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ERI Reports are prepared by researchers affiliated with ERI to disseminate findings from externally funded research. ERI Reports are peer-reviewed and published on the University of Waikato Research Commons, making them credible, citable, and available as a public resource. They also serve to illustrate the diversity of research within ERI and the capabilities of ERI researchers.
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Publication Operational forest restoration plan for Kukutaaruhe Gully: Part 2(Report, Environmental Research Institute, the University of Waikato, 2020-10) Elliot Noe, Elizabeth; Wallace, Kiri Joy; Cornes, Toni; Kirkby, Catherine L.Kukutaaruhe Gully is a minor branch of Hamilton’s extensive gully system, and runs from the corner of Bankwood and Clarkin Road, behind Fairfield College, connecting with Donny Park in the north and out into the Waikato River. The Kukutaaruhe Education Trust was established to support the implementation of the Fairfield Project, which is a partnership between Ngati Wairere, local community and Fairfield College. The project’s goals include the establishment of an ecological and environmental education centre on the approximately 12 ha of land behind Fairfield College and restoration of the adjacent Kukutaaruhe Gully. In 2019, the University of Waikato’s Environmental Research Institute was contracted by the Kukutaaruhe Education Trust to create an Operational Forest Restoration plan for Kukutaaruhe Gully. This is one in a three-part series created together under one contract: • Part 1 of 3 is an Overview of the Kukutaaruhe Gully Restoration Initiative • Part 2 of 3 is this document, the Operational Forest Restoration plan for Kukutaaruhe Gully • Part 3 of 3 is an Ecological Restoration Plan Template.Publication Overview of the Kukutaaruhe Gully restoration initiative: Part 1(Report, Environmental Research Institute, the University of Waikato, 2020-10) Elliot Noe, Elizabeth; Wallace, Kiri Joy; Cornes, Toni; Kirby, Catherine L.Kukutaaruhe Gully is a minor branch of Hamilton’s extensive gully system, and runs from the corner of Bankwood and Clarkin Road, behind Fairfield College, connecting with Donny Park in the north and out into the Waikato River. The Kukutaaruhe Education Trust was established to support the implementation of the Fairfield Project, which is a partnership between Ngati Wairere, local community and Fairfield College. The project’s goals include the establishment of an ecological and environmental education centre on the approximately 12 ha of land behind Fairfield College and restoration of the adjacent Kukutaaruhe Gully. In 2019, the University of Waikato’s Environmental Research Institute was contracted by the Kukutaaruhe Education Trust to create an Overview of the Kukutaaruhe Gully restoration initiative. This is one in a three-part series created together under one contract: • Part 1 of 3 is the first document presented here, an Overview of the Kukutaaruhe Gully Restoration Initiative • Part 2 of 3, the Operational Forest Restoration plan for Kukutaaruhe Gully • Part 3 of 3 is an Ecological Restoration Plan Template.Publication Development of a molecular tool to identify brown bullhead catfish (Ameiurus nebulosus) from environmental DNA in water(Technical Report, Environmental Research Institute, The University of Waikato, 2020-08-21) Hicks, Brendan J.; Cursons, RayThe aim of this work was to develop a molecular tool to positively identify brown bullhead catfish using environmental DNA (eDNA) that is suspended within the water column. The project had five main objectives: 1) to develop a protocol for the collection of eDNA, 2) to select and test primer sets that are specific to brown bullhead catfish, 3) to optimise DNA extraction and amplification, 4) to validate the methodology through sequencing the amplified DNA, and 5) to evaluate its sensitivity by sampling at various sites that had a range of catfish abundances. Water was sampled from Lake Rotoiti from a boat with a 1 litre labelled plastic container attached to a telescopic pole, retrieving water samples about 30 cm above the lake bottom in about 2 m of water depth and from deeper water. Each container was deployed container-opening facing down, and on reaching the desired collection depth, the opening was rotated uppermost to allow the entry of water. The full container was then pulled back to the surface, a plastic screw cap firmly screwed onto the container, and then subsequently placed in a chilly bin on a 20-cm layer of crushed ice. The collection was recorded on a GPS instrument.Publication Characteristics of sub-surface sediments in southern Stella Passage, Tauranga Harbour(Report, Environmental Research Institute, The University of Waikato, 2019) Moon, Vicki G.; De Lange, Willem P.The Port of Tauranga is considering