Maria Grzybkowska

Production estimates of the dominant taxa of Chironomidae (Diptera) in the modified, River Widawka and the natural, River Grabia, Central Poland

Production and community composition of selected taxa of Chironomidae were estimated in cross-sections of the lower course of two lowland rivers, the Widawka and the Grabia. At the selected site, the Grabia has not changed its morphometry for many years, whereas the discharge of the Widawka has increased (mainly due to inputs of coal mine water) by 75% in comparison with its hypothetical natural discharge. In the Widawka, the production value, for 76.7% of total Chironomidae abundance, amounted to 12.45 g dry wt m−2 yr−1, while in the Grabia it amounted to 11.91 g dry wt m−2 yr−1 The annual P : B ranged from 14.5 for large-sized species (Chironomus in the Widawka) to 82.0 for small-sized species (Eukiefferiella in the Grabia). The similar production values estimated for both rivers, despite a three times higher density of Chironomidae in the Grabia, is noteworthy.

Impact of long-term alternations of discharge and spate on the chironomid community in the lowland Widawka River (Central Poland)

Spatial and temporal distribution, abundance and production of macroinvertebrate communities were estimated over two years in a fifth-order section of the Widawka River. Discharge of this river has been increased artificially by coal mine water inputs. Additionally, during the second year, one of the highest discharges of the current 20-year period was recorded. Chironomidae were co-dominant in macrobenthos, both in a straight reach (WIA) and in a meandering site (WIB). More mosaic habitats resulted in higher densities of midges, reaching 6215 ind.m−2 in year 1 and 1141 ind.m−2 in year 2 at WIA, while at WIB 896 densities were ind.m−2 and 257 ind.m−2, respectively. Flooding affected the distribution and abundance of the chironomid assemblages. Recolonization by psammophilous Polypedilum began after the various microhabitats were buried with sand. Chironomid production was estimated on a species-specific basis for the dominant taxa. In year 1 (mean annual water temperature 10.0° C) chironomid production was 12.4 g dry wt m−2 yr−1 1 at WIA and 1.9 g dry wt m−2 yr−1 at WIB. These values sharply decreased in year 2 (mean annual water temperature 9.8° C) reaching 1.9 g dry wt m−2 yr−1 at WIA and 0.4 g dry wt m−2 yr−1 at WIB, as effects of the high spate.

Effect of Flow Fluctuations on Patch Dynamics and Chironomid Distribution in a Medium-Sized Lowland River

ABSTRACT The response of macroinvertebrates to changes in flow was studied in the Drzewiczka River at the downstream end of a whitewater slalom-canoeing track located in the tailwater of a dam. From 1980 to 2002, surface water was released daily, except in the winter, from the reservoir for two-three hours to enable training of canoeists. Discharge ranged from 2.1 to 12.0 m3 s−1 daily during this high discharge fluctuation period (DI), when measured in 2000–2001. The reservoir was emptied for dredging in February 2002, after which the river returned to its natural discharge of about 2 m3 s−1, a time we called the temporary renaturalization period (DII). Monthly samples of environmental variables and macroinvertebrates were collected over the year during DI and DII from distinct visible patches of the bottom including pool, stagnant, submersed macrophytes, bank, and riffle habitats The most obvious changes in the environment in DII were the redeposition of fine mineral particles on the river bottom, increased amounts of fine particulate organic matter, and a transition of submersed macrophytes from the middle part of the river channel to bank habitat. Macroinvertebrate assemblages adapted very quickly to these changes, especially chironomids, which were the prevalent taxa. During DI at each habitat (except the stagnant patch), the Orthocladiinae (periphyton scrapers)/Chironomini density ratio was higher than 1, ranging from 1.2 (at M) to 12.1 (at R); during the DII, this index diminished to 0.7 (at M) to 4.5 (at R). Thus, low water velocity and high amounts of organic matter in DII benefited gathering collectors (Chironomini).

Density, production and life cycle of Brachycentrus subnubilus Curtis (Trichoptera: Brachycentridae) in a lowland river, Central Poland

The annual mean density of Brachycentrus subnubilus a trichopteranspecies with a univoltine life-cycle was 572 ind. m-2. Itconstituted of only 2.1% of the total macrozoobenthos abundance,while this species in terms of biomass exceeded 11.9% of the totalbenthic biomass. Production of Brachycentrus subnubilus was estimated bysize-frequency method was 26.56 g wet weight m-2 and theturnover ratio was 5.7.

Coexistence of fish species in a large lowland river: food niche partitioning between small-sized percids, cyprinids and sticklebacks in submersed macrophytes.

In the spring and summer of each year, large patches of submersed aquatic macrophytes overgrow the bottom of the alluvial Warta River downstream of a large dam reservoir owing to water management practices. Environmental variables, macroinvertebrates (zoobenthos and epiphytic fauna, zooplankton) and fish abundance and biomass were assessed at this biologically productive habitat to learn intraseasonal dynamics of food types, and their occurrence in the gut contents of small-sized roach, dace, perch, ruffe and three-spined stickleback. Gut fullness coefficient, niche breadth and niche overlap indicated how the fishes coexist in the macrophytes. Chironomidae dominated in the diet of the percids. However, ruffe consumed mostly benthic chironomids, while perch epiphytic chironomids and zooplankton. The diet of dace resembled that in fast flowing water although this rheophilic species occurred at unusual density there. The generalist roach displayed the lowest gut fullness coefficient values and widest niche breadth; consequently, intraspecific rather than interspecific competition decided the fate of roach. Three-spined stickleback differed from the other fishes by consuming epiphytic simuliids and fish eggs. The diet overlap between fishes reaching higher gut fullness coefficient values was rather low when the food associated with the submersed aquatic macrophytes was most abundant; this is congruent with the niche overlap hypothesis that maximal tolerable niche overlap can be higher in less intensely competitive conditions.

The food preferences of three-spined stickleback, Gasterosteus aculeatus L., downstream from a dam reservoir.

The food preferences of three-spined stickleback, Gasterosteus aculeatus L., downstream from a dam reservoir Submersed plants appeared in the impounded section of the Warta River as a consequence of low discharge in summer and were colonized by epiphytic fauna dominated by Hydra sp., Simuliidae, and Chironomidae. The three-spined stickleback consumed it voraciously, and their diet composition closely reflected the available food resources. In May their alimentary tracts were filled with Cladocera drifting from the reservoir, and then by the dominant taxa associated with macrophytes, especially chironomid periphyton scrapers. A comparison of dipteran head capsule width in the food resources and in the alimentary tract proved the three-spined stickleback preference for the largest larvae (optimal foraging strategy).

Seasonal dynamics and production of Campsurus violaceus nymphs (Ephemeroptera, Polymitarcyidae) in the Baía River, upper Paraná River floodplain, Brazil

The production of Campsurus violaceus nymphs was investigated from October 1987 to September 1988 in the Baía River, a secondary channel of the Paraná River, Brazil. The annual production of this species during this period was 16.48 g dry wt m-2 y-1and the P:B ratio was 4.9. This low ratio compared to other rivers occurred because the Baía River was strongly influenced by the hydrological regime of the Paraná River, where nymphs migrated to avoid adverse conditions in the river during the flood phase.

Percid occupation of submersed riverine macrophytes: food resource partitioning between perch (Perca fluviatilis L.) and ruffe (Gymnocephalus cernuus L.)

In a reservoir tailwater of the large, lowland Warta River, perch and ruffe coexist in a macrophyte habitat, which develops as a result of low water discharge in the late spring and summer. At the beginning of each year the diet of both percids, when shorter than 100 mm, is dominated by large, benthic Hydropsyche. Later in the year, epiphytic Chironomidae and Simuliidae replace these trichopterans in the perch diet, and benthic Chironomidae replace them in the ruffe diet. Large cladoceran species then become accessory food items for perch. Consequently, the food niche overlap of these two percids during the research period is only marginal.

Diet overlap between two cyprinids: eurytopic roach and rheophilic dace in tailwater submersed macrophyte patches

Abstract From May to August 2004, the available food base and diet of two cyprinid species, eurytopic roach, represented by 75 small specimens, and rheophilic dace, represented by 37 small specimens, were investigated in seasonal patches of submersed aquatic macrophytes (SAM) in the impounded lowland Warta River, Poland. The aim of the study was to recognize spatial and temporal patterns in the feeding of both species in relation to available resources, and to evaluate their food niche overlap. To distinguish homogenous classes of fish alimentary tracts on the basis of their contents, a Kohonen artificial neural network (i.e., a self-organizing map, SOM) was used. Indicator food categories were identified using the IndVal index. Roach and dace partitioned the food niche, which was demonstrated in this study by 1) insignificant values of the Schoeners interspecific diet overlap index on particular sampling occasions, and two SOM sub-clusters (homogenous diet classes) with alimentary tracts almost exclusively of roach (axis of resources), 2) zero or low percentage of specimens of both fish species coming from the same sampling occasions and assigned to any of the remaining homogenous diet classes (axis of time), and 3) absence of roach in May and dace in August in the SAM patches, i.e., on almost half of the sampling occasions (axis of space). The diet overlap was highest when the SAM patches and food base were most developed, which is congruent with the niche overlap hypothesis saying that maximal tolerable niche overlap can be higher in less intensely competitive situations. We recommend the combined application of SOM and IndVal index, which have both previously been used in biocoenology, to the analyses of animal diets. They effectively allowed getting insight into the complex trophic relationships.

Trace metal concentrations in free-ranger, tube-dweller chironomid larvae and a weakly polluted fluvial sediment

Abstract The objective of this study was to analyze macroinvertebrate assemblages dominated by Chironomidae (Diptera) and to assess the protective nature of these midges’ larval tubes against trace metals in the weakly polluted Bzura River. This low order lowland river flows through the Łódź City Municipal Area and is supplied by a large amount of organic matter from ecotones and a polluted roadside. Determination of metal content in sediments and chironomid tissue and tubes was conducted using atomic absorption spectroscopy. Our study has shown that the composition of chironomid assemblages was not determined by trace metals but rather by high organic enrichment, which caused the dominance of two species representing the same trophic group − gathering collectors − but differing in behavior. One of them belongs to free-rangers (Prodiamesa olivacea), while the other (Chironomus riparius) to tube-dweller larvae. Although the accumulation of certain trace metals in the tubes was found, the larvae of both types of behavior had a similar concentration of metals in their tissues, which proves effective metal detoxification in these insects.