title: Toxicity assessment of chlorophenols using a mediated microbial toxicity assay

authors: Pasco, Neil F.

subjects: direct toxicity assessment

abstract: While direct toxicity assessment (DTA) is now widely recognised as a useful tool for environmental risk assessment, many existing tests fail to meet end-user needs. This article describes the significant progress made to the MICREDOX® DTA assay, developed at Lincoln Ventures Ltd, brought about by miniaturising this assay to a multi-well plate format combined with limiting current microelectrode transduction. The benefits have been reduced: preparation time, reduced assay time, lower material costs and a higher level of replication achieved. To validate the precision of the miniaturised format, the concentrations required to cause a 50% decrease in signal (EC50) by an archetypal group of toxicants, the chlorophenols, were determined using two terrestrial bacterial strains, Escherichia coli K12 and Klebsiella oxytoca 13183. The assay time was then reduced by stepwise adjustment of the incubation time, from 60 down to 5 min, and the EC50s reported by E. coli to each of the toxicants after 45, 30, 15 and 5 min incubations were determined. The results obtained match closely with those reported by the Activated Sludge Respiration Inhibition Test and confirm the miniaturised multi-well plate MICREDOX® DTA assay reliably reports representative EC50 values for these toxicants. The previously described trends of increasing toxicity with increasing chlorine substitution and the observation that meta-substituted chlorophenols are more toxic than their ortho-substituted counterparts are also confirmed. The ability to monitor toxicity using terrestrial organisms, in volumes amenable to multi-well microtitre plates and incubations requiring only a few minutes, facilitates the rapid generation of highly reproducible, easy to operate and inexpensive DTA measurements.

text: Toxicity assessment of chlorophenols using a mediated microbial toxicity assay While direct toxicity assessment (DTA) is now widely recognised as a useful tool for environmental risk assessment, many existing tests fail to meet end-user needs. This article describes the significant progress made to the MICREDOX® DTA assay, developed at Lincoln Ventures Ltd, brought about by miniaturising this assay to a multi-well plate format combined with limiting current microelectrode transduction. The benefits have been reduced: preparation time, reduced assay time, lower material costs and a higher level of replication achieved. To validate the precision of the miniaturised format, the concentrations required to cause a 50% decrease in signal (EC50) by an archetypal group of toxicants, the chlorophenols, were determined using two terrestrial bacterial strains, Escherichia coli K12 and Klebsiella oxytoca 13183. The assay time was then reduced by stepwise adjustment of the incubation time, from 60 down to 5 min, and the EC50s reported by E. coli to each of the toxicants after 45, 30, 15 and 5 min incubations were determined. The results obtained match closely with those reported by the Activated Sludge Respiration Inhibition Test and confirm the miniaturised multi-well plate MICREDOX® DTA assay reliably reports representative EC50 values for these toxicants. The previously described trends of increasing toxicity with increasing chlorine substitution and the observation that meta-substituted chlorophenols are more toxic than their ortho-substituted counterparts are also confirmed. The ability to monitor toxicity using terrestrial organisms, in volumes amenable to multi-well microtitre plates and incubations requiring only a few minutes, facilitates the rapid generation of highly reproducible, easy to operate and inexpensive DTA measurements.

year: 2008

title: Acetylene reduction associated with zostera novazelandica Setch. and Spartina alterniflora Loisel., in Whangateau harbour, North Island, New Zealand

authors: Hicks, Brendan J.

subjects: biology

abstract: Nitrogen fixation (acetylene reduction) was investigated in Zostera novazelandica Setch. and Spartina alterniflora Loisel., in the North Island of New Zealand. Moderate rates of acetylene reduction were found in sediments in which plants were growing (means ± 95% confidence limit: 15.2 ± 2.8 |jmol C2H4 nrr2 h~l for Zostera and 24.7 ± 4.6 |amol C2H4 m~2 h"1 for Spartina). Activity was closely correlated with the dry weight of root; (r2 = 0.65, N = 15 for Zostera, and r2 = 0.85, A' =10 for Spartina). Sediment close to the plant beds, but without plants, exhibited only low rates of acetylene reduction (2.9 ± 2.2 and 4.5 ± l.OjLtmol C2H4 m~2 h"1, respectively). Sediments associated with Z. novazelandica and S. alterniflora in New Zealand exhibit moderate rates of nitrogenase activity compared to rates found in other countries. N fixation may contribute significantly to the nutrition of these plants in New Zealand estuaries.

text: Acetylene reduction associated with zostera novazelandica Setch. and Spartina alterniflora Loisel., in Whangateau harbour, North Island, New Zealand Nitrogen fixation (acetylene reduction) was investigated in Zostera novazelandica Setch. and Spartina alterniflora Loisel., in the North Island of New Zealand. Moderate rates of acetylene reduction were found in sediments in which plants were growing (means ± 95% confidence limit: 15.2 ± 2.8 |jmol C2H4 nrr2 h~l for Zostera and 24.7 ± 4.6 |amol C2H4 m~2 h"1 for Spartina). Activity was closely correlated with the dry weight of root; (r2 = 0.65, N = 15 for Zostera, and r2 = 0.85, A' =10 for Spartina). Sediment close to the plant beds, but without plants, exhibited only low rates of acetylene reduction (2.9 ± 2.2 and 4.5 ± l.OjLtmol C2H4 m~2 h"1, respectively). Sediments associated with Z. novazelandica and S. alterniflora in New Zealand exhibit moderate rates of nitrogenase activity compared to rates found in other countries. N fixation may contribute significantly to the nutrition of these plants in New Zealand estuaries.

year: 1990

title: Kaupapa Maori research: An indigenous approach to creating knowledge

authors: Bishop, Russell

subjects: Maori

abstract: This paper seeks to identify how issues of epistemological racism are addressed in practice
within an indigenous Kaupapa (philosophy) Maori approach to research, and how such
considerations may impact on the Western trained and positioned researcher. One fundamental
understanding to a Kaupapa Maori approach to research is that it is the discursive practice
that is Kaupapa Maori that positions researchers in such a way as to operationalise selfdetermination
(agentic positioning and behaviour) for research participants. This is because the
cultural aspirations, understandings and practices of Maori people implement and organise the
research process. Further, the research issues of power; initiation, benefits, representation,
legitimation, and accountability are addressed and understood in practice by practitioners of
Kaupapa Maori research through the development of a participatory mode of consciousness.

text: Kaupapa Maori research: An indigenous approach to creating knowledge This paper seeks to identify how issues of epistemological racism are addressed in practice
within an indigenous Kaupapa (philosophy) Maori approach to research, and how such
considerations may impact on the Western trained and positioned researcher. One fundamental
understanding to a Kaupapa Maori approach to research is that it is the discursive practice
that is Kaupapa Maori that positions researchers in such a way as to operationalise selfdetermination
(agentic positioning and behaviour) for research participants. This is because the
cultural aspirations, understandings and practices of Maori people implement and organise the
research process. Further, the research issues of power; initiation, benefits, representation,
legitimation, and accountability are addressed and understood in practice by practitioners of
Kaupapa Maori research through the development of a participatory mode of consciousness.

year: 1999