Search

Within the ecological assessment of running waters based on benthic macroinvertebrates different levels of taxonomic resolution (species, genus, family and higher) are in use. Although assessment systems are often developed with detailed data on species level, water managers and other end-users could like to use data on higher taxonomic levels to assess the ecological quality of a water body because of limited human or money resources. The question that arises is, if an assessment system built with species level data is also applicable using data with a higher taxonomic resolution. Within the AQEM project a multimetric assessment system was developed to evaluate the ecological quality classes (from bad (1) to high (5) ecological quality) of different stream types throughout Europe. The present study focuses on the question whether the resulting water quality class changes using the AQEM Assessment Software (AAS) with different taxonomic resolutions and if yes, how large the deviations of ecological quality classes from the original classes are and if the deviations are unidirectional. For analyses data from four Austrian and two Dutch stream types were used. It is demonstrated that the assignment of a site to an ecological quality class may change if different taxonomic levels are used. Deviations in both directions (higher/lower ecological quality class) were observed. In most cases the divergence was only one ecological quality class, but also larger deviations occasionally occurred. The causes of changes in the assessment were investigated by separately looking into the underlying metrics of the multimetric system. Some of the evaluated metrics rely on autecological information on species level and are simply not applicable on higher taxonomic levels. Other metrics worked on higher taxonomic levels as well and showed more or less good distinctions between ecological quality classes. It is concluded that the AQEM Assessment Software is not applicable if data on higher taxonomic levels are used. As the deviations were not unidirectional and ranged from one to three ecological quality classes, it is not possible to include a correction factor for using the software with higher taxonomic resolution data.

Stream restoration is one of the answers to the lowland stream deterioration. For making proper choices in stream restoration, one firstly needs to understand the complex spatial and temporal interactions between physical, chemical and biological components in the stream ecosystem. Several ecological concepts on the four dimensions, scale and hierarchy in a stream ecosystem are integrated into the 5-S-model. This model provides the theoretical backbone of the first outline of a decision support system for stream restoration. Stream restoration is developing fast in the Netherlands. In 1991, 70 projects were counted, in 1993 there were 170, and this number increased in 1998 to 206. Positive signs in this increase in the number of stream restoration projects are the increase in the amount of money, in background studies, in improvement of the selection process of stretches to be tackled, and the broadening of the objectives and measures. Negative signs are amongst others that measures often deal onlywith stream hydrology and structures in-stream. The catchment takes no part. Furthermore, bottlenecks often relate to finances and agreement between people and/or organisations. Finally, the first steps towards a decision support system for stream restoration are made. The system presented provides only information based on which measures should be taken. `Where and how' these measures need to be taken remains a challenge for the future.

Oligochaete communities were monitored under semi-natural conditions in experimental ditch mesocosms. Twelve ditches were used in a Before-Control-After-Impact (BACI) experiment to study the effect of the insecticide chlorpyrifos. Another eight ditches were used in a randomized experiment to study the effect of eutrophication. Oligochaete communities were sampled by deploying trays of substratum for colonization over a 20-week period. The experiments were analyzed by multivariate analysis using redundancy analysis and Monte Carlo permutation to assess statistical significance. These novel methods have the advantage over classical multivariate analysis of variance (MANOVA) of being distribution-free and of having no restrictive upper limit on the number of species that can be analyzed simultaneously. In the BACI-experiment no significant effect of chlorpyrifos on oligochaete communities was detected. Eutrophication effects were observed at the higher eutrophication levels in clay ditches. Oligochaete abundances decreased in those ditches. Considerable variation was attributed to stochastic factors given that the ditches were in an early developmental stage when the experiments were initiated. Large-scale experiments such as the ones that we describe require time to develop and stabilize before parameters of community structure like population abundance, can be employed to detect changes associated with water quality manipulations.