Water sources of dominant species in three alpine ecosystems on the Tibetan Plateau, China

Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope （δD and δ^18O） values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species （Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum） in three typical ecosystems （forest, shrub and desert） were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ^18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.     

Determination of antimicrobial resistance and virulence gene signatures in surface water isolates of Escherichia coli

Aims: To determine the occurrence of Escherichia coli harbouring virulence markers of shiga‐ or entero‐toxins and resistance to antimicrobials in surface waters. Methods and Results: Surface water samples were collected at six locations of the river Gomti. E. coli isolates (n = 90) were characterized for their pathogenic potential using polymerase chain reaction to detect virulence genes as well as their sensitivity to antimicrobial agents using disc diffusion methods. In this study, 57·8% of E. coli isolates exhibited resistance to three or more antimicrobial agents. Sensitivity to cephotaxime, gentamicin and norfloxacin was observed in 7·8%, 48·9% and 77·8% of isolates, respectively. Both stx1 and stx2 genes were present in 15·6% of isolates while remaining isolates had either stx1 (17·8%) or stx2 (6·7%). The stx1 gene (33·3%) was more prevalent than stx2 (22·2%). The results indicate that the LT1 and ST1 genes were positive in 21·2% of isolates. Conclusions: The presence of multi‐drug resistance and virulence genes in E. coli isolated from surface water being used for domestic and recreational purposes may result in waterborne outbreaks. Significance and Impact of the Study: The data will be useful in monitoring surface waters for forecasting and management of waterborne outbreaks.     

Sediment and Water Nutrient Characteristics in Patches of Submerged Macrophytes in Running Waters

(1) The relative importance of sediments and water as nutrient sources for submerged macrophytes in running waters is poorly understood. Here we present water and sediment nutrient characteristics within macrophyte patches in Bavarian rivers. (2) No significant differences between early (June/July) and late summer (August/September) sediment nutrient characteristics could be detected within macrophyte patches. Therefore, a single sediment sample per macrophyte patch was considered to be sufficient for characterising nutrient concentrations during the main growing season in running waters. (3) Sediment TP (total phosphorus) is not a useful parameter for predicting trophic status in running waters. Sediment porewater SRP (soluble reactive phosphorus) concentration is not correlated to water body SRP or TP concentration; nor is it correlated with sediment TP content. Potamogeton coloratus, a oligotrophic species, is associated with low overlying and porewater SRP concentrations but high sediment TP content. Eutrophic species, such as Potamogeton pectinatus, are associated with low sediment TP. (4) It is hypothesized that Chara hispida primarily takes up sediment ammonia for nitrogen nutrition. (5) Nutrient characteristics of the water body and the sediment of eight macrophyte species in Bavarian rivers are described.     

干旱区石羊河流域河水孢粉组合特征

石羊河流域初春和仲夏两季不同地点,洪水期、平水期30个河水样孢粉分析显示, 没有人类影响的情况下,河水样孢粉组合是由河流上游径流区的植物孢粉和采样点附近植被孢粉组成的,前者在孢粉组合中至少占30%～60%.河水搬运孢粉的能力非常强,可长距离、大量地搬运孢粉.孢粉组合中河水贡献孢粉的含量较高,如:云杉属(Picea Dietr.)花粉河水的贡献率在中下游可达16.5%和7.7%.采样时间、地点影响河水的孢粉组合和浓度,洪水期是孢粉搬运的主要时期.河水经过水库后,其中孢粉绝大多数沉积在水库中.     

Site fidelity and association patterns in a deep-water dolphin: Rough-toothed dolphins (Steno bredanensis) in the Hawaiian Archipelago

In the Pacific, rough-toothed dolphins ( Steno bredanensis ) are typically found in the open ocean and in deep waters around oceanic islands. We examined habitat use, site fidelity, movements, and association patterns of this species in the main Hawaiian Islands. Sighting rates were highest in depths >1,500 m. There were frequent within- and between-year resightings off the island of Hawai'i, indicating a small population size with high site fidelity. Resighting rates were lower off Kaua'i/Ni'ihau, indicating a larger population size, but with some site fidelity. Two individuals were documented moving from Kaua'i to Hawai'i, a distance of 480 km, but were not seen to associate with dolphins off Hawai'i. Observed movements were consistent with at most 2% dispersal per year between these two areas. Differences in group sizes, habitat use, and behavior imply that movements among the islands may be limited. Little is known about the diet of rough-toothed dolphins in Hawai'i, but they are thought to feed primarily on near-surface species. High fidelity to deep-water areas off the island of Hawai'i likely reflects an increase in the predictability of prey associated with upwelling due to the island mass effect, wind stress curl and cyclonic eddies that form off the island.     

Dry season ecology of riverine tiger beetles in Kruger National Park, South Africa

The life cycles of many African species of tiger beetles (Insecta: Coleoptera: Cicindelidae) exhibit pronounced seasonality, with adult emergence and reproductive activity closely associated with seasonal rains. Anecdotal reports have suggested that adults of certain riverine tiger beetle species may be active during the dry season near perennial water sources. To test this hypothesis, fifteen sites along three perennial rivers in Kruger National Park, South Africa, were surveyed for tiger beetles in early September, 2006. Thirteen sites yielded adult beetles, with six species represented [ Chaetodera regalis (Dejean), Cylindera disjuncta (Dejean), Habrodera nilotica (Dejean), Lophyra neglecta intermediola (Horn), Lophyridia fimbriata imperatrix (Srnka), and Myriochile melancholica (Fabricius)]. Microhabitat associations of adults of all six species and ovipositional/larval substrates of five of the six species are reported, along with observations on predatory and reproductive behaviours and the possible presence of an anti-predator chemical defence in C. regalis and L. fimbriata imperatrix .     

Seasonal patterns of heat loss in wild bottlenose dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>)

This study investigated patterns of heat loss in bottlenose dolphins (Tursiops truncatus) resident to Sarasota Bay, FL, USA, where water temperatures vary seasonally from 11 to 33°C. Simultaneous measurements of heat flux (HF) and skin surface temperature were collected at the body wall and appendages of dolphins during health-monitoring events in summer (June 2002–2004) and winter (February 2003–2005). Integument thickness was measured and whole body conductance (W/m² °C) was estimated using HF and colonic temperature measurements. Across seasons, HF values were similar at the appendages, but their distribution differed significantly at the flipper and fluke. In summer, these appendages displayed uniformly high values, while in winter they most frequently displayed very low HF values with a few high HF values. In winter, blubber thickness was significantly greater and estimated conductance significantly lower, than in summer. These results suggest that dolphins attempt to conserve heat in winter. In winter, though, HF values across the body wall were similar to (flank) or greater than (caudal keel) summer values. It is likely that higher winter HF values are due to the steep temperature gradient between the body core and colder winter water, which may limit the dolphin’s ability to decrease heat loss across the body wall.     

Life history constrains biochemical development in the highly specialized odontocete echolocation system

The vertebrate head has undergone enormous modification from the features borne by early ancestors. The growth of skull bones has been well studied in many species, yet little is known about corresponding soft tissue development. Among mammals, some of the most unusual examples of cranial evolution exist in the toothed whales (odontocetes). Specialized fat bodies in toothed whale heads play important roles in sound transmission and reception. These fat bodies contain unique endogenous lipids, with favourable acoustic properties, arranged in highly organized, three-dimensional patterns. We link variation in developmental rates of acoustic fats with life-history strategy, using bottlenose dolphins and harbour porpoises. Porpoise acoustic fats attain adult configurations earlier (less than 1 year) and at a faster pace than dolphins. The accelerated lipid accumulation in porpoises reflects the earlier need for fully functional echolocation systems. Dolphins enjoy 3-6 years of maternal care; porpoises must achieve total independence by approximately nine months. Further, a stereotypic 'blueprint' for the spatial distribution of lipids is established prior to birth, demonstrating the highly conserved nature of the intricate biochemical arrangement in acoustic tissues. This system illustrates an unusual case of soft tissue development being constrained by life history, rather than the more commonly observed mechanistic or phyletic constraints.     

Planktonic Copepoda of the Upper Paraná River Floodplain lakes (São Paulo and Mato Grosso do Sul,Brazil)

Four series of samples were made during the hydrological cycle of 1992/1993 (October 1992, January, April, and July 1993) to establish the diversity of the planktonic Copepoda community in relation to the trophic state in seven floodplain lakes of the Upper Paraná River system. Sampling was carried out prior to the environmental disturbance caused by the formation of Porto Primavera Reservoir, when 250 km of the Upper Paraná River became standing water in 1998, with the consequent extinction of the original habitats. Nine planktonic species occurred in the Paraná River and floodplain lakes, seven diaptomids and two cyclopids. A trophic state gradient was established, indicating preferences of groups of copepod species for a set of limnological characteristics.     

Migration of bream between the main channel and floodplain lakes along the lower River Rhine during the connection phase

Mature bream (>30 cm L_F) dominated the fish communities in floodplain lakes along the lower River Rhine in The Netherlands, in terms of biomass, in all lakes at all times. In some lakes bream made up 99% of the total fish biomass. While immature, medium–sized bream (10-30 cm) and white bream and roach were abundant in the main channel of the river, these species were almost absent from the floodplain lakes. Inundation of the floodplains did not lead to spatial homogenization of species and length distributions. Small bream (<10 cm) left the floodplains to become resident in the main channel until maturity. Once mature (c. 30 cm), they returned to the lakes during the next inundation and stayed there. Mature bream that moved into the lakes were significantly smaller and had a lower condition than the resident bream. Turbid clay-pits were probably important sources of bream for the lower Rhine and the recruitment of the 0+ year group of bream to the riverine population was influenced by their discharge pattern.