Impact of land use on the faecal microbial quality of hill‐country streams

Faecal contamination of rural streams is of increasing concern in New Zealand. This study assessed hill‐country streams in the Whatawhata district that were impacted by pastoral farming, indigenous forest, or Pinus radiata forest; by measuring Escherichia coli bacteria at 14 sampling sites fortnightly for 2 years. E. coli concentrations were highest in streams flowing through grazed pasture. In both years there was a noticeable seasonal pattern in all streams irrespective of land use, with highest bacterial concentrations in summer and autumn and lowest in winter and early spring. There was no obvious correlation between E. coli concentration and rainfall or stream flow. In those streams impacted by a change in land use from pastoral to pines during the study, E. coli concentration fell rapidly and remained at levels lower than those in streams impacted by either indigenous or 7‐year pine forests. As E. coli was detected in all but two samples, the water in these streams is not suitable for human consumption. The pastoral streams consistently failed to meet stock drinking‐water guidelines (median concentration not greater than 100 E. coli 100 ml^–1) and the forest streams failed to do so in summer. Twenty‐eight percent of pastoral samples, 25% of indigenous forest samples, 14% of 7‐year pine forest samples, and 5% in New Pines stream samples (after planting) had E. coli concentrations associated with a high level of risk for contact recreation (>500 E. coli 100 ml^‐1) and the high concentrations usually occurred in summer.     

Water quality and thermal regime of the Motueka River: Influences of land cover,geology and position in the catchment

We examined the effects of land use, geology, and longitudinal position within the river network on water quality and thermal regime at 23 sites within the Motueka River catchment. The concentrations of suspended solids, nitrate nitrogen, total nitrogen, Escherichia coli, and Campylobacter were higher at sites draining pastoral and horticultural land than in similar‐sized native or plantation forest streams. Average daily mean temperature and minimum temperature in summer and maximum winter temperature were higher in unshaded pastoral and horticultural streams than at native forest sites. Differences in water quality and thermal regime were also observed among sites with contrasting geology. Conductivity, pH, and minimum winter temperatures were highest at sites draining marble terrain. In contrast, longitudinal patterns in water quality and temperature regime along the 120‐km length of the river were relatively weak, although longitudinal patterns in amplitude of daily temperature fluctuation matched theoretical predictions. In this study, differences in land use appeared to have the strongest influence on most water quality and thermal variables examined. However, geology was an important factor explaining variation in certain variables (e.g., pH and conductivity). Longitudinal patterns in water quality and temperature were relatively weak and in many instances were linked with longitudinal patterns in land use and geology rather than catchment location alone.     

Growth and population dynamics of crayfish Paranephrops planifrons in streams within native forest and pastoral land uses

Population dynamics of crayfish (Paranephrops planifrons White) in streams draining native forest and pastoral catchments, Waikato, New Zealand, were investigated from September 1996 to July 1998. Crayfish densities were generally greater in native forest streams because of high recruitment over summer, but varied greatly between streams in both land uses. Peak densities in summer were 9 crayfish m^‐2 in native forest and 6 crayfish m^‐2 in pasture streams, but peak biomass in summer was much greater in pasture streams. Mark‐recapture data showed that crayfish, particularly juveniles, in pasture streams grew faster than in native forest streams, through both greater moult frequency and larger moult increments. Females reached reproductive size at c. 20 mm orbit‐carapace length (OCL) after their first year in pasture streams, but after 2 years in native forest streams. Annual degree days >10°C appeared to explain the differences in the timing of life cycles. Estimates of annual crayfish production (range = 0.8–3.4 g dry weight m^‐2 year^–1) were similar in both land uses, and P/B ratios were between 0.95 and 1.2. Despite deforestation and conversion to pasture, crayfish in these Waikato hill‐country streams have maintained similar levels of annual production to those in native forest streams, although juvenile growth rates have increased and longevity has decreased.     

Faecal indicators and pathogens in selected New Zealand waterfowl

Freshly excreted droppings from Canada geese (n=80), black swans (n=80), ducks (n=80) and gulls (n=80) were collected from sites around New Zealand. The droppings were enumerated for Escherichia coli, enterococci and Salmonella spp., and for the presence/absence of Cryptosporidium spp. Overall prevalence of E. coli and enterococci in samples was 95% and 94%, respectively. Cryptosporidium spp. was detected in 2% of the samples, whereas no Salmonella spp. were detected in the survey. Preliminary estimates of daily microbial outputs suggest that ducks will produce the highest loadings of E. coli and enterococci per bird, whereas Canada geese will produce the highest loadings of Campylobacter spp. per bird. This study provides the first set of indicator and pathogen counts for one of the largest sources of diffuse faecal contamination of natural waters in New Zealand.     

Microcoleus autumnalis and filamentous algae-dominated mats and chlorophyll-a increase with agricultural land use but respond differently to associated nutrient and sediment enrichment

ABSTRACT

This study investigated the impact of pastoral land use and nutrient and fine sediment inputs on Microcoleus autumnalis and filamentous algae-dominated mats, and benthic chlorophyll-a in streams (lower North Island, New Zealand). Surveying and sampling was undertaken monthly at 61 sites spanning a wide gradient in catchment cover and environmental conditions. Two boosted regression tree models were built. The first models included pastoral land cover and five environmental variables as predictors. In the second model pastoral land cover was replaced by nutrient/sediment data. The abundance of the two mat types and chlorophyll-a increased when pastoral land cover was between 20% and 70% (model 1). Replacement of pastoral land cover by nutrient/sediment data (model 2) slightly improved the model fit for all three periphyton variables. Microcoleus autumnalis-dominant mats increased with dissolved inorganic nitrogen concentrations up to ca. 0.6?mg?L^?1, and in streams with more frequent flushes. In contrast, filamentous algal-dominated mats increased with turbidity, and in streams with less frequent flushes. Chlorophyll-a generally followed the response of the dominant periphyton type. Increased knowledge on responses of specific periphyton types, rather than total biomass, to environmental variables is essential to guide effective management strategies.     

Effects of riparian manipulation on stream communities in small streams: Two case studies

The effects of riparian manipulation in New Zealand are described for two case studies, one a short‐term study of the effects of the removal of riparian vegetation on fish, and the second, a long‐term study of the effect of re‐establishment of riparian vegetation on fish and benthic macro invertebrates. The first case study was an experiment carried out between November 2001 and May 2002. Overhanging bank vegetation and in‐stream wood were removed from short reaches of a small pastoral stream that had intact riparian margins, resulting in a change in stream structure with the formation of shallow uniform runs rather than pool and riffle structures as in unmodified reaches. The removal of bank cover and consequential instream habitat changes reduced inanga (Galaxias maculatus) densities by a factor of four within months of vegetation removal, showing the importance of instream cover and habitat to inanga. Adult longfin eel (Anguilla dieffenbachii) also became less abundant in the cleared reaches, but elvers (Anguilla spp.) became more abundant. In the second case study, pastoral sections in two small streams draining from native forest catchments were restored in 1995/96 by planting riparian vegetation and preventing stock access. After 10 years, the restoration efforts had more than doubled the numbers of giant kokopu (G. argenteus) and redfin bullies (Gobiomorphus huttoni), slightly increased numbers of banded kokopu (G. fasciatus), and decreased shortfin eel (A. australis) numbers by about 40%. The macroinvertebrate communities changed so that they became more similar to those at upstream native forest reference sites. These two case studies show that riparian margins can influence the composition of the fish and macroinvertebrate communities in small streams through the effects on cover, instream habitat and probably water temperature. Riparian restoration was most effective for the fish species that use cover and pool habitat.     

Land use,associated eel production,and abundance of fish and crayfish in streams in Waikato,New Zealand

Abstract

The density and biomass of fish and crayfish, and the production of eels, was compared among streams in native forest, exotic forest, and pasture. Populations were estimated by multiple‐pass electroshocking at 11 sites in hill‐country streams in the Waikato region, North Island. Three sites were in native forest, four in exotic forest, and four in pasture. Length of stream sampled at each site was 46–94 m (41–246 m² in area), and catchment areas up stream of the sites ranged from 0.44 to 2.01 km².

A total of 487 fish were caught. The species were longfinned and shortfinned eels, banded kokopu, Cran's and redfinned bullies, and common smelt. Eels were the most abundant fish in all three land‐use types, and shortfinned eels were more abundant at pastoral sites (mean density 1.11 fish m^?2) than longfinned eels (mean density 0.129 fish m^?2). Banded kokopu were present only at forested sites. Mean fish densities were greater at pastoral sites (1.55 fish m^?2) than under either native forest (0.130 fish m^?2) or exotic forest (0.229 fish m^?2). Mean fish biomass was also greater at pastoral sites (89.7 g m^?2) than under native forest (12.8 g m^?2) or exotic forest (19.3 g m^?2). Longfinned eels made a greater contribution to the fish biomass at all sites than did shortfinned eels. Densities of crayfish were high (0.46–5.40 crayfish m^?2), but were not significantly different between land‐use types. Crayfish biomass ranged from 1.79 to 11.2 g m^?2. Total eel production was greater at pastoral sites (mean 17.9 g m^?2 year¹) than at forest sites (mean 2.39 gm^?2 year^?1).     

Food webs in forest and pasture streams in the Waikato region,New Zealand: A study based on analyses of stable isotopes of carbon and nitrogen,and fish gut contents

Abstract

Stable isotopes of carbon (C) and nitrogen (N) were studied in 11 stream communities in the Waikato region of New Zealand. From comparisons of mean δ¹³C and δ¹⁵N values, food webs in the shaded, forest streams were clearly based on allochthonous material (conditioned leaf litter and terrestrial invertebrates). Autotrophs in forest streams were not a significant C source for the food webs. However, the C source of food webs in the unshaded pasture streams appeared to be a mixture of allochthonous and autochthonous material. Conditioned leaf litter appeared to contribute to the pasture stream food webs, and the δ¹³C and δ¹⁵N of some samples of epilithic diatoms indicated their consumption by invertebrates in pasture streams. Fish ate a wide range of aquatic invertebrates; longfinned eels (Anguilla dieffenbachii) and banded kokopu (Galaxias fasciatus) also had a large proportion of terrestrial invertebrates in their diet. Filamentous green algae were found only at pasture sites, where they were sometimes abundant. The wide range of δ¹³C values of filamentous green algae (‐18.8 to ‐29.7‰) complicated understanding of their role in the stream food webs. The δ¹³C values of Cladophora were related to water velocity, with more ¹³C‐enriched values in pools than in runs (‐23.2‰ in pools, mean velocity 0.12 m s^?1; ‐28.1‰ in runs, mean velocity 0.24 m s^?1). Crayfish and the gastropod mollusc Potamopyrgus appeared to be the only invertebrates to eat filamentous green algae.     

Antibiotic resistance in coliform and faecal coliform bacteria from natural waters and effluents

Coliform and faecal coliform bacteria isolated from potable water supplies (springs and wells), streams, seawater, and effluents were examined for the incidence of antibiotic resistance. More than 40% of the coliform and faecal coliform bacteria isolated from drinking water supplies were resistant to one or more antibiotics. In stream and seawater samples, the incidence was increased to more than 60%, and to more than 70% among faecal coliforms isolated from effluents. Approximately 40% of the isolates resistant to streptomycin or tetra‐cycline were able to transfer their resistance determinants to an antibiotic‐sensitive strain of Escherichia coli within 2 h.

Although the widespread use of antibiotics is perhaps the major selective force favouring the increased incidence of antibiotic‐resistant bacteria, antibiotic‐resistant faecal coliforms may also have a selective advantage in natural waters.     

Differences in the distributions of freshwater fishes and decapod crustaceans in urban and forested streams in Auckland,New Zealand

Using data from existing studies, assemblages of freshwater fishes and decapod crustaceans were examined at 39 sites in urbanised catchments and 57 sites in forested (reference) catchments within the greater Auckland region, New Zealand. Eleven native and 1 exotic fish species and 2 native decapod crustacean species were recorded. Species richness and fish Index of Biotic Integrity (IBI) scores were lower overall in streams in urbanised catchments. Shortfin eel (Anguilla australis) and mosquitofish (Gambusia affinis) were more dominant in urban streams; all other commonly occurring species were found significantly more often in reference streams. Non‐diadromous native species (Cran's bully (Gobiomorphus basalts) and freshwater crayfish (Paranephrops planifions)) were absent from urban streams, but relatively abundant in reference streams. This absence of non‐diadromous species, together with the urban occurrence of five diadromous species suggests that migratory barriers pose less of a threat to freshwater communities than physico‐chemical disturbance in streams in the Auckland urban region.     

Shade effects on stream periphyton and invertebrates: An experiment in streamside channels

Abstract

The effects of shade on periphyton and invertebrates were investigated by comparisons in 12 replicate channels beside a pasture stream where shade cloth reduced the photosynthetically available radiation (PAR) by 0, 60, 90, and 98%. Periphytic productivity decreased with increasing shade. Periphyton chlorophyll a was consistently low (< 30 mg m^?2) under 98 and 90% shade and usually low at 60% shade, whereas blooms were common during summer in the unshaded channels. More periphytic taxa occurred in the open than shaded channels and the relative concentration of the photo‐protective pigment beta‐carotene decreased with increasing shade. Nitrate uptake rates by periphyton, measured in separate chamber studies, decreased progressively as shade increased from 60% through 90% to 98%, and were more strongly correlated with gross primary productivity than periphyton chlorophyll a and particulate carbon levels. Total invertebrate and chironomid densities declined significantly as shade increased from 60 to 90% and invertebrate taxa richness declined markedly between 90 and 98% shade. Most collector‐browsing invertebrates (other than chironomids) had similar densities under 0–90% shade and only declined at 98%. This suggests a weak coupling of these invertebrates with local periphyton production and also suggests that energy derived from up‐stream sources may be their most important food in these pastoral streams.     

