Assessment of river health based on an improved entropy-based fuzzy matter-element model in the Taihu Plain,China

Rivers are valuable to human beings because of their various functions. Unfortunately, ecological integrity of rivers has been seriously threatened by human activities, resulting in poor river functions. It is thus necessary to evaluate and maintain river health. Meanwhile, it is challenging to comprehensively assess river health with a single method alone. It is therefore relevant to combine the advantages of multiple methods in river health assessment. By classifying and characterizing river functions, we first established an indicator system for river health assessment in plain river network regions. We then assessed the health status of the Taihu Plain in terms of an improved entropy-based fuzzy matter-element model. We found that the overall health status of the Taihu Plain is below “good”. In particular, the health status of Yang-Cheng-Dian-Mao and Hang-Jia-Hu Region is “moderate”; the Wu-Cheng-Xi-Yu Region displays the poorest natural and social river functions. We also found that flood control is the most important influential factor in river health. Our findings suggest that rivers in the Taihu Plain must be restored to maintain their health, with the Wu-Cheng-Xi-Yu Region that must be restored preferentially, and that the river function of flood control must be improved at the scale of whole watershed. Comparing with other four commonly used comprehensive assessment methods, our improved entropy-based fuzzy matter-element model outperforms in reflecting objective fact and can be applied to river health assessment. Our results are generally consistent with existing studies, confirming that the proposed method for river health assessment is effective and feasible. Therefore, it provides a useful reference for river health assessment in other plain river network regions.     

Diversity of isopods (Crustacea): new data from the Arctic and Atlantic Oceans

New data on the diversity pattern of isopods (Crustacea) from the northern most part of the North Atlantic and the Arctic Oceans is presented. The pattern of diversity with depth is similar at depths <1000m, but differs considerably below about 1000m. In the Arctic the diversity of isopods (expressed both as numbers of species per sled and expected number of species) increased with increased depth to a maximum at depths of about 320 to 1100m, but then declined towards deeper waters. There was a significant increase in numbers per sled and in the expected number of species with increased depth in the northernmost part of the North Atlantic Ocean. Additionally, changes occurred in the relative composition of the shallow and deep water fauna, with asellote isopods being relatively larger part of the isopod fauna in the Arctic than in the northern most part of the North Atlantic. This indicates major faunistic changes occurring at the Greenland-Iceland-Faeroe Ridge, possibly caused by rapid changes in the temperature. Furthermore, that the low diversity of the Arctic deep-sea is a regional phenomenon, and not a part of a large scale latitudinal pattern in the North Atlantic.     

Geographical extent of Arctic char (Salvelinus alpinus) mtDNA introgression in brook char populations (S. fontinalis) from eastern Québec, Canada

The geographical extent of Arctic char ( Salvelinus alpinus ) mitochondrial DNA introgression into brook char ( Salvelinus fontinalis ) populations found in eastern Québec was determined by analysing a total of 598 fish from 29 lakes. The nuclear genome was analysed by protein electrophoresis, whereas the ND-5,6 portion of the mitochondrial genome was analysed by restriction fragment length polymorphism. This survey revealed that introgressed S. fontinalis populations are restricted to only one river subdrainage of the Portneuf basin, where Arctic char is completely absent. Elsewhere, nonintrogressed pure S. fontinalis populations populate the lakes. These findings suggest that the initial hybridization event between the species is ancient and probably occurred shortly after recolonization of the area. At that time, the species would have been in contact and the chances of reproductive isolation mechanisms breaking down would have been high. We discuss the possibility that a combination of biogeographical conditions coupled with positive selection for mtDNA introgression led to the present-day distribution of introgressed S. fontinalis in northeastern North America.     

Peripheral thermoregulation: Haematologic or vascular adaptations

Arctic homeotherms maintain their feet near O°C while standing on much colder surfaces by blood-borne heat input. At 5°C in vivo blood viscosity increased approximately 5 times in arctic wolves and wolverines, and for comparison, in non-cold acclimated man. Such increase in blood viscosity in vivo would reduce perfusion; however, specialized arteriovenous plexuses have evolved in foot pad cutaneous tissues. These augment heat delivery and protect tissues from frost bite.     

Handling stress of female common eiders during avian cholera outbreaks

Researchers often consider the importance of minimizing holding time during research activities; however, the long-term costs of such handling stress is rarely measured explicitly. As part of an ongoing study of common eiders (Somateria mollissima) at a breeding colony in East Bay, Southampton Island, Nunavut, we recorded duration of restraint for females captured during avian cholera epizootics (2007 and 2008) and monitored female fates (breeding probability, onset of laying, and survival) relative to holding time. Probability of death increased with holding time in 2007 from an estimated 0.05 for females held 20 min to 0.33 for females held for 150 min. In 2008, we responded by limiting holding time to <90 min and mortality was no longer positively correlated with holding time, although total mortality was greater due to increased severity of avian cholera. In both years, longer restraint durations delayed onset of egg-laying after capture by 0.5 days for each 10 min of additional restraint but did not prevent breeding. This delay of nest initiation did not enhance survival probability. Our results show that prolonged holding time can exacerbate mortality during epizootics and emphasize the importance of minimizing restraint time in wild birds, especially in the presence of diseases. © 2011 The Wildlife Society.     

Diel methane emissions in stands of Spartina alterniflora and Suaeda salsa from a coastal salt marsh

In this study, we aimed to understand the influence of plant type on the monthly variations of diel CH₄ fluxes from Spartina alterniflora and Suaeda salsa of coastal salt marshes at three growth stages (July, August and September). Dissolved CH₄ concentrations in porewater and sediment redox potentials were monitored, as were aboveground plant biomass and stem densities. CH₄ fluxes exhibited clear monthly variations and peaked in September in the S. alterniflora and S. salsa mesocosms. However, no discernible diel variation was observed in the CH₄ flux in the S. salsa mesocosm, probably due to its weak gas transport capacity. By contrast, notable diel variations of CH₄ flux with the peak of 1.42 and 3.67 mg CH₄ m⁻² h⁻¹ at 12:00 and the lowest of 0.75 and 2.11 mg CH₄ m⁻² h⁻¹ at 3:00 or 6:00 were observed in the S. alterniflora mesocosm on 11 August and 11 September, respectively, but not in July mainly due to low plant biomass masking diel variations in the porewater CH₄ concentration. The ratios of the maximum flux to minimum flux over the course of the day in the S. alterniflora mesocosm on 10 July, 11 August and 11 September were 1.28, 1.89 and 1.76, respectively, and corresponding values for porewater CH₄ concentration were 1.31, 1.39 and 1.17, respectively. CH₄ flux significantly correlated with CH₄ concentration in porewater, and both were significantly related to air temperature. These findings indicate that CH₄ production and CH₄ flux at the middle growth stage (August) exhibited greater responses to changes in air temperature, which in turn induced the higher diel variation. The higher diel cycle for CH₄ flux in August than in September was likely due to the higher proportion of CH₄ oxidized during diffusion within the aerenchyma system. Our results suggest that the extent of diel variations in CH₄ flux may have depended on the gas transport capacity of plants, and the highest diel variation occurred at the middle growth stage.     

Effects of short- and long-term salinity on leaf water relations, gas exchange, and growth in Ipomoea pes-caprae

Ipomoea pes-caprae is widespread in pantropical coastal areas along the beach. The aim of this study was to investigate the salinity tolerance level and physiological mechanisms that allow I. pes-caprae to endure abrupt increases in salinity under brief or prolonged exposure to salinity variations. Xylem sap osmolality (X_osm), leaf water relations, gas exchange, and number of produced and dead leaves were measured at short- (1-7 d) and long- (22-46 d) term after a sudden increase in soil salinity of 0, 85, 170, and 255 mM NaCl. In the short-term, X_osm was not affected by salinity, but in the long-term there was a significant increase in plants grown in presence of salt compared with control plants. After salt addition, the plants showed osmotic stress with temporal cell turgor loss. However, the water potential gradient for water uptake was re-established at 4, 7 and 22 d after salt addition, at 85, 170 and 255 mM NaCl, respectively. In the short-term I. pes-caprae was able to tolerate salinities of up to 255 mM NaCl without significant reduction in carbon assimilation or growth. With the duration of stress, leaf ion concentration continued to increase and reached toxic levels at high salinity with a progressive decrease in photosynthetic rate, reduced leaf formation and accelerated senescence. Then, if high levels of soil salts from tidal inundation occur for short periods, the survival of I. pes-caprae is possible, but prolonged exposure to salinity may induce metabolic damage and reduce drastically the plant growth.     

Single-species versus mixed-species community: which one is better for shore stabilization. A case study of Chongming Island, China

There are five vegetation communities for shore stabilization on the southern coast of Chongming Island: a reed (Phragmites australis) community, a 4-yr-old Salix babylonica-Phragmites australis community (4Sb), an 8-yr-old S. babylonica-P. australis community (8Sb), a 4-yr-old Taxodium ascendens-Phragmites australis community (4Ta), and an 8-yr-old T. ascendens-P. australis community (8Ta). One major question is which is better for shore stabilization: the reed community (a single-species community) or 4Sb, 8Sb, 4Ta and 8Ta (mixed-species communities)? The soil stability index (K) and root length density (RLD) were selected as indicators for evaluating soil stability in response to water erosion. There are two main types of shore facing downward erosion and erosion scarp retreat along the southern coast of Chongming Island, and the erosion period may occur from March to August (scenario 1) or October to December (scenario 2). The assumed erosion period is scenario 1, and 4Sb is the most suitable plant community for preventing erosion scarp failure and mitigating shoreline retreat because it has the greatest K and RLD in the 20-50-cm deep soil layer among all of the vegetation communities within all intertidal zones. Additionally, 4Sb and 8Ta provide the best protection for reducing downward beach face erosion compared to the other vegetation types in the lower intertidal zone (LIT). At the middle intertidal zone (MIT) and higher intertidal zone (HIT), the reed community is optimal for protecting the shore face because it has the greatest K and RLD at 0-20-cm soil among the five vegetation communities in March-April and July-August within the MIT and HIT. Under scenario 2, 4Sb is still the most suitable type for reinforcing the scarp and preventing shoreline retreat. With respect to shore face downward erosion, 8Ta might provide the best protection for beach surfaces within the intertidal zones because it had the greatest K and RLD at 0-20-cm depth among the five vegetation types in November-December within the LIT, MIT and HIT.     

常规腹部立位平片漏诊膈下游离气体原因分析及技术改进

目的：探讨常规腹部立位平片漏诊膈下游离气体的原因及技术改进。方法：15例疑有气腹但腹部立位平片阴性者加拍胸部正位片,观察有无膈下游离气体。结果：15例中12例胸片可显示膈下少量游离气体。结论：X线投照中心线位置不同会影响膈下游离气体的显示,胸片较腹部立位平片更容易显示少量气腹。