title: Computerised tomography indices of raised intracranial pressure and traumatic brain injury severity in a New Zealand sample

authors: Barker-Collo, Suzanne

abstract: After traumatic brain injury (TBI) complex cellular and biochemical processes occur¹ including changes in blood flow and oxygenation of the brain; cerebral swelling; and raised intracranial pressure (ICP).² This can dramatically worsen the damage³ and contributes to mortality.

text: Computerised tomography indices of raised intracranial pressure and traumatic brain injury severity in a New Zealand sample After traumatic brain injury (TBI) complex cellular and biochemical processes occur¹ including changes in blood flow and oxygenation of the brain; cerebral swelling; and raised intracranial pressure (ICP).² This can dramatically worsen the damage³ and contributes to mortality.

year: 2012

title: Phytoplankton dynamics in North Island lakes, New Zealand

authors: Ryan, E.F.

subjects: Freshwater phytoplankton New Zealand Waikato

abstract: The dynamics of phytoplankton were investigated in 40 lakes of the North Island, New Zealand. A range of environmental variables was examined on different temporal and spatial scales in relation to the surface and DCM ( deep chlorophyll maximum) phytoplankton communities in the lakes. The environmental variables that were considered relevant to these communities included turbulent mixing, limitation by light and nutrients, rates of sedimentation or ascent, and zooplankton grazing. 
Cylindrospermopsis raciborskii is a potentially toxic species of cyanobacteria, that in summer 2002-3 formed dense water blooms (> 100 OOO cells/ml) in shallow (max. depth :5 Sm) Waikato peat lakes and a hydro-electric dam on the Waikato River. Net rates of growth calculated within individual lakes demonstrated that C. raciborskii populations grew at rates close to maximum values observed under optimal conditions in laboratory cultures. Changes in species diversity in the lakes prior to and following the invasion of C. raciborskii were assessed. During occasions of C. raciborskii water blooms there was decreased diversity and the phytoplankton assemblage became nearly mono-specific. The shallow lakes in this study have high concentrations of nutrients and low water clarity, which are ideal conditions for growth of C. raciborskii, as it has a competitive advantage at low irradiance but limited capacity for buoyancy. The ability of C. raciborskii to fix nitrogen may also have enhanced its competitive ability amongst other phytoplankton species and, while nutrients were generally considered to be replete, nitrogen was more likely to limit growth of phytoplankton than phosphorus in the lakes studied. 
Lake Tarawera, part of the Rotorua lakes region (area 41.6 km2 and mean depth 50 m), was chosen to investigate variability of phytoplankton biomass with depth and between embayments and a mid-lake station. The variability of DCM depth was contributed by internal seiching, which was most prominent at the edge of the lake. A single mid-lake station was considered representative of lake-wide biomass at the DCM as the differences between stations were small. However, during a bloom of Anabaena lemmermanni, there was large inter-station variability in phytoplankton biomass in the surface mixed layer. Therefore, when quantifying surface populations, particularly buoyant cyanobacterial species which tend to accumulate in bays, discrete samples at a single station and depth may not adequately represent lake-wide biomass. During periods when bloom-forming species are present, several sampling stations should be used to adequately quantify biomass and variability of phytoplankton in the surface mixed layer. 
A population-dynamics theory of sinking phytoplankton, that utilizes interactions between growth limitation by light and nutrients, sinking rates and turbulent diffusion rates, was used to quantify factors contributing to DCM formation in Lake Tarawera. Five 'Modes' of vertical phytoplankton of biomass were categorised relating to four forcing functions. The first mode was a surface chlorophyll maximum (SCM); Mode 2 was a DCM; Mode 3 was a simultaneous double peak of buoyant cyanobacteria and a DCM assemblage; Mode 4 was a linear vertical distribution and Mode 5 was an exponential increase in biomass with depth. The incidence of these distributions and the existence of a DCM were examined in relation to different turbulent diffusion rates{< 0.1 to 10 cm2 s-1 ), sinking rates {+10 to -4 m daf1), and light and nutrient limitation. A DCM was simulated when net growth of the population superceded losses from turbulent diffusion, sinking and zooplankton grazing. Light climate strongly influenced net rates of growth of the DCM assemblage and its position; surface blooms of cyanobacteria could obliterate the DCM by shading cells and suppressing light available for their growth. This finding has important implications for eutrophication of lakes with DCMs, as relatively small changes in surface phytoplankton communities, for example through additional nutrient inputs, could obliterate the DCM. The relevance of the diatom DCM phytoplankton is that it has important ecosystem-level effects through sedimentation of nutrients and organic matter, and transfer of biomass to higher trophic levels resulting from preferential grazing. 
Further examination of DCM communities was carried out in Lake Tikitapu, a small lake (mean depth 18 m, area 1.5 km2 ) in the Rotorua basin. The DCM assemblage in this lake comprised dinoflagellate species. The DCM persisted over the period of thermal stratification, in the metalimnion, and also at a depth where irradiance was approximately 2-3 % of the surface value. Statistical analysis found that the light level at the DCM was more important than the depth of thermocline in determining the depth of the DCM. There was no evidence of diurnal vertical migration of the DCM in Lake Tikitapu, but dispersion of the DCM varied seasonally, whereby the width was strongly positively correlated to the width of the metalimnion (r2 = 0.89, p < 0.01). Light and nutrient incubation experiments provided further evidence for the dominant role of light in influencing the DCM position. There was a biomass decrease in DCM populations that were incubated at high irradiance ( 40 % of surface irradiance ), suggesting that surface irradiances may be damaging or inhibitory to growth. 
A wide range of North Island lakes was investigated in an attempt to delineate the roles of lake mixing, trophic state and light climate in the composition of lake phytoplankton assemblages. For 40 lakes mixing regimes were divided into three classes; stable seasonal stratification, intermittent stratification and mixed, and trophic states were separated in oligotrophic, mesotrophic and eutrophic. In addition, average photosynthetically available radiation experienced by phytoplankton was determined based on integrated levels over the surface mixed layer, and values were divided into three regimes where 5 % or less corresponded to low light, 5 - 20 % to medium light, and > 20 % to high light. Non-metric multi-dimensional scaling (MDS) and analysis of similarities (ANOSIM) were used to detect patterns in phytoplankton composition between lakes and to infer which environmental variables were associated with underlying trends in composition. MDS showed a clear separation of stratified from intermittently stratified and mixed lakes based on phytoplankton composition, and phytoplankton assemblages in stably stratified lakes were significantly different from those in intermittently stratified lakes (p < 0.05) and mixed lakes (p < 0.05). However, results of ANOSIM indicated that trophic state was not a statistically significant factor influencing phytoplankton assemblage composition. Mixing regime therefore provided a more accurate predictor of summer phytoplankton composition than trophic state or light climate, as lakes of different trophic state but similar mixing regime had similar phytoplankton assemblages.
In this study, field work and modelling were used to contribute to the current understanding of spatial and temporal dynamics of phytoplankton in lakes, the roles and interactions of various environmental variables in governing populations, and implications of blooms on assemblage diversity. Phytoplankton assemblage composition and biomass are highly variable, but much of this variation may be explained through detailed analysis. Investigations into the vertical distributions of phytoplankton communities to ascertain the presence of a SCM or DCM, along with quantification of vertical stratification/mixing regimes in lakes, and interactions of buoyancy with horizontal transport in the surface mixed layer, will greatly facilitate in explaining the variability.

text: Phytoplankton dynamics in North Island lakes, New Zealand The dynamics of phytoplankton were investigated in 40 lakes of the North Island, New Zealand. A range of environmental variables was examined on different temporal and spatial scales in relation to the surface and DCM ( deep chlorophyll maximum) phytoplankton communities in the lakes. The environmental variables that were considered relevant to these communities included turbulent mixing, limitation by light and nutrients, rates of sedimentation or ascent, and zooplankton grazing. 
Cylindrospermopsis raciborskii is a potentially toxic species of cyanobacteria, that in summer 2002-3 formed dense water blooms (> 100 OOO cells/ml) in shallow (max. depth :5 Sm) Waikato peat lakes and a hydro-electric dam on the Waikato River. Net rates of growth calculated within individual lakes demonstrated that C. raciborskii populations grew at rates close to maximum values observed under optimal conditions in laboratory cultures. Changes in species diversity in the lakes prior to and following the invasion of C. raciborskii were assessed. During occasions of C. raciborskii water blooms there was decreased diversity and the phytoplankton assemblage became nearly mono-specific. The shallow lakes in this study have high concentrations of nutrients and low water clarity, which are ideal conditions for growth of C. raciborskii, as it has a competitive advantage at low irradiance but limited capacity for buoyancy. The ability of C. raciborskii to fix nitrogen may also have enhanced its competitive ability amongst other phytoplankton species and, while nutrients were generally considered to be replete, nitrogen was more likely to limit growth of phytoplankton than phosphorus in the lakes studied. 
Lake Tarawera, part of the Rotorua lakes region (area 41.6 km2 and mean depth 50 m), was chosen to investigate variability of phytoplankton biomass with depth and between embayments and a mid-lake station. The variability of DCM depth was contributed by internal seiching, which was most prominent at the edge of the lake. A single mid-lake station was considered representative of lake-wide biomass at the DCM as the differences between stations were small. However, during a bloom of Anabaena lemmermanni, there was large inter-station variability in phytoplankton biomass in the surface mixed layer. Therefore, when quantifying surface populations, particularly buoyant cyanobacterial species which tend to accumulate in bays, discrete samples at a single station and depth may not adequately represent lake-wide biomass. During periods when bloom-forming species are present, several sampling stations should be used to adequately quantify biomass and variability of phytoplankton in the surface mixed layer. 
A population-dynamics theory of sinking phytoplankton, that utilizes interactions between growth limitation by light and nutrients, sinking rates and turbulent diffusion rates, was used to quantify factors contributing to DCM formation in Lake Tarawera. Five 'Modes' of vertical phytoplankton of biomass were categorised relating to four forcing functions. The first mode was a surface chlorophyll maximum (SCM); Mode 2 was a DCM; Mode 3 was a simultaneous double peak of buoyant cyanobacteria and a DCM assemblage; Mode 4 was a linear vertical distribution and Mode 5 was an exponential increase in biomass with depth. The incidence of these distributions and the existence of a DCM were examined in relation to different turbulent diffusion rates{< 0.1 to 10 cm2 s-1 ), sinking rates {+10 to -4 m daf1), and light and nutrient limitation. A DCM was simulated when net growth of the population superceded losses from turbulent diffusion, sinking and zooplankton grazing. Light climate strongly influenced net rates of growth of the DCM assemblage and its position; surface blooms of cyanobacteria could obliterate the DCM by shading cells and suppressing light available for their growth. This finding has important implications for eutrophication of lakes with DCMs, as relatively small changes in surface phytoplankton communities, for example through additional nutrient inputs, could obliterate the DCM. The relevance of the diatom DCM phytoplankton is that it has important ecosystem-level effects through sedimentation of nutrients and organic matter, and transfer of biomass to higher trophic levels resulting from preferential grazing. 
Further examination of DCM communities was carried out in Lake Tikitapu, a small lake (mean depth 18 m, area 1.5 km2 ) in the Rotorua basin. The DCM assemblage in this lake comprised dinoflagellate species. The DCM persisted over the period of thermal stratification, in the metalimnion, and also at a depth where irradiance was approximately 2-3 % of the surface value. Statistical analysis found that the light level at the DCM was more important than the depth of thermocline in determining the depth of the DCM. There was no evidence of diurnal vertical migration of the DCM in Lake Tikitapu, but dispersion of the DCM varied seasonally, whereby the width was strongly positively correlated to the width of the metalimnion (r2 = 0.89, p < 0.01). Light and nutrient incubation experiments provided further evidence for the dominant role of light in influencing the DCM position. There was a biomass decrease in DCM populations that were incubated at high irradiance ( 40 % of surface irradiance ), suggesting that surface irradiances may be damaging or inhibitory to growth. 
A wide range of North Island lakes was investigated in an attempt to delineate the roles of lake mixing, trophic state and light climate in the composition of lake phytoplankton assemblages. For 40 lakes mixing regimes were divided into three classes; stable seasonal stratification, intermittent stratification and mixed, and trophic states were separated in oligotrophic, mesotrophic and eutrophic. In addition, average photosynthetically available radiation experienced by phytoplankton was determined based on integrated levels over the surface mixed layer, and values were divided into three regimes where 5 % or less corresponded to low light, 5 - 20 % to medium light, and > 20 % to high light. Non-metric multi-dimensional scaling (MDS) and analysis of similarities (ANOSIM) were used to detect patterns in phytoplankton composition between lakes and to infer which environmental variables were associated with underlying trends in composition. MDS showed a clear separation of stratified from intermittently stratified and mixed lakes based on phytoplankton composition, and phytoplankton assemblages in stably stratified lakes were significantly different from those in intermittently stratified lakes (p < 0.05) and mixed lakes (p < 0.05). However, results of ANOSIM indicated that trophic state was not a statistically significant factor influencing phytoplankton assemblage composition. Mixing regime therefore provided a more accurate predictor of summer phytoplankton composition than trophic state or light climate, as lakes of different trophic state but similar mixing regime had similar phytoplankton assemblages.
In this study, field work and modelling were used to contribute to the current understanding of spatial and temporal dynamics of phytoplankton in lakes, the roles and interactions of various environmental variables in governing populations, and implications of blooms on assemblage diversity. Phytoplankton assemblage composition and biomass are highly variable, but much of this variation may be explained through detailed analysis. Investigations into the vertical distributions of phytoplankton communities to ascertain the presence of a SCM or DCM, along with quantification of vertical stratification/mixing regimes in lakes, and interactions of buoyancy with horizontal transport in the surface mixed layer, will greatly facilitate in explaining the variability.

