Effects of floods on epilithon and benthic macroinvertebrate populations in an unstable New Zealand river

Temporal changes in epilithon biomass and benthic macroinvertebrate density were investigated in the Ashley River, a flood-prone river with an unpredictable discharge regime. Biomass, primary production and respiration of the epilithic community were highest in spring when filamentous algae were present and lowest following two large floods that occurred in close succession. Sixty invertebrate species were taken in benthic samples including 24 species of Trichoptera, 15 Diptera and 4 Ephemeroptera. Larvae of the mayfly Deleatidium (Leptophlebiidae) were numerically dominant and comprised up to 83 % of the fauna in any one month. Mean benthic invertebrate density was highest (9170–18 580 m^{–2) following long periods of low stable flow (< 30 m–3} s^–1) and lowest (230 m^–2) after a major flood (454 m^–3 s^–1). Reductions in benthic density occurred when flow exceeded about 30 m^–3 s^–1, the minimum discharge at which small cobbles are moved. Refuge seeking behaviours, flexible life histories and effective recolonization mechanisms enable the benthos of the Ashley River to persist and recover from frequent, temporally unpredictable disturbances.     

Mayfly production in a Colorado mountain stream: an assessment of methods for synchronous and non-synchronous species

Year-round collections of mayflies (Ephemeroptera) from a Colorado mountain stream allowed critical examination of several methods of calculating production for species with different life cycles. Five of the six numerically dominant species exhibited slow seasonal, univoltine life cycles. Baetis tricaudatus was bivoltine. Two species demonstrated well synchronized development, three species were poorly synchronized and a sixth was intermediate. Mean density and biomass data from each sampling date were used to ascertain the goodness-of-fit of each species to the Allen curve. It is proposed that such information can provide quantitative criteria for identifying species with well synchronized development and thereby determine when it is appropriate to directly apply cohort methods while avoiding time intensive body size (e.g. head width) measurements necessary for size-frequency analyses. In addition, these data demonstrate that species specific production varies with gross changes in elevation.     

The presence of gigartinine in a New Zealand Gracilaria species

Gigartinine, 5-(3-amidinoureido)-2-aminovaleric acid, serves as achemotaxonomic marker to distinguish two species of Gracilaria withvery similar morphologies. Gigartinine was identified by ¹³C-NMRspectroscopy and amino acid analysis of a cold-water extract from Gracilaria sp. nov., collected from a sheltered harbour localityat Blockhouse Bay, Auckland, New Zealand. Levels of this amino acid,naturally ca. 5% by dry weight of seaweed, were able to be depleted andthen restored during a nitrogen pulsing experiment. In contrast, native andpulsed samples of Gracilaria chilensis from Point Arthur, Wellingtonshowed no extractable gigartinine. Although these two species are unableto be distinguished in the field by morphological characteristics, they canbe separated by the presence or absence of gigartinine.     

The harvesting of macroalgae in New Zealand

Several species of algae have been commercially harvested in New Zealand, mainly for extraction of agar and alginates. In the past, the harvest was comprised mostly of shore-cast plants. There has been more recent interest, however, in harvesting attached plants of Pterocladia spp., Porphyra spp., Gracilaria sordida, Durvillaea spp., Macrocystis pyrifera, and Ecklonia radiata. The ecological effects of harvesting attached algae depend largely on the sizes of plants, the season of removal, the patch size of clearances, and the proximity and identity of mature plants. These have not been well-studied for seaweeds in New Zealand, but population and life history studies indicate that harvesting methods affect the continuity of algal resources, at least on a local scale, and are crucial factors in their management.     

Trichothecene production by Fusarium species isolated from grain and pasture throughout New Zealand

Liquid cultures of 200 Fusarium isolates selected to represent the most common species found in autumn pasture (70 isolates) and in grain (130 isolates) grown in New Zealand were analysed for trichothecenes and related compounds. Production of butenolide, cyclonerodiol derivatives and culmorins was also measured. The principal trichothecenes produced were derivatives of either nivalenol (NIV), deoxynivalenol (DON) or scirpentriol (Sctol), in order of frequency. The principal trichothecene producing species were F. crookwellense, F. culmorum and F. graminearum. Isolates of the first two species were predominantly NIV-chemotypes with one or two isolates respectively as Sctol-chemotypes. F. graminearum showed equal quantities of NIV- and DON-chemotypes, with the DON-chemotypes producing primarily 15-acetyldeoxynivalenol (15-ADON).     

Water temperature and upstream migration of glass eels in New Zealand: implications of climate change

Glass eels migrating upstream in a New Zealand river showed a clear preference for water temperatures between 12 and 20°C, with an optimum of 16.5°C. Water temperatures <12°C and >22°C almost completely inhibited migration, which implies that warmer temperatures associated with global climate change might have a detrimental impact on glass eel recruitment in their current ranges. We established this by trapping glass eels of shortfin, Anguilla australis, and longfin, A. dieffenbachii, eels nightly from September to November. Eels caught in 2001 (50,287) outnumbered those caught in 2002 (19,954); shortfin glass eels dominated catches in both years, comprising 91–93% of the catch. Longfins were larger than shortfins, and size and pigmentation in both species increased as the seasons progressed. Temperatures within the migratory season in 2001 showed ∼14-day intervals between maxima that appeared to be associated with the new and full moons.     

Mass distribution in the fronds of macrocystis pyrifera from New Zealand and California

The mass distribution along the fronds of Macrocystis is examined for plants collected from California and New Zealand. Analysis of fronds classified according to length and condition yields polynomial curves for cumulative mass as a function of distance above the holdfast. Models for this functional relationship are discussed. Similarities and differences between the deep-water California plant and the shallow-water New Zealand plant are highlighted.     

Egg characteristics and oviposition behaviour of the aquatic insect orders Ephemeroptera,Plecoptera and Trichoptera in New Zealand: a review

The abundance and distribution of aquatic insects may be controlled by factors at any stage of the life cycle. To understand the potential role of factors affecting egg and adult stages and oviposition, basic information on egg characteristics and oviposition behaviour is required. However, published information on New Zealand Ephemeroptera, Plecoptera and Trichoptera (EPT) is scattered and very limited. This review compiles current knowledge of New Zealand EPT egg characteristics and oviposition behaviour using published information and unpublished observations. Where direct observations are lacking, information on closely related species overseas, and inferences based on female morphology, are included. Eggs show a variety of physical characteristics that may influence egg retention, transport and distribution. Oviposition behaviour is highly selective among some taxa, but appears generalist among others, though the latter may still require specific cues. Identifying and providing for adult, egg and oviposition requirements may be fundamental to re-establishing EPT populations in restored aquatic habitats.     

Hyporheic Production is Substantially Greater than Benthic Production for a Common New Zealand Caddisfly

Life-history and production of Olinga feredayi in both benthic and hyporheic stream habitats were investigated in a pristine Waikato, New Zealand, forest stream over two years to investigate the contribution of hyporheic habitat to total secondary production. O. feredayi had a univoltine life-history with adult emergence occurring from November to March. Larvae with case lengths < 2 mm were present on most dates suggesting delayed egg hatching. Benthic densities were inversely related to maximum peak daily flow in the month prior to sampling, and positively related to the dry mass of particulate organic matter present in samples. Reach-average benthic production calculated by the size-frequency method was 0.024 g DM m⁻² year⁻¹. Hyporheic production was 4.276 g DM m⁻³ year⁻¹ and 6.462 g DM m⁻³ year⁻¹ in colonisation baskets set at 15–30 cm and 30–45 cm within the substratum, respectively, 2.3–3.4 times greater than production in surface baskets (0–15 cm). Averaged out over the reach scale, it was estimated that 96% of annual secondary production of O. feredayi occurred in hyporheic habitats >10 cm below the streambed surface. Our study clearly demonstrates that only sampling benthic habitats can lead to gross under-estimation of population-level annual production, and provides evidence for the role of the hyporheos as a source of secondary production that may partly account for the Allen Paradox.     

The biogeography of three Boeckella species (Copepoda: Calanoida) in New Zealand

The New Zealand distributions of three species of Boeckella (Copepoda, Calanoida), B. triarticulata, B. dilatata and B. hamata are mapped. B. triarticulata is primarily a pond dweller but is also found in reservoirs and shallow lakes. B. dilatata is mainly found in the deeper glacial lakes and ponds in the central region of the South Island and B. hamata has a more widespread distribution in lakes and ponds in the South Island and lower half of the North Island. Differences in temperature optima, food requirements and dispersal ability among the three Boeckella species are related to vicariant events to explain their distribution in New Zealand.     

New Zealand climate in the Neogene and implications for global atmospheric circulation

New Zealand has a good Neogene plant fossil record. During the Miocene it was without high topography and it was highly maritime, meaning that its climate, and the resulting vegetation, would be controlled dominantly by zonal climate conditions. Its vegetation record during this time suggests the climate passed from an ever-wet and cool but frostless phase in the Early Miocene in which Nothofagus subgenus Brassospora was prominent. Then it became seasonally dry, with vegetation in which palms and Eucalyptus were prominent and fires were frequent, and in the mid-Miocene, it developed a dry-climate vegetation dominated by Casuarinaceae. These changes are reflected in a sedimentological change from acidic to alkaline chemistry and the appearance of regular charcoal in the record. The vegetation then changed again to include a prominent herb component including Chenopodiaceae and Asteraceae. Sphagnum became prominent, and Nothofagus returned, but mainly as the subgenus Fuscospora (presently restricted to temperate climates). This is interpreted as a return to a generally wet, but now cold climate, in which outbreaks of cold polar air and frost were frequent. The transient drying out of a small maritime island and the accompanying vegetation/climate sequence could be explained by a higher frequency of the Sub-Tropical High Pressure (STHP) cells (the descending limbs of the Hadley cells) over New Zealand during the Miocene. This may have resulted from an increased frequency of ‘blocking’, a synoptic situation which occurs in the region today. An alternative hypothesis, that the global STHP belt lay at a significantly higher latitude in the early Neogene (perhaps 55°S) than today (about 30°S), is considered less likely because of physical constraints on STHP belt latitude. In either case, the difference between the early Neogene and present situation may have been a response to an increased polar-equatorial temperature gradient. This contrasts with current climate models for the geological past in which the latitude of the High Pressure belt impact is held invariant though geological time.     

Seasonality of macrophytes and interaction with flow in a New Zealand lowland stream

Introduced submerged macrophytes have come to dominate many shallow water bodies in New Zealand, and are a common component of many lowland streams. We investigated the seasonal variation of macrophyte abundance, its influence on flow and channel volume, and the implications of this on stream habitat and functioning in Whakapipi Stream, a typical lowland stream draining a predominantly agricultural catchment.Abundance of macrophytes over the summer was primarily controlled by the phenological cycles of the two dominant species. Mean minimum total macrophyte biomass (36 g m^–2) and cover (7%) occurred in winter (June and August, respectively), and mean maximum biomass (324 g m^–2), and cover (79%) occurred in late summer (March and February respectively). Egeria densa comprised the majority of both cover and biomass during the study period, except early summer (December) when Potamogeton crispus was prevalent in the shallow stream reaches.Macrophyte beds had a major impact on summer stream velocities, reducing average velocities by an estimated 41%. Stream cross-sectional area was maintained at relatively stable levels similar to that recorded over winter, when stream discharge was in the order of seven times greater. The mean velocity distribution coefficient (), and Manning's roughness coefficient (n) were dependent on and displayed a positive linear relationship with macrophyte abundance. The velocity distribution coefficient is recommended as a better indicator of macrophyte effects on velocity in natural streams, as it does not assume uniform velocity, channel depth and slope within the stream reach.Our study shows that submerged macrophytes play an important structuring role within the stream during the summer period, where macrophyte beds act as semi-permeable dams, retarding flow velocities and increasing stream depth and cross-sectional area. This promotes habitat heterogeneity by creating a greater range of flow velocity variation, and also provides large stable low-flow areas. Other likely ecosystem effects resulting from macrophyte/velocity interactions include increased sedimentation, potential for nutrient processing and increased primary production, both by macrophytes and attached epiphyton. The complex architecture of submerged macrophytes and their influence on stream flow may also provide an increased diversity of habitat for other aquatic biota. We propose that management of degraded lowland streams such as the Whakapipi Stream to maintain stretches with moderate quantities of submerged macrophytes interspersed with shaded areas would optimise stream health during low summer flows.     

Patch- and reach-scale dynamics of a macrophyte-invertebrate system in a New Zealand lowland stream

Abundant growths of macrophytes are a common feature of streams in open lowland areas of New Zealand during summer, but the values of these to aquatic biota are poorly understood. We studied the temporal dynamics of, and associations amongst, elements of a macrophyte-invertebrate system to provide an improved information base for lowland stream management. The biomass of macrophytes increased significantly over the four quarterly sampling occasions from 43.8 g m^-2 in June to 370.8 g m^-2 in March; biomass was dominated by Egeria densa on all dates, except in December when Potamogeton crispus was dominant. We did not detect strong associations between epiphyton biomass and invertebrate abundance in our study, but this may reflect the fact that we sampled loosely-adhering epiphyton on young, surface-reaching shoots whereas invertebrates were collected from macrophytes growing through the water column. Density of some invertebrate species per gram dry weight of plant material varied by macrophyte type, with the chironomids Tanytarsus vespertinus and Naonella forsythi displaying positive correlations with Egeria and Potamogeton biomass, respectively. The shrimp Paratya curvirostris accounted for 50% of phytophilous invertebrate biomass, with Chironomidae the only other group to comprise more than 9%. Abundance of total phytophilous invertebrates displayed a positive linear relationship with macrophyte biomass in a sample (0.1 m²), and a humped relationship with species richness, such that highest numbers of taxa occurred at macrophyte biomass levels around 400 g dw m^-2. Our study suggests that intermediate macrophyte biomass levels are likely to enhance macroinvertebrate biodiversity in sandy-bottomed lowland streams. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemical soil conditions in pristineNothofagus forests of New Zealand as compared to German forests

In many German forest soils low base saturation of CEC in deeper soil layers was reported and acidic deposition is seen as the major cause of these findings. To test this hypothesis we sampled 5 New Zealand forest soils from pristine beech (Nothofagus fusca, N. menziesii, N. solandri) sites under climatic and geological conditions comparable to higher elevations in Germany. The soils developed from granite and greywacke. Soil samples were analyzed for pH and the exchangeable cations were extracted with 1M NH₄Cl. The base saturation of all soil profiles was very low, even in deeper layers and was thus similar to the patterns found in many German forest soils. The pH was generally higher in the New Zealand soils as compared to Germany. The reason for the depletion of base cations in deeper soil layers of New Zealand forest soils is most likely the leaching of base cations with HCO₃ ^- resulting from the dissociation of carbonic acid in connection with high amounts of seepage. Thus, under high rainfall conditions, the low base saturation found in deeper layers of forest soils cannot exclusively be attributed to the effects of acidic depositions and land use. ei]Section editor: R F Huettl     

Variations in the alginate content and composition of Durvillaea antarctica and D. willana from southern New Zealand

The brown seaweeds Durvillaea antarctica andD. willana are dominant components of the lowerlittoral and upper sublittoral of exposed rocky shoresin southern New Zealand. Tissue samples of bothspecies, harvested from a site on the south-east coastof South Island over a period of 2 years, wereanalysed for alginate content and composition.Individuals of both species were further separatedinto different blade (lamina and palm) and stipe(cortex and medulla) fractions to assess variationwithin the thallus. On average the alginate contentand frequency of mannuronic acid (F_m) was higherin D. antarctica than in D. willana. Blades contained more alginate than stipes, laminaeand stipes were rich in mannuronic acid whereasholdfasts were rich in guluronic acid. Variations incomposition are considered to reflect the functionaldifferences of the tissue, giving flexibility to bladeand stipe and rigidity to the holdfast. Despitefluctuations in content and composition betweencollection times no seasonal trends in eithercomponent were apparent.     

Two unusual species of <Emphasis Type="Italic">Physalacria</Emphasis> (Basidiomycetes,Agaricales) collected in New Zealand and Papua New Guinea during mycological expeditions by the National Science Museum,Tokyo

Two unusual species of Physalacria from New Zealand and Papua New Guinea are described and illustrated. Physalacria pseudotropica from South Island in New Zealand and P. tropica from Papua New Guinea are recorded for the first time.     

Toxic and noxious phytoplankton in Big Glory Bay,Stewart Island,New Zealand

Diurnal vertical profile sampling of the water column, during a fish killing bloom of the raphidophycean alga Heterosigma akashiwo, revealed a phytoplankton population otherwise composed almost entirely of a variety of dinoflagellates. Of these Glenodinium danicum, Dinophysis acuta, Polykrikos schwartzii, Ceratium furca and Gyrodinium spirale were predominant. The distribution of the major species within the phytoplankton were documented and evidence of synchronous vertical migration of H. akashiwo, G. danicum and P. schwartzii was observed. Extracts of shellfish obtained during the bloom and tested by mouse bioassay showed no PSP toxicity but a marginal degree of DSP toxicity. During a subsequent one year phytoplankton monitoring programme another potentially noxious species (Chaetoceros convolutus) appeared and the seasonal reoccurrence of species present during the bloom (e.g. H. akashiwo) was observed. Important year to year differences in the summer phytoplankton (diatom versus flagellate dominated populations) were apparent and analysis of climate data showed that these differences related to different weather conditions prevailing during the two summer periods sampled. The data suggest the fish killing bloom was giving a chance to develop by a prolonged period of warm, calm weather (during which several heavy rainfall events occurred) leading to stable hydrographic conditions (i.e. stratification) and an increase in the retention time of water within the bay.     

Phylogeny of the Bangia flora of New Zealand suggests a southern origin for Porphyra and Bangia (Bangiales, Rhodophyta)

Analysis of nuclear small subunit ribosomal RNA gene (18S rDNA) sequence data from 123 samples of the red algal genus Bangia from mainland New Zealand has revealed diversity exceeding that reported for the genus from any other region in the world. Our study resolves two New Zealand Bangia taxa basal to the order Bangiales, and five clades of Bangia, four of which include New Zealand members. The basal taxa are separated from each other by 139 bp and differ from all other Bangia taxa in the New Zealand region by 103-163 bp over approximately 1750 bp 18S rDNA sequence data. Our results reveal a Bangia flora of previously unsuspected richness, and show that the simple morphology of these organisms obscures significant levels of genetic diversity. The presence of high diversity and retention of basal taxa in New Zealand Bangia raises the prospect that the southern hemisphere, and particularly eastern Gondwana, is not only a centre of diversity, but a centre of origin for the modern Bangiales.