Hierarchical structure of stream ecosystems: consequences for bioassessment

It has long been recognized that communities and their ecosystems are structured at several, nested spatial scales. But identifying the appropriate scale(s) to collect, analyse and interpret data to answer specific questions about ecosystems has been a vexing problem for ecologists. We collected observations of the benthic invertebrate community and its environment in 10 primarily agricultural tributary streams of the Thames River in southwestern Ontario, Canada. Within each stream we sampled two reaches, in each reach we sampled three riffles, and in each riffle we took three kick samples of invertebrates and characterized the substrate environment. We also characterized the habitat at each of the 20 reaches (10 streams × 2 reaches/stream). Most of the variability in the stream invertebrate community structure (as described with taxonomic richness and the biotic index of tolerance, as well as by the Bray-Curtis distance of the community composition from the mean at a spatial scale) was at larger spatial scales of among streams and between riffles. Much of the substrate and habitat variation was also at the larger spatial scales, as were correlations between the biota and the environment of the benthic invertebrate community. We concluded that for the purposes of bioassessment, characterization of one reach per stream is sufficient, at least in this context, for describing a stream and evaluating its health. Handling editor: R. Norris     

Comparison of two sampling methods for biomonitoring using aquatic macroinvertebrates in the Dos Novillos River, Costa Rica

Benthic macroinvertebrates are the most commonly suggested group of organisms for freshwater biomonitoring and have been extensively studied in temperate areas. On the other hand, the methodology and theoretical background of biomonitoring have not yet been sufficiently adapted to tropical aquatic environments. The main focus of this study was the testing and comparison of two different collection methods in order to determine water quality and possible anthropogenic influences on the river Dos Novillos, Limón, Costa Rica. For the first method, aquatic invertebrates were collected for 120 min with a strainer, from different microhabitats, picked from the substrate and preserved directly in the field with 70% alcohol. For the second method, organic and inorganic materials, including benthic organisms, were gathered from different microhabitats with a D-shaped net for 10 min, with separation and sorting done in the laboratory. Results from five sampling campaigns showed that each sampling method differed in the composition of the fauna collected (Sørensen similarity index = 80%), although water quality categories obtained from the BMWP-CR index showed no differences between the two methods. The advantages and disadvantages of each method are discussed, and according to the results obtained from this study, further testing for an adequate methodology in tropical rivers is still necessary.     

Direct comparison of assessment methods using benthic macroinvertebrates: a contribution to the EU Water Framework Directive intercalibration exercise

The aim of the intercalibration exercise presently performed by the EU is to identify and resolve significant inconsistencies between the ecological quality classifications of EU Member States and the normative definitions of the EU Water Framework Directive. Based on benthic macroinvertebrate data of two European stream types (small siliceous mountain streams and medium-sized lowland streams in Central and Western Europe) we correlated the indices of 10 river quality assessment methods (ASPT, BMWP, DSFI, German Multimetric Index, Saprobic Indices) applied in Austria, Czech Republic, Denmark, Germany, Poland, Slovak Republic, Sweden and United Kingdom. National class boundaries were compared via regression analysis. Assessment methods of the same type (Saprobic Indices, BMWP/ASPT scores) showed best correlation results (R²>0.7). The good quality status boundaries of the national methods deviated up to 25%; thus indicating the necessity to harmonize the national classification schemes. Prerequisites of the presented intercalibration approach are (1) a sufficiently large and consistent dataset representative of the respective common intercalibration types and (2) agreement on common type specific reference conditions.     

Rapid assessment of rivers using macroinvertebrates: A procedure based on habitat-specific sampling,family level identification and a biotic index

Abstract This paper describes a simple and inexpensive procedure for the rapid biological assessment of water quality in rivers and streams in eastern Australia. The procedure involves the standardized collection of samples of 100 macroinvertebrates from defined habitat types within a water body. Specimens are identified to family level only and a biotic index is calculated. Proposed future testing and evaluation are described, and the limitations of the rapid approach are discussed.     

Using aquatic macrophyte community indices to define the ecological status of European lakes

Defining the overall ecological status of lakes according to the Water Framework Directive (WFD) is to be partially based on the species composition of the aquatic macrophyte community. We tested three assessment methods to define the ecological status of the macrophyte community in response to a eutrophication pressure as reflected by total phosphorus concentrations in lake water. An absolute species richness, a trophic index (TI) and a lake trophic ranking (LTR) method were tested at Europe-wide, regional and national scales as well as by alkalinity category, using data from 1,147 lakes from 12 European states. Total phosphorus data were used to represent the trophic status of individual samples and were plotted against the calculated TI and LTR values. Additionally, the LTR method was tested in some individual lakes with a relatively long time series of monitoring data. The TI correlated well with total P in the Northern European lake types, whereas the relationship in the Central European lake types was less clear. The relationship between total P and light extinction is often very good in the Northern European lake types compared to the Central European lake types. This can be one of the reasons for a better agreement between the indices and eutrophication pressure in the Northern European lake types. The response of individual lakes to changes in the abiotic environment was sometimes represented incorrectly by the indices used, which is a cause of concern for the use of single indices in status assessments in practice.     

A comparison of the water balance characteristics of temperate and tropical fly pupae

Abstract Water balance characteristics of temperate zone fly pupae are compared with the characteristics of flies inhabiting the tropics. The flies, all of which were reared without diapause, had very similar equilibrium weights that were quite high (a_v 0.90-0.92), thus implying a limited capacity to absorb water from a subsaturated atmosphere. Likewise, the critical transition temperatures (CTT) were nearly the same for all the flies. Net transpiration rates at 20^oC are a function of size, but the rate is less size dependent as temperature increases. When water loss is examined across a broad temperature range, as described by activation energies, it is apparent that the tropical flies lose water at a greater rate than their temperate zone counterparts. Activation energy may be a good parameter to use in evaluating habitat preference and suitability for a species because it describes water loss as a function of temperature, and thus is likely to be a good indicator of the insect's response to the fluctuating temperatures that occur naturally.     

A proposal for modification of the Belgian biotic index method

Modifications to a standard biological water quality assessment method, used in Belgium since 1979, were studied.As a result, we recommend the following:- samples should be processed live- samples should not be washed through a series of sieves- systematic units represented by only one individual should be included in the calculation of the biotic index.Using this modification, the biotic index can be calculated more rapidly and shows a higher correlation with a chemical water quality assessment index.     

Effect of land use types on stream water quality under seasonal variation and topographic characteristics in the Wei River basin,China

The effect of topographic characteristics of land uses on stream water quality must be addressed for a better understanding of the complex relationship between land use and stream water quality. In this study, Geographic Information System (GIS) and Pearson correlation analysis were used to determine whether there were relationship between land use types and stream water quality at the sub-basin scale in the Wei River basin, China, during the dry and rainy seasons in 2012. Temporal variation of these relations was observed, indicating that the relationships between water quality variables and different land uses were weaker in rainy seasons than that in dry seasons. Compared with other land uses, agriculture and urban lands had a stronger relationship with water quality variables in both rainy and dry seasons. Topographic characteristics of land use were employed to further analyze these relationships. The results showed that seasonal variation also occurred in the complex relationship, and land uses in steeper slopes generally had a stronger influence on stream water quality than those in flatter ones. For the riparian zone of each sampling site, the slope coefficients were weaker than those at the sub-basin scale. Land use type near stream water was generally a better indicator for the effectiveness of water quality. These results suggest that the slope and proximity should be taken into account for better land use management.     

A comparison of the benthic macroinvertebrate communities in a trout stream: Winter and spring 1973 and 1977

The benthic macroinvertebrate riffle community of the Bushkill Creek (Northampton County, PA) was sampled monthly, December through May 1972–73 and 1976–77. Total precipitation in 1972–73 was 22.3 cm more than in 1976–77 and water and air temperatures were also higher. In April and May, community composition (dominant taxa and similarity indices) was less similar than in December, January and February. In April and May there were fewer Hydropsyche (Trichoptera) and Ephemerella (Ephmeroptera) and more Chironomidae (Diptera) and Antocha (Diptera) than in 1973. Total numbers and biomass were lower in 1977 than in 1973. The reduction in Hydropsyche, Ephemerella, biomass and total numbers in Spring 1977 may be due to the scouring effect of ice break up. Inspite of fluctuating environmental conditions the macroinvertebrate community exhibited stability.