摘要:

Recent sediment transport research has demonstrated that microform bed clusters (MBC) are particularly resistant to entrainment during floods and preliminary biological surveys have shown that such structures could be providing important refugia for benthos in streams. We therefore surveyed MBC in a selection of headwater streams, South Island, New Zealand to determine how common such structures are and then related their occurrence to flow variability, relative armouring, reach gradient, and sediment geology/ geometry to obtain a greater understanding of hydrological and hydraulic stream‐scale factors affecting their density and composition. MBC were present in all streams and ranged in density from 0.067 to 0.279 m−2. They occupied up to 4.4% of the surface area of the survey reaches, generally had 2–3 particles (a maximum of 7), and the average size for the largest particles ranged from 18.5 to 42.8 cm. MBC density and percentage site cover was significantly related to the relative armouring, but not to flow variability. The number of sediment particles per cluster was significantly correlated with reach gradient, although sediment geology, and associated geometry of particles, also appeared to be important. Thus, density and structure of MBC appeared to be primarily controlled by the interaction of relative armouring and reach gradient with highest densities and the largest number of cluster particles occurring in steep streams with high bed armouring. These structures were sufficiently common to be playing a significant role as flood refugia for benthos in some high gradient, headwater streams.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516775

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The invertebrate communities associated with dense beds of exotic macrophytes were sampled monthly between June 1993 and June 1994 from three sites in Lake Henley, a small artificial lake in the Southern Wairarapa, North Island, New Zealand and from a small stream flowing into the lake. All communities were dominated by either the gastropodPotamopyrgus antipodarumor by oligochaetes. Community composition was similar at sites within the lake monoculture but changed seasonally. These changes appeared to be predominantly a result of seasonal fluctuations in the presence of filamentous algae on the macrophyte beds. Communities sampled from the stream site had a number of taxa in common with the lake communities but were quite distinctive in terms of the relative abundance of these component taxa. The diversity of the lake phytomacrofauna community, although comparable to similar studies in other New Zealand lakes, had a lower proportion of insect taxa perhaps because of the low floral diversity, the lack of depth variation, the absence of a nearby colonising source or the young age of the lake.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516776

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A set of experiments was carried out to determine what effects periphyton communities could have on near‐bed hydraulic fields. We analysed velocity distribution, skewness and kurtosis coefficients, Reynolds stresses, relative turbulence intensity, coefficient of eddy diffusivity, velocity spectra, and turbulence scales at two flows with, and without, diatom‐dominated periphyton on the bed. We found that turbulence was affected by the periphyton mat selectively. The largest influence occurred for the velocity distribution, Reynolds stress, coefficient of eddy diffusivity, and velocity cross‐spectra. Changes as a result of the periphyton mat were revealed in the large‐scale turbulence structure. The periphyton affected not only the region near the bottom but also the entire logarithmic layer. The periphyton mat increased roughness length by a factor of ≈5 whereas the integral resistance to flow (reciprocal Chezy coefficient and Manning's roughness coefficient) was increased by 20–25%. The microscale turbulence structure was investigated using values of Kolmogorov's microscaleηK. These appeared to be commensurate with the characteristic scales of periphyton filaments. This allowed us to hypothesise that the mechanism of the “periphyton‐turbulence” interaction is connected, to a certain degree, with viscous effects.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516777

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Lake Tarawera is the lake with the clearest water in New Zealand to be invaded by four particularly successful invasive adventive weeds:Ceratophyllum demersum, Egeria densa, Elodea canadensis, andLagarosiphon major. E. canadensiswas the first to invade the lake followed byL. majorwhich became the dominant tall‐growing species to 6 m depth. Comparisons of lake survey data for macrophytes in Lake Tarawera from 1988 and 1993/94 show that marked changes occurred in the composition and patterns of submerged vegetation as a result of a recent invasion byC. demersum. This species was first recorded in 1988 as infrequent, within a restricted area of the lake. Within 5 years it occurred in 52% of the lake profiles, had a depth range of 0.5–15.5 m, and a median average cover estimated to be between 51 and 75% throughout this depth range. The spread ofC. demersumhas been at the expense of native vegetation (particularly Characean meadows) andE. canadensis. E. densawas first recorded at the same time as C.demersumbut has established slowly at localised sites only (<2% shoreline). In Kotukutuku Bay these two species have displaced virtually all other macrophyte species below 2 m depth, withE. densadominating to 10 m depth andC. demersumas a monospecific stand from 10 to 14.5 m. Their abundance in Lake Tarawera suggests that clear‐water New Zealand lakes and their native vegetation could be severely impacted if these presently restricted species become more widely distributed.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516778

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The pH values preferred and avoided by adult stages of inanga(Galaxias maculatus), common bully (Gobiomorphus cotidianus), common smelt(Retropinna retropinna), and redfinned bully(G. huttoni), were determined in a gradient tank (pH ranges of 3.2–11.2). Juvenile stages of inanga, common bully, shortjawed kokopu (Galaxias postvectus), koaro(G. brevipinnis), banded kokopu (G. fasciatus), shortfinned(Anguilla australis)and longfinned (A. dieffenbachii)elvers and glass eels, as well as freshwater shrimp(Paratya curvirostris)were also tested. Most species were found to have pH preferences and all except inanga avoided pH values of above c. 9.5. Adult fish showed stronger preferences than juveniles. An avoidance of pH values below 6.5 was apparent in most species except shortfinned elvers, koaro, and banded kokopu. Results indicate that the range of pH encountered in lowland streams are unlikely to have a major impact on the distribution of most New Zealand native freshwater fish.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516779

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Between March 1990 and March 1994, six cruises were made by Australian, New Zealand, and United States investigators in the Tasman Sea, occupying World Ocean Circulation Experiment repeat hydrographic lines PR11 (30°S) and PR13N (43°S). The northern section was occupied five times, the southern section was occupied four times. All sections measured temperature and salinity from the ocean surface to the bottom. Baroclinic transports through these sections are highly variable, and confirm that there is considerable eddy energy in the East Australian Current. The East Australian Current, when defined to be the main southward flowing branch, has transports varying from 22.2 to 42.2 Sv, although much of this is recirculated. As a result the total transport into the Tasman Sea, between Australia and 173°E, varies from 8.0 to 25.5 Sv. When plotted as a function of season, these transports are well fit by annual‐period sinusoids, suggesting that any interannual variability is aliased by the annual cycle.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516780

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Seven species of turtles and sea snakes have reached New Zealand waters. Analysis of 207 records since 1837 shows that the two main species wereDermochelys coriaceaandPelamis platurus, followed byChelonia mydas. Many marine reptiles probably came from Australian populations and were assisted or carried to New Zealand by the East Australian Current. A peak of records in 1989 coincided with an influx of tropical and subtropical fishes in north‐eastern New Zealand. Nearly 70% of all marine reptile records were between January and May, with few records in winter and spring. Records forD. coriaceadeclined throughout the year, and the same was true forCh. mydasexcept for a secondary peak in October. The summer‐autumn peak in records for these two species may reflect an increased presence or activity during warmer weather.P. platurusoccurred mainly from March to May and was absent from August to December, perhaps because no individuals survive after July. Marine reptiles were mostly recorded in the north of the North Island at 34–38°S latitude; onlyD. coriaceawas widely reported further south. None of the turtles measured had carapaces below 375 mm long, except forCaretta carettafor which juveniles as small as 80 mm were recorded. These juveniles may have hatched at theC. carettabreeding grounds in south‐east Queensland. AllP. platuruswere adults (>500 mm total length) but the smallestLaticauda colubrinawas 295 mm. Nearly 70% of turtles, and some 80% ofP. platurus, were alive when found. About 45% of turtles were washed ashore when found, and 41% were entangled in nets or lines, whereas 95% ofP. platuruswere found washed ashore.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516781

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Differences in some life history characters of the Chilean oyster,Tiostrea chilensis, were examined for three populations in the northern North Island of New Zealand. Previous studies of oyster populations in the South Island have predicted that populations at lower latitudes would produce smaller‐sized larvae and substantial numbers of planktonic larvae. For only one northern population was there some evidence of the release of planktonic larvae. However, larvae from all three northern study populations were smaller in size than reported for all other locations, both in New Zealand and Chile. This was because of a trend for larval size to vary inversely with sea water temperature. The results of this study indicate that life history characters of this species can vary greatly at both the individual and population level. Furthermore, this variability does not always conform to commonly proffered life history principles which assert that planktonic development and small larvae become more common at low latitudes.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516782

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two serine proteases from the viscera of deep‐sea fish, black oreo dory(Allocyttus niger), were purified by hydrophobic, affinity, and cation exchange chromatography. They were designated as chymotrypsins on the basis of substrate specificity and susceptibility to inhibitors. The pH optima of chymotrypsin I and II were 8.6 and 10, respectively. Chymotrypsin II retained a remarkable 80% activity at pH 12.5. Thermal stability of both enzymes was enhanced in the presence of calcium ions. Both chymotrypsins were inhibited by high concentrations of substrate Suc‐AAPF‐NA.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516783

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Samples of epibenthic macrofauna were collected using a small sledge trawl from 40 stations on the Chatham Rise (42°34′‐44°47'S; 175°34'E‐179°03'W) at water depths of 237–2039 m. 218 taxa were collected, predominantly echinoderms, crustaceans, and molluscs. Multivariate analysis based on 85 species indicated three epibenthic communities, the shallowest characterised mainly by crustaceans and two deeper water communities mainly characterised by echinoderms: (1) a community on predominantly sandy sediments on the crest and shallower flanks of the Rise at 237–602 m that included as characteristic speciesMunida gracilis, Phylladiorhynchus pusillus, Campylonotus rathbunae, Pontophilus acutirostris, andAcutiserolis bromleyana(Crustacea),Amphiura lanceolata(Ophiuroidea),Cuspidaria fairchildi, andEuciroa galatheae(Bivalvia); (2) a community associated with muddy sediments at 462–1693 m that includedYpsilothuria bitentaculataandPentadactyla longidentis(Holothuroidea),Brissopsis oldhami(Echinoidea), andAmphiophiura ornata(Ophiuroidea); and (3) a community on muddy sediments at 799–2039 m that includedOphiomusium lymani(Ophiuroidea),Porcellanaster ceruleus(Asteroidea),Gracilechinus multidentatus(Echinoidea), andAeneator recens(Gastropoda). Bathymetric range of the communities was not symmetrical on either side of the Rise; there was a marked submergence on the north side similar to the vertical displacement of the core of the Antarctic Intermediate Water.

ISSN:0028-8330    

DOI:10.1080/00288330.1997.9516784

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor