Světlana Zahrádková

Assessment of Organic Pollution Effect Considering Differences between Lotic and Lentic Stream Habitats

Based on the requirements of the Water Framework Directive, a macroinvertebrate-based assessment system to evaluate the ecological quality of streams has been developed by AQEM project consortium. In the Czech Republic the impact of organic pollution was principal pressure studied, but some morphological degradation of some sampling sites could not be avoided. A multimetric assessment system for three stream types was developed. Detrended Correspondence Analysis was used for the detection of the response of macroinvertebrate communities to the gradient of organic degradation. Significant relationships between abiotic (BOD, TOC, nutrients) and biotic (saprobic index, ASPT) indicators of organic enrichment/eutrophication were identified. Separate storage of the riffle and pool components of each multi-habitat sample allowed differences between these habitats to be com- pared in context of the metrics applied in the assessment system. Lotic and lentic habitats differed in taxonomic composition, ecological traits and biotic indices. The separate assessment of the riffle and pool parts of samples provides additional useful information when combined effects of organic pollution and morphological degradation are to be considered.

The PERLA system in the Czech Republic: a multivariate approach for assessing the ecological status of running waters

The assessment of running water quality has a long tradition in the Czech Republic, but in the past it focused on the evaluation of organic pollution using the saprobic system. Considering the modern trends of stream ecological status evaluation in water management a new assessment system named PERLA was developed. The system is a complex of biological methods of ecological status assessment of running waters and connected activities in the Czech Republic. It involves 300 reference sites with respective biotic and abiotic data and a prediction model using a newly developed software HOBENT. The model generally follows the published mathematical principles of RIVPACS and represents the site specific and stressor non-specific approaches. The HOBENT software allows the prediction of the target assemblage of benthic macroinvertebrates for any site based on a set of environmental variables (latitude, longitude, distance from source, altitude, slope, catchment area, and stream order) which characterise the site. The predicted assemblage can be compared with the fauna observed at the same site. The comparison makes it possible to evaluate the extent of disturbance, expressed by index B. The model allows to evaluate spring, summer, and autumn seasonal data of the majority of wadable streams in the Czech Republic. The practical application of the PERLA system has started in 2001.

Oligochaeta of the Morava and Odra River basins (Czech Republic): species distribution and community composition

The oligochaete fauna of 57 small streams of the Morava and Odra River basins, Czech Republic, was studied during 1997 and 1998. TWINSPAN and CCA (CANOCO) were used to characterize the relationship between oligochaete species, habitat diversity and environmental variables. Chemical oxygen demand (COD), water hardness, NO3−–N, Ca2+, Mg2+, altitude, and substrate type were found to be the primary factors influencing the distribution of aquatic Oligochaeta.

Distribution and biology of mayflies (Ephemeroptera) of the Czech Republic: present status and perspectives

The checklist of mayflies of the Czech Republic now comprises 107 species (30 genera, 16 families), 87 spp. found until 1970 (first research period) and 99 after 1970 (second research period). The distribution of these species in principal river basins (Elbe: 95 spp., Danube: 79 spp. and Oder: 55 spp.), their frequency, abundance and spatial distribution (highest richness in the colline zone: 93 spp.) are summarised. Main species traits (current preference, feeding and locomotion types and life cycle) are presented in tables. Saprobiological characteristics, substantially modified or newly suggested in at least 36 spp., are defined according to the Czech Standard. Four species are classified extinct, 7 critically endangered, 7 endangered, 16 vulnerable and 14 near threatened. Long-term changes caused mainly by morphological degradation of potamal watercourses (extinction and area diminishing, re-occurrence at some sites after decades of very scarce frequency or quantitative changes) are discussed.

Trends in species diversity of lotic stoneflies (Plecoptera) in the Czech Republic over five decades

An unusual data set of Plecoptera, very sensitive aquatic insects, allow diversity changes to be estimated for 175 streams in the Czech Republic between two periods, 1955–1960 and 2006–2011. Substantial overall declines in Plecoptera biodiversity were found. Three‐quarters of the species studied declined in their frequency of occurrence, 48% of which were estimated have undergone a reduction of >30%. Overall, streams either at lowland or submontane altitude, particularly large rivers, lost the most species. A significant decrease in local species biodiversity was found in streams up to 700 m a.s.l., especially in small rivers. The taxonomic dissimilarity between contemporary and previous assemblages increased from montane to lowland altitudes (from ˜30 to ˜70%) and was the same in streams of different size (˜50%). Partitioning of dissimilarity showed that the overall change in dissimilarity was primarily driven by changes in species richness; however, species replacement was not negligible. The results demonstrated that aquatic insect biodiversity (Plecoptera in particular) is substantially declining in Europe, probably to a similar or greater extent than terrestrial insects, with potential implications for biodiversity of running waters. Plecoptera showed a complex response to habitat change, including loss of pollution‐sensitive species and habitat‐specialists as well as common species, which, in some cases, counterbalanced their losses by concurrent colonisation of new sites.

Comparison of mayfly (Ephemeroptera) taxocenes of permanent and intermittent Central European small streams via species traits

The recurrent drying out of small streams in past decades has shown an urgent need to pay attention to the impact of global climate change. The objectives of this study were to describe the effect of drying out on the composition of the mayfly taxocene and evaluate the relevance of individual species traits for survival of mayflies to drying out. The mayfly taxocenes of two model localities, one at an intermittent and one at a permanent brook, were investigated in 2002, 2003 and 2005. Compared with the permanent stream, the taxocene of the intermittent stream was short of nine species, foremost rheobionts and high oxygen demand species. To explain further differences between both stream types in survival and recolonisation ability, 15 species traits were evaluated. These included so-called “ecological traits” (e.g., habitat and substrate range, density, distribution, current velocity adaptation) and “biological traits” connected with life cycle and larval/adult adaptations. Species showing the highest number of advantageous traits (with only exception of Electrogena sp. cf. ujhelyii — species of taxonomically unclear status) were able to successfully survive under the unfavourable conditions of the intermittent brook. Biological traits considered more important in many respects seem to be good predictors for assessing sensitivity to extreme temperature changes, hydrological regime fluctuations and the survival/recolonisation ability of species in exposed habitats.

ABIOTIC STREAM TYPES AND SPECIES ASSEMBLAGES: IS THERE ANY SIMPLE LINKAGE? CZECH STREAMS AND BENTHIC MACROINVERTEBRATES AS AN EXAMPLE

Ecological status assessment of water bodies according to the European Water Framework Directive (WFD) is generally based on the comparison of a reference and observed status. There are two basic approaches to define the reference conditions for a particular water body: a site-specific and a type-specific. For the latter, required by the Directive, it is necessary to create a typology of water bodies. The Directive offers two ways (system A, system B) of their inherence based on abiotic descriptors. Within the assessment based on biological elements, various metrics derived from the species assemblage composition are used. The type-specific approach is associated with a multimetric system, i.e. sets of metrics for selected stressors and specific water body types (AQEM consortium 2002). The site-specific approach, which is independent on typology and deals with abiotic conditions (descriptors) of a particular site or stretch, is associated with predictive models like the British RIVPACS (WRIGHT et al. 1993) or analogous the Czech PERLA (KOKES et al. 2001). More or less detailed knowledge of biotic and abiotic conditions of pristine or near natural sites is necessary for both approaches. Due to the fact that the metrics are generally derived from taxonomic composition of the species assemblages, a correspondence between types and these assemblages is essential for the truthfulness of the type-specific approach. Therefore, the selection of abiotic descriptors should be done very carefully. The correspondence among species assemblages of reference sites and abiotic types was tested on Czech streams and benthic macroinvertebrates.

A Prediction Model of Running Waters Ecosystem in the Czech Republic Based on Mayfly Taxocenes of Undisturbed Rhithral Streams

Samples of mayfly larvae and main environmental variables from 80 undisturbed. localities evenly distributed in the Czech Republic were taken and measured during 1994–1997. Data were examined by TWINSPAN and by canonical correspondence analysis (CCA) to define mayfly taxocenes characteristic of different areas and to prepare a mayfly database for a prediction model of effects of environmental changes (HOBENT). To test the general applicability of the model, mayfly species composition at 13 localities was compared to a hypothetical, desired taxocenes. Although restricted only to a part of aquatic macroinvertebrate communities (mayflies), this procedure permitted evaluation of environmental degradation of other 13 localities. Despite some restrictions, the planned total number of 400 background localities seems to be sufficient for successful application of this prediction model.