title: Seasonal Variation in Bivalve Antioxidant Enzymes: Can they be used as indicators of heavy metal contamination?

authors: Gibson, Aimee Clare

subjects: Biomarkers

abstract: Seasonal variations in the activity of several enzymes (glutathione reductase (GR), glutathione S-transferase (GST), and glutathione peroxidase (GPx)) involved in the glutathione cellular defence system were measured in whole tissues of the common New Zealand cockle (Austrovenus stutchburyi) as biomarkers of oxidative stress.  Three sites (Glendowie, Panmure, and Tiraumea) were sampled in Tamaki Estuary, Auckland, New Zealand, that represented a heavy metal contamination gradient.  These sites were selected as metal contaminants can affect the activity of antioxidant enzymes by increasing the formation of reactive oxygen species, therefore these enzymes have been proposed as biomarkers of diminished health.  Cockles from the three sites were expected to show differences in enzyme activities due to the gradient in metal levels.  Sites were sampled monthly over a thirteen month period, from April 2007 - April 2008.  Environmental co-variables (sediment silt-clay fraction, organic matter content, chlorophyll a, median grain size, cockle condition index, water temperature and salinity) were also measured in order to relate biomarker activities to them.  From these measures it was established that a gradient existed in sediment properties, water parameters, and condition index, among the three study sites.  Condition index significantly correlated with both GPx (r = 0.761) and GST (r = 0.721) activity, therefore condition index provides a good measure of overall health.  The silt-clay fraction of the sediment also showed a significant negative correlation with both GPx (r = -0.558) and GST (r = -0.498).  GPx was the only enzyme to have significant correlations with metal concentrations including, Pb sediment concentration (r = -0.561), Cu sediment concentration (r = -0.539) and Cu tissue concentration (r = -0.530).  Therefore this enzyme showed the most promise as a biomarker of contamination.  The highest GPx and GST activities were measured in cockles from Glendowie, this site was characterised by lower concentrations of metals.  There was seasonality observed in the activity of GPx and GST.  The activity of these enzymes greatly increased from January onwards, and remained elevated for the remainder of the sampling period (until April 2008) this increase however, was more pronounced at Glendowie.  The increase in enzyme activity in January could have been the result of a number of reasons including 1) changes in the cockles metabolic status due to gonadal development and spawning 2) a combination of environmental co-variables not measured in this study, or 3) a recovery from a stress event that occurred prior to sampling.  Both GST and GPx showed promise as biomarkers of contamination; however GR did not as there were little differences in enzyme activities among sites.  Further annual sampling at these sites should be carried out to determine if the increased GST and GPx activities in summer were the result of an abnormal event or a typical seasonal variation that occurs annually.

text: Seasonal Variation in Bivalve Antioxidant Enzymes: Can they be used as indicators of heavy metal contamination? Seasonal variations in the activity of several enzymes (glutathione reductase (GR), glutathione S-transferase (GST), and glutathione peroxidase (GPx)) involved in the glutathione cellular defence system were measured in whole tissues of the common New Zealand cockle (Austrovenus stutchburyi) as biomarkers of oxidative stress.  Three sites (Glendowie, Panmure, and Tiraumea) were sampled in Tamaki Estuary, Auckland, New Zealand, that represented a heavy metal contamination gradient.  These sites were selected as metal contaminants can affect the activity of antioxidant enzymes by increasing the formation of reactive oxygen species, therefore these enzymes have been proposed as biomarkers of diminished health.  Cockles from the three sites were expected to show differences in enzyme activities due to the gradient in metal levels.  Sites were sampled monthly over a thirteen month period, from April 2007 - April 2008.  Environmental co-variables (sediment silt-clay fraction, organic matter content, chlorophyll a, median grain size, cockle condition index, water temperature and salinity) were also measured in order to relate biomarker activities to them.  From these measures it was established that a gradient existed in sediment properties, water parameters, and condition index, among the three study sites.  Condition index significantly correlated with both GPx (r = 0.761) and GST (r = 0.721) activity, therefore condition index provides a good measure of overall health.  The silt-clay fraction of the sediment also showed a significant negative correlation with both GPx (r = -0.558) and GST (r = -0.498).  GPx was the only enzyme to have significant correlations with metal concentrations including, Pb sediment concentration (r = -0.561), Cu sediment concentration (r = -0.539) and Cu tissue concentration (r = -0.530).  Therefore this enzyme showed the most promise as a biomarker of contamination.  The highest GPx and GST activities were measured in cockles from Glendowie, this site was characterised by lower concentrations of metals.  There was seasonality observed in the activity of GPx and GST.  The activity of these enzymes greatly increased from January onwards, and remained elevated for the remainder of the sampling period (until April 2008) this increase however, was more pronounced at Glendowie.  The increase in enzyme activity in January could have been the result of a number of reasons including 1) changes in the cockles metabolic status due to gonadal development and spawning 2) a combination of environmental co-variables not measured in this study, or 3) a recovery from a stress event that occurred prior to sampling.  Both GST and GPx showed promise as biomarkers of contamination; however GR did not as there were little differences in enzyme activities among sites.  Further annual sampling at these sites should be carried out to determine if the increased GST and GPx activities in summer were the result of an abnormal event or a typical seasonal variation that occurs annually.

