ERI Reports

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https://hdl.handle.net/10289/16658

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.

Now showing 1 - 5 of 84

Utuhina Stream 2006-2020: In-stream alum dosing effects on fish and aquatic invertebrates
(Report, Environmental Research Institute, School of Science, The University of Waikato, 2021-06) Ling, Nicholas
This report presents the results of an on-going assessment of the fish and aquatic macroinvertebrate communities of the Utuhina Stream, Lake Rotorua, from 2006 to 2020, and an assessment of the bioavailability of aluminium in fish and kōura to satisfy Bay of Plenty Regional Council’s annual resource consent conditions 9.6, 9.8 and 9.7, respectively, for consent 65321 for the discharge of alum to the Utuhina Stream. Macroinvertebrates, fish and kōura (freshwater crayfish) were sampled from one control and two treatment reaches of the Utuhina Stream annually. Common bully (Gobiomorphus cotidianus) is the dominant species in the fish community of the Utuhina Stream. Kōura (Paranephrops planifrons) and juvenile trout were always present at all sites but variable in abundance. Differences in species abundance from year to year are most likely due to flood-related disturbances to stream bank morphology and in-stream vegetative cover or physical displacement of fish. No obvious effects of alum dosing on stream fish or macroinvertebrate communities were observed between the upstream control site and sites downstream of the alum discharge. Several other fish species were occasionally captured during sampling and the regular occurrence of juvenile koaro from 2016 to 2019 is possible evidence of this taonga species becoming established in the Utuhina. Analysis of stream macroinvertebrates also showed no consistent differences between the upstream control site and the sites downstream of the alum dosing. Overall, all sites were characterised as fair to good quality for a soft-bottomed stream. Some evidence of aluminium bioaccumulation was seen in some tissues of common bully (gills and liver) in some years, resulting from continuous alum dosing of the Utuhina Stream, but there was no evidence of bioaccumulation of aluminium in the tissues of kōura. Alum exposure in these species does not appear to affect their health or abundance in the stream. iii Overall, continuous alum discharge does not appear to negatively impact the ecology of the lower Utuhina and improvements in the ecological condition of the Utuhina Stream will be achieved by ongoing riparian restoration and mitigation of the impacts of flood flows.
Assessment of trophic state change and lake health in selected lakes of the Auckland region based on zooplankton assemblages: 2012-2019
(Report, Environmental Research Institute, The University of Waikato, 2021) Duggan, Ian C.; Hussain, Ebrahim
This report provides an assessment of eight natural lakes in the Auckland region, from zooplankton samples collected between 2012 and late 2019 at a frequency of six to eight samples per year. From these samples, the lakes have been assessed to establish their trophic state, the proportion of nonnative zooplankton species, and the proportion of crustacean zooplankton relative to rotifers. Inferred trophic states of the lakes based on zooplankton composition has been generally ranked in a similar manner over time; of the lakes sampled over the entire period, Lake Tomarata typically had the best inferred water quality (generally as mesotrophic, though late in the study it sat near the eutrophic boundary). The median Trophic Level Index (TLI) based on zooplankton for this lake was 3.5 between 2015 and 2019. Lake Whatihua, only sampled from late-2017, was also assessed to contain species typical of mesotrophic conditions (median TLI = 3.4). For the remaining lakes, median TLI values based on zooplankton composition between 2015 and 2019 were; Rototoa 3.5 (mesotrophic), Wainamu 4.0, Pupuke 4.3 (both eutrophic) and Kuwakatai 5.2 (supertrophic; sampling ceased in August 2017). Lakes Kereta and Spectacle were not assessed during the 2015- 2019 time period. Lake Pupuke rapidly declined in water quality in 2019, to have hypertrophic assessments at the end of the study; this is consistent with reported high chlorophyll a concentrations at this time. Lake Tomarata was assessed to have declining water quality based on zooplankton composition, in common with traditional TLI assessments. However, this lake was assessed to have higher water quality overall, and to diverge in assessments by 1.2 TLI units; this may in part be due to elevated TN concentrations in this lake, not reflected in concentrations of TP or chlorophyll a, which may unduly affect traditional TLI assessments for this lake. The other long-term lakes, Waimanu, Pupuke and Rototoa, all has assessments within 0.5 TLI units when comparing the traditional and rotifer inferred TLI systems. The proportion of non-native species and the proportion of crustacean zooplankton relative to rotifers both showed promise as monitoring tools for the Auckland lakes. Two non-native species were recorded in the lakes, with various levels of dominance. Daphnia galeata was recorded in all of the monitored lakes, while Skistopiaptomus pallidus was recorded in Lake Kereta only. For the proportions of non-native species, Lake Tomarata was least affected, with samples comprising 4.9% non-native species on average. Data from 2012 and 2013 indicated that the overall relative abundances of the calanoid copepod Skistodiaptomus pallidus in Lake Kereta were far lower than they were in the year’s immediately following invasion in late 2008. No new non-native species were recognised in the monitored lakes during this survey, although an unusual occurrence of the copepod Boeckella propinqua was recorded in Lake Whatihua; this species has otherwise been found from natural lakes only in the central North Island, although has been recorded previously in Auckland dams. On average, larger crustaceans dominated over the smaller rotifers in all of the Auckland lakes monitored. Lake Rototoa was the least crustacean dominated (53%), followed by lakes Tomarata (58%), Kereta (68%), Spectacle (78%), Whatihua (79%), Wainamu (81%), Pupuke (88%), and Kuwakatai (95%) was the most crustacean dominated. Lake Wainamu appears to have reduced proportions of crustaceans between 2018 and 2019 relative to the 2012 to 2017 period, which may indicate this lake is undergoing a change in its trophic ecology; control of pest fish ceased in this lake in 2015, including of European perch (Perca fluviatilis), which may be reducing the importance of larger, more visible crustaceans.
The coastal habitats of Tairawhiti: A review of the scientific, local, and customary knowledge
(Report, Environmental Research Institute, 2021) Ross, Philip M.
In Aotearoa/New Zealand, regional councils and unitary authorities have a range of responsibilities for decision making in the coastal and marine area (CMA). The New Zealand Coastal Policy Statement (2010), in policy 11, sets out requirements for avoiding significant adverse effects on species, habitats and ecosystems, and section 67 of the Resource Management Act (1991) indicates that regional plans must give effect to the New Zealand Coastal Policy Statement. For regional councils to be able to successfully manage indigenous marine biodiversity (composed of species, habitats and ecosystems) they must have some understanding of the types of biodiversity present within a region’s CMA, and knowledge of the spatial distribution of that biodiversity. For regions such as Auckland and Northland biodiversity in the CMA has been relatively well described. For example, the Department of Conservation has compiled a marine habitat map for the Northland section of the Northeast Marine Bioregion, which covers an area of 1.34 million hectares of coastal habitat from Ahipara to Mangawhai (https://www.nrc.govt.nz/resource-library-summary/research-and-reports/coastal/). This knowledge makes it much easier for councils to develop coastal plans that provide appropriate protections and management outcomes. In other regions, less information is available which can make it difficult to put in place appropriate environmental management. The Gisborne Region (Tairawhiti) is a region for which there is comparatively little information available regarding marine biodiversity and the distribution of coastal habitats. The region has been under-represented in coastal research to date, which is largely a consequence of its remoteness to institutions conducting research in the CMA (Universities, CRIs and other research providers). Consequently the Gisborne District Council (GDC), the unitary authority responsible for Tairawhiti, does not have readily available and robust information about the marine and coastal environments of the region. This lack of knowledge spans the range of coastal habitats which GDC has the task of managing under the Resource Management Act (1991). As a first step towards gathering the information required to better manage the Tairawhiti CMA, this report collates and summarises the available scientific, local and customary knowledge on the extent, location and state of marine and estuarine habitats within the Tairawhiti region. In addition to the collation of this information, additional objectives for this report include: identifying gaps in the information base; recording information that might explain how pressures and activities within the region may have altered coastal habitats; providing advice on priorities for additional work required to fill knowledge gaps; and where possible, include mātauranga Māori in accordance with tikanga. With this knowledge, GDC will be in a better position to facilitate the development of a Regional Plan for Tairāwhiti to set the strategic direction for growth, development and resource management over the next 30 years.
Sediment aluminium content of Lakes Rotorua and Rotoehu: 2020 monitoring survey
(Report, Environmental Research Insitute, 2021) Tempero, Grant Wayne; Davies-Calway, Celeste Jade
The application of aluminium sulphate (alum) to freshwater systems is commonly undertaken in order to restrict the availability of dissolved reactive phosphate (DRP), thereby reducing phytoplankton growth. Alum treatment of inflows to Lake Rotorua was initiated in 2006 and to Lake Rotoehu in 2011. As of December 2020, a total of 773 tonnes of aluminium had been dosed to Lake Rotorua and 124 tonnes to Lake Rotoehu. Improvements in water quality have been subsequently observed in Lake Rotorua with values of the Trophic Lake Index (TLI) decreasing from 4.8 to 4.2. In contrast, water quality has not significantly improved in Lake Rotoehu and alum dosing was halted from July 2018 to December 2020 while a review was conducted. The University of Waikato was contracted by the Bay of Plenty Regional Council to conduct on-going monitoring of sediment aluminium concentrations in lakes Rotorua and Rotoehu as part of their resource consent conditions for alum dosing of inflows to these lakes. In addition to sediment total aluminium content, the proportion of amorphous (non-crystalline) aluminium was assessed. Amorphous aluminium is recognised as the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from the water column. It was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing. Fifteen sediment cores were taken from Lake Rotorua in December 2020. Previous surveys had reported little aluminium accumulation in the main basin of Lake Rotorua, with aluminium accumulation primarily occurring near the outlet to the Utuhina Stream and the 45 m deep crater north of Motutara Point. Based on this information, coring locations were modified from previous surveys with seven near-shore and crater sites sampled and the number of main basin sites sampled reduced to eight. The background sediment aluminium content for the main basin of Lake Rotorua is approximately 5 g Al kg-1 dry weight. The current survey supports the findings of previous sediment surveys with the main depositional areas for alum derived aluminium being the surface (1–4 cm depth) sediments of Te Ruapeka Bay, which can reach 12 g Al kg⁻¹ and the crater north of Motutara Point at ~8 g Al kg⁻¹. There was no apparent accumulation of aluminium beyond background levels to the east of Sulphur Bay or in the main basin of Lake Rotorua. In Lake Rotoehu, seven sites were surveyed in December 2020, extending from the mouth of the Waitangi Stream out into the main basin of the lake. Results were similar to those reported by Tempero and Hamilton (2016), with background sediment aluminium content approximately 5-6 g Al kg⁻¹. Alum derived aluminium was primarily accumulating in Te Wairoa Bay close to the discharge point of the Waitangi Stream with levels exceeding 25 g Al kg⁻¹ However, the two-year cessation of alum dosing resulted in a small decline of ~5 g Al kg⁻¹ in the surface sediments. Despite a five-fold increase in total aluminium content in Te Wairoa Bay over background levels, amorphous aluminium content appears to have declined due to the 2-year halt in alum dosing and aging of alum floc to the mineral gibbsite. There was no evidence of aluminium accumulation in the main basin of Lake Rotoehu.
Assessment of impacts of mechanical spat harvesting on the surf clams of Te Oneroa a Tōhē
(Report, 2020) Ross, Philip M.
Much of the mussel spat used to seed mussel aquaculture farms throughout New Zealand is sourced from Te Oneroa a Tōhē (90 Mile Beach) in Te Hiku (far north of New Zealand). The mussel spat washes ashore attached to seaweed and hydroids where it is collected by spat harvesters and transported to mussel farms around the country to be on-grown. The collection of Te Hiku spat and seaweed was originally done by hand. However, the methods used have evolved over time and mussel spat is now primarily collected using mechanical loaders operating in the surf zone. Local iwi, hapu and the wider community have recently voiced their concerns about the impacts of this harvesting method. Specifically, there are concerns about the impact of loaders operating on top of toheroa (Paphies ventricosa) and tuatua (Paphies subtriangulata) beds or other shellfish inhabiting in the intertidal and subtidal areas of Te Oneroa a Tōhē. Consequently, research into the ecological impacts of mechanical spat harvesting was conducted to address the concerns of the community and inform the management of the Te Hiku spat fishery. This research aimed to examine the ecological impacts of a ‘worst case scenario’ by (1) simulating an intensity of spat harvesting activity much greater than would be anticipated in the ‘real world’ and (2) conducting the research at high density tuatua beds where impacts would potentially be greatest. Adult toheroa were not targeted in the experiment to avoid unnecessary impacts on already depleted toheroa populations. At each of three sites on Te Oneroa a Tōhē, nine spat harvesting loaders were repeatedly driven in and out of the surf, over shellfish beds, for 75 minutes leading up to the low tide. Once loader activity ceased, a sampling team made up of mana whenua, local primary school children, spat harvesters and staff from MPI, Te Ohu Kaimoana and the University of Waikato collected clams from the intertidal area. Collections were made from both impact and control (non-impact) sites, where (a) the number of crushed shells was quantified and (b) the self-righting and burying abilities of tuatua from impact and control areas were compared to provide an estimate of sub-lethal effects. There was no detectable impact of mechanical spat harvesting loaders on tuatua (or the juvenile toheroa that were present in the sampled tuatua beds) when these surf clams were either fully or partially buried in sands of Te Oneroa a Tōhē. Rates of shell damage were less 2 than 6.1% and were similar in impact and control areas indicating much of the observed shell damage was caused by the sediment corers that were used to extract samples from the beach. Similarly, being driven over by loaders did not affect the ability or speed at which tuatua were able to right and bury themselves in the sediment. When standing on end these clams appear robust to the forces exerted by loaders upon the sediment surface. However, beach cast clams (both tuatua and toheroa), lying on top of the sediment on their sides are vulnerable to crushing by vehicles. This includes juvenile clams that ‘float’ to the beach surface where multiple loader passes liquefy the surface sediment. Mortality in these beach cast clams was not well captured by the sampling methodology used in this study, but was observed at two of the three sites sampled. It was not possible to quantify this type of mortality during this study. However, the number of clams crushed on the beach surface was small relative to the high abundances of clams within the sediment and the impact is not considered ecologically significant at the scale the individual shellfish beds or the entire beach. Overall, there was nothing observed during the course of this experiment to suggest that mechanical harvesting is having a significant ecological effect on the toheroa or tuatua of Te Oneroa a Tōhē. Mechanical spat harvesting did result in some clam mortality during the course of this experiment, and it is likely that some mortality will occur in the future when clams are present on the beach surface. However, the level of mortality observed, and anticipated, is unlikely to compromise the viability of either clam species. To minimise clam mortality caused by spat harvesting, loader operators should endeavour to avoid areas where large numbers of surf clams are either beach cast or are observed washing around in the shallow subtidal. It would also be prudent, because of the depressed state of toheroa populations on Te Oneroa a Tōhē, for spat harvesters to have up-to-date information about the location of toheroa beds and avoid them where possible. It should be noted that concerns have been raised as to whether the driving of loaders during this study was equivalent to real world operations. However, the collection of operational data during this experiment, the proposed installation of GPS trackers on all loaders and the use of observers will allow for monitoring and enforcement of operating procedures established in the industry code of practise.

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