Hauraki Gulf Research Articles

Bryde's whales (Balaenoptera cf. brydei Olsen 1913) in the Hauraki Gulf and northeastern New Zealand waters

Bryde's whales (Balaenoptera cf. brydei Olsen 1913) in the Hauraki Gulf and northeastern New Zealand waters

A wind shift: Integrating curriculum for education for sustainable development

Abstract: For seven years, trainee teachers in the Pre‐Service Secondary Teacher Education Programme at Massey University College of Education, Albany campus, have integrated their curriculum areas to model the processes school students could follow in environmental education and education for sustainable development using Motutapu, an island adjoining Rangitoto in the Hauraki Gulf Marine Park, as the context for their actions. Evaluation of the programme indicates that it is empowering to learn about connections between subject areas and the potential for school students to have a hand in creating a sustainable future and to participate in real world concerns.

Exploiting sensory ecology to reduce seabird by-catch

In a previous study, we reported that deploying small amounts of biogenic oil derived from the livers of school sharks (Galeorhinus galeus) was effective in reducing the numbers of seabirds attending fishing vessels and seabird diving activity in the Hauraki Gulf, New Zealand. This seabird assemblage was numerically dominated by Flesh-footed Shearwaters (Puffinus carneipes) and the globally vulnerable Black Petrel (Procellariaparkinsoni). The results suggested that the oil deterrent operated via an olfactory or chemesthetic mechanism. Here we compare the deterrent effects of shark- liver oil with three other fish oils, in the Flesh-footed Shearwater-Black Petrel assemblage. We also report on trials assessing the deterrent efficacy of shark-liver oil and one other fish oil in an assemblage including four species of albatrosses (Diomedea spp., Thalasarcche spp.), Southern and Northern Giant-Petrels (Macronectes giganteus and M. halli), and Cape Petrels (Daption capense). Shark-liver oil was the most effective deterrent of the four fish oils tested in the Flesh-footed Shearwater—Black Petrel assemblage, but it did not deter albatrosses, giant-petrels or Cape Petrels from attending vessels. Thus, the deterrent was effective only on burrow-nesting seabird species. These results may provide further support for our speculation that the deterrent operates via an olfactory mechanism, while corroborating other work linking life-history characteristics of seabirds to their sensory ecology. We recommend research to investigate the mechanism and active ingredients by which shark-liver oil deters some species of seabirds. We also suggest testing fish oils on White-chinned (Procellaria aequinoctialis) and Grey (Procellaria cinerea) Petrels, and Sooty Shearwaters (Puffinus griseus), as well as in other areas occupied by Flesh-footed Shearwaters, to assess further potential for this natural oil or its ingredients to reduce by-catch of seabird species globally.

Assessing the Risk of an Aquaculture Development on Shorebirds Using a Bayesian Belief Model

ABSTRACT One of the largest Ramsar-designated wetlands in New Zealand is located at Miranda, in the Hauraki Gulf, at the head of a large sheltered embayment (the Firth of Thames). The habitat is particularly significant in that it supports large populations of nationally important, and Arctic migratory, shorebirds. At present regulatory authorities are processing applications for a new marine farming region in the Firth and both regulators and stakeholders have expressed a desire to investigate possible interactions between the possible marine farms and the Ramsar wetland. The specific objective of this study was therefore to use existing information to investigate the risks of the possible aquaculture activities on the ability of the southern Firth habitats to support shorebirds. The study involved the development of a hazard assessment, and then investigating risk pathways through the use of a Bayesian network model, and a complex systems model. The hazard assessment identified multiple pathways through which the farms may interact with the wetland habitat; including through changes to primary productivity, detrital pathways and sediment dynamics. Furthermore, both the Bayesian network model and complex systems model suggested that the ability of the habitat to support shorebirds is nonlinearly dependent on both the habitat size, and quality; both of which could potentially be influenced by the establishment of the farms.

