摘要:

Effects of water velocity on the accumulation of periphyton and silt were investigated in two unenriched rivers (Tongariro and West Kowai Rivers) of New Zealand. Artificial substrata were incubated for up to 5 weeks in areas of moderate (0.2–0.5 m s−1) and high (0.6–0.9 m s−1) velocity. In the Tongariro River, periphyton accrual was significantly higher in moderate velocities than in high velocities, but not in the West Kowai River. The accumulation of silt was significantly higher under the moderate velocity treatment in both rivers. Silt densities were closely correlated with periphyton chlorophyllaand stepwise multiple regression analysis indicated that periphyton biomass was a more significant determinant of silt densities than water velocity. Neither chlorophyllanor silt densities showed any significant variation with depth within the ranges measured (0.2–0.6 m). Several floods occurred during the study period and these, together with water velocities greater than c. 0.3 m s−1, tended to affect periphyton ash‐free dry mass (AFDM) and silt more than they affected chlorophylla.It appeared that growing periphyton were resisting the effects of high shear stress and that unattached inorganic and organic particles were flushed from the periphyton matrix during higher flows. Spatial variation in periphyton and silt accrual as functions of velocity and depth were too variable to be useful for prediction of abundance and distribution using hydraulic‐habitat models.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516767

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Leaf breakdown, colonisation by invertebrates, food choice by a facultative shredder, and composition and activity of the microflora of leaves of three native and three introduced trees were investigated in a small headwater stream, South Island, New Zealand. Leaves of each species were immersed and collected after 1, 32, 60, and 95 days to measure mass loss and invertebrate colonisation. Additional leaves collected after 60 days were used for food choice and respiration experiments, and others taken after 95 days (some species) were examined with scanning electron microscopy. Leaf breakdown rates followed the sequence: elm > red beech > willow > mahoe > oak > mountain beech. Elm (introduced) and mahoe (native) supported the highest invertebrate densities, but shredders were most abundant on willow (introduced) and red beech (native) leaves. In laboratory choice trials the facultative shredderOlinga jeanaeshowed a preference for elm and red beech leaves which were fastest to break down and had high respiration rates. We found that leaves of introduced trees can be preferred by shredders and hence, no strong associations were apparent between shredders and these native trees.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516768

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Twenty‐eight meltwater samples were collected from Scott Base, Cape Evans, Cape Royds, Marble Point, Vanda Station, and along the length of the Onyx River, in the McMurdo Sound area of Antarctica during the summers of 1992/93 and 1993/94. Samples were analysed for major components, and for heavy metals at ultra‐trace levels. The sample sites included biologically active ponds, glacier melt water, lake water, roadside drains, and rivers. Sample salinities varied widely, but heavy‐metal concentrations were uniformly low except where significant human impacts would have been expected. Concentrations of silver, mercury, lead, copper, cadmium, chromium, nickel, and zinc were higher at Scott Base than in the other areas and were dominantly associated with coarse particulates. Natural sources of metals may be local lithology, but chemical and mechanical processes within the soils and solutions affect the distributions of different metals.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516769

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Wairakei geothermal power station on the west bank of the Waikato River 10 km north of Lake Taupo, New Zealand, discharges a warm mixture of cooling water and geothermal steam condensate to the river. This discharge contains at least two chemical species of mercury (Hg): elemental mercury (Hg0) at a mean concentration of 42 μg m−3; and other unidentified species, not reducible by acidic stannous chloride, at a mean concentration of 79 μg m−3. The annual discharge to the river of total Hg is 46.5 kg (CI9542.0–51.8) of which 19.3 kg (CI9518.3–20.0) is Hg0. On average 53 g d−1of Hg0is discharged from the Wairakei station to the river and 50 g d−1of Hg0flows out of Lake Aratiatia, the reservoir formed for the Aratiatia hydro‐electric power station 3 km down‐stream from the Wairakei station. The residence time of the condensate in Lake Aratiatia varies between 1.5 h at high river flow and 12 h during winter when water is accumulated in the lake overnight. The warm condensate initially floats on the surface of the river but only a small proportion of the Hg0is lost to the atmosphere. Furthermore, the short residence time of the condensate in the lake probably limits the extent to which other mechanisms can remove Hg0from the river water. For these reasons it is concluded that most of the Hg0discharged to the river from the Wairakei station remains as Hg0in the water flowing out of Lake Aratiatia. Fine‐grained bed sediments in Lake Aratiatia are an insignificant sink for Hg because of their very small area and relatively low total Hg concentrations. It seems likely, therefore, that the non‐reducible forms of Hg discharged with the condensate also remain in the river water and pass out of the lake.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516770

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Eight benthic foraminiferal associations are recognised in Wanganui Bight and Queen Charlotte Sound, New Zealand, based on cluster analysis of census data from 52 sediment samples. Distribution of the four associations in Wanganui Bight correlates with increasing water depth:Elphidium charlottense/Haynesina depressula/ Patellinella inconspicuaassociation (17–27 m);Patellinella inconspicua/ Quinqueloculina suborbicularisassociation (20–42 m);Cassidulina carinata/Miliolinella subrotundataassociation (42–66 m); andCassidulina carinata/Bulimina submarginata(72–109 m). The four associations in Queen Charlotte Sound are:Quinqueloculina seminula/Elphidium advenum/Haynesina depressulain sandy shallows (0.5–7 m);Epistominella vitreal Haynesina depressulain shallows of the outer Sound (4–12 m);Elphidium vellai/Haynesina depressulain the mouth of the Sound (9–25 m); andNonionella flemingi/ Notorotalia finlayiin a muddy, sheltered basin (25–42 m). The most important physical factors influencing benthic foraminiferal distribution patterns in these two areas appear to be the characteristics of the water (e.g., temperature, turbidity, salinity) and factors that vary with water depth (e.g., wave and current energy, substrate, light penetration, food availability). Species diversity (α, H) and the relative abundance of planktic foraminiferal tests are mostly greater in the open sea conditions of Wanganui Bight than in Queen Charlotte Sound. In Wanganui Bight both generally increase with increasing depth, although there is a local diversity peak at 70–80 m depth.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516771

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Specific diagnostic characters are reviewed and redefined for the genusPolymastiain northern New Zealand waters, to provide a framework for the recognition of new species, and for the revision and redefinition of other Polymastiidae. Eight new species ofPolymastiaare described, andPolymastia fuscaBergquist,P. hirsutaBerquist, andP.cf.massilisCarter are redescribed in the light of new material. Species ofPolymastiawhich contain exotyles and centrotylote oxea in addition to the usual megasclere complement, provided the opportunity to redefine the polymastid generaProteleia, andTylexocladus, which would typically have been reserved respectively, for sponges with these spicules. Anew species ofTylexocladusis described from the Chatham Rise in southern New Zealand, providing a first record of the genus from this location. A new genusAcanthopolymastiais established for southern ocean Polymastiidae with acanthose centrotylote oxea, withAtergia acanthoxaKoltun from Antarctica as the type species. Two additional species from New Zealand and the Norfolk Ridge, New Caledonia are described, and all are compared to Atlantic species of the same genera. Suggestions for partitioning of shallow‐waterPolymastiaspecies are put forward.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516772

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Thecal plate morphology and paralytic shellfish poisoning (PSP) toxin spectra produced by three strains of a smallAlexandriumspecies isolated from the Marlborough Sounds, New Zealand were examined. Although these cells displayed minor morphological features described in the literature as characteristic of bothA. minutumandA. lusitanicum, the former designation was adopted. High performance liquid chromatography (HPLC) analysis of culture extracts showed the toxin profiles to consist predominantly of various proportions of the carbamate toxins GTX1, GTX2, GTX4, neoSTX, and STX. These toxin profiles were similar to those observed in other New Zealand isolates ofA. minutum. They were however rather different from those observed in this species elsewhere in the world though the specific toxicity of these cells (1.8–2.2pgSTX equivalents per cell) was similarly low.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516773

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516774

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor