title: Physiological effects of aluminium in relation to diel pH changes on fish and kōura

authors: Fensham, Emily

subjects: Physiology

abstract: Alum (aluminium sulphate, Al₂(SO₄)₃) dosing is used to reduce eutrophication of lakes by sequestering phosphorus and preventing its uptake by phytoplankton for growth. When applied to water at circum-neutral pH, alum forms aluminium hydroxide (Al(OH)₃), a precipitate that is benign at environmentally relevant concentrations and moderate concentrations. However, at low and high pH, dissolved ionic aluminium species evolve which are known to be toxic to a range of aquatic organisms. In the Rotorua lakes, alum dosing occurs under circum-neutral pH (6–8) conditions, however, transiently elevated pH (10) conditions may occur due to algal uptake of carbon dioxide (CO₂) for photosynthesis. Under elevated pH, particulate Al(OH)₃ solubilises to form aluminate (Al(OH)₄⁻), which can interfere with osmoregulation and respiration. Similarly, at circumneutral pH, solid Al(OH)₃ predominates and is generally benign, but in high concentrations can irritate and damage gill tissue causing inflammation and excess mucus production which impairs oxygen uptake, CO₂ elimination, and ultimately causing death. The effects of aluminium under intermittent elevated pH on fish gill function, respiration rates, and metabolism have not yet been investigated.

This study investigated the impacts of aluminium on rainbow trout (Oncorhynchus mykiss), common bully (Gobiomorphus cotidianus), and kōura (Paranephrops planifrons) osmoregulation and respiration under diurnal pH cycles, through two experiments. The first being a dose exposure study whereby rainbow trout and kōura were exposed to alum derived aluminium at 2 mg L⁻¹ under diel pH cycling (pH 7–10) over 10 days. Measured parameters included haematocrit, haemoglobin, mean cell haemoglobin concentration (MCHC), and blood plasma osmolarity in rainbow trout and haemolymph osmolarity in kōura. A significant increase (Student’s t-test, P <0.05) in the mean cell haemoglobin concentration (MCHC) in the rainbow trout control group indicated erythrocyte swelling, suggesting a generalised stress induced response. However, other haematological variables such as plasma and haemolymph osmolarity, haematocrit and haemoglobin concentrations were not significantly different (Student’s t-test, P >0.05) between control and treatment groups. Histological examination of kōura and rainbow trout gill tissue was also conducted, with abnormalities observed within both the control and treatment groups for each species. However no significant differences (Kolomogorov-Smirnov, P >0.05) were observed between groups. It was concluded that organisms can physiologically compensate for aluminium induced stress and disturbance at the gills.

A second experiment utilised intermittent flow respirometry to determine mass specific metabolic oxygen consumption rates (MO₂) of rainbow trout, common bully, and kōura exposed to 2 mg Al L⁻¹ and diel pH fluctuations (pH 7–10) over 60 hours. It was expected that precipitation of dissolved aluminium onto the gill surface during pH transitions and/or binding of dissolved aluminium species would inhibit the respiratory gas exchange resulting in increased gill ventilation from hypoxic and hypercapnic conditions. There was a significant negative correlation (Pearson’s, r² = 0.34, P <0.0001) between pH and MO₂ possibly indicating kōura are sensitive to the experimental conditions. However, there were no consistent trends in differences between control and treatment groups for any of the tested species. Data interpretation was hindered by the necessity to exclude samples from the rainbow trout and common bully control groups due to aberrations in the oxygen sensor data. However, mean MO₂ was within expected ranges for rainbow trout and kōura, indicating that significant respiratory impacts were not occurring within the period of exposure. Although definitive conclusions could not be made regarding changes to MO₂ in response to aluminium and diel pH cycling, it is unlikely that acute impacts would result from these conditions in the natural environment.

From this research it is concluded that the combined impacts of aluminium and diel pH cycling are unlikely to cause acute osmoregulatory or respiratory impairment or cause death in kōura, common bully, or rainbow trout.