Effects of fine sediments on settlement and survival of the sea urchin Evechinus chloroticus in northeastern New Zealand

Populations of the sea urchin Evechinus chloroticus were monitored at wave-exposed low-sediment reefs and wave-sheltered high-sediment reefs in the Hauraki Gulf, northeastern New Zealand. Urchin populations on both wave-exposed and sheltered reefs were dominated by adults. Wave-exposed reefs supported higher densities (2.7 to 9.6 ind. m–2) than did wave-sheltered reefs (0.1 to 6.6 ind. m–2). Juvenile urchins (<30 mm test diameter [TD]) were 25 times more abundant on wave-exposed reefs. Urchin settlement of 0.2 to 0.6 ind. 100 cm–2 was recorded at wave-exposed reefs but was undetectable at wave-sheltered reefs. Laboratory experiments were conducted to assess whether the volumes of sediment loads observed on sheltered reefs could affect the survivorship of early life stages of urchins in the absence of other environmental factors. Results indicated that fine sediments at one-third and two-thirds of concentrations found on wave-sheltered reefs inhibited the settlement of larvae and reduced the survival of urchin recruits (2 to 5 mm TD) and juveniles (10 to 30 mm TD). Survival rates of juveniles were higher than for more recent recruits, suggesting size-dependent mortality. A lack of significant differences between high and low treatments in all experiments suggests that urchin settlement and survival can be affected negatively at low levels of sediment that are common in natural environments.

Tsunami washover deposits, Tawharanui, New Zealand

Barrier dunes on the northern side of the Tawharanui Peninsula, north of Auckland, New Zealand, appear to have been overtopped by extreme waves that have deposited two large sand washover lobes in a back beach wetland. Present-day storm surges and storm waves are incapable of overtopping the barrier dunes. However, historical data and numerical models indicate tsunamis are amplified by resonance within the adjacent bay and Hauraki Gulf. Further, the location of nearshore reefs in close proximity to the washover lobes suggests that the interaction between tsunamis and the reefs further amplified the waves at those locations. The presence of a distinctive pumice (Loisels Pumice) within the washover deposits suggests that the deposits are associated with a 15th Century eruption from the submarine Mt Healy caldera located northeast of New Zealand.

Adventive occurrence in New Zealand of the scale‐worm Paralepidonotus ampulliferus (Annelida: Polychaeta: Polynoidae)

The distinctive polynoid Paralepidonotus ampulliferus is known to be distributed across the Indian Ocean and the western Pacific Ocean, and is present around much of the Australian coast. It is reported here for New Zealand for the first time, and a description is provided. The scale‐worm has been found subtidally in Whangarei Harbour, and is widespread around the soft‐shores of Waitemata Harbour (Auckland) and nearby Hauraki Gulf inlets, with the earliest record dating from late 1998. Surveys before 2003 in Waitemata Harbour, Whangarei Harbour, and elsewhere around New Zealand had not detected the species. Its presence in New Zealand is evaluated as unlikely to have been achieved without human‐mediated assistance.

Genetic variation in island populations of tuatara (Sphenodon spp) inferred from microsatellite markers

Tuatara (Sphenodon spp) populations are restricted to 35 offshore islands in the Hauraki Gulf, Bay of Plenty and Cook Strait of New Zealand. Low levels of genetic variation have previously been revealed by allozyme and mtDNA analyses. In this new study, we show that six polymorphic microsatellite loci display high levels of genetic variation in 14 populations across the geographic range of tuatara. These populations are characterised by disjunct allele frequency spectra with high numbers of private alleles. High F ST (0.26) values indicate marked population structure and assignment tests allocate 96% of all individuals to their source populations. These genetic data confirm that islands support genetically distinct populations. Principal component analysis and allelic sequence data supplied information about genetic relationships between populations. Low numbers of rare alleles and low allelic richness identified populations with reduced genetic diversity. Little Barrier Island has very low numbers of old tuatara which have retained some relictual diversity. North Brother Island’s tuatara population is inbred with fixed alleles at 5 of the 6 loci.

Clostridia dominate 16S rRNA gene libraries prepared from the hindgut of temperate marine herbivorous fishes

Bacterial diversity in the microbial communities of posterior gut sections of three temperate marine herbivorous fish species from New Zealand was characterised using Amplified Ribosomal DNA Restriction Analysis, and 16S rRNA gene amplification and sequencing methods. The fish were collected in 1999–2000 in the Hauraki Gulf, New Zealand (35°54’–36°24’S, 174°48’–175°25’E). The gastrointestinal bacterial communities of Kyphosus sydneyanus (Gunther, 1886) (F. Kyphosidae), Odax pullus (Forster in Bloch and Schneider, 1801) (F. Labridae) and Aplodactylus arctidens Richardson, 1839 (F. Aplodactylidae) were dominated by five clades of bacteria, four of which belong to recognized clostridial clusters. The clone libraries of K. sydneyanus and O. pullus contained sequences from most of these clades, but were dominated by members of clostridial clusters XI and XIVa, respectively. The clone library of A. arctidens was dominated by members of clostridial cluster XIVb and an unassigned cluster containing Eubacterium desmolans and Papillibacter cinnaminovorans. The finding that strains of Firmicutes dominated the gastrointestinal microbial communities of all three fish species is consistent with the results of similar studies on terrestrial vertebrate herbivores. This work thus contributes to the view that gastrointestinal symbionts in some marine herbivorous fishes may play a similar role to those in terrestrial vertebrate herbivores studied to date.

Sources and diagenetic status of organic matter in the Hauraki Gulf, New Zealand: Evidence from the carbon isotopic composition of d- and l-amino acids

The origin of sedimentary organic matter and the influence of microbial reworking in the Hauraki Gulf, New Zealand, were determined using the stable carbon isotopic compositions of sedimentary d- and l-amino acids. Core top sediments from three offshore and five inner Gulf sites were collected using a multi-corer. After correction for microbial alteration of original source materials, source apportionment of l-amino acids indicated that the organic matter at the outer Gulf sites was predominantly derived from a marine source, whereas the inner Gulf sites reflected a terrestrial source. The isotopic compositions of d-amino acids were consistent with preferential microbial utilization of marine organic matter in the outer Gulf and preferential utilization of terrestrial material in the inner Gulf. Microbial reworking was most prevalent at the outer Gulf sites where up to 58% of the total hydrolyzable amino acids (THAA) were derived from microbial synthesis. Although the inner Gulf sites contained relatively less reworked material, the microbial contribution to the THAA pool ranged from 40 to 50%. This study showed that the sediment carbon dynamics in the Hauraki Gulf are complex as microbial reworking influences the isotopic compositions of the sedimentary organic matter throughout the Hauraki Gulf.

Development of an age - length structured model of the Hauraki Gulf - Bay of Plenty snapper (Pagrus auratus) population

The development of a population model in which population state is defined by a matrix of numbers at age and length is described. Functional forms for processes that fitted Hauraki Gulf–Bay of Plenty (New Zealand) snapper (Pagrus auratus) population data were developed. The model was fitted to: commercial and research samples of proportions at age and length, commercial samples of proportions at age, tag–recapture estimates of numbers at length, a catch per unit effort abundance index, and sea surface temperature data. For each age–length element of the state matrix, the model determines a transition vector that gives a distribution of non-negative growth increments. Mean growth is both length- and age–length-dependent, but also varies between years. Annual mean growth and annual year-class strength were both found to be positively related to sea surface temperature, but during different seasons. It was also found that variations in growth between years resulted in moderate and sustained fluctuations in population biomass. Diagnostic tools that were helpful in fitting the age–length data are described, and potentially fruitful model developments are suggested.

A new location for the Poor Knights spleenwort (Asplenium pauperequitum, Aspleniaceae) on The Forty Fours, Chatham Islands, New Zealand

Documentation is made of the discovery of the Poor Knights spleenwort, (Asplenium pauperequitum) in a sample of vascular plant specimens collected from The Forty Fours. These islands are the easternmost outlier of the Chatham Islands archipelago. Hitherto this fern had been believed endemic to the Poor Knights Islands and Mokohinau Islands of the Hauraki Gulf, off eastern Northland, North Island, New Zealand. Frond and spore morphology together with chloroplast DNA sequences were used to confirm its identity. Whether this fern disjunction of some 1245 km is the result of vicariance or longdistance dispersal is discussed and long‐distance dispersal of fern spores or whole sporangia is considered most likely.

Impacts of Ecotourism on Short-Beaked Common Dolphins (&lt;I&gt;Delphinus delphis&lt;/I&gt;) in Mercury Bay, New Zealand

Short-beaked common dolphins (Delphinus delphis) often are found in large aggregations offshore from the eastern coast of New Zealand. They are the primary target of at least six marine mammal tourism operations from Whakatane to the Hauraki Gulf. This report details the first longterm investigation of interactions between tourists and common dolphins. During a 3-y study offshore from Whitianga on the Coromandel Peninsula, 105 focal group follows, totaling 118 h of observations were conducted from a 5.5-m, rigid-hull inflatable boat. Seventy-two of these observations were conducted in the absence of the tour boat (baseline), and 33 with the tour boat. Baseline data were compared with “tour boat” data to assess changes in dolphin behaviour resulting from the tour boat approaching and swimmers entering the water to snorkel with the dolphins. Common dolphins responded with a relatively predictable pattern to approaching boats. Initial attraction (mean duration 8 min) typically was followed by neutral behaviour (mean duration 57 min) and eventually replaced by boat avoidance. Smaller dolphin groups showed boat avoidance sooner and more frequently than larger groups. When swimmers entered the water, dolphins only spent an average of 2 min in their vicinity. Throughout encounters, they maintained a distance of at least 3 m from the nearest swimmer. During half of the attempted swims, dolphins did not change their course or their activity in response to swimmers. Swimmers had a better chance of a sustained interaction when the group of dolphins was large (> 50 individuals) and/or the number of swimmers in the water was small (< 5). The results of this study suggested that common dolphins can be affected by tourism; however, adherence to New Zealand’s Marine Mammals Protection Regulations and the current low level of tourism appear to minimise the impact on this species.

Assessment of size at maturity and gonad index methods for the scallop Pecten novaezelandiae

Size at sexual maturity and gonad indices appropriate for measuring reproduction were examined in the scallop Pecten novaezelandiae at two sites in the Hauraki Gulf, New Zealand. Size at maturity was assessed using gonad visual grading and allometric calculation methods. Size of the smallest mature individual varied from 52 to 59 mm shell height between sites. In general, 50% of scallops were mature at 60 mm and 100% were mature at 65 mm. Small differences in size at maturity between sites may be related to differences in environmental conditions that affect growth rates. Our results were broadly similar to those reported from the South Island, however direct comparisons were compromised by the wide range of methods and definitions used in previous studies. Here we applied a method that directly scaled gonad mass to shell height, removing the need for a reference mass, and combined it with an objective method to establish size at maturity that will facilitate future comparisons.

Physical fluxes, pelagic ecosystem structure, and larval fish survival in Hauraki Gulf, New Zealand

The ecosystem supporting snapper (Pagrus auratus) larvae was studied during three spring–summer (November–January 1985–1988) spawning seasons in Hauraki Gulf, New Zealand. Upwelling-favourable winds caused more incursion of shelf water into the Gulf in 1985–1986 and 1986–1987 than in 1987–1988, but in the first two seasons, the winds were relatively weak. Stronger winds in 1987–1988 drove greater vertical diffusivity and correlated with greater mixed-layer primary biomass and productivity. Effects of vertical mixing appeared to dominate horizontal incursion of upwelled shelf water in supporting upper water column productivity. The more productive 1987–1988 season had greater abundances of nauplii, copepodites, adult copepods, cladocerans, chaetognaths, hydromedusae, decapod larvae, and numerous larval fish taxa (including snapper). There was much higher survival of snapper between the late-stage egg and post-first-feeding larval stages in 1987–1988, which correlated spatially and temporally with high larval prey densities. Neither higher egg production, fewer predators, nor less horizontal advection accounted for these strong larval snapper cohorts. We hypothesize that larval competence improved within the superior larval feeding environment, reducing predatory losses. The ecosystem response to wind mixing may partially explain the correlation of sea temperatures with recruitment, previously observed for the Hauraki Gulf snapper stock.

Paleoecology of an early Miocene, rapidly submerging rocky shore, Motuketekete Island, Hauraki Gulf, New Zealand

More than 70 macrofossil taxa (including 14 bivalves, 6 gastropods, 8 corals, 4 echinoderms, and 10 barnacles) are recorded from early Miocene (Otaian) Kawau Subgroup strata (Cape Rodney Formation and Motuketekete Limestone, lower Waitemata Group) at Motuketekete Island, Hauraki Gulf, north of Auckland City. Both in situ and transported fossils occur in deposits of greywacke boulder conglomerate, cobble to pebble conglomerate/sandstone, bioclastic calcareous grainstone, and an allochthonous breccia debris event unit, which correspond to lithofacies A, C, D, and E, respectively, of Ricketts et al. Greywacke boulders accumulated at the base of a greywacke paleocliff or sea stack that was planed off at its top to form a shore platform during the Miocene. A >2 m long, 16 cm thick coral colony grew atop a mixed substrate of boulders, pebbles, and sand, and exhibits two successional regrowth phases following debris‐influx events. Boulders and cobbles bored by pholadid bivalves (Parapholas aucklandicum Powell) are common in these basal bouldery talus deposits. A diverse suite of macrofossils, including chaliciform corals, occurs in somewhat finer grained deposits that buried the greywacke basement and boulder talus pile, and indicates either slightly deeper or more turbid conditions in the shallow photic zone. The cross‐bedded, bioclastic Motuketekete Limestone overlies these coarse‐grained Cape Rodney Formation units. Its fauna indicates deepening, with replacement of shallow by offshore taxa (e.g., Crenostrea with Bathylasma), as the Waitemata Basin underwent rapid tectonic subsidence and redeposition of sediments with the onset of subduction along the Hikurangi convergent margin. A newly identified lens of “upper breccia” (lithofacies E) in the Motuketekete Limestone contains rounded blocks of colonial coral and Tertiary siltstone. The Motuketekete occurrence of lithofacies E extends the known geographic range of this geologically instantaneous deposit; it records a regional tectonic event that is interpreted as an avalanche/debris flow triggered by faulting. The breccia appears to be a reliable marker for local lithostratigraphic correlation in lower Waitemata strata exposed north of Auckland. Appendices provide a systematic analysis of the barnacle fauna and the description of a new gastropod species, Bolma (Bolma) ballancei. The overall biotic content of the Kawau Subgroup, especially those taxa associated with hard substrate community development, indicate warm subtropical conditions similar to those found elsewhere in northern New Zealand during the early Miocene.

Karenia concordia sp. nov. (Gymnodiniales, Dinophyceae), a new nonthecate dinoflagellate isolated from the New Zealand northeast coast during the 2002 harmful algal bloom events

A new nonthecate dinoflagellate, Karenia concordia Chang & Ryan sp. nov., is described from a culture isolated during the October 2002 toxic outbreaks in the Hauraki Gulf, New Zealand. Typically, the conical epicone of the cell is dorsally convex and ventrally concave, giving it a ‘droop-nose’ look similar to the Concord supersonic aircraft. Karenia concordia may be separated from all the other closely related species by having a very long, straight apical groove which extends beyond the sulcal intrusion and towards the edge of the cingulum on the ventral surface; it is mostly hidden beneath a ‘flap’ of transparent membrane on the lower right margin of the right epicone. This is the longest apical groove found in the genus to date. Moreover, the groove is located within a ‘keel-like’ structure or crest which extends from the apex to the sulcal intrusion on the ventral surface of the cell. The position of the spherical nucleus in the cell is variable, but it is predominantly in the left hypocone.

New and remineralised nutrient supply and ecosystem metabolism on the northeastern New Zealand continental shelf

The nutrient dynamics of the NE New Zealand shelf and adjacent Hauraki Gulf are described, with the aim of relating the along- and cross-shelf physical circulation to co-occurring supplies of new and remineralised nutrients, and ecosystem metabolism. Chemical and biological properties were studied over four research voyages in early spring to late summer in 1996–1997, coincident with the physical oceanography (Zeldis et al. this issue). Upwelling prevailed in early spring to early summer, but between early and late summer upwelling ceased and there was a marked transition toward downwelling and strongly stratified conditions on the shelf. The upwellings caused extensive loading of the inner-shelf water column and Hauraki Gulf bottom waters with nitrate. However, significant increases in phytoplankton biomass were not observed, probably because of dilution of shelf phytoplankton stocks by upwelling, and mismatch of voyages with delayed bloom development. Between spring and late summer, the shelf and Hauraki Gulf evolved strongly from net autotrophic toward net heterotrophic ecosystem metabolism, as indicated by decreasing ratios of new-to-regenerated nitrogen (N) stocks and of chlorophyll- a to phaeopigment, and increases in apparent oxygen utilisation (AOU). The effect of this transition on supply rates of new and remineralised N and silica in shelf waters was examined using a three end-member mixing model. Nitrate was the dominant N species remineralised near-bed, whereas ammonium remineralisation dominated shallower in the water column. Silica trapping and denitrification on the inner shelf were evident from stoichiometries of remineralisation. Vertical and along-shelf patterns in remineralisation were found, apparently related to benthic remineralisation, current speed and sediment type. Remineralised nutrients and AOU were concentrated by strong stratification in bottom waters in late summer, but on a water-column integrated basis, no seasonal change in remineralisation rates was evident. Nevertheless, with the large decrease in advected (i.e. upwelled) nutrients in late summer, the maintenance of significant remineralised nutrient supply appeared to be important for sustaining the chlorophyll- a stocks in late summer over the shelf.

Circulation over the northeastern New Zealand continental slope, shelf and adjacent Hauraki Gulf, during spring and summer

The physical oceanography of the northeastern New Zealand slope, shelf and adjacent Hauraki Gulf is investigated, to determine the forcing of the along- and cross-shelf non-tidal residual circulation. Cross-correlation and empirical orthogonal function analyses of current meter data clearly separated wind-forced upwelling and downwelling Ekman dynamics in the shelf circulation, from dynamics over the outer shelf and slope, which were dominated by longer-period variability of the East Auckland Current (EAUC). Moored thermistor and satellite temperature data mapped three inner-to-mid-shelf upwellings in early spring to early summer. Between early and late summer, however, upwelling ceased and there was a marked transition toward downwelling and strongly stratified conditions on the shelf and in Hauraki Gulf. The offshore extent and temporal response of the upwellings to winds were in approximate agreement with theory. Moored thermistor and CTD data obtained during four research voyages showed the internal hydrological structures of the shelf and slope watermasses from early spring to late summer. While the forcing for shelf circulation arose largely from local winds, far-field effects associated with the EAUC caused shallow (<60 m depth) subtropical surface water intrusions across the shelf/slope boundary in late summer and near-bed onshore flows at the shelf edge, possibly through bottom Ekman-layer effects. These results describe the physical dynamics underpinning the chemical and biological ecosystem responses to seasonally varying upwelling and downwelling, and surface water intrusion, described in an accompanying paper (Continental Shelf Res. (2004), this volume).

Comparison of multiple techniques to evaluate reproductive variability in a marine bivalve: application to the scallop Pecten novaezelandiae

Reproduction and spawning of the scallop Pecten novaezelandiae were monitored at four sites in the Hauraki Gulf, New Zealand, from July 2000 to July 2001. A visual grading system based on the macroscopic appearance of the gonad was developed and tested, and changes in visual grade, quantitative histology, and standardised gonad mass were used to describe seasonal and spatial patterns in gametogenesis and spawning. Visual grade was significantly correlated with histological and gonad mass data (r 2 = 0.74–0.87) and validated as an accurate method for measuring reproduction in P. novaezelandiae. Visual grading facilitates rapid assessment of reproductive condition and can be conducted non-destructively, thus providing a tool allowing long-term studies of individual spawning behavior in relation to environmental signals. Scallops exhibited episodic spawning, with spawning events detected in spring, summer, autumn, and even early winter. Gonad recovery and subsequent gamete development and maturation were apparent between spawnings. Within-season variability in gonad size and condition could be the result of multiple (serial) spawnings during a season. The timing of spawning varied among populations, probably reflecting differences in environmental conditions that influenced reproduction. However, the largest spawning events occurred at all sites in early summer (December/January), coincident with wind-driven upwelling conditions.