient co-limitation for the December period, but results for the winter and spring periods were inconclusive. There has also been increasing recognition that nutrient availability in limnetic systems may vary in response to seasonal changes in external and external loading and even to isolated storm events. 
The University of Waikato was contracted to investigate potential changes in nutrient limitation within Lake Rotorua at sub-monthly time-scales, and to determine if alum dose rates could be optimised to take advantage of periods of phosphorus limitation. Phytoplankton nutrient limitation growth assays were conducted on a fortnightly basis from mid-October 2020 to May 2021. In addition to determination of lake surface nutrient and chlorophyll a concentrations, triplicate 1 L phytoplankton samples were spiked with either phosphorus (0.1 mg-P L⁻¹), nitrogen (1 mg-N L⁻¹) or phosphorus (0.1 mg-P L⁻¹) and nitrogen (1 mg-N L⁻¹) and incubated for 5-days under a single light intensity of 100 μmol m⁻²s⁻¹ PAR at lake surface temperature and photoperiod. Phytoplankton growth responses were measured as comparative chlorophyll a, comparative biomass and net biomass growth. Summarised results from the 16 assays along with the predicted nutrient state from the stoichiometric mass ratio of TN:TP are presented in the table below. 
Under the test conditions nitrogen limitation was indicated for most of the summer months (December–March) and nutrient co-limitation during the spring and late autumn. Only short (~2 weeks) periods of P-limitation were observed, one of which was associated with an intensive storm event at the end of March. These seasonal fluctuations in nitrogen and phosphorus supply are similar to those observed in other temperate limnetic systems. In the spring, external nitrogen and phosphorus loading is high, then decline in the summer as rainfall and associated inflows wane. During the summer, internal loading becomes more important in polymictic lakes due to repeated internal nutrient cycling from stratification and mixing events. This results in phosphorus limitation in the spring, transitioning to nitrogen limitation or colimitation (primarily nitrogen) in the summer, and then returning to phosphorus/colimitation during the winter due to increased nitrogen-loading from the catchment from increased catchment discharge. 
Due to the modest periods of phosphorus limitation indicated by the assays, there appears to be little potential for optimisation of alum dose rates in order capitalise on natural periods of phosphorus limitation. Further, changes in phytoplankton community composition and abundance appear to be more strongly driven by physical environmental factors such as temperature, light and wind speed, than nutrient availability. Although alum dosing is effective in removing DRP from the Utuhina and Puarenga inflows, its assumed effectiveness in reducing internal phosphorus loading in Lake Rotorua requires further evaluation.

year: 2022