text: Physiological effects of aluminium in relation to diel pH changes on fish and kōura Alum (aluminium sulphate, Al₂(SO₄)₃) dosing is used to reduce eutrophication of lakes by sequestering phosphorus and preventing its uptake by phytoplankton for growth. When applied to water at circum-neutral pH, alum forms aluminium hydroxide (Al(OH)₃), a precipitate that is benign at environmentally relevant concentrations and moderate concentrations. However, at low and high pH, dissolved ionic aluminium species evolve which are known to be toxic to a range of aquatic organisms. In the Rotorua lakes, alum dosing occurs under circum-neutral pH (6–8) conditions, however, transiently elevated pH (10) conditions may occur due to algal uptake of carbon dioxide (CO₂) for photosynthesis. Under elevated pH, particulate Al(OH)₃ solubilises to form aluminate (Al(OH)₄⁻), which can interfere with osmoregulation and respiration. Similarly, at circumneutral pH, solid Al(OH)₃ predominates and is generally benign, but in high concentrations can irritate and damage gill tissue causing inflammation and excess mucus production which impairs oxygen uptake, CO₂ elimination, and ultimately causing death. The effects of aluminium under intermittent elevated pH on fish gill function, respiration rates, and metabolism have not yet been investigated.

This study investigated the impacts of aluminium on rainbow trout (Oncorhynchus mykiss), common bully (Gobiomorphus cotidianus), and kōura (Paranephrops planifrons) osmoregulation and respiration under diurnal pH cycles, through two experiments. The first being a dose exposure study whereby rainbow trout and kōura were exposed to alum derived aluminium at 2 mg L⁻¹ under diel pH cycling (pH 7–10) over 10 days. Measured parameters included haematocrit, haemoglobin, mean cell haemoglobin concentration (MCHC), and blood plasma osmolarity in rainbow trout and haemolymph osmolarity in kōura. A significant increase (Student’s t-test, P <0.05) in the mean cell haemoglobin concentration (MCHC) in the rainbow trout control group indicated erythrocyte swelling, suggesting a generalised stress induced response. However, other haematological variables such as plasma and haemolymph osmolarity, haematocrit and haemoglobin concentrations were not significantly different (Student’s t-test, P >0.05) between control and treatment groups. Histological examination of kōura and rainbow trout gill tissue was also conducted, with abnormalities observed within both the control and treatment groups for each species. However no significant differences (Kolomogorov-Smirnov, P >0.05) were observed between groups. It was concluded that organisms can physiologically compensate for aluminium induced stress and disturbance at the gills.

A second experiment utilised intermittent flow respirometry to determine mass specific metabolic oxygen consumption rates (MO₂) of rainbow trout, common bully, and kōura exposed to 2 mg Al L⁻¹ and diel pH fluctuations (pH 7–10) over 60 hours. It was expected that precipitation of dissolved aluminium onto the gill surface during pH transitions and/or binding of dissolved aluminium species would inhibit the respiratory gas exchange resulting in increased gill ventilation from hypoxic and hypercapnic conditions. There was a significant negative correlation (Pearson’s, r² = 0.34, P <0.0001) between pH and MO₂ possibly indicating kōura are sensitive to the experimental conditions. However, there were no consistent trends in differences between control and treatment groups for any of the tested species. Data interpretation was hindered by the necessity to exclude samples from the rainbow trout and common bully control groups due to aberrations in the oxygen sensor data. However, mean MO₂ was within expected ranges for rainbow trout and kōura, indicating that significant respiratory impacts were not occurring within the period of exposure. Although definitive conclusions could not be made regarding changes to MO₂ in response to aluminium and diel pH cycling, it is unlikely that acute impacts would result from these conditions in the natural environment.

From this research it is concluded that the combined impacts of aluminium and diel pH cycling are unlikely to cause acute osmoregulatory or respiratory impairment or cause death in kōura, common bully, or rainbow trout.

year: 2022

title: The effects of mask-wearing and teleneuropsychological assessment on people's memory performance on neuropsychological tests

