Isolation of Laribacter hongkongensis, a novel bacterium associated with gastroenteritis, from drinking water reservoirs in Hong Kong

AIMS: Freshwater fish has been found to be the reservoir of Laribacter hongkongensis, a recently discovered bacterium associated with community-acquired gastroenteritis. However, little is known about the ecology of this bacterium in the aquatic environment. We carried out a surveillance study to investigate the presence of L. hongkongensis in water and freshwater fish from 10 drinking water reservoirs in Hong Kong. METHODS AND RESULTS: Using membrane filtration, L. hongkongensis was isolated from the waters of six reservoirs, with numbers ranging from 1 to 12 CFU l(-1). Higher recovery rates were observed in summer and during days of higher water and ambient temperatures. Of 27 freshwater fish collected from the reservoirs, L. hongkongensis was recovered from the intestines of two fish, a Goldfish and a Nile tilapia. Overall, 35 different pulsed-field gel electrophoresis patterns are found among the 59 isolates recovered from water and the two isolates from freshwater fish. CONCLUSIONS: The present report represents the first to demonstrate the presence of L. hongkongensis in natural water environments. SIGNIFICANCE AND IMPACT OF THE STUDY: Although it is unlikely that treated, drinking water is an important source of L. hongkongensis-associated gastroenteritis, one should be aware of the possibility of other contaminated water as a source of human infection.     

湘西地区不同淡水生境的齿蛉科幼虫多样性特征

齿蛉科昆虫隶属于昆虫纲广翅目,是重要的环境指示生物.本研究调查了湘西地区的齿蛉科幼虫的分布情况,并分析了齿蛉科幼虫在不同生境类型中的多样性特征.共采集到东方齿蛉Neoneuromus orientalis、炎黄星齿蛉Protohermes xanthodes、花边星齿蛉Protohermes costalis和中华斑鱼Neochauliodes sinensis4种齿蛉科幼虫.东方齿蛉仅在自然保护区和自然河流分布,炎黄星齿蛉和花边星齿蛉广泛分布于各种流水生境类型,中华斑鱼蛉除在各种流水生境类型中分布外,在静水的小型水库也有分布.自然河流的齿蛉科幼虫多样性指数H'最高,其余由高到低依次为自然保护区、旅游景区、自然溪沟和农业区;丰富度指数R趋势与H'指数相似,但农业区R指数高于旅游景区.本研究表明,不同种类齿蛉科幼虫在湘西地区的分布情况存在差异,自然条件优越的生境类型中齿蛉幼虫多样性指数较高.     

Recent sedimentation in a freshwater reservoir in SW-Finland: The diatomological and chemical evidence of sediments on the development of the water body

A freshwater reservoir was dammed from the Baltic Sea in 1965. The recent sediments and the processes of accumulation in the reservoir have been investigated. The physical, chemical and diatom analyses of the sediments were carried out at 5 sampling points in order to dinstinquish the freshwater sediments from the underlying brackish sediments as well as to date the freshwater sediments. The pattern of sedimentation in the reservoir is described on the basis of these results and conclusions are drawn regarding the development of the water body. In interpretating the diatomological and the chemical results from the recent sediments certain common features are highlighted.     

Interbasin water transfer, riverine connectivity, and spatial controls on fish biodiversity

Background

Large-scale inter-basin water transfer (IBWT) projects are commonly proposed as solutions to water distribution and supply problems. These problems are likely to intensify under future population growth and climate change scenarios. Scarce data on the distribution of freshwater fishes frequently limits the ability to assess the potential implications of an IBWT project on freshwater fish communities. Because connectivity in habitat networks is expected to be critical to species'' biogeography, consideration of changes in the relative isolation of riverine networks may provide a strategy for controlling impacts of IBWTs on freshwater fish communities.

Methods/Principal Findings

Using empirical data on the current patterns of freshwater fish biodiversity for rivers of peninsular India, we show here how the spatial changes alone under an archetypal IBWT project will (1) reduce freshwater fish biodiversity system-wide, (2) alter patterns of local species richness, (3) expand distributions of widespread species throughout peninsular rivers, and (4) decrease community richness by increasing inter-basin similarity (a mechanism for the observed decrease in biodiversity). Given the complexity of the IBWT, many paths to partial or full completion of the project are possible. We evaluate two strategies for step-wise implementation of the 11 canals, based on economic or ecological considerations. We find that for each step in the project, the impacts on freshwater fish communities are sensitive to which canal is added to the network.

Conclusions/Significance

Importantly, ecological impacts can be reduced by associating the sequence in which canals are added to characteristics of the links, except for the case when all 11 canals are implemented simultaneously (at which point the sequence of canal addition is inconsequential). By identifying the fundamental relationship between the geometry of riverine networks and freshwater fish biodiversity, our results will aid in assessing impacts of IBWT projects and balancing ecosystem and societal demands for freshwater, even in cases where biodiversity data are limited.     

Phytoplankton Fluctuations during an Annual Cycle in the Coastal Lagoon of Cullera (Spain)

The seasonal variation and the vertical distribution of the phytoplanktonic population of the lagoon of Cullera, an elongated coastal lagoon with estuarine circulation of water, has been studied in three sampling stations: mouth, centre and source. Seasonal variation is determined by a marine-freshwater interaction. In winter, the sea influence is important, a marine water wedge of anoxic water arrives at the sampling station located at the source and marine and brackish water species dominate the phytoplankton. Also marine species of zooplankton and fish enter the system, which may then be considered as exploited by the sea. In spring the marine wedge retreats from the source but remains in the centre and mouth, salinity diminishes, vertical mixing persists and phytoplankton is dominated by Cyclotella species. From late spring to autumn the freshwater influence prevails and a sharp stratification of the water is produced in the stations at the mouth and the centre, by means of a steep halocline coincident with an oxycline. The phytoplankton in this period follows a typical succession like those described in freshwater eutrophic lakes. Vertical distribution of phytoplankton is determined by the presence of the oxycline, originated by the marine water wedge, whose depth varies seasonally but which is always present in the mouth and centre of the lagoon; only few species of algae can be found below its level.     

Long-term follow-up studies confirm the stability of the latent reservoir for HIV-1 in resting CD4+ T cells

Latent HIV-1 persists in resting memory CD4+ T cells, even in patients receiving highly active antiretroviral therapy (HAART). It has been unclear how stable this latent reservoir is and whether its persistence reflects replenishment by low-level viremia. Here we show that even in treated patients who have had no detectable viremia for as long as 7 years, the reservoir decays so slowly (t(1/2) = 44 months) that eradication is unlikely.     

River inter linking in India: status,issues, prospects and implications on aquatic ecosystems and freshwater fish diversity

India is a vast country in terms of natural resources and considered one of the mega- biodiversity countries in the world. The freshwater aquatic resources of the different river basins are unevenly distributed in space and time and the country is suffering from the increasing population and shortage of all kind of natural resources like water. To fulfill the water demand and mitigate flood and drought, Indian Government has been planning a huge scheme encompassing the Himalayas and most of India, by linking all major rivers through interlinking canals systems and building several dams. Though the concept of interlinking of rivers is novel and new in India, it had rather initiated long back in other countries of ancient civilization. This is considered as one of the options to remedy spatial mismatch in water availability and demand. To overcome those, National Water Development Agency (NWDA) has taken up massive project and nearly 30 links have been proposed to interlink the major rivers. The Government of India has approved the country’s first river interlinking project on Ken–Betwa and a MOU has been signed among the states of Uttar Pradesh and Madhya Pradesh and the Union Government. The feasibility report of most of the links have been completed and detailed project reports of Ken–Betwa River link is expected to be finalized soon. Our study indicated presence of rich fish diversity and threatened fishes in river Betwa and improved aquatic environment in river Ken which makes it a high priority area in view of proposed interlinking. The current state of knowledge indicates that large dams, interbasin transfers and water withdrawal from rivers have many negative as well as positive impacts on freshwater aquatic ecosystem. As regards to the impact on fish and aquatic biodiversity, there could be positive as well as negative impacts. The present paper is aimed at explaining and synthesizing the long term plan and its implications, creating baseline database, requirement of appropriate technology, manpower and related issues especially with reference to riverine aquatic ecosystem and conservation of fish biodiversity.     

Pervasive decline of subtropical aquatic insects over 20 years driven by water transparency,non-native fish and stoichiometric imbalance

Insect abundance and diversity are declining worldwide. Although recent research found freshwater insect populations to be increasing in some regions, there is a critical lack of data from tropical and subtropical regions. Here, we examine a 20-year monitoring dataset of freshwater insects from a subtropical floodplain comprising a diverse suite of rivers, shallow lakes, channels and backwaters. We found a pervasive decline in abundance of all major insect orders (Odonata, Ephemeroptera, Trichoptera, Megaloptera, Coleoptera, Hemiptera and Diptera) and families, regardless of their functional role or body size. Similarly, Chironomidae species richness decreased over the same time period. The main drivers of this pervasive insect decline were increased concurrent invasions of non-native insectivorous fish, water transparency and changes to water stoichiometry (i.e. N : P ratios) over time. All these drivers represent human impacts caused by reservoir construction. This work sheds light on the importance of long-term studies for a deeper understanding of human-induced impacts on aquatic insects. We highlight that extended anthropogenic impact monitoring and mitigation actions are pivotal in maintaining freshwater ecosystem integrity.     

Trophic relationships and ecosystem functioning of Bakreswar Reservoir,India

Reservoirs are artificial water bodies having social application and hybrid characters of both river and lake. Thorough analysis of water quantity and quality is necessary to ensure the health of these ecosystems, as they are considered one of the major water sources in developing countries. Biological subsystem of reservoirs consists of both autotrophs and heterotrophs in the open zone and littoral zone. These components are critical for freshwater aquatic food webs. Bakreswar reservoir has been selected as the current study site. Static model representing ecosystem trophic structure is developed through Ecopath with Ecosim software and is analysed to obtain idea about the ecosystem functioning and functioning. This reservoir is found to be approaching maturity but with vulnerabilities being present as is evident from the studies of ecosystem attributes, transfer efficiencies, mixed trophic impact, niche overlap and other attributes. Good assemblage of biota like macrophytes, zooplankton etc. is observed, thus presenting some diversity in the food web. Based on the primary production to respiration ratio, this system can be categorized as a moderately mature and healthy ecosystem but is vulnerable to perturbations as is evident by low values of connectance index and system omnivory index. Comparatively low Finn cycling index indicates that this system is approaching maturity but is vulnerable. With a pedigree index of 0.459, the model is well suited for the study site. The knowledge thus obtained for this reservoir can be utilized to form proper management strategies to facilitate successful conservation management and proper resource utilization.     

Zooplankton community of Bakreswar reservoir: Assessment and visualization of distribution pattern using self-organizing maps

Self-organizing maps, otherwise known as Kohonen-maps, are one form of unsupervised artificial neural networks that can produce two-dimensional plots from multidimensional data. This tool is especially useful in community pattern analyses and has been previously used in spatial pattern analysis with different perspectives. The present study aims to find zooplankton's community pattern in the Bakreswar reservoir ecosystem. Bakreswar reservoir is a freshwater ecosystem in the Birbhum district of West Bengal, India. The reservoir is primarily used to supply freshwater to the Bakreswar thermal power plant. However, the local villages around the reservoir depend on it for drinking water and fishing sustenance. The data used in this study was collected over two years from three different stations. Thus, in addition to describing the spatial pattern of community distribution of zooplankton groups, the temporal variation was also studied. It is observed in the study that the four major groups of zooplankton – Copepoda, Cladocera, Ostracoda, and Rotifera – react differently to the different environmental attributes. Primarily directed by the physical environmental factors, the effect of the chemical factors on the patterning is also evident from the study. Copepods are the dominant group in the system, closely followed by cladocerans and rotifers. But this observation changes at different stations and throughout the study period. The temperature profiles of the reservoir primarily direct the occurrence of ostracods and rotifers, whereas cladocerans and copepods are inclined more towards a chemical factor directive. Rotifers are dominant in the monsoon, whereas the post-monsoon and winter seasons show an increased presence of copepods and cladocerans. The overall observation that the reservoir's water quality is good, and the trophic structure is healthy is in accordance with previous studies as well.     

Restoration of Freshwater Intertidal Habitat Functions at Spencer Island, Everett, Washington

In November 1994 dikes were breached around Spencer Island, restoring tidal inundation and connections to the Snohomish River estuary, Washington. Approximately 23.7 ha (58.5 ac) of palustrine wetlands previously dominated by Phalaris arundinacea (reed canarygrass) now experience diurnal tides and are in the process of transition to a freshwater tidal system. It was expected that brackish water would accompany the return of tidal influence to the site, but post‐project monitoring has revealed little evidence of salinity. Pre‐ and post‐project monitoring of changes in habitat function included aerial photography, vegetation and fish sampling, and benthic prey studies. To date site changes include (1) die back of pre‐project vegetation, development of tidal mudflat, and emergent wetland habitats, with recruitment of vegetation typical of freshwater tidal wetlands; (2) presence of juvenile coho, chum, and chinook salmon that feed on invertebrate prey typical of the site; (3) presence of three distinct benthic invertebrate assemblages in the project area; and (4) some invasion by Lythrum salicaria (purple loosestrife). The unexpected freshwater conditions, the lack of published information about tidal oligohaline marshes in the Pacific Northwest, the use of the site by endangered salmonid species, and the invasion by an undesired plant species underscore the importance of long‐term monitoring at the site.     

Isolation of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> from Open Ocean and Comparison with Freshwater,Clinical, and Animal Isolates

Pseudomonas aeruginosa is an opportunistic pathogen responsible for morbidity and mortality in humans, animals, and plants. This bacterium has been regarded to be widely present in terrestrial and freshwater environments, but not in open ocean environments. Our purpose was to clarify its presence in open ocean, and their genotypic and physiological characteristics were compared with those of isolates from clinical, animal, and freshwater sources. Water samples were collected from freshwater, bays, and offshore environments in Japan. Sixty-two isolates, including 26 from the open ocean, were identified as P. aeruginosa by phenotypic characteristics and the BD Phoenix System. Pulsed-field gel electrophoresis (PFGE) was performed on all strains, together with 21 clinical and 8 animal strains. The results showed that open ocean strains are composed of a few genotypes, which are separated from other strains. Although some clinical isolates made a cluster, other strains tended to mix together. Different antibiotypes were observed among marine isolates that had similar PFGE and serotyping patterns. Some were multidrug-resistant. Laboratory-based microcosm study were carried out to see the responses of P. aeruginosa toward increased NaCl concentrations in deionized water (DW). Marine strains showed better survival with the increase, whereas river and clinical strains were suppressed by the increase. These findings illustrate the potential significance of open ocean as a possible reservoir of P. aeruginosa, and there may be clones unique to this environment. To our knowledge, this is the first report on the presence and characterization of P. aeruginosa in the open ocean.     

Genome characteristics and environmental distribution of the first phage that infects the LD28 clade,a freshwater methylotrophic bacterial group

Bacteriophages infecting major groups of freshwater heterotrophic bacteria have been rarely isolated, hampering analyses of freshwater viromes. Here, we report the isolation and genomic characterization of P19250A, the first phage that infects the LD28 clade, an abundant freshwater methylotrophic bacterial group. P19250A was isolated from Lake Soyang, an oligotrophic reservoir, using an LD28 strain as a host. Morphological and genomic analyses revealed that P19250A is a lytic siphovirus with a ～38.6‐kb genome. To analyze the distribution of P19250A genome within its habitat, six seasonal viral metagenome (virome) samples were prepared from Lake Soyang. Through binning analysis of freshwater viromes, P19250A was shown to be the most highly assigned freshwater phage that infects heterotrophic bacteria (up to 8.21%) in five viromes. Furthermore, when freshwater virome data collected worldwide were analyzed, P19250A genome also showed high abundance, especially in Lough Neagh, UK, where P19250A genome was recorded as the most abundant bacteriophage. From metagenome analysis, the proportion of P19250A‐assigned reads showed seasonal fluctuation following the abundance of the LD28 clade in Lake Soyang. These results showed that P19250A would be an essential resource for analyses of freshwater viromes, and also suggest that phages of other abundant freshwater bacteria need to be isolated for better understanding of freshwater viruses.     

Organochlorine Pesticides and Polychlorinated Biphenyls in Tissues of Landlocked Kokanee Salmon from Tolmachevskoye Reservoir,Kamchatka

Concentrations of organochloride pesticides (OCPs) and polychlorinated biphenyls (PCBs) that were obtained in landlocked kokanee salmon (Oncorhynchus nerka kennerlyi) from the Tolmachevskoye Reservoir, Kamchatka, correspond to the levels found in freshwater bodies of background areas around the world. The spatial distribution of PCBs and OCPs in kokanee at the spawning ground and in the deepwater part of the reservoir, as well as its distribution in the kokanee organs, indicate the atmospheric input of contaminants and the ongoing technogenic impact, which was generated during the establishment and operation of the Tolmachevskoye Reservoir. The contaminants that enter from these sources into the water column are incorporated into the food web of the water body. The permissible consumption of kokanee fillet from the Tolmachevskoye Reservoir and caviar from red salmon from the Kuril Lake by population is 10–26 kg and 1.2 kg per year respectively.     

Bacteria and viruses in the water column of tropical freshwater reservoirs

In tropical freshwater reservoirs of Sri Lanka, which are linked in an aquatic network, bacterial abundance and production as well as virus abundance, frequency of viral infection and virus production were investigated together with a set of nutrient species (Kjeldahl-N, NO3-N, total P, soluble P, PO4-P). At two characteristic seasons (wet season, dry season), samples were taken from two types of reservoirs (new upland impoundment and ancient, shallow lowland reservoir), each during 4 days at various depths of the entire water columns. Kjeldahl-N and total P were greatly elevated in the wind-mixed water body of the shallow impoundment during the dry season, whereas the deeper reservoir type exhibited no obvious seasonality. In SYBR green trade mark -stained samples, bacterial abundance showed no seasonal pattern in either reservoir type. Bacterial secondary production, however, was significantly elevated in the entire water column of the shallow impoundment under wind-mixed conditions in the dry season. Highest abundance of virus particles and elevated frequency of bacteria containing mature phages were also observed in the shallow reservoir during the dry season indicating favourable conditions for virus propagation. Data from this aquatic network show that most virus parameters, such as abundance or frequency of visibly infected cells, were positively linked to bacterial abundance and production, but also to organic nitrogen or some phosphorus species. We calculated that between 13.2% and 46.1% of the bacterial standing stocks would be subjected to virus-mediated mortality. Estimates of bacteriophage production revealed that from 10 x 10(9) up to 98 x 10(9) phages were produced per litre and day. Bacteria and viruses in the studied tropical freshwater system appear to be linked to various environmental conditions and may affect processes at the ecosystem scale.     

Demographic Stochasticity, Environmental Variability, and Windows of Invasion Risk for Bythotrephes Longimanus in North America

Biological invasions are a leading threat to freshwater biodiversity worldwide. A central unanswered question of invasion ecology is why some introduced populations establish while most fail. Answering this question will allow resource managers to increase the specificity and effectiveness of control efforts and policy. We studied the establishment of spiny water flea (Bythotrephes longimanus) in the United States and Canada by modeling introduction failure caused by demographic stochasticity, environmental variation, and seasonal environmental forcing. We compared predicted establishment rates with observed invasions of inland lakes in Ontario, Canada. Our findings suggest that environmental forcing can cause “windows” of invasion opportunity so that timing of introductions might be a greater determinant of population establishment than demographic stochasticity and random environmental variation. We expect this phenomenon to be exhibited by species representing a wide range of life histories. For spiny water flea in North America, a large window of invasion opportunity opens around the fourth week of May, persists through the summer, and closes with decreasing water temperatures in autumn. These results show how timing of introductions with respect to seasonally forced environmental drivers can be a key determinant of establishment success. By focusing on introductions during windows of invasion opportunity, resource managers can more effectively control invasion rates.     

Aspects of the life history of a freshwater population of the mummichog,Fundulus heteroclitus (Pisces: Cyprinodontidae), in the Bronx River,New York,U.S.A.

A freshwater population of the mummichog, Fundulus heteroclitus, was sampled during summer and autumn 1979, from the Bronx River, New York. Other occurrences in freshwater of this common estuarine cyprinodontid fish have been noted in Pennsylvania, New Hampshire and Canada. In the Bronx River, this species is a significant part of the fauna and is one of the few species found throughout the river system. Specimens were examined to determine the growth and diet. It appears that this freshwater population does not differ from its brackish water conspecifics with respect to age structure, growth rate and feeding behavior.     

Complete genome sequence of the gliding freshwater bacterium Fluviicola taffensis type strain (RW262)

Fluviicola taffensis O'Sullivan et al. 2005 belongs to the monotypic genus Fluviicola within the family Cryomorphaceae. The species is of interest because of its isolated phylogenetic location in the genome-sequenced fraction of the tree of life. Strain RW262(T) forms a monophyletic lineage with uncultivated bacteria represented in freshwater 16S rRNA gene libraries. A similar phylogenetic differentiation occurs between freshwater and marine bacteria in the family Flavobacteriaceae, a sister family to Cryomorphaceae. Most remarkable is the inability of this freshwater bacterium to grow in the presence of Na(+) ions. All other genera in the family Cryomorphaceae are from marine habitats and have an absolute requirement for Na(+) ions or natural sea water. F. taffensis is the first member of the family Cryomorphaceae with a completely sequenced and publicly available genome. The 4,633,577 bp long genome with its 4,082 protein-coding and 49 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

石佛寺水库对周围环境的影响

石佛寺水库对周围环境的影响裴铁,范世香,韩绍文,迟振文（中国科学院沈阳应用生态研究所,１１００１５）王鉴成（辽宁省水利电力厅,沈阳１１０００３）ＩｍｐａｃｔｓｏｆＳｈｉｆｏｓｉＲｅｓｅｒｖｏｉｒｏｎＩｔｓＡｄｊａｃｅｎｔＥｃｏｌｏｇｉｃａｌＥｎｖｉｒ...