Jan Helešic

Trophic levels and functional feeding groups of macroinvertebrates in neotropical streams

Feeding strategies are typical traits reflecting the adaptation of species to environmental conditions. This concept is currently developed in some water quality systems (e.g. Index of Trophic completeness) and the structure of functional feeding groups (FFGs) could form part of a unified measure across communities differing in taxonomic composition. However, in South America, information about the FFG classification of invertebrates in streams is almost absent and existing studies using FFG structure follows classification from North America. But even taxonomically related species may have different diets in tropical and temperate areas and therefore, studies about FFG structure in neotropics could be biased. For this reason, we determined diet composition, trophic level and FFGs, using gut contents analysis and mouthpart observations of 49 macroinvertebrate taxa (mostly at genus level) from neotropical streams. We observed that practically all macroinvertebrates fed upon fine detritus which indicates the importance of this food resource in neotropical streams. As the assignment to a single FFG does not accurately reflect the functional profile of taxa, we transcribed the affinity of taxa to each FFG using fuzzy codes. Finally, we published the coding of diet composition and FFG of the taxa examined, which could be used in future community analyses of lotic ecosystems in the Neotropical zone.

Trends in background levels of persistent organic pollutants at Kosetice observatory, Czech Republic.

A multimedia sampling of ambient air, wet deposition, surface water, sediment, soil and biota has been performed at Kosetice background observatory in the southern Czech Republic since 1988. An integrated monitoring approach was applied to assess the current state, anthropogenic impacts, and possible future changes of terrestrial and freshwater environments. Average PCB concentrations in the individual matrices calculated from ten years of sampling on multiple sites varied between 2 ng g(-1) in sediment and 7 ng g(-1) in soil or moss. DDT concentrations were lower in moss and needles (2 ng g(-1) and 4 ng g(-1), respectively) than in sediment (11 ng g(-1)) and soil (20 ng g(-1)), while the HCH level was higher in moss and needles (5 ng g(-1) and 6 ng g(-1), respectively) than in soil or sediment (1 ng g(-1) and 2 ng g(-1), respectively). The highest average level of PAHs was found in soil (600 ng g(-1)), while it was lower in needles (230 ng g(-1)), moss (210 ng g(-1)) or sediment (210 ng g(-1)). Time related trends of concentration levels of persistent organic pollutants in all matrices were investigated. Moss and needle trend patterns resembled those of the ambient air, showing a slight concentration decrease of all compounds, except for hexachlorobenzene. The soil, water and sediment concentrations showed a similar decrease of PAHs, PCBs, and HCHs, but there was no clear trend for DDTs and HCB.

Habitat preferences of aquatic Oligochaeta (Annelida) in the Rokytná River, Czech Republic - a small highland stream

Research was carried out to determine aquatic oligochaete habitat preferences in the Rokytna River (Thaya River basin), a sixth order highland stream in the Czech Republic during the period of April 1999–April 2001. Quantitative samples were collected and current velocity and basic physico-chemical variables were measured monthly in four typical habitats in the Rokytna River. During this study, 28, 842 individuals representing 44 oligochaete species or higher taxa were collected. Temporal variability of proportional occurrence of trophic groups found on selected habitats (gathering collectors and grazers) was analysed. Habitat preferences of oligochaete species were evaluated by Canonical Correspondence Analysis (CANOCO). Biochemical oxygen demand (BOD) and nitrate (NO 3 − ) ion concentration were the most important variables explaining the distribution of Oligochaeta along the first axis. Current velocity (at 40% of the depth) and presence of oligochaetes associated with the habitat where gravel bars never formed were the most important variables along the second axis. Both axes were correlated with the temperature, reflecting the sampling in summer along the first axis and sampling in late spring along the second axis. The amount of organic matter (BOD) and concentrations of NO 3 − ions represented both oligochaete food source and decomposition products contributing to the growth of algae. Current velocity and preferred habitat explained the spatial pattern of oligochaete distributions.

Project tocoen ‐ the fate of selected organic pollutants in the environment part XXI. ‐ The contents of PAHs, PCBs, PCDDs/Fs in sediments from Danube river catchment area

As a part of cooperation between Chemical Time Bombs Program and Project TOCOEN, the contamination of sediments in Moravian and Slovakian part of Danube river catchment area by PAHs, PCBs, PCDDs/Fs was determined. The total contents of PAHs ranged between 25.5 and 4,690.3 ng•g‐1, PCBs between 4.9 and 232 ng•g‐1 and PCDDs/Fs were detected at one site in concentration 0.0005 pg•g‐1 TEQ.

Temporal and spatial macroinvertebrate variance compared: crucial role of CPOM in a headwater stream

The aim of the present study was to estimate the extent to which macroinvertebrate assemblages in a headwater stream are determined by environmental conditions and temporal dynamics. Six mesohabitats defined by substratum were sampled monthly throughout one year, environmental conditions at each sampling point being precisely described. Environmental variables could be truncated into two main gradients related to (a) the availability of food and space resources (CPOM) and (b) hydraulic conditions. The response of the macroinvertebrate assemblage to the environmental gradients and temporal dynamics were analyzed using GAM and (p)RDA. Twice as high portion of variance in the faunal data was attributed to environmental gradients compared to temporal dynamics. Total abundance, as well as the abundance of almost all feeding groups, was dependent on the availability of food and space resources (CPOM), while their proportions were determined by the quality of food resources driven by hydraulic conditions. Temporal dynamics was of lower importance. Our results suggest the role of CPOM be crucial in woodland headwater streams, as it greatly enhances habitat quality, serving both as a food source to dominant shredders and a space source to most macroinvertebrates.

Seasonal dynamics of Bythonomus lemani and Bothrioneurum vejdovskyanum (Oligochaeta, Annelida) in relation to environmental variables

The seasonal dynamics of Bythonomus lemani (Lumbriculidae) were studied for the first time and the knowledge of Bothrioneurum vejdovskyanum (Tubificidae) was extended based on four quantitative samples of oligochaetes taken monthly in the Rokytná River (Czech Republic) during a two-year study (April 1999–April 2001). The influence of water temperature, velocity, depth, discharge, pH, conductivity, dissolved oxygen amount and biochemical oxygen demand (BOD) on their life cycles was evaluated. Habitat preferences of the juvenile and adult stages were recorded. Time series analysis was used to determine the worm densities, seasonality and trends. For Byth. lemani one distinct reproduction cycle per year was found and this was regulated by temperature, while Both. vejdovskyanum showed a one-year cycle not significantly dependent on measured environmental variables. The overall trend was an increase in density for Byth. lemani and a decrease in density for Both. vejdovskyanum. Byth. lemani showed a significant negative correlation between the trend of its density and BOD concentration.

Ecology of Leuctra geniculata (Plecoptera: Leuctridae), an atlantomediterranean species on the north-eastern border of its area

The first records of Leuctra geniculata Stephens, 1836 in the north-eastern border of its area (the Czech Republic) are presented and an overview of references, synonyms and distribution of the species is given. The ecological preferences of the species, supported by chemical and hydromorphological parameters, are defined. Probable dissemination paths into the Czech Republic and the supposed life cycle of the species are discussed. Photographs of morphological characters, SEM photos of eggs, associated macroinvertebrate assemblages (EPT taxa) and maps of distribution are included.

Nonparametric evaluation of environmental parameters determining the occurrence of stonefly larvae (Plecoptera) in streams

Abstract: This study explored the relationship between the occurrence of stonefly species, stream type and basic environmental conditions. Only 13 taxa, out of 115 species occurring in catchments investigated in the Czech Republic (Soldán, Zahrádková, Helesšic, Dušek and Landa, 1998), were selected for this study. The environmental parameters chosen were those that characterized the hydraulic and physical environments of almost all the streams: slope, current velocity, discharge regime, bottom roughness, current type (Reynolds number and Froude number). Organic water pollution, characterized as BOD5 and saprobity, was intentionally not embodied in the evaluation, because the chosen sampling sites were in streams which proved to have minimal or almost no organic pollution. The relationships between the occurrence of stoneflies and the stream types (as set out by Illies and Botosaneanu, 1963) were evaluated on the basis of chi-square tests. For two species (Nemurella pictetii - crenal and Perla burmeisteriana - epipotamal) there was strong evidence of affinity to the stream type. The following parameters were shown to have a statistically significant influence on stonefly communities: slope, substrate roughness, current velocity and current type (Reynolds number and Froude number). For the most abundant individual species, Perla burmeisteriana, Isoperla grammatica, Leuctra albida, Leuctra nigra and Isoperla sudetica the influence of the investigated factors on occurrence and species abundance was assessed.

Spring fens as a unique biotope of stonefly larvae (Plecoptera): species richness and species composition gradients

Western Carpathian spring fens (groundwater-fed wetlands characterised by specific vegetation) represent a rare and unique biotope whose aquatic insects have not been studied until now. Therefore, the aims of this study were to describe the taxocoenosis of stoneflies and to determine the main environmental factors controlling species composition. The study was carried out in 2006 at 15 sites in the borderland of the Czech Republic and Slovakia. The species richness was surprisingly high. 12 out of all 33 recorded species developed in fens, the others inhabited small springbrooks in the vicinity of fens. The structure of stonefly taxocoenosis was influenced by season and substrate characteristics of the studied fens. The main gradient in species data represented change of species composition from species dwelling in fens with coarse substrate and without vegetation over species reaching high numbers in fine sediment fens to a species found exclusively in fens overgrown by sedges.

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.