The role of reeds in the functioning of ecosystems and their significance for zoobenthos in the coastal lagoons is poorly understood. We hypothesise that next to the spatial zonal differentiation of abiotic factors in the apparently homogeneous habitat of reeds, benthic macroinvertebrate fauna is also unevenly distributed, and differs in taxonomic and functional diversity, as well as density and biomass across the reed stand. The research was carried out in the Vistula Lagoon (southern Baltic) along three designated sectors arranged parallel to the shoreline and differing in distance from the shore and depth. Mean density of reed stems in the analysed stand was within the range of values reported from different American and European wetlands. Regardless of the location within the reeds and the season, the fauna was dominated by detritivorous Tubificinae and larvae of Chironomidae. The highest diversity, density, and biomass of fauna were found in the middle littoral zone, and the lowest in the outer zone adjacent to the open water. The presented data support our hypothesis predicting the existence of a spatial variation pattern in the composition and distribution of macroinvertebrates in response to the changing zonal habitat conditions within the reed stand.
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The study was performed in five fourth-order tributaries of the Bystrzyca Lubelska River (Eastern Poland, Lublin Upland), differing in the degree of river-bed transformation and level of pollution. Hydro-morphological methods (descriptive method by Ilnicki and Lewandowski - IL, and index method by Oglecki and Pawlat - OP) and biological indices based on the composition of zoobenthos (Diversity - D, and index based on proportions between the density of Oligochaeta and Chironomidae - O/Ch) permitted distinguishing of four classes, from II to V. The distinguishing of only two quality classes (III and IV) was possible by means of physical-chemical methods and by benthic index BMWP_PL. Those two methods seem to show the lowest sensitivity to the spatial variability of the environment quality. The BMWP_PL index was the least sensitive to year-to-year environmental changes, and O/Ch was the most sensitive. Relatively high conformity was obtained between hydro-morphological assessments performed by means of the OP and IL methods. Results obtained by means of these tools weakly corresponded with the physical-chemical assessments. The latter assessments were the most similar to those obtained by means of the BMWP_PL (degree of similarity = 57%) and D (47%) indices, and considerably less in the case of O/Ch (36%). The BMWP_PL and D indices better corresponded with the results of the hydro-morphological assessment performed by means of the IL method than with those performed by means of the OP method while D index showed a reverse pattern. The O/CH index proved useful for the assessment of the degree of organic pollution of the river’s water, but not the sediments.
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Non-native species exert considerable pressure on aquatic ecosystems; accordingly, they are treated as biopollutants. The Vistula Lagoon, one of the largest brackish water bodies in the Baltic, has become a part of the central corridor for hydrobionts migrating in the direction of western Europe and species expanding in inshore waters. Ten non-indigenous species of benthic invertebrates from five different biogeographical regions have been found in the western part of the Lagoon. Their considerable abundance relative to the numbers and abundance of native species testifies to the high level of biopollution there. The integrated biological contamination index (IBC) calculated for the macrobenthos in the western Vistula Lagoon was 4 and corresponds to the Lagoon's poor ecological status.
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Research relating to the subject of this paper was conducted on the Tywa River between September 1996 and July 1998. In the samples, invertebrates were found belonging to 46 species, 26 genera, and two subfamilies. In the 1996 season, the highest abundance was observed among Tanypodinae (larvae) at 10,878 ind. m-2; among Chironominae (larvae) it was 9,965 ind. m-2; and among Tubifex tubifex it was 2,605 ind. m-2. The maximum total density of macrozoobenthic forms in the Tywa River was at station no. 1, where it amounted to 23,953 ind. m-2. The quantitative structure in the 1997 season was lower than in the 1996 season, and the highest abundance was for Simulium sp. (larvae) at 5,196 ind. m-2; for, Tanypodinae it was 3,360 ind. m-2; and for Dreissena polymorpha it was 4,721 ind. m-2; and for Theodoxus fluviatilis – it was 4,114 ind. m-2. In this season, the biodiversity of the macrozoobenthic community was the highest of all seasons. In 1998, the qualitative structure of the macrozoobenthic community was low: Hirudinea disappeared, and the quality of the community was almost four times lower than in 1996. The river’s fast current, its diverse substratum, its very good oxygenation, and moderate concentrations of organic matter created conditions appropriate for species that differ in their requirements.
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The influence of submerged macrophytes on composition, abundance and distribution of epiphytic and benthic chironomids was investigated in five lakes differing in the development of vegetation cover. Studied lakes represented three types, classified according to the concept of Alternative Stable States as: macrophyte dominated MD (dense vegetation), phytoplankton-macrophyte dominated PMD (sparse, patchy vegetation) and phytoplankton dominated PD (lack of submerged vegetation). Both zoocenosis responded differently to the changes in macrophyte cover. The density and biomass of benthic midges (density and biomass per m[^2] of bottom surface) were visibly higher in the patchy vegetated lakes; the abundance of epiphytic chironomids did not show any regularity. The species composition of epiphytic chironomids differed visibly between particular lake types, changed with the decrease of macrophyte cover. The composition of benthic midges was similar in all lake types. The studies showed at strong dependence of the proportion of epiphytic to benthic chironomids on the cover of macrophytes. In MD lakes the phytophilous midges were more abundant than benthic; in PMD lakes we observed the opposite pattern.
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The aim of the investigations was to determine the effect of hypoxia and anoxia on the osmoregulation of Corophium volutator. The experiments were performed at salinities of 3.0, 6.6,15.0, and 25.0 PSU in conditions of hypoxia (saturation = 30% O2) and anoxia at a constant temperature of 10°C. Control experiments in aerated water were conducted simultaneously. Hypoxia (saturation = 30% O2) had no statistically significant effect on the osmoregulation of C. volutator after either 6 h or 48 h. However, after 6 h it did lower the osmotic concentration slightly. After 6 h anoxia had no effect on osmoregulation, but no subsequent effects of this factor (after 24 and 48 h) were detectable due to high animal mortality. Anoxia also had no effect on osmoregulation after 24 h at salinities of 15.0 and 25.0 PSU or 48 h at 15.0 PSU.
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The bottom fauna inhabiting two types of ecotones: 1) the transition zone between land and lake water, and 2) the border of a macrophyte bed and open water, situated in different types of littoral, distinguished mainly according to the structure and distribution of macrophytes was studied. The investigations were carried out in five harmonious lakes (from mesotrophic to highly eutrophic) and in one disharmonious (humoeutrophic) in July and September of 1996 and 1997. Both the species composition of zoobenthos and the relative abundance of the most numerous taxa (Tubificidae and larvae of Chironomidae) in ecotones did not seem to depend much on the type of littoral but rather upon the nature of the bottom sediments. The influence of lake fertility in harmonious lakes was clearly expressed mostly in the land-water ecotones where it was demonstrated by the drop of chironomids and increase in tubificidis and predators in total faunal abundance with a rise of lake trophism. The clear pattern in vegetation bed-open water ecotones concerned solely predators which contribution to the total faunal abundance tended to increase with a rise of lake trophic status. The ecotones of the disharmonious lake did not show much differences in comparison with the harmonious lakes except extremely low faunal density in vegetation-open water ecotone, bening totally predominated by chironomids. In both harmonious lakes and in disharmonious one the highest faunistic similarities were found within the same types of ecotones, while the two types differed greatly.
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The chemical composition and biotic structure were studied in ecotonal zones of six trophically differentiated lakes in the region of Polesie Lubelskie (Eastern Poland). High qualitative and quantitative differentiation of zoocenoses (zooplankton and zoobenthos) usually occured in each ecotonal zone of every lake studied. The highest diversity occured among microinvertebrates (zoopsammon and zooplankton).
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The riverine faunal responses was shown in relation to environmental changes arising from flow regulations in the Warta River downstream of the man-made Jeziorsko Reservoir. Two study sites were chosen for studies: one above the backwater (WAA) and the second in the tailwater (WAB) of the reservoir. The investigations were begun in 1988/1989 and repeated in the next three annual cycles: 1991/1992, 1992/1993 and 1995/1996. Chironomidae and Oligochaeta dominated in terms of density and biomass at both sites of the Warta River. At the beginning of the dam's functioning the pattern of macrobenthic spatial distribution was similar at both sites. But latter, in two last study summers water management resulted in a reduction of stream flows below their natural levels in the tailwater. These reductions in seasonal flow variability caused the greatest changes in biotic communities. Firstly the shoreline region in the tailwater enlarged and contracted in response to dam operations; the bottom was sometimes stranded (exposure to air) thus many macrobenthic groups were eliminated. Secondly Cladophora glomerata and macrophytes that developed in habitat several meters from the banks appeared to be responsible for substantial increase in abundance, especially of orthoclad midges. Additionally the retention of FPOM due to filtration by a dense bed of macrophytes created favourable conditions for pelophilus taxa, large sized taxa of Chironomini. Finally these mechanisms in opposite tendencies equalled - chironomids reached similar density in the backwater and tailwater.
Basing on investigations of bottom suiface sediments of the outer Puck Bay (1995, 1999) and the inner Puck Bay (1987, 199 I, 1996), their condition and the absolute quality was determined in accordance with the adopted classification { 3]. Carried out at the same time investigations of the condition and composition of phyto- and zoobenclws allowed determining the relationships between the biotic and abiotic components of the Puck Bay bottom. In the paper, results of correlation analysis are presented. They indicate strong relationships between selected systems of components. These results show also that loading of the sediments with organic matter has a significant influence on the properties of the environment and on the biocenoses of the investigated water area.
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