摘要:

Lowland streams in agricultural areas are often considered degraded because of high turbidity, high biomass of adventive macrophytes, and a predominance of fine bed substrates. Invertebrate faunas in these streams are being increasingly used in biomonitoring, and an understanding of factors affecting their distribution and abundance is important for interpreting the results of these studies. We measured physico‐chemical parameters and sampled macroinvertebrate faunas on inorganic substrates, wood, and macrophytes to investigate factors influencing invertebrate distribution and abundance in Waikato, New Zealand, lowland streams, and to evaluate six biotic indices and a rapid bioassessment protocol for lowland stream environments. At most sites, invertebrate faunas were dominated numerically on all substrate types by the hydrobiid snailPotamopyrgus antipodarum(Gray), the eusirid amphipodParacalliope, and Diptera (mostly the chironomidNeonella forsythiiBoothroyd and the blackflyAustrosimuliumspp.). Stepwise regression analyses indicated that densities of some common taxa on inorganic substrates (0.1 m‐2) and macrophytes (g‐1wet weight) were correlated with combinations of reach water depth, percentage of bed covered by macrophytes or sand/silt, and water quality factors including conductivity, water temperature, and measures of dissolved oxygen (DO) concentration and magnitude of diel fluctuation. These factors and also the amount of wood present explained 36–87% of the variation in several of the biotic indices examined on different substrate types. Some taxonomic (no. of taxa) and compositional (% dominant taxon) indices appeared sensitive to measured habitat conditions, and this may affect their utility for detecting water quality impacts in lowland streams. Percent Ephemerop‐tera, Plecoptera, and Tricoptera (EPT), and the Macroinvertebrate Community Index (MCI) and its quantitative analogue (QMCI) reflected factors thought to be more associated with direct and indirect effects of riparian and catchment land use on water quality (DO, conductivity, temperature, macrophyte cover). Comparison of indices derived from intensive and rapid bioassessment sampling yielded significant regressions with slopes that were not significantly different to 1 for % EPT and MCI. These indices appear to be particularly useful for rapid bioassessment of lowland stream environments.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516802

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Laboratory tank experiments were used to determine the effect of turbidity levels ranging from 0–640 Nephelometric Turbidity Units (NTU) on mean feeding rates for each species. Mean feeding rates for banded kokopu (Galaxias fasciatus), smelt (Retropinna retropinna), inanga (G. maculatus), and common bullies (Gobiomorphus cotidianus) were all reduced by increased turbidity, but significantly so only for banded kokopu and inanga. Banded kokopu was the most sensitive species as feeding rates at 20 NTU were significantly lower than in clear water, compared with levels over 160 NTU for the other species. Feeding rates for redfinned bullies (Gobiomorphus huttoni) increased with turbidity up to 40 NTU then decreased. Reductions in feeding rate at elevated turbidity levels were the result of a reduced inability to feed, rather than to stress, as exposure to the highest turbidity level did not reduce feeding motivation or appetite. Feeding tests in the dark indicated that, whereas vision was important for feeding by all species, banded kokopu and common bullies had a comparatively well‐developed ability to feed using non‐visual senses. Non‐visual feeding may have reduced the impact of high turbidity levels on feeding for these two species, and could confound attempts to determine the effects of turbidity on visual feeding on live prey.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516803

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Kinleith pulp and paper mill discharges effluent into the Kopakorahi arm of Lake Maraetai (New Zealand) resulting in an effluent gradient defined by the effluent visibility (Secchi disc), transmittance (465 nm), temperature, and oxygen level that is discernible at least as far down stream as the adjoining Lake Waipapa. This effluent gradient is reflected in the composition of the fauna caught in fyke nets which at the most effluent‐exposed sites is dominated by goldfish (Carassius auratus) and is depauperate in pollution‐sensitive species such as freshwater crayfish (Paranephrops planifrons) and trout (Salmo truttaandOncoryhynchus mykiss) In 1991 the Kinleith mill undertook substantial process modifications which have resulted in improvements in the water quality of the discharge. Secchi disc visibilities have increased markedly at the most effluent‐exposed sites since modernisation of the mill and similar improvements have been observed in light transmittance. A seasonal trend in water temperature not previously observed was recorded at the most effluent‐exposed sites following modernisation, and dissolved oxygen levels at these sites rose markedly. Improvements in the water quality of the recipient since the mill modernisation are reflected in changes in the sampled fauna in particular the occurrence of trout at sites from which they were previously absent.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516804

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new freshwater macroinvertebrate‐based biotic index derived from the Quantitative Macroinvertebrate Community Index (QMCI) is proposed for use with coded‐abundance data collected from stony New Zealand streams using hand nets. The SQMCI (Semi‐Quantitative MCI) responds to changes in community dominance in a similar manner to the QMCI, but requires fewer replicate samples to achieve the same precision. In situations where macroinvertebrate densities are not required, the SQMCI provides a similar assessment to the QMCI with less than 40% of the effort, thus reducing the cost and/or improving the scientific defensibility of biomonitoring programmes. Variability of biotic indices must be known to enable detection of significant differences in water quality between streams, at different sites in the same stream, or between times at the same site. Best estimates of MCI and QMCI standard deviations have been updated, and newly derived for the SQMCI, for use in two statistical procedures for testing for significant differences between paired index values.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516805

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Twenty‐three lowland streams throughout the Waikato region, New Zealand, in catchments having a wide range of land uses and intensities, were monitored continuously over 3–4‐day periods for changes in dissolved oxygen (DO) and temperature. A single‐station diurnal curve model, DOFLO (Dissolved Oxygen at Low Flow), was used to produce reach‐averaged values for:K2(20), the reaeration coefficient at 20°C;Pmax., the maximum daily rate of photosynthetic production of oxygen;R20, the daily respiration rate at 20°C; andQ10, the ratio of respiration rates 10°C apart. In addition, 24‐h average values for the ratioP/Rwere calculated and maximum and minimum values of DO and temperature tabulated for each site. Values ofK2(20)(0.05–40 d‐1, median 6.0 d‐1) were in broad agreement with values calculated using a modified form of the O'Connor‐Dobbins equation. Values of gross primary production in daylight (0.5–29.2 g m‐2d‐1) calculated fromPmax. (1.75–86.5 g m‐3d‐1) were similar to data reported for other streams in agriculturally developed catchments in New Zealand and North America. Respiration rates (3.50–55.0 g m‐3d‐1) were generally larger than values reported in the literature, andP/Rratios were mostly well below 1.0, indicative of heterotrophic respiration associated with decaying vegetation and other organic inputs and consistent with diurnal DO excursions of 40 to ≥120% saturation being commonly observed. Maximum daily temperatures up to 25.7°C (median 20.5°C) were weakly negatively correlated with DO minima. Five groupings of streams were identified from DOFLO parameter values, withK2(20)being most critical in regulating average DO deficits.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516806

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A calibrated two‐dimensional finite‐element model, which handles flooding/drying of intertidal areas, complemented by field data, has produced information on tidal propagation in Manukau Harbour, New Zealand with reasonably good accuracy. Excluding the upper‐harbour inlets, c. 50% of both the amplification and phase lag in the dominant M2tidal constituent occurs through the deep 10‐km‐long entrance channel to Puponga Point. The calculation of tidal residuals has isolated flood‐directed and ebb‐directed residual circulation respectively on either side of Puponga Point, which is a typical pattern for alternating flows around headlands. The model has established the dominance of tidal‐driven over wind‐driven circulation in most of the harbour except in the upper intertidal areas. Wind‐driven circulation in the inner Harbour is characterised by downwind flows over intertidal sand banks with pressure‐driven return flows (vertically averaged) in the deeper main channels. Tidal dissipation rates are sufficiently high to inhibit the onset of any summer stratification.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516807

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Several sea lion species are known to occasionally hunt fur seals for food, but there have been few reports of New Zealand (Hooker's) sea lions{Phocarctos hookeri) hunting and eating New Zealand fur seals (Arctocephalus forsteri) We describe the first reported incidence ofP. hookerieatingA. forsteripups in mainland New Zealand, and present evidence suggesting that it was active predation rather than scavenging. In late April, early May, and early September 1997 we found three sea lion regurgitations containing the remains of fur seal pups on Otago Peninsula, New Zealand. One contained three plastic tags formerly placed on three different female fur seal pups from a nearby breeding colony. When ingested at least two of the three identifiable pups fell within the lower condition quartile calculated from pups at their natal colony. The incidence of such predation may increase with increasing densities of both fur seals and sea lions in Otago, but the impact on the trends in fur seal populations is, and should remain, low.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516808

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Compared to other stretches of the New Zealand coast, very little is known about the cetacean fauna off the West Coast of the South Island. The purpose of this paper is to describe the near‐shore distribution and abundance of dolphins in that area by summarising the results of two major studies. Between February 1995 and February 1997, 97 day trips were undertaken from Westport, Greymouth, and Jackson Bay in a small boat to survey the near‐shore distribution of dolphins. Between July 1994 and February 1997, 283 field days were spent on the water in Doubtful Sound studying the local bottlenose dolphin (Tursiops truncatus) population of c. 63 individuals. At the same time, three longer surveys were undertaken into other fiords of Fiordland which indicated the presence of further populations. Altogether, five delphinid species were recorded in various abundances. Small‐medium‐sized groups of Hector's dolphins (Cephalorhynchus hectori) with 1–60 individuals were observed in almost all areas of Westland in winter as well as in summer. Maximum densities peaked at 5–18 individuals per nautical mile of coastline between Cape Foulwind and Hokitika. Dusky and common dolphins (Lagenorhynchus obscurusandDelphinus delphis) occurred almost exclusively in summer in groups of 2–150 individuals, often with calves, especially at Cape Foulwind and Jackson Head. Bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca) were observed rarely off Westland, but occurred more frequently in Fiordland.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516809

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Data from six sea level sites on the Canterbury coast, New Zealand, were analysed for short period (1–4 h) waves. Persistent waves with periods of 3.4 h in Pegasus Bay and 2.4 h in the Canterbury Bight were found. Their amplitude and phase are highly variable. Edge waves of similar period were found in simulations using a 2‐dimensional, harmonic, shallow water, numerical model. Numerical and analytical modelling showed that the offshore decay in amplitude may be approximated by Stokes zero‐mode edge waves, but the numerical model revealed that the detailed structure of the offshore decay is more complicated than can be explained by analytical models using a semi‐infinite sloping beach. Rotation appears to have little effect. In Pegasus Bay the edge waves are trapped laterally between the northern extent of the bay and Banks Peninsula and offshore by the shelf. In the Canterbury Bight they are trapped laterally between Banks Peninsula and the curvature of the coast and offshore by the shelf. The origin of the waves and the reason for their variability are unclear, but may be the result of the non‐linear interaction between semidiurnal tides and meteorological effects.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516811

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Strombus vomer vomer(Roding 1798) is recorded from north‐eastern Northland, New Zealand, the first record of the family Strombidae from New Zealand Recent fauna. Some other New Zealand records of tropical and subtropical Mollusca are commented upon.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516812

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor