title: Relationships between cyanobacteria and water colour in Central North Island lakes of contrasting trophic status

authors: Reed, Lisa

subjects: Cyanobacteria

abstract: Nutrient enrichment of lakes and rising global temperatures promote the proliferation of cyanobacteria. Cyanobacterial blooms are becoming more widespread and increasing in frequency, size and duration, causing a cascade of detrimental changes to freshwater ecosystems. Improved lake monitoring techniques are required for early detection of bloom initiation to allow mitigation measures to be better targeted. Recent studies suggest remote sensing of the reflectance spectra of lakes can be a valuable tool to map the distribution of potentially toxic cyanobacteria in near-real time, though as yet, these are not widely used in New Zealand. In this study, three Rotorua and five Waikato Lakes were sampled to determine hyperspectral reflectance, phytoplankton composition and biovolume, chlorophyll a, phycocyanin concentrations, and optically active constituents. The data obtained were used to develop algorithms to examine the utility of reflectance data to aid in estimations of chlorophyll a and phycocyanin concentrations and phytoplankton composition with a particular focus on cyanobacteria. Results show that relationships amongst reflectance-related attributes, including chromophoric dissolved organic material, suspended solids and absorption properties of phytoplankton and pigment concentrations varied among the lakes and, to varying extents, over time. Properties of specific regions of reflectance spectra could be used to predict concentrations of these two pigments, but reflectance was not effective in separating the effects of phytoplankton composition from the other optically active variables. The two algorithms best suited these lakes for estimation of chlorophyll a and phycocyanin showed strong relations with the observed pigments at R2 = 0.83 and R2 = 0.92, respectively. This suggests reflectance spectra and the appropriate algorithm can be used to yield estimations of chlorophyll a and phycocyanin concentrations within inland waters with a wide variation of bio-optical characteristics. Such information could contribute to the development of an early warning system to predict cyanobacterial biovolume in New Zealand lakes using remote sensing.

text: Relationships between cyanobacteria and water colour in Central North Island lakes of contrasting trophic status Nutrient enrichment of lakes and rising global temperatures promote the proliferation of cyanobacteria. Cyanobacterial blooms are becoming more widespread and increasing in frequency, size and duration, causing a cascade of detrimental changes to freshwater ecosystems. Improved lake monitoring techniques are required for early detection of bloom initiation to allow mitigation measures to be better targeted. Recent studies suggest remote sensing of the reflectance spectra of lakes can be a valuable tool to map the distribution of potentially toxic cyanobacteria in near-real time, though as yet, these are not widely used in New Zealand. In this study, three Rotorua and five Waikato Lakes were sampled to determine hyperspectral reflectance, phytoplankton composition and biovolume, chlorophyll a, phycocyanin concentrations, and optically active constituents. The data obtained were used to develop algorithms to examine the utility of reflectance data to aid in estimations of chlorophyll a and phycocyanin concentrations and phytoplankton composition with a particular focus on cyanobacteria. Results show that relationships amongst reflectance-related attributes, including chromophoric dissolved organic material, suspended solids and absorption properties of phytoplankton and pigment concentrations varied among the lakes and, to varying extents, over time. Properties of specific regions of reflectance spectra could be used to predict concentrations of these two pigments, but reflectance was not effective in separating the effects of phytoplankton composition from the other optically active variables. The two algorithms best suited these lakes for estimation of chlorophyll a and phycocyanin showed strong relations with the observed pigments at R2 = 0.83 and R2 = 0.92, respectively. This suggests reflectance spectra and the appropriate algorithm can be used to yield estimations of chlorophyll a and phycocyanin concentrations within inland waters with a wide variation of bio-optical characteristics. Such information could contribute to the development of an early warning system to predict cyanobacterial biovolume in New Zealand lakes using remote sensing.

year: 2022

title: Cost-effective mitigation of greenhouse gas emissions from different dairy systems in the Waikato region of New Zealand

authors: Adler, Alfredo A.

subjects: dairy production

abstract: The New Zealand dairy industry produces approximately 17% of this country's total greenhouse gas emissions (GHG-e) and it is also this nation's largest export industry. The industry needs to reduce GHG-e under proposed policy directives and for ongoing market security. Given these pressures, there is the need to identify cost-effective management strategies to reduce on-farm GHG-e. The objective of this study was to investigate how the management of dairy farms in the Waikato region of New Zealand could change to minimise the abatement costs associated with GHG-e mitigation. Three typical farm systems importing low (less than 10%), medium (10–20%), and high (more than 20%) amounts of supplement are modelled using a non-linear optimisation model.

A reduction in nitrogen fertiliser application was the production factor that changed the most to achieve the cap in all of the simulated systems, followed by a reduction in stocking rate. With the prices used in this study, decreasing farming intensity by reducing nitrogen fertiliser by 21–42% and stocking rate by 8–10% represented a cost of $68–$119/ha and a production reduction of 54–117 kg MS/ha for the three systems studied. Improving reproductive performance proved to be effective in reducing GHG-e, allowing for fewer replacement cows to be supported. However, it did not have a significant effect on profit when emissions were unconstrained. Nitrification inhibitors and stand-off pads were not identified as useful mitigation options, given their high cost relative to de-intensification.

text: Cost-effective mitigation of greenhouse gas emissions from different dairy systems in the Waikato region of New Zealand The New Zealand dairy industry produces approximately 17% of this country's total greenhouse gas emissions (GHG-e) and it is also this nation's largest export industry. The industry needs to reduce GHG-e under proposed policy directives and for ongoing market security. Given these pressures, there is the need to identify cost-effective management strategies to reduce on-farm GHG-e. The objective of this study was to investigate how the management of dairy farms in the Waikato region of New Zealand could change to minimise the abatement costs associated with GHG-e mitigation. Three typical farm systems importing low (less than 10%), medium (10–20%), and high (more than 20%) amounts of supplement are modelled using a non-linear optimisation model.

A reduction in nitrogen fertiliser application was the production factor that changed the most to achieve the cap in all of the simulated systems, followed by a reduction in stocking rate. With the prices used in this study, decreasing farming intensity by reducing nitrogen fertiliser by 21–42% and stocking rate by 8–10% represented a cost of $68–$119/ha and a production reduction of 54–117 kg MS/ha for the three systems studied. Improving reproductive performance proved to be effective in reducing GHG-e, allowing for fewer replacement cows to be supported. However, it did not have a significant effect on profit when emissions were unconstrained. Nitrification inhibitors and stand-off pads were not identified as useful mitigation options, given their high cost relative to de-intensification.

year: 2013

title: Māori language interfaces

authors: Keegan, Te Taka Adrian Gregory

abstract: This paper considers the usability of the interface and the ramifications for te reo Māori if the interface language, the messages displayed in those text boxes, is written in te reo Māori.

text: Māori language interfaces This paper considers the usability of the interface and the ramifications for te reo Māori if the interface language, the messages displayed in those text boxes, is written in te reo Māori.

year: 2017