authors: Rich, Tiffany

abstract: In the wake of the Coronavirus disease (COVID-19), the standardised conditions of neuropsychological assessments were greatly impacted to prevent the spread of COVID-19. Neuropsychological assessment conditions were altered to be conducted remotely on Zoom (teleneuropsychological) or continued in-person with the use of face masks. The changes to standardised assessment conditions led to an increase in people’s worries around assessment, made it harder to hear the assessor which led people to increase their listening effort and created more ambiguous non-verbal social cues (Bottalico et al., 2020; Aguilar & Leguizamon, 2021). These additional assessment aspects may be leading to increased pressure on people’s cognitive load by taking up more of their cognitive resources and attention, then leaving less cognitive resources to focus on the assessment. Moreover, memory tests require high rates of attention and focus to accurately encode, manipulate and retrieve information that is presented. However, the added pressure on cognitive load leaves less available cognitive resources to focus on the memory tests, which in turn may influence people’s performance on these tests. When cognitive load is overloaded, people have issues with attention, encoding and later retrieving or remembering that same information (Lezak et al., 2004). To determine whether the changes to assessment conditions (test environment and mask-wearing) impact people’s memory performance, we conducted a 2x2 mixed methods design (between-subjects factor: test environment (zoom/in-person), within-subjects factor: mask-wearing (mask/no mask). Our sample consisted of 64 participants, aged 18-59, with 43 females, 20 males and 1 participant who preferred to self-describe. Participants were included based on a screening criteria and were required to complete a range of neuropsychological tests for two sessions, either via Zoom or in-person, 1-2 weeks apart. All participants completed one session with the assessor wearing a mask and one session without. Participants scores were compared on the Verbal Learning, Digit Span and Verbal Fluency subtests between the test environments (Zoom/In-person) and mask-wearing (Mask/no mask) variables, to assess their impacts on people’s memory functioning. Results showed no significant differences between participants’ performance on these tests between the in-person and teleneuropsychological assessments or mask-wearing compared to no mask. A statistically significant but not clinically significant interaction effect was found on Verbal Learning trial 5, where participants performed the worst in the Zoom condition when the assessor was wearing a mask. This result was not clinically significant and overall, our results suggest teleneuropsychological assessment and mask wearing during assessment do not impact people’s memory performance and, therefore, are valid and reliable methods of assessment in a population aged 18-59 years with no cognitive impairments. However, we did find that the alternate forms used for the Verbal Learning subtest were not equivalent. Participants’ performed statistically significantly worse and recalled fewer words on the Crawford Verbal Learning test compared to the Rey Auditory Verbal Learning Test (RAVLT). This result was not clinically significant but is a clinically meaningful finding for neuropsychologists in New Zealand to consider when administering alternate forms of the RAVLT test.

text: The effects of mask-wearing and teleneuropsychological assessment on people's memory performance on neuropsychological tests In the wake of the Coronavirus disease (COVID-19), the standardised conditions of neuropsychological assessments were greatly impacted to prevent the spread of COVID-19. Neuropsychological assessment conditions were altered to be conducted remotely on Zoom (teleneuropsychological) or continued in-person with the use of face masks. The changes to standardised assessment conditions led to an increase in people’s worries around assessment, made it harder to hear the assessor which led people to increase their listening effort and created more ambiguous non-verbal social cues (Bottalico et al., 2020; Aguilar & Leguizamon, 2021). These additional assessment aspects may be leading to increased pressure on people’s cognitive load by taking up more of their cognitive resources and attention, then leaving less cognitive resources to focus on the assessment. Moreover, memory tests require high rates of attention and focus to accurately encode, manipulate and retrieve information that is presented. However, the added pressure on cognitive load leaves less available cognitive resources to focus on the memory tests, which in turn may influence people’s performance on these tests. When cognitive load is overloaded, people have issues with attention, encoding and later retrieving or remembering that same information (Lezak et al., 2004). To determine whether the changes to assessment conditions (test environment and mask-wearing) impact people’s memory performance, we conducted a 2x2 mixed methods design (between-subjects factor: test environment (zoom/in-person), within-subjects factor: mask-wearing (mask/no mask). Our sample consisted of 64 participants, aged 18-59, with 43 females, 20 males and 1 participant who preferred to self-describe. Participants were included based on a screening criteria and were required to complete a range of neuropsychological tests for two sessions, either via Zoom or in-person, 1-2 weeks apart. All participants completed one session with the assessor wearing a mask and one session without. Participants scores were compared on the Verbal Learning, Digit Span and Verbal Fluency subtests between the test environments (Zoom/In-person) and mask-wearing (Mask/no mask) variables, to assess their impacts on people’s memory functioning. Results showed no significant differences between participants’ performance on these tests between the in-person and teleneuropsychological assessments or mask-wearing compared to no mask. A statistically significant but not clinically significant interaction effect was found on Verbal Learning trial 5, where participants performed the worst in the Zoom condition when the assessor was wearing a mask. This result was not clinically significant and overall, our results suggest teleneuropsychological assessment and mask wearing during assessment do not impact people’s memory performance and, therefore, are valid and reliable methods of assessment in a population aged 18-59 years with no cognitive impairments. However, we did find that the alternate forms used for the Verbal Learning subtest were not equivalent. Participants’ performed statistically significantly worse and recalled fewer words on the Crawford Verbal Learning test compared to the Rey Auditory Verbal Learning Test (RAVLT). This result was not clinically significant but is a clinically meaningful finding for neuropsychologists in New Zealand to consider when administering alternate forms of the RAVLT test.

year: 2023

title: Toitu Te Moananui a Toi – The Effects of the MV Rena on the Water Quality, Chemistry and Zooplankton of Otaiti (Astrolabe Reef)

authors: Dempsey, Te Puea Toni

subjects: metal contamination

abstract: Humans have had a profound effect on the world’s oceans, particularly through pollution. Marine pollution incidents are particularly important and increasingly involve both petrochemical and metal contamination. The effects of complex high level, point source pollution events such as ship wrecks on larval recruitment to reef environments is not well understood. Larval settlement is heavily influenced by chemical cues, hence pollution events could have a long term influence on reef ecology, and the likelihood that planktonic zooplankton can entrain contaminants into the reef food web is also of concern.
This thesis aims to address concerns from local Tangata Whenua, government, researchers, stakeholders and the public about the long term recovery of Otaiti following the MV Rena shipwreck and subsequent reef contamination. The incident is a complex one involving metallic container debris contamination along with oil. Research focussed on assessing the effects of water borne contamination surrounding the wreck site in order to examine acute and chronic responses of planktonic invertebrates: (1) the influence of Rena and associated debris to the chemistry and quality of water in the benthic zone around the wreck, (2) the toxicity of contaminants to survivorship of zooplankton, and (3) the influence on contaminant plumes to zooplankton recruitment behaviour of Otaiti.
There is a clear effect from the Rena and its associated debris field on the water quality and chemistry of Otaiti. Aluminium and copper for example, were consistently elevated in dissolved and total metal concentrations around the debris field. Laboratory based exposure of zooplankton to realistic concentration gradients of Rena contaminated sediments resulted in increased mortality with increased contaminant concentrations. Behavioural responses of pelagic and settling invertebrates to Rena pollution influenced sediment highlighted sensitivity to associated contaminant plumes. This could have significant ecological implications to the recruitment behaviour of other planktonic organisms that rely on reef conspecifics and chemical cues to initiate settlement.
Ecological concepts such as ecosystem function and biodiversity dynamics (including recruitment) relate the life force and longevity of a system. Key concerns within the scope of this research were highlighted that may have implications to Tangata Whenua decision making in assessing the Mauri of Otaiti. It can be implied that the Rena continues to impact the Mauri of Otaiti due to the presence of contaminants within the debris field.

text: Toitu Te Moananui a Toi – The Effects of the MV Rena on the Water Quality, Chemistry and Zooplankton of Otaiti (Astrolabe Reef) Humans have had a profound effect on the world’s oceans, particularly through pollution. Marine pollution incidents are particularly important and increasingly involve both petrochemical and metal contamination. The effects of complex high level, point source pollution events such as ship wrecks on larval recruitment to reef environments is not well understood. Larval settlement is heavily influenced by chemical cues, hence pollution events could have a long term influence on reef ecology, and the likelihood that planktonic zooplankton can entrain contaminants into the reef food web is also of concern.
This thesis aims to address concerns from local Tangata Whenua, government, researchers, stakeholders and the public about the long term recovery of Otaiti following the MV Rena shipwreck and subsequent reef contamination. The incident is a complex one involving metallic container debris contamination along with oil. Research focussed on assessing the effects of water borne contamination surrounding the wreck site in order to examine acute and chronic responses of planktonic invertebrates: (1) the influence of Rena and associated debris to the chemistry and quality of water in the benthic zone around the wreck, (2) the toxicity of contaminants to survivorship of zooplankton, and (3) the influence on contaminant plumes to zooplankton recruitment behaviour of Otaiti.
There is a clear effect from the Rena and its associated debris field on the water quality and chemistry of Otaiti. Aluminium and copper for example, were consistently elevated in dissolved and total metal concentrations around the debris field. Laboratory based exposure of zooplankton to realistic concentration gradients of Rena contaminated sediments resulted in increased mortality with increased contaminant concentrations. Behavioural responses of pelagic and settling invertebrates to Rena pollution influenced sediment highlighted sensitivity to associated contaminant plumes. This could have significant ecological implications to the recruitment behaviour of other planktonic organisms that rely on reef conspecifics and chemical cues to initiate settlement.
Ecological concepts such as ecosystem function and biodiversity dynamics (including recruitment) relate the life force and longevity of a system. Key concerns within the scope of this research were highlighted that may have implications to Tangata Whenua decision making in assessing the Mauri of Otaiti. It can be implied that the Rena continues to impact the Mauri of Otaiti due to the presence of contaminants within the debris field.

year: 2015