port developments that would require capital dredging of a section of the southern Stella Passage to achieve depths comparable to the northern Stella Passage. Seismic profiles, core samples, and CPT data were collected by the University of Waikato and OPUS for the area impacted by proposed development. The core samples were analysed for sediment texture, including assessment of the fines (silt + clay) content. Four main stratigraphic units were identified from the available data. These were, in order of increasing stratigraphic depth and age: Holocene sand; Pleistocene alluvial fan; Pleistocene organic silt; and Pleistocene terrestrial and shallow marine sand. In general, the fines content increased with depth and age. Younger units thin southwards along Stella Passage, resulting in increasing fines content southwards along the channel.Publication Puarenga Stream alum dosing – summary of effects on lake biota 2013/2014(Report, Environmental Research Institute, The University of Waikato, 2014-11) Ling, NicholasContinuous alum dosing of the Puarenga Stream commenced in early 2010 to reduce inflows of dissolved reactive phosphorus to Lake Rotorua. Analyses of bioaccumulation in the tissues of macrobiota were undertaken in February 2013 and February 2014 for comparison to comparable samples obtained prior to and shortly after the commencement of alum dosing. No significant effects of alum dosing could be distinguished. Bioavailable aluminium in the vicinity of Sulphur Bay appears to be primarily influenced by the major geothermal activity of this region. No significant differences in aluminium bioaccumulation were observed in any species compared to samples obtained prior to the commencement of alum dosing. Continuous alum dosing of the Puarenga Stream since 2010 apparently has not resulted in adverse effects to Lake Rotorua shoreline biota nor caused any apparent increase in aluminium bioaccumulation in lake biota in the vicinity of Sulphur Bay.Publication Utuhina Stream monitoring 2014: Effects of continuous alum dosing on fish and aquatic invertebrates(Report, Environmental Research Institute, The University of Waikato, 2015) Ling, NicholasThis report presents the results of an ongoing assessment of the fish and aquatic macroinvertebrate communities of the Utuhina Stream from 2006 to 2014, and an assessment of the bioavailability of aluminium in fish and koura to satisfy annual resource consent conditions 9.6, 9.8 and 9.7, respectively, for the discharge of alum. Macroinvertebrates, fish and koura were sampled from one control and two treatment reaches of the Utuhina Stream in August 2014. Catch rates for common bully, juvenile trout and koura have fluctuated across all sites since monitoring began in 2006. Common bully, koura and juvenile trout were present at all sites. Differences in species abundance compared with previous years is most likely due to flood related disturbances to stream bank morphology and vegetative cover. No obvious effects of alum dosing on stream fish or macroinvertebrate communities were observed.Publication Assessing effects of changes to nutrient loads on Lake Tarawera water quality: Model simulations for 2010 to 2020(Report, Environmental Research Institute, The University of Waikato, 2020-12) Abell, Jonathan Michael; McBride, Chris G. ; Baisden, W. TroyLake Tarawera is a nationally significant lake that is highly valued by tangata whenua, local residents and the regional community. Monitoring shows that lake water quality does not presently meet the target, based on a Trophic Level Index (TLI) value of 2.6 identified in the Tarawera Lakes Restoration Plan1. Between 2010 and 2020 annual observed TLI was frequently as high as 2.9. Managing nutrient loads to the lake is necessary to achieve desired lake water quality and interim nutrient reduction targets have been established. An objective of this study was to evaluate these targets by improving estimates of ‘sustainable nutrient loads’, which are the external loads of nitrogen and phosphorus that would result in meeting the TLI target.Publication Catchment and lake water quality modelling to assess management options for Lake Rerewhakaaitu(Report, Environmental Research Institute, The University of Waikato, 2020) Cho, Eunju; Hamilton, David P.; McBride, Chris G.Lake Rerewhakaaitu in the Bay of Plenty Region of North Island, has one of the most intensively farmed lake catchments in New Zealand. Nitrate concentrations in two surface stream inflows to the lake show substantial and statistically significant increases, between 1995 and 2015, however, lake water quality has remained relatively stable. The lake is polymictic (i.e., it mixes frequently) and is partly perched, with an effective hydrological catchment of approximately 10% of the surface topographic catchment. We used the hydrodynamic-ecological model DYRESM-CAEDYM to examine the relationship between inflow quantity and quality, and lake water quality. A groundwater model (MODFLOW) provided groundwater discharge values from the hydrologically effective catchment, to the lake model (DYRESM-CAEDYM). The model successfully reproduced the magnitude and dynamics of field measurements, as evidenced by low statistical error. Based on a novel uncertainty analysis that allows for assessment of forcing factors that contribute to model error, a component of the statistical error was identified to be due to lake water level variations, which was attributed to ecological changes in the littoral (shallow-water) zone of the lake. The calibrated model was used with a set of scenarios to examine land use change within the effective hydrological catchment, as well as climate change. Establishment of the lake model was subject to several areas of substantial uncertainty, including derivation of stream inflows by statistical modelling (rather than direct observation), hydrological uncertainty with regard to drainage pathways in the lake catchment, and reliability of some nutrient measurements in the lake and streams. Nevertheless, the present model can be considered among the most sophisticated tools available with which to inform lake management decisions. Model results suggest that improved land management efforts within the wider topographic catchment will have only minor impacts on Lake Rerewhakaaitu water quality, but within the hydrologically effective catchment land use improvements to decrease losses of nitrogen and phosphorus to the lake will be important. Maintaining and/or enhancing the forested area within the hydrologically effective catchment and potentially retiring (to indigenous vegetation) some of the area, as well as maintaining the riparian buffer of the lake, will help to maintain water quality of Lake Rerewhakaaitu. The model predicted that a future warmer climate would likely increase the duration of temperature stratification in the water column, leading to more deoxygenation of bottom waters and a decline in water quality. Offsetting this with maintaining and enhancing vegetation in the riparian area and hydrologically effective catchment may help to offset these effects.Publication Estimated catchment loads of nitrogen and phosphorus to the Rotorua Te Arawa Lakes(Report, Environmental Research Institute, The University of Waikato, 2021) McBride, Chris G.; MacCormick, Alastair; Verburg, PietThe Rotorua Te Arawa Lakes are central to the identity of their region, of immense historical and cultural importance, and provide ecosystem services that underpin biodiversity, conservation and socioeconomic aspirations of the community. The diversity of water quality in the lakes reflects their catchments, which are diverse in topography, hydrogeology and intensity of land use, ranging from the largely undeveloped land around lakes Tikitapu and Okataina, to highly developed forestry and pastoral land around lakes Rerewhakaaitu, Rotorua and Okaro. Lake water quality is strongly linked to nutrients received by each lake from surface flows and groundwater springs. It therefore follows that management of lake water quality requires a good understanding of nutrient loads derived from the landscape, as does the assessment or prediction of the in-lake effects of catchment-based management initiatives aimed at improving lake water quality.Publication Lake water quality modelling to assess management options for Lake Hayes(Report, Environmental Research Institute, The University of Waikato, 2019) McBride, Chris G.; Muraoka, Kohji; Allan, Mathew GrantLake Hayes is an important ecological, historical and cultural asset to the Otago Region. The lake and its catchment have been substantially altered from their natural condition, including conversion of the catchment from forest to pasture, invasion of the lake by non-native macrophytes, blooms of cyanobacteria (blue-green algae) and lake Trophic Level Index has increased over recent years (Figure A). Since 2010 the lake has been characterised by very poor water quality and pronounced summer algal blooms. This has attracted public attention and provided impetus from community and stakeholders to assess available management options for restoring water quality in the lake. This report examines the drivers of poor water quality and associated algal blooms in the lake, and assesses various management options that have been either specifically proposed for Hayes, or have proven effective for other lakes in New Zealand and globally. Here we report on monitoring undertaken by Otago Regional Council in the catchment (surface inflows) and in the lake. Primarily, we apply state-of-the-art computer models to simulate physical, chemical, and biological processes within the lake. These simulations are then used to evaluate a range of management scenarios to provide guidance on the likely effects of management options.Publication Seasonal changes in phytoplankton nutrient limitation: Lake Rotorua(Report, Environmental Research Institute, The University of Waikato, 2020) Tempero, Grant WayneThe management of macronutrient availability is central for reducing harmful algal blooms and the restoration of aquatic ecosystems. While there is some dispute as to the need for phosphorus (P) only control versus P and nitrogen (N) control, scientific opinion generally supports dual nutrient control in New Zealand lakes. Previous nutrient limitation studies of Lake Rotorua conducted during the 1970s and 1980s reported N limitation to varying degrees. This period coincided with the disposal of sub-optimally treated municipal wastewater to the lake, resulting in significant P loading and resultant algal blooms. Land disposal of wastewater was initiated in 1991 reducing nutrient loads to the lake, however, no further nutrient limitation studies were conducted until the summer of 2004 when N and P co-limitation was reported. From the mid-2000s water quality improved from a Trophic Lake index (TLI) of approximately 4.8 to 4.2, a change likely driven, in part, by sediment P depletion following the change to land disposal of wastewater and the initiation of alum dosing in 2006.Publication Waiwhakareke Natural Heritage Park 2018 long-term plot monitoring: Report on ecological restoration progress(Report, Environmental Research Institute, The University of Waikato, 2000) Farnworth, Bridgette; Wallace, Kiri Joy; Cornes, Toni S.This report was requested by Tui 2000 Inc. and the Hamilton City Council (HCC) as a means of tracking terrestrial restoration progress at Waiwhakareke Natural Heritage Park (WNHP). WNHP is a cutting-edge urban ecological restoration project in which ecosystems representative of the Waikato region are being reconstructed from scratch on public land (formally pastoral land) in Kirikiriroa Hamilton. Large-scale projects of this nature are becoming more common around the globe due to growing emphasis on restoring nature in urban areas. While this report quantifies the remarkable ecological restoration success achieved at WNHP though investments by Tui 200 Inc., HCC and other partners over the years, it also contributes to scientific theory. Ecological restoration is a newly developing scientific field and hence WNHP presents a unique opportunity for ecologists to improve restoration practice and also learn from the results.Publication Waiwhakareke Natural Heritage Park 2022 ground truthing(Report, Environmental Research Institute, The University of Waikato, 2022) Nepia, Rachel E.This report presents the findings of routine monitoring of Waiwhakareke Natural Heritage Park (WNHP) in preparation for enrichment and infill planting in 2023 to 2024. The monitoring was carried out during September 2022 and included 44 plots across 10 polygons in landforms designated as kauri forest, rimu/tawa forest, swamp shrubland, pukatea-kahikatea forest and kahikatea-pukatea-swamp maire forest. Plot size and number in each polygon were selected to represent a sample area of 5 % of the total polygon area. In each plot the plants were counted by height class, and a percentage of canopy cover was estimated. Vegetation composition, canopy openness, regeneration and plant mortality are discussed in the report. These observations were considered with recommended planting plans generated by the WNHP planting tool, and changes were recommended to provide finalised planting plans. We recommend that this data is regularly fed back into the tool to refine recommended planting plans based on observed patterns of survival.Publication Sediment aluminium content of Lake Okaro: 2021 monitoring survey(Report, Environmental Research Institute, The University of Waikato, 2023) Tempero, Grant WayneThe application of aluminium salts such as polyaluminium chloride and aluminium sulphate has been widely used to assist in the remediation of eutrophic freshwater ecosystems. Aluminium binds to phosphorus, reducing its availability for phytoplankton growth, with the additional benefit that sediment phosphorus is reduced under anoxic lake conditions. Since 2013, alum (aluminium sulphate) has been applied twice per year to Lake Okaro to reduce dissolved reactive phosphorus availability. The lake’s annual Trophic Lake Index has decreased from 5.5 in the early 2000s to 4.5 in 2020. Alum dosing has resulted in the addition of 3.8 t of aluminium to the lake, however, the spatial distribution and sediment accumulation rate of alum derived aluminium has not been investigated. The University of Waikato was contracted by the Bay of Plenty Regional Council to survey sediment aluminium concentrations in Lake Okaro to determine the distribution and accumulation of alum derived aluminium. In addition to sediment total aluminium content, the proportion of amorphous (non-crystalline) aluminium was assessed. Amorphous aluminium is the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from uptake by phytoplankton. It was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing.Publication Hamilton City long-tailed bat survey: Annual monitoring report, 2022(Report, Environmental Research Institute, The University of Waikato, 2022) Caskey, Laura; Tempero, Grant WayneDeforestation, urbanisation and the introduction of mammalian predators has resulted in a significant decline of New Zealand’s long-tailed bat (Chalinolobus tuberculatus or pekapeka-tou-roa), which is currently classified as threatened, nationally critical. Hamilton City is one of three urban areas with confirmed long-tailed bat populations. Since 2016, annual city-wide surveys have been conducted by Project Echo, a multi-agency advocacy group for Hamilton City bats. The purpose of the annual surveys is to monitor for changes in bat activity and habitat use throughout Hamilton City, this report presents findings from the 2022 survey. A total of 72 automatic bat monitors (ABMs) were deployed across 20 historically monitored sites and 52 spatially distributed sites, as specified by a Master Sample design. Acoustic bat monitors (Model AR4) were deployed for approximately 3 weeks, however, only 14 ABMs remained operational for the full 3-weeks, with 30 units failing to operate for more than 4 days. ABM failure was ascribed to the use of older rechargeable batteries. Despite this, a total of 6,734 bat passes were detected from 19 sites, compared to detections at 18 sites from 64 deployments in the 2021 city survey. Similar to previous years, most bat activity was recorded in the south of the city, in close association with the Waikato River and the Mangakotukutuku gully system. There were also six passes recorded in the central city (Site 67, Tristram Street) along with multiple detections in the Hillcrest, Fairfield and Melville residential areas. This data supports the continued use of the Master Sample survey design for the selection of survey sites. While it is advantageous to retain a proportion of previously monitored sites (~25%) for continuity of data, the Master Sample design has improved the proportion of habitats surveyed with greater coverage of residential areas and the inclusion of commercial and industrial areas which have rarely been surveyed. The reduced number of operational ABM nights is likely to have substantially reduced the sensitivity of the survey to identify locations of low bat activity, as well as the magnitude of detections in high activity areas. Therefore, it is recommended that the data be treated with caution if making comparisons to previous or similar surveys. On-going annual city-wide bat surveys will help identify key habitat areas for conservation and enhancement, in addition to helping understand the effects of urban development and intensification. This is of particular importance given the ongoing and proposed future development in the south of the city, which raises concerns for the preservation of current bat habitats and their connectivity to the city.Publication Ōhiwa Harbour Delft3D sediment transport modelling to support the National Policy Statement on Freshwater (NPS-FM)(Report, Environmental Research Institute, The University of Waikato, 2023) Bryan, Karin R.; Stewart, B.; Rahdarian, Amin; Rautenbach, C.A suspended sediment transport model was set up for Ōhiwa Harbour, which was validated against in situ observations collected between 19/4/21 and 17/5/21. Four sediment grain size fractions were modelled; two cohesive (silt) sediment grain size fractions, and two non-cohesive (sand) sediment grain size fractions. Characteristics of these grain size fractions were selected based on a sensitivity analysis and the match of modelled suspended sediment to the magnitude and temporal patterns recorded at the observation stations. Suspended non-cohesive grain size fractions reflect local current strengths at the sites measured, whereas cohesive grain size fractions are advected longer distances by the ebbing or flooding currents. Sediment loading was input at the freshwater discharge points using loading scenarios provided by the Bay of Plenty Regional Council. Sediment loading was converted to a concentration and discharge, and input into the model as a cohesive sediment grain size fraction. Model scenarios were run for 1 year in blocks of 3 months, using the environmental conditions (discharge, wind, tides) from 2014 as a base-case scenario. Loading scenarios consisted of contemporary, natural, RCP45 and RCP85 conditions. A 7-day model “warm up” period prior to each of the 3-month blocks was discarded.Publication Tauranga Harbour DELWAQ nutrient modelling to support the implementation of the National Policy Statement on Freshwater (NPS-FM)(Report, Environmental Research Institute, The University of Waikato, 2022) Bryan, Karin R.; Stewart, Benjamin ThomasA DELWAQ nutrient model coupled to a Delft3D hydrodynamic model was set up for Tauranga Harbour and surrounding shelf, and run for three months during summer and three months during winter for 5 years. Model results were summarised in 34 different regions, aligned to the BoPRC reporting of sensitive receiving environments in Tauranga Harbour. Prior to undertaking the 5-year DELWAQ modelling, a sensitivity analysis was undertaken to tune key modelling parameterisations (primarily sediment denitrification). Nutrient and salinity outputs from the 5-year runs were compared against BoPRC monitoring data to assess performance. Salinity was generally over 30 ppt even in winter, except very near freshwater input zones. Flushing time varied substantially across the harbour from less than one day to 9 days.Publication Waitangi Soda Springs alum dosing – Bioavailability of aluminium 2011-2020(Report, Environmental Research Institute, The University of Waikato, 2021) Ling, NicholasContinuous alum dosing of the Waitangi Soda Springs at Lake Rotoehu commenced in 2011 to reduce inflows of dissolved reactive phosphorus to Lake Rotoehu. Analyses of bioaccumulation in the tissues of kōura and goldfish from Lake Rotoehu were undertaken on animals collected annually since 2013 to determine the bioavailability and bioaccumulation of aluminium. Lake Rotoehu kōura and goldfish collected in 2013 showed slightly elevated aluminium concentrations in the gills indicating enhanced exposure to aluminium but little evidence for significant bioaccumulation in tissues. Concentrations in goldfish liver and gills were highest in 2016, but not significantly different to goldfish collected from Lake Rotorua in 2013 and flesh concentrations were low. Analyses of animals collected in 2020 confirm these earlier findings with no evidence of enhanced bioaccumulation of aluminium in Lake Rotoehu biota.Publication Boat electrofishing salvage of fish in the Lower Mangamahoe Dam reservoir(Report, Environmental Research Institute, The University of Waikato, 2022) Hicks, Brendan J.; Powrie, Warrick; Larkin, Greg; Smith, AngelaThe aim of the survey was to salvage fish from the Lower Mangamahoe Dam reservoir before dewatering and dam removal. We used the University of Waikato’s 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 140 fish weighing an estimated 37.0 kg along 8 fishing tracks sites on 24 February 2022. These tracks comprised 2,807 lineal m and 11,228 m2 in area. Shortfin eels (Anguilla australis) and common bullies (Gobiomorphus cotidianus) were the only fish species present. Mean density of eels caught was 2.9 fish 100 m–2 and mean biomass was 7.84 g m–2. The eels and bullies were transferred to sites downstream in the Waiwhakaiho River by iwi members of the two hapū - Ngāti Te Whiti and Ngāti Tawhirikura. Water clarity, expressed as black disc distance (BDD, 1.05 m), was good for a shallow lake, and water temperature and water conductivity were close to optimum for electrofishing. Poor water clarity can reduce the efficiency of electrofishing, so we left time after fishing each track for the sediment suspended by the propellor wash to sink before refishing a track.Publication Aluminium content in near-shore sediments of Lake Rotorua(Report, Environmental Research Institute, The University of Waikato, 2019) Tempero, Grant WayneThe application of alum (aluminium sulphate) is widely used for lake restoration. Aluminium binds dissolved reactive phosphate (DRP), reducing its availability to phytoplankton and inhibiting algal blooms. The Bay of Plenty Regional Council has conducted continuous alum dosing of the Utuhina Stream since 2006 and the Puarenga Stream from 2010 to 2018. This has resulted in the addition of more than 730 tonnes of aluminium to Lake Rotorua. Improvements in Lake Rotorua water quality occurred concurrently with peak alum dosing, although sediment surveys conducted in 2012 and 2015 were unable to locate significant depositional areas of aluminium floc in the main basin of Lake Rotorua. Elevated amorphous aluminium (i.e., recently deposited aluminium) was reported at sites closest to the Utuhina and Puarenga discharge points in the 2015 sediment survey, indicating that aluminium was potentially accumulating in the nearshore zone. The University of Waikato was contracted by the Bay of Plenty Regional Council to conduct a follow-up survey of near-shore sites along the southern edge of Lake Rotorua. In addition to sediment total and amorphous aluminium content, total phosphorus content was also determined. Amorphous aluminium is recognised as the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from the water column. For this study it was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing.