Complex effects of acidification, habitat properties and fish stock on littoral macroinvertebrate assemblages in montane standing waters

Littoral macroinvertebrates in acidified waterbodies are affected by the interaction of acidification and local environmental conditions. Understanding the interplay of these factors in the structuring of communities is essential for interpreting responses to and/or recovery from acidification. Here, we analyse the species composition and richness of littoral macroinvertebrates in a range of acidified montane standing waters in relation to water chemistry, littoral characteristics and fish stock. The main species composition gradients were related to pH and conductivity; however, considerable variation along these gradients was associated with local habitat characteristics (changing water levels and littoral structure) and concentration of ionic aluminium and dissolved organic carbon. Although fish stock effects were confounded by correlated acidity, we observed a significant decline in abundance of macroinvertebrates vulnerable to fish predation at sites with fish stock. Overall, littoral macroinvertebrates of acidic waterbodies were diverse due to the heterogeneity of local habitat properties, despite they were dominated by acid-tolerant species. Acidic humic sites with dense, heterogeneous littoral vegetation were species-rich, hosting numerous habitat specialists and rare species, while chronically acidified lakes with high aluminium concentrations and sparse littoral vegetation had species-poor assemblages, characteristic of strong acid-stress. Water level manipulation resulted in serious assemblage impoverishment, overriding the effects of more favourable water chemistry. This study shows that the littoral fauna of acidic waterbodies is structured by complex effects induced by local factors in addition to acidity, resulting in acid-stressed assemblages with relatively high variability, emphasising a need to analyse local habitat factors when evaluating the impact of acidification on macroinvertebrates.

Ecological conditions of the Waterchestnut (Trapa natans L.) in the Danube Delta (Romania)

The diversity of water body types in the Danube Delta offers appropriate ecological niches for the colonisation of frequently large stands of the waterchestnut (Trapa natans). Their phytocoenoses were observed in slowly running and standing waters from clear, sediment-poor, to turbid and sediment-rich waters on muddy ground. Trapa natans occurs in standing, and slowly running, waters and is well adapted to fluctuation of water level changes. The water dynamics is responsible for the composition of accompanying species of the phytocoenoses. The particular zonation, demonstrated by a cross section shows the adaption to the structure and the water flow of certain water bodies. Comparing older and newer research data, a decline of the populations of waterchestnuts became visible.

Tasserkidrilus cf. americanus (Clitellata, Naididae) – A new record from Slovakia confirms the dissimilarity between the European and North American populations

The main objective of this study is to present a new record of Tasserkidrilus cf. americanus found in a channel near the Tešmak swamp in Slovakia (Central Europe) and to compare its morphological features and habitat requirements with those of populations occurring in North America and Europe. The new specimens are similar to those found in The Netherlands and Belgium, but dissimilar to previously reported North American material of T. americanus, reopening the question of whether the European form is a separate species. The European form has the penis sheaths approximately twice as long as and wider than the North American form and may inhabit slow-flowing or standing waters of a eutrophic character, which is in conflict with the current knowledge on the morphology and ecology of North American populations. Further investigation is necessary to solve the questions about the origin and taxonomic relationship of the European population to other populations.

Assessing trophic state of surface waters of Służewiecki Stream (Warsaw)

Phosphorus (P) is one of the key nutrient compounds for phytoplankton grow. In the conducted work, eutrophication indexes were used for the assessment of eutrophication level of water course (Służewiecki Stream) and the waters of nearby lakes (Bottom Berensewicz’s Pond, Wyścigi Pond, Wilanowskie Lake). Calculating eutrophication indexes were based on the most important indicators which is crucial for eutrophication process: total phosphorus (TP), total nitrogen (TN), chlorophyll a (Chl(a)) and water transparency. The research revealed that the concentration of phosphorus and nitrogen in the analysed waters determined intensity of trophic processes. The average concentration of both indicators was high: 0.81 mg/l TP and 6.8 mg/l TN. During this research, two approaches were used: trophic state index (TSI) and trophic level index (TLI). TSI (TP) in Służewiecki Stream were, respectively: 83 and 6.5 whilst for standing waters (lake and ponds) 87 and 6.6. Both indexes indicated high trophic state and confirmed that eutrophication is a serious endangerment for analysed surface waters. Calculated indexes used in the assessment were sufficient and effective for sustainable water protection and management of water quality in Służewiecki Stream and in standing waters.

Rarely mentioned species in Hungary: Can we step into the same lake?

International and national protection strategies and directives focus mainly on macroscopic organism and attempt to maintain their endangered habitats. However, microscopic communities are also threatened by decreasing biodiversity and many species including freshwater algae can disappear without even knowing they were present in the habitat. Defining rarity of microscopic taxa is not easy. The species’ rarity is based on detailed knowledge of distribution and abundance of species. But only limited information is available about rare algal species especially in a given ecoregion. Reducing the data gaps, here, we present altogether 20 phytoplankton taxa rare in Hungary: three species of Chlorophyceae, eight species of Trebouxiophyceae, two taxa of Euglenophyceae, one-one species of Cyanobacteria, Bacillariophyceae and Mediophyceae and three species of Xanthophyceae. One of them, the Cylindrotheca gracilis is on the Hungarian Red List. Physical and ecological characteristics of standing waters where these species were found as well as their former occurrence all over the world are also reviewed.

Zróżnicowanie przestrzenne wybranych składników biogennych w śródpolnych oczkach w Polsce Północnej = Spatial differentiation characterising selected biogenic components in mid-field kettle ponds of northern Poland

Closed basins are important and fixed elements of a post-glacial landscape, in which they may occupy rather a large percentage of the total area. Sometimes these fill to become bodies of water known as kettle ponds. Each such basin has its own closed catchment at the surface and, owing to the limited circulation of matter in these types of depressions, biogenic components often accumulate to excess. In that context, the work detailed here had as its main objective the identification of sources of biogenic substances like nitrates, ammonium-nitrogen and phosphates, with a view to determining the range of variability characterising their presence in small mid-field ponds present in the catchments of two of northern Poland’s rivers, i.e. the Parsęta and the Borucinka. Most of the kettle ponds under study could not be said to have particularly high contents of nitrate, given an average for the bodies of water studied within the Parsęta basin equal to 2.98 mg·dm-3. There was nevertheless considerable variability in concentrations of the ion – ranging from 0 to as much as 51.30 mg·dm-3. It was the “Sadkowo” pond that might be singled out here for its extremely high concentration (the aforesaid maximum value of 51.30 mg·dm-3; along with a mean value of 13.41 mg·dm-3). In this case a local factor is likely to have been operating – i.e. areal runoff pollution from fields involving nitrogenous compounds. Ponds in the Borucinka catchment had only low concentrations of nitrate, with a mean value for all kettle ponds studied there of just 0.24 mg·dm-3 (with values in the overall range 0 to 2.17 mg·dm-3). Concentrations of the analysed component were thus lower in the Borucinka catchment than in the Parsęta basin, with a key influencing factor likely to have been the sizes of the bodies of water studied. The Parsęta-basin examples were in fact smaller kettle ponds whose catchment features and morphometric parameters are such as to ensure higher concentrations of biogenic (especially nitrogenous) compounds in any standing waters. Mean concentrations of ammonium ions obtained for the Parsęta basin were of 0‑2.41 mg·dm-3, the value averaged for the six ponds being 0.95 mg·dm-3. However, four other Parsęta-basin ponds excluded from the study in fact reported very high values for NH4 + – of up to 25.55 mg·dm-3. The Borucinka catchment again contrasted with the Parsęta basin, with noted concentrations of ammonium-nitrogen both low and of limited variability (in the 0‑1.88 mg·dm-3 range). The average figures for all the depressions studied there was 0.09 mg·dm-3. The situation as regards the two forms of nitrogen was thus similar, with concentrations lower in the catchment of the Borucinka and higher in the basin of the Parsęta. Sizes of bodies of water would seem to be a factor influencing spatial differentiation of NH4 + concentrations. Where phosphate was concerned, kettle ponds within the Parsęta basin had a mean concentration of 0.57 mg·dm-3, with reported values from one pond to another ranging from 0 to 4.46 mg·dm-3. The Borucinka p ds again had lower concentrations of this biogenic substance across a narrower range of values (0 to 3.69 mg·dm-3, mean 0.19 mg·dm-3).