title: Flows of water and nutrients to Lake Tarawera and connected lakes

authors: Wilson, Nicola Jane

subjects: Lake

abstract: Lake Tarawera is a large, deep lake located within the Taupō Volcanic zone, 12 km south-east of Rotorua. Seven smaller lakes within the “Greater Lake Tarawera catchment” (Lakes Ōkareka, Ōkaro, Ōkataina, Rerewhakaaitu, Rotokakahi, Rotomahana and Tikitapu) contribute flows to Lake Tarawera via groundwater and/or surface water. The quantity and quality of flows from these connected lakes is important in assessing hydrological inputs to Lake Tarawera.

Groundwater is recognised as a large component of the flow to Lake Tarawera, and previous investigations have been undertaken in the Greater Lake Tarawera catchment to assess groundwater resources and groundwater quality. Despite the extensive work of past researchers, there remain substantial uncertainties on the hydrology and chemistry of groundwater fluxes to Lake Tarawera.

This research aims to improve understanding of groundwater flows in the Greater Lake Tarawera catchment using a water balance approach and to assess and describe the fluxes of water and nutrient loads to Lake Tarawera and hydraulically connected lakes under different climate and land use scenarios. The stable isotopes of water, ẟ²H and ẟ¹⁸O, in groundwater and surface water have been used alongside water balances to supplement understanding of groundwater flow paths and hydraulic connections between lakes.

While previous research has focused on annual means to describe water fluxes and nutrient loads, with no expression of uncertainty, this research describes a range of annual water fluxes and nutrient loads. The ranges bracket the feasible possibilities of fluxes and loads, and account for interannual climatic variation, scientific uncertainties, and land use change, providing a means for policy makers to test outcomes of potential policy decisions.

Analysis of stable isotopes of water have been undertaken from groundwater collected from 11 locations and surface water from 26 locations. Isotopic analysis suggests that the location of lake-to-lake groundwater connections are not widespread and isolated to localised areas. Flow gains observed in the Tarawera River downstream of the Tarawera Falls are largely sourced from rainfall.

Annualised water balances and nutrient loads from 1972 to 2018 have been quantified for the Greater Tarawera Lakes and their catchments. The workflow has been automated using the R statistical computing language and a web-based tool that performs water balance calculations and nutrient load estimates has been developed using Shiny R technology. It is available for viewing at https://nickiwilson.shinyapps.io/TaraweraMsc/.

Evaporation can have a significant effect on the water fluxes and nutrient load to the lakes.  This research considers land use, land cover, and soil water stress in the calculation of evaporation and provides the most accurate evaporation estimations in the Greater Lake Tarawera catchment to date. Groundwater contributes 62% of the inflows to Lake Tarawera, and 70% of this groundwater is estimated to have been recharged from outside of its local catchment. Approximately 20% of the current nutrient load to Lake Tarawera is received from the catchments of its connected upstream lakes.  Management of nutrient loads to Lake Tarawera should consider flow and nutrient loading in upstream lake catchments, and opportunities for improvement include better land management practices and the reticulation of wastewater.

text: Flows of water and nutrients to Lake Tarawera and connected lakes Lake Tarawera is a large, deep lake located within the Taupō Volcanic zone, 12 km south-east of Rotorua. Seven smaller lakes within the “Greater Lake Tarawera catchment” (Lakes Ōkareka, Ōkaro, Ōkataina, Rerewhakaaitu, Rotokakahi, Rotomahana and Tikitapu) contribute flows to Lake Tarawera via groundwater and/or surface water. The quantity and quality of flows from these connected lakes is important in assessing hydrological inputs to Lake Tarawera.

Groundwater is recognised as a large component of the flow to Lake Tarawera, and previous investigations have been undertaken in the Greater Lake Tarawera catchment to assess groundwater resources and groundwater quality. Despite the extensive work of past researchers, there remain substantial uncertainties on the hydrology and chemistry of groundwater fluxes to Lake Tarawera.

This research aims to improve understanding of groundwater flows in the Greater Lake Tarawera catchment using a water balance approach and to assess and describe the fluxes of water and nutrient loads to Lake Tarawera and hydraulically connected lakes under different climate and land use scenarios. The stable isotopes of water, ẟ²H and ẟ¹⁸O, in groundwater and surface water have been used alongside water balances to supplement understanding of groundwater flow paths and hydraulic connections between lakes.

While previous research has focused on annual means to describe water fluxes and nutrient loads, with no expression of uncertainty, this research describes a range of annual water fluxes and nutrient loads. The ranges bracket the feasible possibilities of fluxes and loads, and account for interannual climatic variation, scientific uncertainties, and land use change, providing a means for policy makers to test outcomes of potential policy decisions.

Analysis of stable isotopes of water have been undertaken from groundwater collected from 11 locations and surface water from 26 locations. Isotopic analysis suggests that the location of lake-to-lake groundwater connections are not widespread and isolated to localised areas. Flow gains observed in the Tarawera River downstream of the Tarawera Falls are largely sourced from rainfall.

Annualised water balances and nutrient loads from 1972 to 2018 have been quantified for the Greater Tarawera Lakes and their catchments. The workflow has been automated using the R statistical computing language and a web-based tool that performs water balance calculations and nutrient load estimates has been developed using Shiny R technology. It is available for viewing at https://nickiwilson.shinyapps.io/TaraweraMsc/.

Evaporation can have a significant effect on the water fluxes and nutrient load to the lakes.  This research considers land use, land cover, and soil water stress in the calculation of evaporation and provides the most accurate evaporation estimations in the Greater Lake Tarawera catchment to date. Groundwater contributes 62% of the inflows to Lake Tarawera, and 70% of this groundwater is estimated to have been recharged from outside of its local catchment. Approximately 20% of the current nutrient load to Lake Tarawera is received from the catchments of its connected upstream lakes.  Management of nutrient loads to Lake Tarawera should consider flow and nutrient loading in upstream lake catchments, and opportunities for improvement include better land management practices and the reticulation of wastewater.

year: 2022

title: Determination of ribonuclease sequence-specificity using Pentaprobes and mass spectrometry

authors: McKenzie, Joanna Leigh

subjects: Mycobacteria

abstract: The VapBC toxin-antitoxin (TA) family is the largest of nine identified TA families. The toxin, VapC, is a metal-dependent ribonuclease that is inhibited by its cognate antitoxin, VapB. Although the VapBCs are the largest TA family, little is known about their biological roles. Here we describe a new general method for the overexpression and purification of toxic VapC proteins and subsequent determination of their RNase sequence-specificity. Functional VapC was isolated by expression of the nontoxic VapBC complex, followed by removal of the labile antitoxin (VapB) using limited trypsin digestion. We have then developed a sensitive and robust method for determining VapC ribonuclease sequence-specificity. This technique employs the use of Pentaprobes as substrates for VapC. These are RNA sequences encoding every combination of five bases. We combine the RNase reaction with MALDI-TOF MS to detect and analyze the cleavage products and thus determine the RNA cut sites. Successful MALDI-TOF MS analysis of RNA fragments is acutely dependent on sample preparation methods. The sequencespecificity of four VapC proteins from two different organisms (VapCPAE0151 and VapCPAE2754 from Pyrobaculum aerophilum, and VapCRv0065 and VapCRv0617 from Mycobacterium tuberculosis) was successfully determined using the described strategy. This rapid and sensitive method can be applied to determine the sequence-specificity of VapC ribonucleases along with other RNA interferases (such as MazF) from a range of organisms. Published by Cold Spring Harbor Laboratory Press.

text: Determination of ribonuclease sequence-specificity using Pentaprobes and mass spectrometry The VapBC toxin-antitoxin (TA) family is the largest of nine identified TA families. The toxin, VapC, is a metal-dependent ribonuclease that is inhibited by its cognate antitoxin, VapB. Although the VapBCs are the largest TA family, little is known about their biological roles. Here we describe a new general method for the overexpression and purification of toxic VapC proteins and subsequent determination of their RNase sequence-specificity. Functional VapC was isolated by expression of the nontoxic VapBC complex, followed by removal of the labile antitoxin (VapB) using limited trypsin digestion. We have then developed a sensitive and robust method for determining VapC ribonuclease sequence-specificity. This technique employs the use of Pentaprobes as substrates for VapC. These are RNA sequences encoding every combination of five bases. We combine the RNase reaction with MALDI-TOF MS to detect and analyze the cleavage products and thus determine the RNA cut sites. Successful MALDI-TOF MS analysis of RNA fragments is acutely dependent on sample preparation methods. The sequencespecificity of four VapC proteins from two different organisms (VapCPAE0151 and VapCPAE2754 from Pyrobaculum aerophilum, and VapCRv0065 and VapCRv0617 from Mycobacterium tuberculosis) was successfully determined using the described strategy. This rapid and sensitive method can be applied to determine the sequence-specificity of VapC ribonucleases along with other RNA interferases (such as MazF) from a range of organisms. Published by Cold Spring Harbor Laboratory Press.

year: 2012

title: Ecological Survey of Tauranga Harbour

authors: Ellis, Joanne I.

abstract: This report summarises the results of biological and physical data collected from a broad scale intertidal survey of Tauranga Harbour conducted between December 2011 and February 2012. The survey was designed to understand more fully the role of various anthropogenic stressors on the ecology of the harbour. The research was conducted as part of the Manaaki Taha Moana (MTM) programme. The wider research project aims to restore and enhance coastal ecosystems and their services of importance to iwi/hapū, by working with iwi to improve knowledge of these ecosystems and the degradation processes that affect them.
In this report we assess the health of macrofaunal benthic communities (bottom-dwelling animals) as well as trends in sediments, nutrients and contaminants. The results indicate that the sites identified as most impacted were generally located in the upper reaches of estuaries in some of the locations least exposed to wind, waves and currents. In addition, the biological community composition characterising sites with different sediment textures, nutrient and contaminant loadings were found to vary. Sediments within Tauranga Harbour were predominantly sandy with the percentage of mud within a similar range as measured for other New Zealand estuaries. The exceptions included Te Puna Estuary and Apata Estuary, which experience higher rates of sedimentation.
Heavy metal contamination in sediments is often highly correlated with the percentage of mud content due to the adherence of chemicals to fine sediments and/or organic content. It is, therefore, not surprising that heavy metal concentrations were also highest in the depositional inner areas of the harbour, such as Te Puna Estuary. The heavy metal contaminant levels within Tauranga were well below relevant guideline thresholds and lower than concentrations measured in many other estuaries in New Zealand and overseas. Although the three metals recorded were found to be highly correlated, zinc levels tended to be closer to guideline thresholds for possible biological effects.
Sediment nutrient concentrations in the harbour tended to decline with distance from the inner harbour and associated rivers. Te Puna Estuary showed comparatively high nitrogen and phosphorus loadings. Comparison of sediment nutrient concentrations with other New Zealand estuaries indicates that the Tauranga Harbour sits within a range typical for slightly to moderately enriched estuaries. Although total phosphorus was low compared with other estuaries, total N:P ratios suggest Tauranga Harbour is still limited by nitrogen.
We developed a BHM using statistical ordination techniques to identify key stressors affecting the ‘health’ of macrofaunal communities. Sediments, nutrients and heavy metals were identified as key ‘stressors’, i.e. variables affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The ecological assemblages generally reflected gradients of stress or pollution very well. However, the CAP models for sedimentation and contamination performed best. In general, the multivariate models were found to be more sensitive to changing ecological health than simple univariate measures (abundance, species diversity, evenness and Shannon-Wiener diversity). This finding has also been reported in the literature where univariate measures based on abundance and diversity were only able to detect significant differences between the most and least disturbed sites, but were not able to differentiate between smaller relative changes in ecological health. Hence univariate measures were less sensitive to smaller degradative changes in community composition. For Tauranga Harbour, ordination models based on community composition appear to be a more sensitive measure of ‘health’ along an ecological gradient and should enable long term degradative change from multiple disturbances to be assessed. This BHM approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state.
The key species at ‘healthy’ and ‘impacted’ sites as determined from the CAP models were also identified. Species at ‘impacted’ sites can be considered to be tolerant to the stressor (i.e. sediment, nutrients or contaminants), while species with high abundances at only ‘healthy’ sites are sensitive to increasing stressors. We developed species response models for 20 taxa. Although the type of response differed by taxa and stressor, variation in the abundance of most of the taxa modelled was most likely to be better predicted by sedimentation. Unimodal responses were almost always observed in response to nutrients, while declines or skewed unimodal responses were most often observed in response to sedimentation and metals.
The results from this study are consistent with models of macrofaunal species occurrence with respect to sediment mud content developed across a range of New Zealand estuaries by Thrush et al. (2003). Within this report we extend this analysis by also developing models of macrofaunal species occurrence with respect to nutrient and contaminants loadings. Ultimately such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat changes in sediments, nutrients and metals.
In conclusion, Tauranga Harbour is a predominantly sandy harbour with slight to moderate enrichment and low levels of heavy metal contaminants. Sites identified as most impacted by elevated sediments, heavy metal contaminants and nutrients were generally located in the upper reaches of estuaries in some of the least exposed locations. To some extent, this reflects the natural progression of an estuary from land to sea; however, the rates of accumulation of sediments and nutrients have been accelerated as a result of anthropogenic land-based activities. Sediments and contaminants were found to explain the largest variance in benthic communities. Species response models suggest that taxa were either sensitive to elevated sediments, nutrients loading or contamination at all levels, or sensitive to these stressors beyond a critical point.

