Can Tolerant Diatom Taxa be Used for Effective Assessments of Human Pressure?

Because lately the low bioindicative value of tolerant species from different taxonomic groups is often questioned, in this study, we hypothesized that tolerant diatoms may be used for effective temporal assessments of human pressure. We tested this on the lowland Bzura River in central Poland, on 156 diatom samples (DSs) from two study periods of 1972 with extremely severe point‐source water pollution and of 2002–2004, where the complex wastewater management in the river catchment improved water quality considerably. Out of the total 295 diatom species recorded in the samples, only 133 tolerant ones were included in the study. Patterns in their abundance were recognized with a Kohonen artificial neural network (self‐organizing map, SOM), whereas the species significantly associated with each SOM cluster of diatom samples were identified with the indicator value (IndVal) index and the Monte Carlo test. If the hypothesis tested was not supported, the assignation of DSs to the SOM clusters would be random. However, the separation of DSs from 1972 and 2002–2004 was almost perfect because the number of exceptions was as low as 4.5%. In addition, the relatively high number (64 out of 133) of tolerant species significantly associated with any SOM cluster (and respective environmental conditions at sites from which samples assigned to it come) supports the hypothesis tested. This means that almost half of the studied species are not evenly distributed in particular clusters as might be expected for highly tolerant species. The study proves that the abundances of many diatom species, currently classified as tolerant, carry quite precise information on the differences in the quality of the environment, and indicates those tolerant diatom species whose bioindicative potential may be highest. Copyright © 2014 John Wiley & Sons, Ltd.     

Using Benthic Indicator Species and Community Gradients to Optimize Restoration in the Arid,Endorheic Walker River Watershed,Western USA

The challenge of restoring watersheds in arid regions often requires the development of novel scientific tools to guide management. The Walker Basin Program was created to reverse ecological decline in an arid, endorheic watershed through scientifically guided restoration. As part of this programme, 3 years of benthic macroinvertebrate samples were collected seasonally at 10 sites that represent the diversity of river environments from the high‐mountain headwaters to a desert terminal lake. Samples were analysed to quantify baseline conditions in reference and degraded reaches of river and identify opportunities and constraints for aquatic community restoration. Naturally harsh environments in the lower river characterized by high temperatures and low base flow combined with a weak understanding of reference conditions to limit the utility of commonly used indices for quantifying biotic integrity. A flexible approach was employed using a combination of indicator species analysis, cluster analysis, canonical correspondence analysis, and community tolerance indices to evaluate the variation of benthic macroinvertebrate community composition across a set of environmental gradients. Results demonstrate that benthic communities in the watershed are primarily influenced by a longitudinal gradient related to elevation. A strong secondary community gradient caused by anthropogenic nutrient loading may constrain restoration effectiveness in some parts of the watershed. Restoration activities should improve water quality conditions and initially target areas of the watershed less affected by nutrient loading. Results also demonstrate that benthic communities shift longitudinally. These shifts should be monitored to inform adaptive management of restoration actions. Copyright © 2014 John Wiley & Sons, Ltd.     

THE ROLE OF STREAMS OF DIFFERENT SIZES IN RECOVERY OF FISH FAUNA IN THE PILICA RIVER CATCHMENT

Fish and lampreys were sampled by electrofishing in the Pilica River tributaries (the Vistula catchment, Poland) in 1992–1994 and 2003–2005. The patterns in fish assemblages were recognized on the basis of fish biomass using Kohonen's self‐organizing map (SOM) technique, combined with the indicator values (IndVal) for assessment of associations of fish species with particular SOM regions (and respective environmental conditions). Although the fish samples were clustered mostly according to the stream features (size, regulation, and pollution), a weaker temporal gradient indicated a recovery of the ichthyofauna in some smaller streams. The larger tributaries served as sources of colonisers for both the Pilica and the smaller streams. The differences between SOM subclusters in the quality of the aquatic environment were effectively presented with certain biological measures, including the dominances of potentially large species and non‐psammophilous rheophils, which are proposed as good bioindicators. It is worth mentioning that some closely related species (ide and dace, silver bream and bream, golden loach and spined loach, and Ukrainian lamprey and brook lamprey) were significantly associated with different SOM regions (and respective environmental conditions), perhaps in this way avoiding competition. Copyright © 2013 John Wiley & Sons, Ltd.