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In order to evaluate the ecological health condition of Zhanghe River Watershed, an adapted Benthic Index of Biotic Integrity (B-IBI) was developed. Macro-invertebrates were sampled at 12 monitoring stations which were grouped into two condition categories (reference and impaired stations) according to the level of degradation. A total of 47 benthic macroinvertebrates taxa were identified, in which aquatic insects 33 taxa, Mollusca 8, Annalida 3 and Crustacea 3 taxa. Based on macro-invertebrate assemblages characters of this area, 18 candidate biological metrics in four categories, including taxonomic richness, community composition, pollution tolerance, trophic guild, and value distribution, were chosen. In which, four metrics were excluded because of low values or narrow distribution range. Discriminatory power between reference and impaired stations was analysed using box-plots, and six metrics were excluded because the medians of the box-plot inside the inter quartile range. Of all the rest eight metrics, four were not suitable for B-IBI index system because of their high Pearson correlation (| r | 0.75). Finally, total taxa, percentage of Crustacea and Mollusca, percentage of tolerant taxa and percentage of predators were screened out to form a B-IBI index system. Ratio scoring method for B-IBI index was used to get a uniform score. Evaluation criterion was established based on the 25 percentiles value of reference stations. Assessment results using B-IBI showed 5 of sampling stations were in ‘healthy’ and ‘sub-healthy’ state, 3 were in ‘fair’ state, and 4 were in ‘poor’ or ‘very poor’ state of the whole watershed.
The aim of this study was to verify whether the biogeochemical features (e.g. concentration of nutrients, oxygen consumption, mineralization rate, Eh) of sediments changed by the zebra mussel or its shell deposits differ from those in the ambient soft bottom, and how these differences are related to the structure of benthic macroinvertebrates. In 2006 three sampling sessions were carried out in the Curonian Lagoon, SE Baltic Sea, at three pre-defined sites, corresponding to different bottom types: zebra mussel bed, zebra mussel shell deposits and bare soft sediments. Similarity analysis of biogeochemical parameters indicated that bottom sediments covered with zebra mussel shell deposits were rather distinct from the other bottom types because of the lowest total organic matter mineralization rate and highest organic carbon, total phosphorus and total nitrogen content. The parameters measured in the zebra mussel bed did not deviate conspicuously from the values observed in bare bottoms, except for the higher rate of oxygen consumption in the upper sediment layer. Unsuitable anoxic conditions on the one hand and the ‘attractive’ shelters provided by zebra mussels on the other hand may promote the epifaunal life style in the habitats formed by dense zebra mussel clumps.
Sediments are the major source of pollution in surface waters of the Pacific Northwest Region of the USA. The purpose of this study is to evaluate the relationship between SMI water quality scores at 76 sampling sites in eight watersheds and the observed soil erosion rates on adjacent landscapes. The water quality SMI scores in streams were obtained using stream macro invertebrates as an indicator of water quality, while soil erosion rates were determined by observation on adjoining landscapes during periods of maximum precipitation. Soil erosion rates of <2, 2–5, 5–15, 15–25 and >25 mt/ha/yr were observed at 9, 20, 45, 14 and 12% of the sampling sites, respectively. Landscapes with erosion rates of less than 5 mt/ha/yr generally resulted in good water quality in adjacent streams; however, when soil erosion rates on adjacent landscapes exceeded 5 mt/ha/yr SMI water quality scores were less than good 86% of the time. Strong signifi cant relationships were observed between SMI water quality rating and observed soil erosion rates. Consequently, land management or rehabilitation practices that reduce soil erosion rates to levels below 5 mt/ha/ /yr should improve stream water quality.
A natural reach of montane stream (length 96 m and 7 m width) was grided into 150 cells (2 × 2 m). Density and biomass of fish (Salmo trutta L. and Cottus poecilopus Heckel) were estimated at each cell, as well as stream depth, current velocity, Froude number, bed granulation and its roughness were measured, and benthic samples from exposed bricks were collected from mid August to early October. The analysis of spatial patterns of seven variables (five abiotic and two biotic ones) and fish occurrence from the period of highest organisms’ abundance confirmed that two fish species were separated within the stream space and sculpin showed close association to benthic prey. The PCA pointed to the highest loadings of abiotic habitat variables (64% of the total variance) indicating importance of hydraulics (stream velocity and Froude number) and bed characteristics (stream depth and bed roughness) in distribution of fish communities in pristine low order streams.
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