year: 2009

title: A novel ‘FlocDrifter’ platform for observing flocculation and turbulence processes in a Lagrangian frame of reference

authors: MacDonald, Iain T.

abstract: A novel drifter platform was used to measure the properties of aggregated particles called flocs—a key component of sediment transport in muddy environments. Also concurrently measured were turbulence, suspended sediment concentration (SSC), velocity, and salinity in both Lagrangian and Eulerian frames of reference. In Lagrangian mode the system performed well in a heavily sediment-laden river, providing measurements over a large spatial scale. The platform navigated itself through a complex geometry encompassing many bends and significant depth changes. Observed velocities relative to the drifter and salinities indicated that the drifter motion was almost Lagrangian with minimal slippage between the drifter and the water motion. The small amount of slippage that did occur was sufficient to ensure that the drifter oriented itself into the oncoming flow. 
High-quality in situ images of flocs were collected using a high-magnification floc camera (FlocCam). An automatic image analysis routine was developed to identify and characterize flocs within each FlocCam image, employing an artificial neural network (ANN) to ensure that only in-focus particles were included in the analyses. The results indicated that the FlocCam system had an upper working SSC limit of around 350–400 mg L⁻¹. 
The SSC estimates show that the drifters encountered considerable variability as they were advected downstream; however, concentrations predominantly remained under the image processing threshold of 350–400 mg L⁻¹. The system captured the evolution of floc characteristics over short spatial scales (hundreds of meters). The median floc size (d₅₀) was found to be positively correlated with SSC (r² = 0.5). A comparison between Eulerian and Lagrangian floc histories can then be used to evaluate the role of antecedent conditions within the flocculation process.

text: A novel ‘FlocDrifter’ platform for observing flocculation and turbulence processes in a Lagrangian frame of reference A novel drifter platform was used to measure the properties of aggregated particles called flocs—a key component of sediment transport in muddy environments. Also concurrently measured were turbulence, suspended sediment concentration (SSC), velocity, and salinity in both Lagrangian and Eulerian frames of reference. In Lagrangian mode the system performed well in a heavily sediment-laden river, providing measurements over a large spatial scale. The platform navigated itself through a complex geometry encompassing many bends and significant depth changes. Observed velocities relative to the drifter and salinities indicated that the drifter motion was almost Lagrangian with minimal slippage between the drifter and the water motion. The small amount of slippage that did occur was sufficient to ensure that the drifter oriented itself into the oncoming flow. 
High-quality in situ images of flocs were collected using a high-magnification floc camera (FlocCam). An automatic image analysis routine was developed to identify and characterize flocs within each FlocCam image, employing an artificial neural network (ANN) to ensure that only in-focus particles were included in the analyses. The results indicated that the FlocCam system had an upper working SSC limit of around 350–400 mg L⁻¹. 
The SSC estimates show that the drifters encountered considerable variability as they were advected downstream; however, concentrations predominantly remained under the image processing threshold of 350–400 mg L⁻¹. The system captured the evolution of floc characteristics over short spatial scales (hundreds of meters). The median floc size (d₅₀) was found to be positively correlated with SSC (r² = 0.5). A comparison between Eulerian and Lagrangian floc histories can then be used to evaluate the role of antecedent conditions within the flocculation process.

year: 2015

title: Taking Taniwha seriously

authors: Kingsbury, Justine

subjects: intercultural understanding

abstract: Taniwha are powerful water creatures in te ao Māori (the Māori world/worldview). Taniwha sometimes afect public works in Aotearoa New Zealand: for example, consultation between government agencies and tangata whenua (the people of the land) about proposed roading developments sometimes results in the route being moved to avoid the dwelling place of a taniwha. Mainstream media responses have tended to be hostile or mocking, as you might expect, since on the face of it the dominant western scientifc worldview has no place for beings like taniwha. However, in the 2020s, there appears to be an increased willingness to engage with te ao Māori. In this spirit, this paper proposes a way for non-Māori to begin to take taniwha more seriously, taking as its starting point the work of Dan Hikuroa on the practical usefulness of taniwha pūrākau (traditional narratives) in encoding information about natural hazards. The focus of this paper is narrow, but aspects of the strategy it proposes may be generalisable both to other aspects of te ao Māori and to other bicultural and multicultural contexts.

text: Taking Taniwha seriously Taniwha are powerful water creatures in te ao Māori (the Māori world/worldview). Taniwha sometimes afect public works in Aotearoa New Zealand: for example, consultation between government agencies and tangata whenua (the people of the land) about proposed roading developments sometimes results in the route being moved to avoid the dwelling place of a taniwha. Mainstream media responses have tended to be hostile or mocking, as you might expect, since on the face of it the dominant western scientifc worldview has no place for beings like taniwha. However, in the 2020s, there appears to be an increased willingness to engage with te ao Māori. In this spirit, this paper proposes a way for non-Māori to begin to take taniwha more seriously, taking as its starting point the work of Dan Hikuroa on the practical usefulness of taniwha pūrākau (traditional narratives) in encoding information about natural hazards. The focus of this paper is narrow, but aspects of the strategy it proposes may be generalisable both to other aspects of te ao Māori and to other bicultural and multicultural contexts.

year: 2022-11-10