text: Ecological Survey of Tauranga Harbour This report summarises the results of biological and physical data collected from a broad scale intertidal survey of Tauranga Harbour conducted between December 2011 and February 2012. The survey was designed to understand more fully the role of various anthropogenic stressors on the ecology of the harbour. The research was conducted as part of the Manaaki Taha Moana (MTM) programme. The wider research project aims to restore and enhance coastal ecosystems and their services of importance to iwi/hapū, by working with iwi to improve knowledge of these ecosystems and the degradation processes that affect them.
In this report we assess the health of macrofaunal benthic communities (bottom-dwelling animals) as well as trends in sediments, nutrients and contaminants. The results indicate that the sites identified as most impacted were generally located in the upper reaches of estuaries in some of the locations least exposed to wind, waves and currents. In addition, the biological community composition characterising sites with different sediment textures, nutrient and contaminant loadings were found to vary. Sediments within Tauranga Harbour were predominantly sandy with the percentage of mud within a similar range as measured for other New Zealand estuaries. The exceptions included Te Puna Estuary and Apata Estuary, which experience higher rates of sedimentation.
Heavy metal contamination in sediments is often highly correlated with the percentage of mud content due to the adherence of chemicals to fine sediments and/or organic content. It is, therefore, not surprising that heavy metal concentrations were also highest in the depositional inner areas of the harbour, such as Te Puna Estuary. The heavy metal contaminant levels within Tauranga were well below relevant guideline thresholds and lower than concentrations measured in many other estuaries in New Zealand and overseas. Although the three metals recorded were found to be highly correlated, zinc levels tended to be closer to guideline thresholds for possible biological effects.
Sediment nutrient concentrations in the harbour tended to decline with distance from the inner harbour and associated rivers. Te Puna Estuary showed comparatively high nitrogen and phosphorus loadings. Comparison of sediment nutrient concentrations with other New Zealand estuaries indicates that the Tauranga Harbour sits within a range typical for slightly to moderately enriched estuaries. Although total phosphorus was low compared with other estuaries, total N:P ratios suggest Tauranga Harbour is still limited by nitrogen.
We developed a BHM using statistical ordination techniques to identify key stressors affecting the ‘health’ of macrofaunal communities. Sediments, nutrients and heavy metals were identified as key ‘stressors’, i.e. variables affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The ecological assemblages generally reflected gradients of stress or pollution very well. However, the CAP models for sedimentation and contamination performed best. In general, the multivariate models were found to be more sensitive to changing ecological health than simple univariate measures (abundance, species diversity, evenness and Shannon-Wiener diversity). This finding has also been reported in the literature where univariate measures based on abundance and diversity were only able to detect significant differences between the most and least disturbed sites, but were not able to differentiate between smaller relative changes in ecological health. Hence univariate measures were less sensitive to smaller degradative changes in community composition. For Tauranga Harbour, ordination models based on community composition appear to be a more sensitive measure of ‘health’ along an ecological gradient and should enable long term degradative change from multiple disturbances to be assessed. This BHM approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state.
The key species at ‘healthy’ and ‘impacted’ sites as determined from the CAP models were also identified. Species at ‘impacted’ sites can be considered to be tolerant to the stressor (i.e. sediment, nutrients or contaminants), while species with high abundances at only ‘healthy’ sites are sensitive to increasing stressors. We developed species response models for 20 taxa. Although the type of response differed by taxa and stressor, variation in the abundance of most of the taxa modelled was most likely to be better predicted by sedimentation. Unimodal responses were almost always observed in response to nutrients, while declines or skewed unimodal responses were most often observed in response to sedimentation and metals.
The results from this study are consistent with models of macrofaunal species occurrence with respect to sediment mud content developed across a range of New Zealand estuaries by Thrush et al. (2003). Within this report we extend this analysis by also developing models of macrofaunal species occurrence with respect to nutrient and contaminants loadings. Ultimately such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat changes in sediments, nutrients and metals.
In conclusion, Tauranga Harbour is a predominantly sandy harbour with slight to moderate enrichment and low levels of heavy metal contaminants. Sites identified as most impacted by elevated sediments, heavy metal contaminants and nutrients were generally located in the upper reaches of estuaries in some of the least exposed locations. To some extent, this reflects the natural progression of an estuary from land to sea; however, the rates of accumulation of sediments and nutrients have been accelerated as a result of anthropogenic land-based activities. Sediments and contaminants were found to explain the largest variance in benthic communities. Species response models suggest that taxa were either sensitive to elevated sediments, nutrients loading or contamination at all levels, or sensitive to these stressors beyond a critical point.

year: 2017