year: 2006

title: Indigenous Language Usage in a Digital Library: He Hautoa Kia Ora Tonu Ai.

authors: Keegan, Te Taka Adrian Gregory

subjects: indigenous language

abstract: The research described in this thesis examines indigenous language usage in a digital library environment that has been accessed via the Internet.

By examining discretionary use of the Māori Niupepa and Hawaiian Nūpepa digital libraries this research investigates how indigenous languages were used in these electronic environments in 2005. The results provide encouragement and optimism to people who are striving to retain, revitalise and develop the use of indigenous languages in information technologies. The Transaction Log Analysis (TLA) methods used in this research serve as an example of how web logs can be used to provide significant information about language usage in a bilingual online information system. Combining the TLA with user feedback has provided insights into how and why clients use indigenous languages in their information retrieval activities. These insights in turn, show good practice that is relevant not only to those working with indigenous languages, indigenous peoples or multilingual environments, but to all information technology designers who strive for universal usability.
This thesis begins by describing the importance of using indigenous languages in electronic environments and suggests that digital libraries can provide an environment to support and encourage the use of such languages. TLA is explained in the context of this study and is then used to analyse aspects of te reo Māori usage in the Niupepa digital library environment in 2005. TLA also indicates that te reo Māori was used by international clients and this usage differed to te reo Māori usage by national (Aotearoa) clients. Findings further reveal that the default language setting of the Niupepa digital library had a considerable impact on te reo Māori usage. When the default language was set to te reo Māori not only were there more requests in te reo Māori but there was also a higher usage of te reo Māori in the information retrieval activities. TLA of the Hawaiian Nūpepa digital library indicated that the Hawaiian language was also used in a digital library. These results confirm that indigenous languages were used in digital library environments. 
Feedback from clients suggests reasons why indigenous languages were used in this environment. These reasons include the indigenous language content of the digital library, the indigenous language default language setting of the digital library and a stated desire by the clients to use the indigenous language. The key findings raise some interface design issues and support the claim that digital libraries can provide an environment to support the use of indigenous languages.

text: Indigenous Language Usage in a Digital Library: He Hautoa Kia Ora Tonu Ai. The research described in this thesis examines indigenous language usage in a digital library environment that has been accessed via the Internet.

By examining discretionary use of the Māori Niupepa and Hawaiian Nūpepa digital libraries this research investigates how indigenous languages were used in these electronic environments in 2005. The results provide encouragement and optimism to people who are striving to retain, revitalise and develop the use of indigenous languages in information technologies. The Transaction Log Analysis (TLA) methods used in this research serve as an example of how web logs can be used to provide significant information about language usage in a bilingual online information system. Combining the TLA with user feedback has provided insights into how and why clients use indigenous languages in their information retrieval activities. These insights in turn, show good practice that is relevant not only to those working with indigenous languages, indigenous peoples or multilingual environments, but to all information technology designers who strive for universal usability.
This thesis begins by describing the importance of using indigenous languages in electronic environments and suggests that digital libraries can provide an environment to support and encourage the use of such languages. TLA is explained in the context of this study and is then used to analyse aspects of te reo Māori usage in the Niupepa digital library environment in 2005. TLA also indicates that te reo Māori was used by international clients and this usage differed to te reo Māori usage by national (Aotearoa) clients. Findings further reveal that the default language setting of the Niupepa digital library had a considerable impact on te reo Māori usage. When the default language was set to te reo Māori not only were there more requests in te reo Māori but there was also a higher usage of te reo Māori in the information retrieval activities. TLA of the Hawaiian Nūpepa digital library indicated that the Hawaiian language was also used in a digital library. These results confirm that indigenous languages were used in digital library environments. 
Feedback from clients suggests reasons why indigenous languages were used in this environment. These reasons include the indigenous language content of the digital library, the indigenous language default language setting of the digital library and a stated desire by the clients to use the indigenous language. The key findings raise some interface design issues and support the claim that digital libraries can provide an environment to support the use of indigenous languages.

year: 2007