Survival capacity in water of Arcobacter species under different temperature conditions

Aims:  To assess the survival capacity in vitro of arcobacters in water at temperatures applied in the food industry.
Methods and Results:  Four strains of each Arcobacter species were inoculated in potable water and water with 1% organic material and stored at 4, 7, 20, 52, 56 and 60°C. Samples were taken at known time points and the numbers of bacteria were determined on Arcobacter -selective medium. All Arcobacter species remained viable for a temperature-dependent period of time, although Arcobacter butzleri displayed a significant longer survival and heat resistance . No significant intraspecies differences were detected, resulting in no definite identification of origin or strain dependency. The survival period for all species was prolonged in the presence of the organic material only for the low temperatures.
Conclusions:  The present study demonstrates that water can act as a reservoir and as a potential source of Arcobacter contamination to humans and animals.
Significance and Impact of the Study:  This study assessed for the first time the survival of all human-related Arcobacter species in water. Particularly A. butzleri showed to be the most robust species with regard to temperature which is interesting as that species is often found in human clinical specimens.     

The affects of artificial water availability on large herbivore ranging patterns in savanna habitats: a new approach based on modelling elephant path distributions

Aim  Artificial water points are often used in protected savanna ecosystems to maintain populations of large herbivores. However, these interventions lead to increased ranging and foraging pressure and can negatively impact important habitats and species. This study investigated the influence of artificial water provision on the foraging and movement paths of an African elephant population and modelled the impact of changing water availability on sensitive habitat types.
Location  Tembe Elephant Park (TEP), KwaZulu-Natal, South Africa.
Methods  We mapped and classified 414 km of elephant movement and foraging paths in a 300-km² fenced protected area. The data were analysed to determine the relationship between path size, distribution and distance to water. We also used a logistic modelling approach to explore the predicted effects of removing artificial water points on path distribution.
Results  Elephant paths were unevenly distributed throughout the habitats of TEP and the most established and heavily used paths were found closest to water. We also discovered a number of elephant 'rest areas' along the paths, which were distinct clearings that tended to be close to water and in sand forest habitat. Our model predicted that the removal of artificial water points would reduce the area crossed by elephant paths by 79%, leading to an 89% reduction in the presence of elephant paths in sand forest.
Main conclusions  Our study provides further evidence that manipulating surface water availability can be a useful tool for managing large herbivore impacts on vegetation and acts as the basis for further research on the trade-offs between conservation objectives.     

Agricultural use of water

Irrigation for agricultural purposes is one of the essential claims on available water resources. Those resources have not been adequately utilized in many countries for a variety of reasons. Where finance has been allocated to irrigation schemes, the schemes have tended to be large-scale, and the performance often disappointing. Alternatively, small-scale irrigation schemes, while receiving less support and encouragement, can often be more effective. For both large-scale and small-scale irrigation schemes, the responses of individual farmers and village communities are critical factors. More technologies need to be developed that are adapted to local needs, resources and aspirations within the context of current socio-economic practices. Obviously, the wider the range of technologies available, the more likely it will be that the technology most appropriate to existing conditions will be identified and used.     

Scientific quality of tourism environmental impact assessment

1. The scientific quality of environmental impact assessment (EIA), as exemplified by major tourism developments in Australia, is very poor.
2. Methods are inadequately specified.
3. Sampling is inadequately replicated in space or time.
4. Significant parameters are often ignored.
5. Impact predictions are rarely quantitative or testable and frequently are inaccurate.
6. Monitoring programmes generally are inadequate to detect likely impacts.
7. As an exercise in applied science, EIA fails to meet the most fundamental quality criteria.
8. As a tool in public decision-making, EIA needs much better applied science.     

Diatoms as indicators of water quality in some English urban lakes

SUMMARY. 1. The paper describes diatom communities from a series of linked urban lakes in relation to water chemistry and uses multivariate statistical techniques to show how indicator groups can he defined.
2. Diatoms are classified into ecological groups using two-way species indicator analysis (TWINSPAN). Each ecological group is associated with a specific range of water-quality conditions. The headwater stream environments are differentiated from the lake habitats at level 1. At level 2 of TWINSPAN. the sampling sites are grouped into five ecological groups, according to their water chemistry and irrespective of the time of year.
3. Detrended correspondence analysis (DCA) and principal components analysis (PCA) provide two statistically independent methods of assessing the environmental gradients along which the ecological groups are distributed. The most important physico-chemical parameters are total hardness, specific conductance and pH, followed by phosphates and nitrates.
4. Ecological groups I-V correspond to an environmental gradient ranging from the forested headwaters, which are acidic, of low specific conductance, total hardness and nutrient content, through the urban lakes, which are alkaline and of relatively high total hardness, specific conductance and nutrient content.
5. Twelve site groups are identified at level 3 of TWINSPAN, each of which corresponds to a narrower range of water-quality conditions within the ecological groupings. A specific diatom assemblage is associated with each site group.
6. Benthic diatoms form an integral part of the diatom assemblages found in the water column and this is identified as a topic for further study.     

Maternal body volume constrains water uptake by lizard eggs in utero

1. Flexible shelled eggs of squamate reptiles normally take up substantial amounts of water, and swell accordingly, during development. However, most water uptake occurs after oviposition, beginning immediately or soon after oviposition, and water uptake is severely restricted in eggs that are retained in utero past the normal time of oviposition.
2. These observations suggest that some aspect of retention in the oviductal environment limits the amount of water eggs can absorb prior to oviposition.
3. This paper presents evidence, from two species of Sceloporus lizard, supporting the hypothesis that limited space within the mother's body cavity physically constrains the ability of eggs to expand, and thereby their ability to absorb water. When adjusted for maternal body size, the water content of a female's clutch of eggs is negatively correlated with the dry mass of her clutch (the space available in the body cavity is finite, and thus a greater dry mass content leaves less volume for water).
4. If such a constraint on water uptake is widespread, it can have important implications for our understanding of the evolution of viviparity, the costs of reproduction, and the determinants of reproductive output in squamate reptiles.     

Oviposition site selection by Mansonia mosquitoes on water lettuce

Abstract. 1. Viable Mansonia egg masses occur in nature on both the upper and under surfaces of Pistia stratiotes (L.) leaves. Upper-surface masses were from Mansonia dyari Belkin, Heinemann & Page, but lower-surface oviposition was attributable to both M. dyari and M. titillans Walker.
2. Upper-surface egg masses were often out of water but were concentrated near a wet-dry stain line on the leaf. Lower-surface masses were laid underwater within 3 mm of the leaf edge, except for those oviposited through fenestrations caused by insect damage.
3. Oviposition varied seasonally and masses were most numerous between August and December when water lettuce plants were large and crowded. Egg masses were clumped on plants and leaves and concentrated on mature or mature-old leaves that subtended mean angles of 28–34° from the horizontal.
4. On intact plants in cages, M. dyari laid egg masses on both leaf surfaces in approximately the same proportions as observed in nature. On detached leaves floating flat on the water, M. dyari laid all masses on under surfaces.
5. At 20 and 25°C, egg development of M. dyari required 17.4 and 8.8 days (means), these being significantly longer than the mean times for M. titillans. Some larvae from eggs that hatched in the absence of water survived 72 h in the eggshell.
6. Upper-surface oviposition by M. dyari may be an adaptation to the crowded growth of water lettuce, the mosquito's favoured host plant, whose leaves are largely out of water. Leaf ageing and subsidence cause submergence of most upper-surface eggs by the time of hatching.     

Suspension and settlement of particles in flowing water: comparison of the effects of varying water depth and velocity in circulating channels

SUMMARY. 1. An experimental study is described, designed to test the hypothesis that the loss of particles from suspension in flowing water follows an exponential decay function, the exponent of which is influenced more by water depth than water velocity. Successive experiments employed suspensions of Lycopodium spores which were introduced into one of the FBA's circulating channels maintained at its Watcrston site, Dorset, under different combinations of water depth and pumping rate.
2. In each experiment, the concentration of introduced spores indeed declined exponentially through time. The bulked, transformed data-set also conformed well to a single regression against a common time scale and which explained over 94% of the accumulated variances.
3. The variance unexplained by the regression was apportioned among components distinguishing between experiments, experimental differences in starting concentration, water depth and pumping rate (velocity). This analysis revealed that, after elimination of different initial concentrations, only water depth produced a significant effect, through its relation to the settling velocity of the Lycopodium . Thus, the hypothesis was not invalidated: water depth and not Row velocity proved to be the main controlling variable determining the rale of sinking loss in these experiments. Flow velocity is, nevertheless, an important component only in the sense that it influences the horizontal distance travelled by the residual spore suspension through the time period required for complete settlement.
4. The consequences of experimental findings are applied to the maintenance of planktonic diatoms in rivers: both the survival of a potential growth inoculum and its downstream dispersion are strongly time-dependent and are enhanced by greater channel depths.     

An inexpensive device for sampling large volumes of lake water from discrete depths

SUMMARY 1. A sampler was developed that displaces surface water which is replaced with water from a sampling tube at a set depth.
2. The displacement sampler is inexpensive, easy to build, and is capable of collecting water at 7.5 I min⁻¹.
3. Phytoplankton photosynthesis was higher in water from the displacement sampler than in water collected with a Van-Dorn bottle. Subsequent experiments indicated this was due to inhibition caused by the Van-Dorn bottle.     

Cladocera and geochemical evidence from sediment cores show trophic changes in Polish dystrophic lakes

Change in the trophic state of lakes is a topic of primary interest for limnologists and paleolimnologists, but also for governments in many countries. These changes can be the result of the natural evolution of lake ecosystems, but nowadays are most often connected with human activity influencing water bodies. In this article, we reconstruct changes in the lake productivity and trophic state in three dystrophic (humic) lakes located in Northern Poland. Sediments from these lakes, which are part of a national park, were submitted to Cladocera and chemical composition analyses. Currently, the trophic state of these lakes has been described based on the water's chemical composition, and they have been classified as undisturbed ecosystems with a stable trophic state. The main objective of this study was to evaluate whether these lakes have been stable and undisturbed ecosystems during the past centuries and therefore whether they can be classified as natural and pristine. The results of subfossil Cladocera analysis and sedimentary geochemical analysis confirmed the specific nature of studied lakes. However, our results were surprising and showed that during the last 200 years two of the three lakes have undergone distinct trophic changes, while one of them has barely changed at all.     

Microhabitat selection by the fishfly larva, Parachauliodes japonicus, in relation to its mode of respiration

SUMMARY. 1. Larvae of Parachauliodes japonicus (Megaloptera: Corydalidae) were tracked in streams using miniature radio-transmitters.
2. Larvae usually stayed under stones in shallow water for several days, but occasionally moved about on the stream bed at night.
3. Larvae possess a pair of respiratory tubes on abdominal segment VIII, which can be used as a snorkel to obtain oxygen from the atmosphere. Because respiratory rates decreased as dissolved oxygen decreased, larvae turned to air-breathing under lowered oxygen conditions. When in shallow water, they can alter respiratory mode from aquatic respiration to air breathing instantly by raising their caudal respiratory tubes to the surface of the water.
4. Microhabitat selection and respiratory behaviour are compared with those obtained previously for Protohermes grandis larvae, which belong to the same family and often inhabit the same stream as P. japonicus , but which have gill tufts on abdominal segments I-VII instead of respiratory tubes. The respiratory constraint on microhabitat preference by aquatic insects is discussed.     

Limnology in the new century: c.21 topics for research

This is an invited view of the research topics likely to challenge limnologists during the early years of the twenty-first century. The annotated list of topics nominated is personal and is not intended to be comprehensive, but it ranges over developments in the understanding of limnological processes, the refinement of methodologies founded on rapid advances in technology, and the enhancement of the application of science to critical issues in resource management. However, better ways of valuing, transferring, and even organizing limnological science need to be devised. Received: October 25, 1999 / Accepted: December 7, 1999     

Secretion-grooming in the water bug Plea minutissima: a chemical defence against microorganisms interfering with the hydrofuge properties of the respiratory region

Abstract. 1. The water bug Plea minutissima Leach (Hemiptera: Pleidae) from time to time crawls out of the water and distributes secretion from its metathoracic glands over the ventral part of its body. By this 'secretion-grooming' antiseptic gland substances, mostly hydrogen peroxide, are applied to the hydrofuge hairs which hold the respiratory air bubble.
2. When the bugs are prevented from leaving the water, their mortality increases significantly, and individuals lacking the air bubble are observed. Examination of such bugs with Scanning Electron Microscopy techniques reveals bacteria growing on their hydrofuge hairs, whereas in bugs allowed to secretion-groom the hairs are not contaminated by microorganisms.
3. Artificial application of diluted metathoracic gland secretion on the body surface of P. minutissima kills bacteria, while specific ciliates, which never colonize the respiratory region, are not harmed by the secretion.
4. It can be concluded that secretion-grooming prevents the contamination of the hydrofuge respiratory region that leads to the wetting of the hydrofuge respiratory regions, resulting in the loss of the air bubble, and, finally, the drowning of the animals.
5. Other possible functions of the secretion, such as chemical defence against predators or wetting of the body surface, could not be demonstrated or seem unlikely.     

A multi-lake study of seasonal variation in lake surface evaporation using MODIS satellite-derived surface temperature

Knowledge of the evaporative loss from lakes and reservoirs is critical to water resources managers as well as to the overall understanding of the water balance in a given basin, geographical region, or continent. Existing methods for ascertaining evaporation from lakes and reservoirs include point measurements, water balance and mass transfer calculations, and proxy measurements using a pan. Point measurements using the eddy flux covariance method can be accurate, but are resource intensive and unsuited for determining spatial variation over a lake, or for obtaining measurements over many lakes. Mass balance methods cannot provide spatial variability and their accuracy depends on other portions of the water balance that can be challenging to obtain, such as leakage. Similarly, relatively recently deployed scintillation methods provide only an average for a strip across a lake and are also resource intensive and not suited for multi-lake studies. Evaporation pan measurements can also be used, though their accuracy is poor. Herein, we use a combination of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite measurements of water surface temperature, measurements of wind speed, air temperature, and relative humidity from local NWS stations, and a mass transfer method, to demonstrate multi-lake evaporation measurements. Specifically, the seasonal variation in evaporation is obtained for the five major lakes in the Savannah River Basin (in South Carolina, USA): Lakes Jocassee, Keowee, Hartwell, Russell, and Thurmond. Since this approach requires only an existing satellite resource with global coverage and existing NWS stations, this method can potentially be ported to any lake where there is a nearby meteorology station. Hence, this method could be used by both water resource managers and limnologists alike. The possibility is discussed of extending this approach beyond a single basin to encompass an entire geographical region or continent.     

Sedimentation in a large lake: the importance of fluctuations in water level

1. A sediment trap study was conducted in the central basin of Lower Lough Erne, Northern Ireland.
2. The material caught was low in organic matter, ash weight was 77% of dry weight on average.
3. Mass deposition of material was shown to be correlated with lake water level. When lake water level fell or rose above the middle range, the amount of material caught by the trap increased markedly. The effect was exaggerated by an unusually dry summer in 1995 which caused abnormally low water levels in the lake.
4. Comparison of Erne data with Windermere shows similar deposition rate of many substances, but the deposition rate of iron is thirteen times higher in Erne than in Windermere, and iron made up 39% of the ash weight in the Erne trap data.
5. Only 17% of the silica removed from the water column during diatom growth was recovered in the trap over the same time period.
6. Trap data are compared with historical data for sediment deposition and the implications of sediment focusing are discussed.     

Viable ultramicrocells in drinking water

Aims:  To examine the diversity of cultivable 0·2 micron filtrate biofilm forming bacteria from drinking water systems.
Methods and Results:  Potable chlorinated drinking water hosts phylogenetically diverse ultramicrocells (UMC) (0·2 and 0·1  μ m filterable). UMC (starved or dwarf bacteria) were isolated by cultivation on minimal medium from a flow system wall model with polyvinyl chloride (PVC) pipes. All cultivated cells (25 different isolates) did not maintain their ultra-size after passages on rich media. Cultured UMC were identified by their 16S ribosomal DNA sequences. The results showed that they were closely related to uncultured and cultured members of the Proteobacteria, Actinobacteria and Firmicutes. The isolates of phylum Actinobacteria included representatives of a diverse set of Actinobacterial families: Micrococcaceae, Microbacteriaceae, Dermabacteraceae, Nocardiaceae and Nocardioidaceae.
Conclusions:  This study is the first to show an abundance of cultivable UMC of various phyla in drinking water system, including a high frequency of bacteria known to be involved in opportunistic infections, such as Stenotrophomonas maltophilia, Microbacterium sp., Pandoraea sp. and Afipia strains.
Significance and Impact of the Study:  Chlorinated tap water filtrate (0·2 and 0·1  μ m) still harbours opportunistic micro-organisms that can pose some health threat.     

Extensive physiological integration in intact clonal systems of Carex arenaria

1 Carex arenaria forms large clonal fragments (up to 12 m long) in environments in which soil-bound resources limit growth.
2 We hypothesized that extensive integration of C. arenaria would facilitate the exploitation of scarce and patchily distributed soil resources and that the continued functioning of old roots would enable exploitation of resources that are temporally variable.
3 We used labelling with ¹⁴C and acid fuchsin to study the degree and extent of physiological integration and root function of intact clonal systems of C. arenaria in a sand dune area in south Sweden.
4 The uptake and translocation of dye suggests that old roots remain capable of taking up water and nutrients, in contrast with negative reports from previous studies. Water was translocated both acropetally and basipetally.
5 Thirty per cent of the assimilated carbon was found to be translocated towards the growing apex. Smaller, but significant, amounts of carbon were translocated basipetally throughout the fragments (17–74 ramet generations).
6 The results are discussed in terms of the source–sink relations of large clonal systems in the field. The translocation patterns are considered in relation to soil moisture and nutrient availability.     

The ecology of brown trout Salmo trutta in English chalk streams

SUMMARY. .1. Chalkstream trout are fast-growing, short-lived with a stable age structure that is a consequence of the lack of extremes in the abiotic environment, especially of water temperature and flow.
2. Levels of secondary (invertebrate) production arc high and there is no evidence that interspecific or intraspecific competition for food resources limits growth.
3. Dietary studies show a broad similarity between trout and other species, but indicate differences that reflect variations in the micro-habitat distributions between fish species.
4. Trout numbers appear to be limited initially by the availability of gravel spawning areas, and then by areas suitable for newly-emerged fry. Reduction in stream discharge in the spring, either naturally or by man, can lower the number of 0+ trout that survive.
5. Eels are not important predators on trout eggs or fry. but a reduction in pike numbers can lead to a decrease in the mean weight of pike. Small pike do not pose a serious threat to stocked yearling trout.     

A Proposed Framework for the Management of Water Quality in Arid-Region Lakes

For arid-region lakes, management conflicts are likely to occur between quantity and quality of water supplied: increasing quantity of water supply can lead to water quality deterioration. Such conflicts can best be resolved within an effective management program based on awareness and cooperation at all levels of water management from policy makers to experts. We propose a general framework for designing effective water resource management programs for lakes based on concrete definitions of management criteria such as water quality. The proposed system requires close interaction between policy makers, water resource managers, water suppliers and users, hydrological engineers and limnologists. The significance of mathematical modeling as a self-organizing tool of the management program is emphasized, especially with regards to designing limnological investigations directed toward lake management. We illustrate the application of this approach to water resource management in arid-region lakes (Lake Kinneret, Israel and Lake Sevan, Armenia), where artificial variability of lake morphometry due to water use is a forcing function affecting water quality.     

Riverine landscapes: taking landscape ecology into the water

1. Landscape ecology deals with the influence of spatial pattern on ecological processes. It considers the ecological consequences of where things are located in space, where they are relative to other things, and how these relationships and their consequences are contingent on the characteristics of the surrounding landscape mosaic at multiple scales in time and space. Traditionally, landscape ecologists have focused their attention on terrestrial ecosystems, and rivers and streams have been considered either as elements of landscape mosaics or as units that are linked to the terrestrial landscape by flows across boundaries or ecotones. Less often, the heterogeneity that exists within a river or stream has been viewed as a `riverscape' in its own right.
2. Landscape ecology can be unified about six central themes: (1) patches differ in quality (2) patch boundaries affect flows, (3) patch context matters, (4) connectivity is critical, (5) organisms are important, and (6) the importance of scale. Although riverine systems differ from terrestrial systems by virtue of the strong physical force of hydrology and the inherent connectivity provided by water flow, all of these themes apply equally to aquatic and terrestrial ecosystems, and to the linkages between the two.
3. Landscape ecology therefore has important insights to offer to the study of riverine ecosystems, but these systems may also provide excellent opportunities for developing and testing landscape ecological theory. The principles and approaches of landscape ecology should be extended to include freshwater systems; it is time to take the `land' out of landscape ecology.