Waikato River Research Articles

Abundance of larval native and nonnative fishes in floodplain habitats of the lower Waikato River, New Zealand

The floodplains of many large rivers worldwide are important spawning and nursery habitats for multiple fish species. We investigated the potential importance of different floodplain habitats for fish larvae. Samples were collected from 14 sites along the Waikato River, northern New Zealand, from September to October 2010. Larval fishes were identified using traditional morphological identification and DNA analyses. Our results revealed high densities of invasive koi carp and goldfish larvae in flooded terrestrial habitats compared to other habitat types. Species richness was highest in the wetland habitat. Redundancy analysis revealed that koi carp and goldfish abundances were strongly positively correlated with chlorophyll a concentrations and zooplankton densities. Floodplain habitats seem to be important habitat for larvae of both native and introduced fish species in the lower Waikato River. Because introduced larval fish out-numbered native fishes in floodplain habitats managers should consider implementing measures that at key times provide controlled access to floodplain habitats for native species and also limit access of introduced fishes.

Spatial and temporal patterns of carbon flow in a temperate, large river food web

Using natural abundances of stable carbon (δ13C) and nitrogen (δ15N) isotopes, we quantified spatial and temporal patterns of carbon flow through the main channel food web in the lowland section of New Zealand’s longest river, the Waikato River. The study was undertaken with the objective of determining whether the Waikato River conforms to contemporary theoretical concepts regarding carbon flow in large river food webs. Potential organic carbon sources and invertebrate and fish consumers were sampled from three different hydrogeomorphic zones on six occasions, representing a range of seasonal and flow conditions. In line with the predictions of the riverine productivity model and riverine ecosystem synthesis, autochthonous algae and biofilms were the most important basal carbon source contributing to consumer biomass. These were often supported by C3 aquatic macrophytes and allochthonous C3 riparian plants. The relative importance of organic carbon sources differed between zones and appeared to change depending on season, presumably in response to water temperature and flow, particularly in the unconstrained zone of the lower river. We also demonstrate that to draw robust conclusions, consideration must be given to quantifying the isotopic signatures of organisms lower in the food web, as these can change significantly between sampling times and hydrogeomorphic zones.

Effects of flow on lateral interactions of fish and shrimps with off-channel habitats in a large river-floodplain system

Off-channel habitats play a crucial role in the life-cycles of many riverine fish species, but lateral movements of fish into these habitats are poorly understood. We tested how flow dynamics affects the movement of fish and shrimps between the main river channel and different types of off-channel habitats: a riverine lake and a wetland. Our study site was the lower Waikato River, North Island, New Zealand, where there are numerous off-channel habitats. Fish were sampled using directional fyke nets. Shortfin eel (Anguilla australis) migrated mostly into the wetland at night, particularly during high river flows. Common bullies (Gobiomorphus cotidianus) were most abundant during the day and in low-discharge conditions, moving mostly into the riverine lake, whereas freshwater shrimp (Paratya curvirostris) moved mostly into the wetland. High numbers of non-native larval common carp (Cyprinus carpio) moved out of the wetland with retreating flood water. This study emphasises the importance of lateral connectivity and flooding in functioning of this river system where numerous native fish, but also exotic fish, used off-channel habitats. Floodplain management strategies should promote ‘controlled connectivity’ measures that provide access for native species at key times while limiting opportunities for introduced species to utilise their favoured off-channel habitats.

SPATIAL VARIATION OF STRUCTURAL AND FUNCTIONAL INDICATORS IN A LARGE NEW ZEALAND RIVER

ABSTRACTThe ecological responses of large rivers to human pressure can be assessed at multiple scales using a variety of indicators, but little is known about how the responses of ecological indicators vary over small spatial scales. We sampled phytoplankton, zooplankton and macroinvertebrates and measured river metabolism and cotton strip breakdown rates (loss in tensile strength) in contrasting habitats along a 21‐km urban‐industrial reach on a constrained section of the Waikato River, New Zealand's longest river. Rates of gross primary production (2.8–7.8 g O2/m2/d) and ecosystem respiration (3.5–12.7 g O2/m2/d) did not differ consistently between near‐shore (2–3 m from river side) and far‐shore (ca. 10 m from side) locations, urban and industrial reaches or between autumn and spring sampling occasions. Rates of cotton decay (−k) ranged from 0.014 to 0.112 per day and were typically faster at far‐shore locations and in the section of river receiving industrial inputs, but slower in spring compared with autumn. Nonmetric multidimensional scaling analysis of phytoplankton and zooplankton data did not reveal spatial patterns relating to pressure or location (embayment, edge, mid‐river). However, the macroinvertebrate ordination suggested distinct communities for the mid‐river benthos compared with near‐shore communities and a distinction between sites in the urban reach and the industrial reach. Our results suggest that large‐river macroinvertebrate communities and cotton decay rates can be influenced to varying degrees by reach‐scale pressures and local habitat conditions. Monitoring designs in spatially complex rivers should account for habitat heterogeneity that can lead to differences in structural and functional indicator responses. Copyright © 2012 John Wiley & Sons, Ltd.

Metal removal via particulate material in a lowland river system

Twelve month surveys of acid-soluble and dissolved trace metal concentrations in the lower Waikato River (in 1998/9 and 2005/6) showed abnormally low particulate Fe, Mn, Cu, Pb and Zn concentrations and mass flux in autumn, when the suspended particulate material (SPM) had a relatively high diatom and organic carbon content, and low Fe and Al content. Dissolved Mn, Cu and Zn concentrations also decreased in autumn, while dissolved Fe and Pb concentrations were unaffected. While SPM settlement under the low river flow conditions present in autumn can explain the removal of particulate metals, it does not explain dissolved metal removal. SPM-metal interaction was therefore investigated using seasonal monitoring data, experimental adsorption studies, sequential extraction and geochemical modelling. Pb binding to SPM occurred predominantly via Fe-oxide surfaces, and could be reliably predicted using surface complexation adsorption modelling. Dissolved Mn concentrations were controlled by the solubility of Mn oxide, but enhanced removal during autumn could be attributed to uptake by diatoms. Zn and Cu were also adsorbed on Fe-oxide in the SPM, but removal from the water column in autumn appeared augmented by Zn adsorption onto Mn-oxide, and Cu adsorption onto the organic extracellular surfaces of the diatoms.

The Key Actors of Waikato River Co-Governance

The Waikato River is an important New Zealand waterway with a long history of people making claims to it, including Treaty of Waitangi claims by Māori for guardianship and ownership rights. The claims process has most recently culminated in Waikato-Tainui and the Crown signing a 2009 Deed of Settlement for the river.1 The 2009 deed establishes a new co-governance structure for the river, with equal Māori and Crown representation. However, what has also transpired from the agreement is the emergence of a new guard of Māori decision-makers who have challenged and displaced the traditional Kīngitanga (King Movement) leaders as the main power-brokers of the Waikato River. Before Waikato-Tainui's most recent river negotiators there were a number of other Waikato ancestors who contributed to strengthening the relationship between Waikato Māori and the Waikato River. Prominent Kīngitanga leaders such as Princess Te Puea Herangi, Sir Robert Mahuta, Te Arikinui (paramount chief) Te Atairangikaahu and successive Māori kings are recognized as mediating the relationship between Waikato Māori and the Waikato River.

Otolith microchemistry of koi carp in the Waikato region, New Zealand: a tool for identifying recruitment locations?

We assessed differences in the otolith microchemistry of koi carp, a colour variant of the invasive common carp Cyprinus carpio, at various locations in the Waikato region of New Zealand. Although koi carp are abundant here, little is known about where and in what habitats they breed. We investigated the feasibility of determining the natal habitats of adult koi carp (in the Waikato River, selected tributaries, and riverine lakes in the catchment) using otolith elemental signatures and employing laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Differences in elemental concentrations in water among the sites indicated that variation in otolith microchemistry was likely. Ratios of manganese (Mn), rubidium (Rb), strontium (Sr), and barium (Ba) to calcium (Ca) in otolith edges differed significantly among the sites, and Sr:Ca in the water and otoliths was positively correlated. A discriminant function analysis using Rb, Sr, and Ba accurately classified the otolith edge signatures of koi carp from some locations, but the otolith signatures of koi carp caught from adjacent locations were often indistinguishable. This suggests that our results could have been confounded by either (1) recent movement of koi carp or (2) a lack of differences in water chemistry among sites. Taken together, these results demonstrate that otolith microchemistry can be used to test retrospectively for koi carp migration between sites on a broad scale in theW aikato region, but fine-scale movements may not be detectable

Predictability of Heavy Precipitation in the Waikato River Basin of New Zealand

Abstract This paper investigates the predictability of heavy precipitation in the economically important Waikato River basin of New Zealand. A 2-yr archive of Global Forecast System (GFS) model data to +180 h for the period August 2005–August 2007 forms the basis of the study. GFS model predictions of precipitation are compared to surface measurements from 22 stations in and around the river basin. Categorical hit rate and bias, threat score, false-alarm ratio, probability of detection, RMSE, skill score, and mean error are all plotted as a function of model lead time for the 2-yr period. The general synoptic structures of heavy precipitation events are often identified at long lead times. An example is shown for January 2006 when heavy rainfall is identified by GFS at +150 h, accurate location and timing is given at +48 h. Precipitation amounts are systematically underpredicted by GFS and the spatial distribution of rainfall is limited by model resolution. The value of GFS lies in its ability to provide early warning of potential heavy precipitation. Three heavy rainfall events were selected for higher-resolution Weather Research and Forecasting (WRF) model simulation. The WRF model produced more realistic geographical distributions of precipitation but cannot compensate for errors in the global model. WRF underpredicts precipitation for all three cases; the best simulation generates 92% of observed precipitation. Unobserved spurious convective rainfall can be generated by the WRF model following the passage of a frontal weather system. A possible mechanism is suggested that links this to underpredicted frontal rainfall.

Movements of Radio- and Acoustic-Tagged Adult Koi Carp in the Waikato River, New Zealand

Abstract The movement of koi, a highly colored variant of common carp Cyprinus carpio, was monitored for 18 months in the Waikato River, New Zealand, with both radiotelemetry and acoustic telemetry. Koi had large total linear ranges (mean, 39 km), and most fish (74%) monitored for more than 250 d traveled between the Waikato River and lateral habitat. Differences in total linear range and mean daily movement between years suggest a behavioral response associated with reduced habitat availability during periods of low flow. The movements of koi were highly variable and infrequent, suggesting that important long-range movements are missed in short-term studies (<250 d), resulting in underestimations of total linear range. Our data suggest that large numbers of koi could have been intercepted traveling between lateral habitat and the Waikato River during 1 of 2 years, indicating that point source removal would be highly effective. Received June 12, 2009; accepted January 20, 2011

Framework for evaluating management interventions for water-quality improvement across multiple agents

It is difficult to accurately predict the impacts of policies for control of nonpoint-source pollution because analytical frameworks incorporating agent heterogeneity are rare. This paper overcomes this limitation through describing a new framework in which the behaviour of individual firms is explicitly represented by large, complex models calibrated to baseline information. Disaggregation allows the simulation of policies that require uniform reductions in pollutant load or those that allow different rates of abatement between firms to achieve a given nutrient target at least cost, as with the trading of pollution entitlements. The reduction of nitrate leaching from intensive dairy production in a catchment of the Waikato River in New Zealand is used as an illustrative application. It is highlighted that satisfaction of water-quality standards will incur substantial costs within this region. Overall, the framework is notable for its integration of multiple modelling techniques from diverse disciplines and its focus on the behaviour of individual agents. Moreover, it can easily be applied elsewhere where sufficient information is available.

Access to minerals

Controversy over access to minerals is not recent. For example, in 2011 the Supreme Court will hear the Paki v Attorney General case, involving Māori claims to continued interests in the bed of the Waikato River. In 1903, under the Coal Mines Amendment Act of that year, the beds of all ‘navigable’ rivers in New Zealand were taken because of a concern at the time about coal being mined under river beds. That law remains in force under the Crown Minerals Act 1991 (CMA) (section 11(2)). The case arises because there has never been a clear understanding of what ‘navigable’ means.

The fate of antimony in a major lowland river system, the Waikato River, New Zealand

Antimony is an element that is becoming of increasing concern as an environmental contaminant. Geothermal systems are a source of Sb into some fresh waters of New Zealand’s North Island. The purpose of this research was to determine the factors controlling the behaviour of geothermally-derived Sb in the large lowland Waikato River system. The Waikato River is New Zealand’s longest and most utilised river. Antimony in the system exhibited mainly conservative behaviour, and seasonally variable dilution was found to be the most important control on Sb concentrations. The most significant potential removal process was identified as adsorption of Sb onto suspended particulate material (SPM). The adsorption of Sb onto the SPM is enhanced at low (<5) pH conditions, and in the anoxic base of stratified lakes. There was evidence that the adsorption of Sb is mainly onto Fe oxides in SPM, and changes with changing Fe concentrations. Therefore, Sb adsorption was higher in winter (when Fe concentrations in SPM were higher) than in summer. In Lake Ohakuri, which was stratified during the late summer/early autumn of 2007, there was also potential for removal of Sb as Sb2S3 in the presence of sulfide formed in the anoxic layer. The behaviour of Sb was conservative through the estuary at the mouth of the river. Antimony was compared to As, a metalloid often assumed to exhibit behaviour similar to Sb in aquatic environments. It was found that while the removal processes affecting Sb will also affect As, the inverse did not necessarily apply. Arsenic will adsorb more readily to SPM than Sb and, while there was evidence for bioaccumulation of As by freshwater macrophytes, there was no such evidence for Sb.

Recruitment of Anguilla spp. glass eels in the Waikato River, New Zealand. Evidence of declining migrations?

The timing of Anguilla spp. glass eel recruitment into the Waikato River, North Island, New Zealand, was studied over a 2 year period (2004-2005). While glass eels of both the shortfin eel Anguilla australis and the endemic longfin eel Anguilla dieffenbachii were caught, the former comprised >97% of the species composition. There was a positive correlation of glass eel migrations with spring tides, with peak migration periods typically occurring within a few hours of the peak of high tide, and between 2 and 4 days after the day of spring tide. Both water temperature and discharge had significant inverse relationships with glass eel catches, with temperature explaining >30% of the variance in catch periodicity. Comparison of catch data 30 years apart showed that main migration periods appear to occur several weeks earlier today than previously. Reduced catch per unit effort and duration of runs from recent years' sampling (compared with the 1970s) indicate that a reduction in recruitment may also have occurred during this period, something recorded in other temperate species of Anguilla.

Movement, social cohesion and site fidelity in adult koi carp, Cyprinus carpio

Abstract Koi carp is an ornamental variant of the common carp, Cyprinus carpio L., that was introduced to New Zealand in the 1960s and has since become a major aquatic pest. A total of 1265 wild adult koi carp were caught by boat electric fishing, dart tagged and released at multiple sites in the lower Waikato River and associated lakes and wetlands between September 2002 and February 2005. Subsequent recaptures by boat electric fishing and recreational fishing returned 76 koi carp (6% of all tagged fish). Of these, 85% were recaptured less than 5 km from their release site; only one fish moved more than 50 km. On seven occasions, pairs or small groups of koi carp (20% of all tag returns) that had previously been tagged and released at the same locations and times were subsequently recaptured together after considerable periods of time at liberty (mean 551 days ± 419 SD). Adult koi carp in the Waikato River showed a high degree of site fidelity, exhibited prolonged social groupings and females moved downstream more often than males.

Sedimentology and allostratigraphy of post-240 ka to pre-26.5 ka lacustrine terraces at intracaldera Lake Rotorua, Taupo Volcanic Zone, New Zealand

Lake Rotorua partially occupies a nearly circular 20 km diameter volcano-tectonic depression formed at c. 240 ka by eruption of the voluminous Mamaku Ignimbrite. Three distinct lacustrine littoral terraces, defined on the basis of contrasting geomorphology and field relations, and separated by tephrostratigraphically dateable unconformities and basin-floor disconformities, fringe much of the lake basin. They are here correlated with former high-stands of the lake which resulted from the blockage and re-establishment of a number of alternative outlets due to tectonic activity and volcanism at both the host and adjacent volcanic centres. The unconformities allow division of the deposits into three allostratigraphic units, each of which is then characterised by elevation and sediment provenance. The < 240 ka, post-Mamaku alloformation comprises the highest terrace (up to 415 mASL), and represents the high-stand of an intracaldera lake accumulated in the newly created basin after the eruption of the Mamaku Ignimbrite. Considerable uncertainty surrounds the initial direction of overflow from this level, but the lake may have drained southwards for a period through the Hemo Gorge, through the Ngakuru Graben/Kapenga Caldera area and into the Waikato River catchment. The second alloformation, consisting of volcaniclastic sediments forming shoreline and littoral terraces at c. 380 m elevation developed after the eruption of the 60 ka Rotoiti/Earthquake Flat pyroclastic flows from the neighbouring Okataina Volcanic Centre blocked northern and southern routes out of the lake basin. A northeasterly outlet subsequently became established at a lower level through tectonic subsidence of the Tikitere Graben, creating a drainage path into the Haroharo caldera from where it flowed into the Bay of Plenty via the Kawerau Canyon. The post-36 ka Hauparu alloformation forms the third shoreline terrace at elevations up to 349 mASL. It is the product of a temporary high-stand from blockage of the Tikitere Graben drainage path by pyroclastic debris from the voluminous 36 ka Hauparu eruption. Subsequently, episodic growth of the Haroharo resurgent dome complex between 25 and 9 ka in the adjacent Okataina Volcanic Centre forced Lake Rotorua to rise above its post-Hauparu lowstand level to an elevation where it could overtop a drainage divide on the northern rim of Lake Rotoiti and gain access to the catchment of the Kaituna River, hence establishing the current outlet channel.

Pilot plant experiments at Wairakei Power Station

In the mid-1990s, several pilot plants were constructed at Wairakei to either improve the operational and economic performance of the power station or to mitigate the environmental effects of discharges to the Waikato River. The results of the following investigations are discussed: (1) fluid flow dynamic effects on silica scaling; (2) production of silica sols of predetermined particle size to evaluate the potential for generating commercial grade silica products; (3) use of “sulfur oxidising bacteria” for the abatement of dissolved hydrogen sulphide in cooling water; (4) removal of arsenic from separated geothermal water; (5) steam line condensate corrosion; and (6) measurement and modelling of steam scrubbing in Wairakei's long steamlines.

Making a Place: Mangakino 1946-1962

In between Whakamaru (1949-56) and Maraetai (1946-53) dams, on the Waikato River, sits Mangakino. Planned and built from c.1948 to 1951, by the Town Planning section of the Ministry of Works, the civic centre was to provide housing and services for the work force on the Maraetai scheme. The architectural design of these dams has previously been discussed as the work of émigré architect, Fredrick Neumann/Newman (Leach), and the town, as that of Ernst Plischke (Lloyd-Jenkins, Sarnitz). In 1949 the plan for Mangakino was published, alongside the plan for Upper Hutt, in the February-March edition of the Design Review. As two "rapidly growing towns," Upper Hutt and Mangakino are briefly reviewed in the context of two essays ("Who wants community centres?" and "Community Centres" by HCD Somerset), an outline of the curriculum of the new School of Architecture and Town Planning, run by the Wellington Architectural Centre, and notification of the 1948 Town Planning Amendment Act. As published in the Design Review, the plan of Mangakino includes a church in the south west, with the sporting facilities to the north and Rangatira Drive flanking a shopping strip on the east. The church sits in a field of grass, isolated and apparently serene. In the drawing published in the monograph Ernst Plischke, however, this building has been cropped off. Focusing on the case of Mangakino, this essay will review the discourse of town planning for secular and religious community in the late 1940s. This era, framed by the end of World War II and the deepening of the Cold War, is seen as the context for industrial action, a changing sense of nationalism, and small town New Zealand as the site of civil dispute.

Spatial patterns in the composition of shallow‐water macroinvertebrate communities of a large New Zealand river

Identifying the environmental factors influencing biotic patterns in large rivers will assist with extrapolating biological monitoring results to broader scale conclusions about river condition. In the present study, we collected macroinvertebrates and physico‐chemical data at 47 shallow‐water (<1‐m deep) sites, including nine sites at major tributary junctions, during summer along the lower Waikato River, North Island, New Zealand. Macroinvertebrate communities were dominated by a few relatively abundant and widespread taxa. Upper site samples were characterised by high relative abundances of Diptera, but the significance of this group declined further downstream where Crustacea became more dominant. Overall, more taxa (36) were found at tributary junctions than at mainstem sites within four hydrogeomorphic zones (22–31 taxa per zone). Significant differences among faunal groups identified in a cluster analysis on relative abundance data were detected for the percentage of wood sampled, and for water conductivity which increased downstream at mainstem sites and was high at some junction sites. Non‐metric multidimensional scaling of percentage abundance data revealed differences in community composition among zones, and among some mainstem and tributary junction sites. Geographic position (easting and northing) was significantly correlated with taxa richness and community evenness (Pielou) at mainstem sites (excluding tributary junctions), reflecting an increase in sample diversity and less equitable taxonomic dominance with distance down river. Overall, these results point to an interplay between habitat patchiness and successional and hydrogeom orphic processes influencing macroinvertebrate community composition in the lower Waikato River. Such multiscale variations need to be accounted for in the design of invertebrate biomonitoring programmes if they are to represent the ecological condition of large river environments.

Carotenoid depletion and ovarian dysfunction in common bully exposed to a New Zealand pulp mill effluent

In a previous cumulative impacts assessments of fish populations along the Waikato River, New Zealand, reduced ovary pigmentation was observed in the common bully ( Gobiomorphus cotidianus) with an associated reduction in recruitment in the pulp mill-impacted Kopakorahi Arm of Lake Maraetai compared to an upstream reference site. Carotenoid pigments are typically responsible for the yellow to red colouration of fish eggs and a number of functions for these pigments such as pro-vitamins and antioxidants have been proposed. The purpose of the current study was first to quantify the observed pigment reduction and then to establish possible consequences of carotenoid deficiency. Significantly lower levels of all measured carotenoids were observed in the ovaries of fish from below the mill outfall compared to the reference site. Using in vitro incubations of ovarian follicles, it was also found that these fish had a significantly reduced ability to produce the sex steroids testosterone and estradiol. This study demonstrates changes in ovarian carotenoids associated with pulp mill effluent exposure. Significantly reduced biosynthetic capacity of ovarian follicles demonstrates reproductive endocrine disruption potential associated with exposure to this particular effluent. These results may provide an important link between reproductive dysfunction, oxidative stress and food chain modifications in pulp mill-impacted systems.

New Zealand risk management approach for toxic cyanobacteria in drinking water

Cyanobacterial blooms are common seasonal phenomena occurring worldwide in fresh, estuarine and coastal waters, including those used for drinking-water supplies, recreation and stock watering. In New Zealand, the frequency of blooms and their geographic spread is likely to grow with increasing eutrophication and global climate change. The New Zealand Ministry of Health has recently developed national criteria for assessing and managing the risk of toxic cyanobacteria in drinking-water supplies. This paper investigates a cyanobacterial bloom incident in the summer 2002/03 in the Waikato River and hydro lakes, which are a major drinking-water supply for Hamilton City and many other smaller towns along the river. The procedures invoked by the Hamilton City Council and other authorities to deal with this bloom event are considered in terms of the best practice of the day and compared with the Drinking-Water Standards for New Zealand 2005. The presence of cyanobacteria has significant economic effects because of increases in water supply treatment costs or the need to use an alternative source, and there are also social effects from the disruption of recreational use of water bodies and loss of confidence in the quality of reticulated, treated water supplies. Notional evaluation of economic cost of monitoring regimes and control, based on the Waikato River cyanobacterial bloom incident, is also given. The multi-barrier and process-control risk management approach, reliant on good vertical communication systems between central and local government, is an advanced approach useful for any country that regularly experiences cyanobacterial problems.