摘要:

Shellfish may bioaccumulate a variety of chemicals, some of which are mutagenic or carcinogenic to humans. Mutagenicity tests provide an integrated way of detecting these chemicals. This paper describes the application of two such tests to New Zealand shellfish in laboratory and field situations. The bacterial mutagenicity test gave positive results on a nitric acid extract of green‐lipped mussels (Perna canaliculus) that had been exposed to model carcinogens under laboratory conditions. When applied to Pacific oysters (Crassostrea gigas) that had been sampled from four different sites in the Manukau Harbour, the same methods detected mutagenic activity which varied both by date and area sampled. The micronucleus assay gave a readily scored measure of chromosome damage in gill tissues in both mussels and oysters, but presented some practical problems in field studies. Our studies emphasise the need to sample within a short time interval, and the advantage of using a complementary package of bacterial mutagenicity and gill micronucleus assays.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516729

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Grazing by microzooplankton on phytoplankton in Manukau Harbour was measured by size‐fractionated dilution experiments at monthly intervals from October 1994 to October 1995. Grazing rates were always highest on the < 5 μn size fraction, the smallest size fraction measured. These rates ranged from 0.3 to 1.3 d−1and were highest in November and March; values did not appear to vary with grazer abundance. Grazing rates on the < 5 μm phytoplankton exceeded growth rate by more than’ a factor of two in June when growth rate was seasonally depressed; but for most of the year the grazing rate averaged about 90% of growth rate. Grazing rates on the 5–22 μm phytoplankton were lower in magnitude, and were a lower percentage of phytoplankton growth rate than those on the < 5 μm size fraction. Grazing on the > 22 μm phytoplankton was measurable only during the February bloom of the large diatomOdontella sinensis. The grazing rate was low, being a small percentage of phytoplankton growth rate in that size fraction. Mathematical simulation of the growth of the < 5 μm phytoplankton in the harbour showed that the observed grazing rates were sufficient to prevent this size fraction from blooming.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516730

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A wild and a cultured greenshell mussel (Perna canaliculus) population were compared for biochemical genetic variation at seven polymorphic and four monomorphic allozyme loci. Significant heterozygote deficiencies were observed for all polymorphic loci (La—1,La—2,Lap, Lgg—1,Lgg— 2,Pgi, andPgm) for both populations (except thePgilocus of the wild mussel population). Genotypic disequilibrium was calculated for both populations: genotypic frequencies were significantly non‐random at three pairs of loci among the wild mussels, and significantly non‐random at three different pairs of loci among the cultured mussels. All six pairs of loci which exhibited significant genotypic disequilibrium involved amino‐peptidases, suggesting that these loci form a linkage group, and that neither thePginor thePgmloci are associated with this group. Exact tests for population differentiation based upon population‐specific allele distributions indicated that four of the polymorphic loci were significantly heterogeneous among the two populations, whereas the remaining three polymorphic loci were not. Based upon the private allele system, the number of migrants (Nm) between the populations was estimated to be 2.009, which, according to the private allele system, represents a high level of gene flow. These findings are discussed with regard to the population biology and genetic structure of this species.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516731

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Human viruses are a common contaminant of shellfish affected by human sewage wastes. They are difficult to detect as they are not easily separated from shellfish tissue. This paper describes a modification of the polyethylene glycol (PEG) precipitation technique for recovery of enteroviruses and F‐specific bacteriophages from the Pacific oyster (Crassostrea gigas) and the green‐lipped mussel (Perna canaliculus). Modifications adopted were the use of only the digestive gland tissue for virus extraction, resuspension of the primary PEG pellet in 4 volumes of eluent, and the introduction of a secondary PEG precipitation to reconcentrate the virus containing extract. The recovery rate of the virus extraction process was not affected by introduction of the secondary concentration step (overall recovery remained at 60–70% of the virus input). The advantages of reduction of tissue residue in the extract, smaller final volume, and the ability to process 2–3 times the number of individual shellfish for the same effort, improve the practicality of the method.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516732

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Three species of introduced marine macroalgae are reported for Wellington Harbour (North Island, New Zealand). One of these,Polysiphonia senticulosa(Ceramiales, Rhodophyta) is illustrated from New Zealand for the first time, and the known distributional ranges of two species,Striaria attenuata(Dictyosiphonales, Phaeophyta) andAntithamnionella ternifolia(Ceramiales, Rhodophyta), are extended to the North Island.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516733

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A survey of pesticides in groundwater throughout New Zealand was conducted in 1994 by the Institute of Environmental Science and Research for various Regional and District Councils. Wells were selected on the basis of the importance of each aquifer to the region, the proximity of particular land uses, and the extent of application of pesticides in the area—recognising that shallower, unconfined aquifers would be more at risk than deeper aquifers. Throughout New Zealand, 79 wells were sampled plus 39 wells sampled during a more intensive survey in Marlborough. There were no wells with pesticides detected above the Maximum Acceptable Value (MAV) for drinking water, indicating that all the water tested was suitable for drinking. Pesticides were detected in 13 out of the total of 79 wells (16.5%) excluding the Marlborough survey. If this survey is included, then 16 out of a total of 118 wells (13.6%) showed detectable pesticides. Most (78%) pesticide concentrations were below 1 mg m−3with 52% below 0.25 mg m−3. In total 10 different pesticides were detected, with the triazine group occurring most often. Contaminated wells were significantly shallower, had higher water tables, had less depth between the water table and the well screen, and had slightly lower temperatures than uncontaminated wells.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516734

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The distribution and abundance offish was investigated over 2 years at 78 sites in Redjacks Creek and adjacent tributaries draining native, exotic, and mixed forest catchments within the Grey River system, South Island, New Zealand. The abundance of diadromous fish decreased with altitude and distance from the sea, whereas the abundance of non‐diadromous fish species, especially dwarf galaxias (Galaxias divergens), increased with altitude and distance from the sea. Species abundance varied with average stream depth and velocity, generally in accordance with micro‐habitat preferences. The relative influences of diadromy, land use, and physical habitat on fish distribution and abundance were difficult to separate. Differences in fish abundance in the three land‐use categories were often attributable to differences in physical habitat. Nevertheless, there were indications that land use and its effect on the stream environment was influencing the distribution of some fish species. Ammocoetes (Geotria australis) were least abundant in native forest catchments, whereas dwarf galaxias and bluegilled bullies (Gobiomorphus hubbsi) were abundant in those catchments. Banded kokopu (Galaxias fasciatus) were associated with in‐stream cover and only found in the smallest streams sampled. The abundance of torrentfish (Cheimarrichthys fosteri) and bluegilled bullies declined over the study period, and three fish species were found in catchments adjacent to Redjacks Creek, but not in Redjacks Creek or its tributaries. Suspended sediment produced by mining and logging activities may have caused low fish diversity and changes in fish abundance in Redjacks Creek

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516735

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Using irradiance profile data from 11 New Zealand lakes of different water clarity and reflectance, we tested the fit of linear regression and Weibull models to underwater light profiles. The diverse optical characteristics of the lakes provided a wider test of the applicability of the model to lakes other than the more humic stained lakes used in an earlier Norwegian investigation. Measurements comprised down and upwelling vector irradiance, scalar irradiance, and in‐air vector irradiance sampled at a frequency of once every 2 seconds with a data‐logger. Log‐linear regression models proved inferior to the non‐linear Weibull function in several respects. Owing to appreciable curvature of the light profiles, log‐linear models produced significant bias for estimates of depth‐specific irradiance, in spite of the extremely close regression fits (r2≥99%). The completely specified linear model (log‐linear regression including the intercept and incident irradiance, LR2) yielded significantly biased predictions ofVm(the midpoint of the euphotic zone, taken as 10% of incident irradiance), whereas the Weibull predictions were statistically unbiased. For the 1% irradiance depth (Veu), the LR2 model almost coincided with Weibull estimates. Employing linear models is likely to give biased estimates of underwater irradiance at depths aboveVeu. We recommend that, where precise estimates of underwater irradiance are required, for example when modelling light‐dependent biological processes, non‐linear rather than the traditional log‐linear models should be applied.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516736

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An analysis of trends was made for the 14 physical/chemical determinands measured monthly over the period 1989–93 at 77 river sites distributed throughout New Zealand's North and South Islands. This has used non‐parametric Kendall slope estimators and associated tests, accounting for seasonality, which have been applied to both the raw data and to flow‐adjusted data (flows in much of the North Island trended downward over the period). Results indicate a general improvement in water quality, particularly in the South Island. Downward national trends, for both raw and flow‐adjusted data, were found for water temperature, BOD5, NH4‐N, NOx‐N and TP. Upward national trends, again for both raw and flow‐adjusted data, were found for dissolved oxygen, visual clarity, conductivity, and g340/g440(indexes of dissolved colour). No national trends are reported for pH or DRP. Downward trends for turbidity and TN were seen in the raw data only. A general characterisation of the dependence of these determinands on river flow is presented.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516737

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A broadscale survey of 118 streams was made throughout New Zealand's South Island to establish relationships between aquatic bryophytes and selected environmental variables. Bryophytes were found in 95 of the streams examined, and covered large areas of the substratum (mean cover of 17%, maximum cover of 86%). TWINSPAN analysis revealed the existence of five sample groupings, of which one supported no bryophytes. Streams without bryophytes typically flowed through developed catchments (pasture or pine) composed of easily eroded rocks. Nutrient levels were high in these streams, and low‐flow events were also common. Streambed stability was low, reflecting lack of stable bedrock and boulder substrata. TWINSPAN identified two major groups of streams with bryophytes: those supporting mosses and those supporting liverworts. These streams differed from those without bryophytes by having a higher streambed stability, and fewer low‐flow events. These two variables thus appear fundamental in controlling aquatic bryophyte distribution patterns. Flood events had no significant impact on these plants once they grew on stable substrata. No differences in stream stability, or substrate composition, were found between streams dominated by mosses and those dominated by liverworts. Catchment geology, land use, water quality, and the number of high‐flow events differed between these streams, suggesting that these factors influenced what type of bryophyte community occurred.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516738

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor