RESUMEN
Fish are vital in river ecosystems; however, traditional investigations of fish usually cause ecological damage. Extracting DNA from aquatic environments and identifying DNA sequences offer an alternative, noninvasive approach for detecting fish species. In this study, the effects of environmental DNA (eDNA), coupled with PCR and next-generation sequencing, and electrofishing for identifying fish community composition and diversity were compared. In three subtropical rivers of southern China, fish specimens and eDNA in water were collected along the longitudinal (upstream-downstream) gradient of the rivers. Both fish population parameters, including species abundance and biomass, and eDNA OTU richness grouped 38 sampling sites into eight spatial zones with significant differences in local fish community composition. Compared with order-/family-level grouping, genus-/species-level grouping could more accurately reveal the differences between upstream zones I-III, midstream zones IV-V, and downstream zones VI-VIII. From the headwaters to the estuary, two environmental gradients significantly influenced the longitudinal distribution of the fish species, including the first gradient composed of habitat and physical water parameters and the second gradient composed of chemical water parameters. The high regression coefficient of alpha diversity between eDNA and electrofishing methods as well as the accurate identification of dominant, alien, and biomarker species in each spatial zone indicated that eDNA could characterize fish community attributes at a level similar to that of traditional approaches. Overall, our results demonstrated that eDNA metabarcoding can be used as an effective tool for revealing fish composition and diversity, which is important for using the eDNA technique in aquatic field monitoring.
RESUMEN
The utilization of food resources by aquatic consumers reflects the structure and functioning of river food webs. In lotic water systems, where food availability and predator-prey relationships vary with gradient changes in physical conditions, understanding diet assimilation by local communities is important for ecosystem conservation. In the subtropical Liuxi River, southern China, the relative contribution of basal resources to the diet assimilation of functional feeding groups (FFGs) was determined by stable carbon (13C) and nitrogen (15N) isotope analyses. The output of Bayesian mixing models showed that diatom-dominated periphyton (epilithic biofilm), aquatic C3 plants (submerged hydrophytes), and suspended particulate organic matter (SPOM) associated with terrestrial C3 plants contributed the most to the diet assimilation of FFGs in the upper, middle, and lower reaches, respectively. The relative contribution of consumer diet assimilation was weighted by the biomass (wet weight, g/m2) of each FFG to reflect resource utilization at the assemblage level. From the upper to the lower reaches, the spatial variation in the diet assimilation of fish and invertebrate assemblages could be summarized as a longitudinal decrease in periphyton (from 57%-76% to <3%) and an increase in SPOM (from <7% to 51%-68%) with a notable midstream increase in aquatic C3 plants (23%-48%). These results indicate that instream consumers in the Liuxi River rely more on autochthonous production (e.g., periphyton and submerged hydrophytes) than on terrestrially derived allochthonous matter (e.g., terrestrial plants). The pattern of resource utilization by consumers in the mid-upper Liuxi River is consistent with findings from other open subtropical and neotropical rivers and provides evidence for the riverine productivity model. Our study indicates that protecting inherent producers in rivers (e.g., periphyton and submerged hydrophytes) and restoring their associated habitats (e.g., riffles with cobble substrate) are conducive to aquatic ecosystem management.
RESUMEN
OBJECTIVE: To systematically review the efficacy and safety of beclomethasone nasal spray in the treatment of chronic adenoid hypertrophy in children. METHODS: We computerized searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (issue1, 009), MEDLINE (1950 to August 2008), EMbase (1984 to August 2008), CNKI (1994 to September 2008), and VIP (1989 to August 2008), WANFANG DATA, Annual Review-s and Elsevier Science. Also the reference lists of all papers were identified for further trials. All searches were initially performed in May 2007 and updated in April 2009.Randomized controlled trials (RCT) and quasi-RCTs were identified and analyzed according to the Cochrane Handbook for Systematic Reviews of Interventions. RESULTS: Three RCT were included. Meta-analysis was not performed due to heterogeneity and the data were summarized in a narrative format. The trials showed that higher doses of beclomethasone (336 microg/d, 400 microg/d) might improve the nasal obstruction symptoms and reduce adenoid size in children with adenoid hypertrophy. CONCLUSIONS: Higher and subsequently half doses of beclomethasone (336 microg/d, 400 microg/d) can improve the nasal obstruction symptoms in children with adenoid hypertrophy.The improvement appears to be associated with a reduction of adenoid size. Because of a lack of the RCT, further studies are required to support the use of beclomethasone as a first-line approach for these children.
