title: A validation study of phycocyanin sensors for monitoring cyanobacteria in cultures and field samples

authors: Hodges, Caroline Marie

subjects: Phycocycanin

abstract: Cyanobacteria are photosynthetic prokaryotes present in almost all terrestrial and aquatic environments. Under favourable conditions of high nutrient inputs, high water temperature and adequate light, they can rapidly multiply and form blooms. Cyanobacterial blooms are harmful to aquatic processes as they reduce the amount of irradiance within the water column and some have the ability to produce toxins which pose a risk to human and animal health. Cyanobacterial blooms are becoming prevalent worldwide as a result of increased anthropogenic influences. To enable accurate risk assessment of drinking water reservoirs, water bodies for recreational use and to assist in the understanding of bloom dynamics, cyanobacterial biomass must be quantified. Traditionally this was done via grab sampling, the use of microscopy and measurements of chlorophyll-a concentration using spectrophotometry. These methods do not allow samples to be collected and analysed at a frequency that provides meaningful spatial and temporal resolution. Additionally, they can be time consuming, expensive and require taxonomic expertise. 

Measurements of chlorophyll-a concentration can provide an estimate of overall phytoplankton biomass but cannot differentiate between eukaryotic cells and cyanobacteria. However, the fluorescent pigment phycocyanin is specific to cyanobacteria and has a unique fluorescence signature which can enable the estimation of cyanobacteria biomass. Methods to detect phycocyanin fluorescence have been integrated into handheld sensors which can be used as a proxy for estimation of cyanobacterial biomass in situ. However, robust validation of these sensors is rarely undertaken. Previous use of fluorescence sensors suggest that there may be multiple sources of interference of the optical signal. The aim of this study was to assess the performance of commercially-available phycocyanin sensors using a combination of culture-based laboratory experiments and a field investigation.

The laboratory studies showed strong linear relationships between phycocyanin and chlorophyll-a fluorescence from sensors and cyanobacterial biovolume obtained by microscopy. This was observed across a range of cell concentrations for solitary (e.g. Microcystis sp.) and filamentous species (e.g. Aphanizomenon sp.). However this linear relationship was not observed with colonial and some filamentous cyanobacteria (Microcystis sp., Nodularia spumigena, and Dolichospermum sp.). Further investigation suggested that the morphology of densely aggregated species inhibited the penetration of light into the colony, resulting in an underestimation of phycocyanin. These results highlight a potential limitation for the use of phycocyanin sensors in situ as colonial and filamentous cyanobacteria are often observed. Other potential limitations for the use of phycocyanin sensors include natural variations in light intensity which can cause photobleaching; reducing fluorescence, as well as increased variability of phycocyanin fluorescence with changes in temperature.  

Field experiments during this study showed that extracellular phycocyanin from lysed cells could in some instances account for more than 20% of the total phycocyanin fluorescence. The field study also showed a strong linear relationship between measurements of phycocyanin fluorescence and cyanobacterial biovolume. However measurements of chlorophyll-a were poorly correlated to cyanobacterial biovolume. The results from the field experiments indicate that phycocyanin sensors may be a valuable tool to monitor cyanobacteria biomass in the field. Collectively, this data highlights the potential for the use of phycocyanin sensors to obtain high frequency data on cyanobacterial biomass, while also demonstrating limitations for their use in situ. Further study is needed to determine more definitively the effects of these potential limitations on phycocyanin measurements and which supplementary parameters could be measured in order for the data collected to be more robust and informative.

text: A validation study of phycocyanin sensors for monitoring cyanobacteria in cultures and field samples Cyanobacteria are photosynthetic prokaryotes present in almost all terrestrial and aquatic environments. Under favourable conditions of high nutrient inputs, high water temperature and adequate light, they can rapidly multiply and form blooms. Cyanobacterial blooms are harmful to aquatic processes as they reduce the amount of irradiance within the water column and some have the ability to produce toxins which pose a risk to human and animal health. Cyanobacterial blooms are becoming prevalent worldwide as a result of increased anthropogenic influences. To enable accurate risk assessment of drinking water reservoirs, water bodies for recreational use and to assist in the understanding of bloom dynamics, cyanobacterial biomass must be quantified. Traditionally this was done via grab sampling, the use of microscopy and measurements of chlorophyll-a concentration using spectrophotometry. These methods do not allow samples to be collected and analysed at a frequency that provides meaningful spatial and temporal resolution. Additionally, they can be time consuming, expensive and require taxonomic expertise. 

Measurements of chlorophyll-a concentration can provide an estimate of overall phytoplankton biomass but cannot differentiate between eukaryotic cells and cyanobacteria. However, the fluorescent pigment phycocyanin is specific to cyanobacteria and has a unique fluorescence signature which can enable the estimation of cyanobacteria biomass. Methods to detect phycocyanin fluorescence have been integrated into handheld sensors which can be used as a proxy for estimation of cyanobacterial biomass in situ. However, robust validation of these sensors is rarely undertaken. Previous use of fluorescence sensors suggest that there may be multiple sources of interference of the optical signal. The aim of this study was to assess the performance of commercially-available phycocyanin sensors using a combination of culture-based laboratory experiments and a field investigation.

The laboratory studies showed strong linear relationships between phycocyanin and chlorophyll-a fluorescence from sensors and cyanobacterial biovolume obtained by microscopy. This was observed across a range of cell concentrations for solitary (e.g. Microcystis sp.) and filamentous species (e.g. Aphanizomenon sp.). However this linear relationship was not observed with colonial and some filamentous cyanobacteria (Microcystis sp., Nodularia spumigena, and Dolichospermum sp.). Further investigation suggested that the morphology of densely aggregated species inhibited the penetration of light into the colony, resulting in an underestimation of phycocyanin. These results highlight a potential limitation for the use of phycocyanin sensors in situ as colonial and filamentous cyanobacteria are often observed. Other potential limitations for the use of phycocyanin sensors include natural variations in light intensity which can cause photobleaching; reducing fluorescence, as well as increased variability of phycocyanin fluorescence with changes in temperature.  

Field experiments during this study showed that extracellular phycocyanin from lysed cells could in some instances account for more than 20% of the total phycocyanin fluorescence. The field study also showed a strong linear relationship between measurements of phycocyanin fluorescence and cyanobacterial biovolume. However measurements of chlorophyll-a were poorly correlated to cyanobacterial biovolume. The results from the field experiments indicate that phycocyanin sensors may be a valuable tool to monitor cyanobacteria biomass in the field. Collectively, this data highlights the potential for the use of phycocyanin sensors to obtain high frequency data on cyanobacterial biomass, while also demonstrating limitations for their use in situ. Further study is needed to determine more definitively the effects of these potential limitations on phycocyanin measurements and which supplementary parameters could be measured in order for the data collected to be more robust and informative.

year: 2016

title: Unusual microorganisms observed in New Zealand hot springs

authors: Patel, B.K.C.

subjects: biology

abstract: A technique is described for studying hot spring microbial morphotypes by using electron microscope grids incubatedin situ. Such studies revealed the presence of filaments bearing swollen saclike structures in a number of New Zealand hot springs. There was considerable variation in the size, structure, and morphology of the filaments and the saclike structures.

text: Unusual microorganisms observed in New Zealand hot springs A technique is described for studying hot spring microbial morphotypes by using electron microscope grids incubatedin situ. Such studies revealed the presence of filaments bearing swollen saclike structures in a number of New Zealand hot springs. There was considerable variation in the size, structure, and morphology of the filaments and the saclike structures.

year: 1986

title: Equity, inclusivity and shared humanity:  Addressing intergenerational failure of schooling for Māori

authors: Egan, Margaret

subjects: Equity of Māori learners

abstract: Despite decades of education reform aimed at Māori students succeeding in schooling, the New Zealand education system’s failure to engage effectively with Māori is persistent with Māori underachievement remaining chronic and seemingly intractable.
This thesis examines the interface between leadership and professional learning in a single sex secondary school during their engagement with Te Kotahitanga (Unity of Purpose). The school’s leaders were focused on closing the achievement gap between Māori and non-Māori students and asserted that if students remained engaged at school into the senior year levels, they were more likely to “achieve success”. Te Kotahitanga’s initial focus on teaching and learning in the junior years 9 and 10 presented a potential solution. As this school began to engage with Te Kotahitanga, Ka Hikitia (to step up), a strategy aimed at Māori students achieving educational success as Māori, was launched. Thus, a mandate for school reform focused on Māori potential supported the professional learning provided by Te Kotahitanga.
The findings, presented as quantitative and qualitative evidence, show that school leaders focused on their teachers implementing a more culturally responsive and relational pedagogy at Years 9 and 10 in order to close the achievement gap between Māori and their non-Māori peers. They believed that this would prepare Māori students for the more formal and traditional learning experience required in the senior school, aimed at getting through important national qualifications. While teachers and leaders who were fully engaged in Te Kotahitanga transformed the classroom experiences for their junior and senior learners, not all teachers and leaders engaged, therefore not all learners experienced the change in pedagogy throughout their time at this school. The findings also uncover layers of bias within the school and its community which prevented Māori families from contributing to their children’s education on their own terms. The two key foci, closing the achievement gap between Māori and non-Māori and retaining Māori students into the senior school obfuscated a focus on shared humanity, equity, belonging and better engagement for all.
While this research took place in New Zealand with Māori students these findings can contribute to those involved with school reform especially those in other colonised countries where indigenous students and their families face similar issues.

text: Equity, inclusivity and shared humanity:  Addressing intergenerational failure of schooling for Māori Despite decades of education reform aimed at Māori students succeeding in schooling, the New Zealand education system’s failure to engage effectively with Māori is persistent with Māori underachievement remaining chronic and seemingly intractable.
This thesis examines the interface between leadership and professional learning in a single sex secondary school during their engagement with Te Kotahitanga (Unity of Purpose). The school’s leaders were focused on closing the achievement gap between Māori and non-Māori students and asserted that if students remained engaged at school into the senior year levels, they were more likely to “achieve success”. Te Kotahitanga’s initial focus on teaching and learning in the junior years 9 and 10 presented a potential solution. As this school began to engage with Te Kotahitanga, Ka Hikitia (to step up), a strategy aimed at Māori students achieving educational success as Māori, was launched. Thus, a mandate for school reform focused on Māori potential supported the professional learning provided by Te Kotahitanga.
The findings, presented as quantitative and qualitative evidence, show that school leaders focused on their teachers implementing a more culturally responsive and relational pedagogy at Years 9 and 10 in order to close the achievement gap between Māori and their non-Māori peers. They believed that this would prepare Māori students for the more formal and traditional learning experience required in the senior school, aimed at getting through important national qualifications. While teachers and leaders who were fully engaged in Te Kotahitanga transformed the classroom experiences for their junior and senior learners, not all teachers and leaders engaged, therefore not all learners experienced the change in pedagogy throughout their time at this school. The findings also uncover layers of bias within the school and its community which prevented Māori families from contributing to their children’s education on their own terms. The two key foci, closing the achievement gap between Māori and non-Māori and retaining Māori students into the senior school obfuscated a focus on shared humanity, equity, belonging and better engagement for all.
While this research took place in New Zealand with Māori students these findings can contribute to those involved with school reform especially those in other colonised countries where indigenous students and their families face similar issues.

year: 2022