Water quality in New Zealand rivers: current state and trends

River water quality, particularly in lowland catchments, is a matter of concern to the New Zealand public. We assessed river water quality and biological state and trends using data from more than 900 monitoring sites. Parallel state and trend analyses were carried out using all sites and a subset of lowland river sites. Median water-quality state in urban and pastoral land-cover classes was poorer than in exotic forest and natural land-cover classes, and lowland sites in the urban and pastoral classes had the poorest water quality. Nutrient and Escherichia coli concentrations increased and visual clarity and Macroinvertebrate Community Index scores decreased as proportions of catchments in high-intensity agricultural and urban land cover increased. Ten-year trends (2004–2013) indicated recent improvements in ammoniacal nitrogen, dissolved reactive phosphorus and total phosphorus in the pastoral and urban classes, possibly reflecting improved land management. In contrast, trends in nitrate-nitrogen in the exotic forest and cool-dry/pastoral classes indicated worsening conditions.     

Prey availability and diet of juvenile brown trout (Salmo trutta) in relation to riparian willows (Salix‐spp.) in three New Zealand streams

Macroinvertebrate benthos and drift and the diet of juvenile brown trout (Salmo trutta) were investigated in willowed and non‐willowed sections of three New Zealand streams during summer. The abundance and biomass of the principal macroinvertebrate taxa in the benthos and daytime drift differed in relation to riparian willow (Salix spp.) density, but the trends were not consistent across all three streams. Crustacea, Ephemeroptera, Trichoptera, and Diptera comprised a major proportion of the diet of juvenile trout. Diets of trout from non‐willowed and willowed sections were dissimilar in three of five pair‐wise comparisons. In all three streams, juvenile trout fed selectively, with the amphipod Paracalliope fluviatilis, ephemeropteran Deleatidium, and trichopterans Aoteapsyche and Hydrobiosidae being the preferred prey. Their avoidance of the gastropod Potamopyrgus antipodarum, trichopteran Oxye‐thira albiceps, coleopteran Hydora, and drift of terrestrial origin appeared to occur in all streams. Total abundance and biomass of invertebrates drifting during the day described the potential prey available to juvenile brown trout better than did the abundance and biomass of benthic invertebrates.     

Obelia (Cnidaria,Hydrozoa, Campanulariidae): a microphagous,filter‐feeding medusa

Obelia is used in many zoology textbooks to exemplify the Hydrozoa life cycle. The body plan of Obelia medusae, however, is unique among the Hydrozoa. Contrary to all other hydromedusae, Obelia medusae do not derive from a medusary nodule, have neither a velum nor a subumbrellar cavity, the umbrella is flat, and swimming is achieved by umbrellar flapping and does not involve jet propulsion. The medusae of most Obelia species do not grow well on a diet of Artemia salina nauplii, the usual food for laboratory‐reared hydrozoans, and their rearing is often difficult. Previous observations reported that Obelia medusae might eat phytoplankton, driven to the mouth by movements of both the bell and the tentacles. To evaluate the efficiency of this feeding mechanism, we gave a suspension of genetically modified Escherichia coli expressing GFP to starved, newly released medusae of both O. dichotoma and Clytia hemisphaerica (the other campanulariid genus with medusae). Obelia medusae are able to concentrate bacteria in their gastric cavity, whereas Clytia medusae are not. Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous and filter‐feeding medusa, at least at the onset of its medusan life. As Cnidaria evolved before their current metazoan prey, their ancestral diet was probably microphagous. Obelia’s microphagous feeding habits could thus represent an example of the ancestral feeding condition in Cnidaria, but the apomorphic characters of its medusa suggest that its body architecture is not ancestral, and that its microphagy evolved relatively recently.     

Seasonal growth in brown trout in two New Zealand streams

Brown trout Salmo trutta Linn, were marked with individual tags and recaptured throughout a year in two small Canterbury streams. The growth recorded showed a marked seasonal variation which differed in pattern in the two streams. There was a considerable difference in the growth rate between the two populations and fish transferred from the slow‐growth stream to the faster‐growth stream showed an immediate response to the change.     

Sewage-derived bacteria monitored in a marine water column by means of captive mussels

Batches of mussels, Mytilus edulis, obtained from a sewage-free shore were introduced into the water column at a sewage polluted site and the changed content (Escherichia coli, faecal streptococci) was assessed after immersion periods of 2 to 40 h. Rapid bacterial uptake was demonstrated; changes were analysed with respect to immersion period, revealing that 2h was satisfactory. The numbers of bacteria varied with height in the water column; mussels from the sea bed contained higher numbers of E. coli than mussels immersed just below the surface except for mussels withdrawn at, and for about 3h after, low water (LW). These observations were shown to be related to the characteristics of the e effluent and tidal systems operative at the site.     

Effects of sample size on numerical estimates of diel prey consumption in a fish population

Numerical data based on stomach content analysis of the zooplanktivorous freshwater fish, Retropinna semoni, were used to examine the effect of fish sample size on mean counts of dominant prey items. Fifty adult R. semoni were collected from throughout the open‐water of Lake Benanee, Australia at each of five times over a diel period. Bootstrapping was used to generate confidence intervals around sample means, and markedly more accurate means were obtained from samples collected in the day than the night. High variation in night samples was the by‐product of a diurnal feeding regime. Traditional sample sizes of 10 to 15 stomachs resulted in reasonable confidence intervals of sample means derived from collections on the first day, corresponding to uniform feeding patterns in the population. However, increased sample sizes were required to describe more complex feeding behaviour on the second day, when a proportion of the population switched to an alternative prey source.     

Regime shifts between clear and turbid water in New Zealand lakes: Environmental correlates and implications for management and restoration

We reviewed lakes in New Zealand reported to have undergone regime shifts between macrophyte‐dominated clear water states and de‐vegetated, turbid states. Regime‐shifting lakes (RSLs) occurred along a wide latitudinal gradient. We obtained catchment land‐use data as well as data on the occurrences of introduced (non‐indigenous) macrophytes and herbivorous and benthivorous fish for the 37 RSLs and for 58 lakes with similar maximum depths and climates, but which had not been reported to have undergone regime shifts. All RSLs had a maximum depth <20 m and mean annual surface air temperature between 9 and 16°G Regime shifts were positively related to the percentage of the catchment in pasture and negatively related to the percentage of the catchment in forest. The occurrences of the introduced macrophyte Egeria densa and the introduced fish, Ameiurus nebulosus (catfish), Carassius auratus (goldfish), Scardinius erythrophthalmus (rudd), Cyprinus carpio (koi carp), and Tinca tinca (tench), were significantly correlated to regime shifts in lakes. Although the presence of other introduced aquatic macrophytes was not significantly correlated with RSLs, the number of exotic fish taxa present in lakes was strongly positively correlated with increasing prevalence of regime shifts. The strength of the correlations between land use and introduced species versus regime shifts illustrates a number of factors which could be managed to reduce the susceptibility of lakes to regime shifts and to restore lakes that have become de‐vegetated. Our findings also suggests that regime shifts in lakes were unlikely to have been common in New Zealand lakes before anthropogenic deforestation and introductions of introduced aquatic taxa.     

Te(IV)对螺旋藻胁迫作用的光谱学研究

用光谱法研究了 Te(IV)对螺旋藻(Spirulina maxima)的胁迫作用.各实验组添加 Te(IV)的时间均在第5~7天,累积添加质量浓度为从450~650 mg/L.结果表明,各 Te(IV)胁迫实验组中活藻体悬浮液的吸收光谱特征峰强度均不同程度地下降.而在440、580 nm 激发所得的荧光发射光谱峰位置不变,峰强度下降.但干粉的荧光光谱与活藻体悬浮液有明显不同,干粉中的藻胆体的能量传递过程受阻.各试验组干藻粉的红外光谱无明显差异     

The potential food poisoning hazard of Vibrio parahaemolyticus in New Zealand Pacific oysters

The level of Vibrio parahaemolyticus was generally very low in Pacific oysters sampled from 4 New Zealand oyster farms between November 1982 and May 1983. Of the 149 samples collected, only one was found to contain greater than the 1000 organisms g^‐1regarded as the maximum allowable by international standards (International Commission on Microbiological Specifications for Foods 1982: Micro‐organisms in Foods, Vol. 2. Academic Press, New York). V. parahaemolyticus was detected in 57% of the oyster samples, but 95% of these contained less than 10 organisms g^‐1. Maximum levels appeared to coincide with high water temperatures at the farm sites. Chilling, freezing, and depuration reduced V. parahaemolyticus numbers in oysters after harvest. However, holding at ambient temperatures (19–25°C) resulted in up to a 35‐fold increase in organism numbers with a maximum after one day. The food poisoning hazard from V. parahaemolyticus in New Zealand‐grown Pacific oysters thus appears to be minimal. Recommendations are made to keep harvested shellfish cool and to chill them as soon as practical.