The alien and potentially invasive species Elodea nuttallii was observed for the first time in Slovenia's Drava River in 2007, when its huge biomasses were observed at some locations. Changes in biomass of submerged macrophyte communities and abiotic factors such as water temperature, discharge and level were monitored at two impoundments of the Drava River (2009, 2010 and 2011). The correlations between abiotic factors and developed final biomass were assessed to determine if the level of abiotic factors has an impact on the final biomass and invasive behaviour of E. nuttallii. The results obtained showed that biomass of E. nuttallii was not excessive in 2009 and 2010, while in the year 2011 it developed huge biomass at locations, which were not directly exposed to the main water current. The biomass of Myriophyllum spicatum was also higher in 2011 in comparison with 2009 and 2010 but not in such high degree. The key factor for the development of the final biomass of E. nuttallii was the water temperatures in winter and spring and also the point at which water temperatures in spring surpassed 10°C. The invasive behaviour of E. nuttallii is expected in the years with higher temperatures in January and March and at the locations which are not directly exposed to the main water current. We assume that continuation of the deposition of silt in the impoundments of the Drava River could contribute to invasive behaviour of species E. nuttallii in the years with mild winters and warmer springs.

In this study, we investigated variation in offspring size (OS) of Daphnia magna in relation to multiple maternal traits and environmental variables. Data originated from laboratory experiments conducted at different feeding scenarios. The mother daphnids had different life-history traits and were reared under various feeding and density conditions. OS showed linear relationships with maternal traits, varying positively with maternal body size, age and brood number, and negatively with brood size and with the amount of ingested carbon. OS increased exponentially with crowding. Using stepwise multiple regression analysis, we developed an empirical model for the OS variation with the relevant maternal and environmental variables. Density dependence was considered by multiplying the resulting model by a density-effect function. We found that the ingested carbon and the maternal body size were the strongest determinants of the observed variation in the OS, whereas the brood size had the least impact on OS. Additionally, the brood number had no significant effect in determining the variability in the OS. The validity of the multivariate model was tested against an independent dataset. The model accurately predicted the OS despite several genetic and environmental differences compared with the data used for parameterization.

For the first time, a faunistic list of the Chironomidae fauna of Greece is presented along with its ecological distribution. Chironomidae larvae and pupal exuviae were collected from 61 locations in mainland Greece during 2006–2008. 76 taxa (genera to species) were recorded. The genera Potthastia, Brillia, Euorthocladius, Synorthocladius, Tvetenia and Xenochironomus are recorded for the first time from Greece. Furthermore, 12 species are new for Greece and five are new for mainland Greece. Chironomidae collected from running waters were analysed with ordination techniques. The results revealed that Chironomidae assemblages were distinguished into three ecoregions with distinct climatic, geological and hydrochemical features. Running waters in Northwestern Greece were generally dominated by species tolerant to water acidification. Chironomids typical of eastern uplands preferred relatively slow current and soft bottom sediments. Assemblages of the southern Peloponnese Peninsula were represented by species of relatively fast flowing, warm streams. However, these are only preliminary results and many more data are needed to justify this ecological distinction of Chironomidae assemblages. This is the first study contributing to the knowledge of a rather neglected insect group of the Greek fauna. It is expected that more species remain to be identified and recorded and future works will contribute to this initial faunal list.

Corbicula fluminea, is one of the most successful invasive species in fresh and brackish waters. Dispersal is one of the most determinant steps in the invasive process, and the full understanding of the mechanisms involved in this step is critical for adequate pest management both in the wild and in industries affected by this species’ biofouling activity. A mucous drogue line produced by mucocytes packed along the inner demibranchs of the clams’ gills seem to play an important role in assisting drifting and hence dispersal. Two Asian clam populations geographically separated (one in the USA and the other in Portugal), investigated at different times of the year, were reported to differ in terms of mucous drogue line production and floating. In this study, genetics and seasonality effects were hypothesized to explain the difference between the populations. To test these hypotheses, the two populations were genetically compared, and the Portuguese one was followed for 14 months to record the animals’ mucous drogue line production and flotation capabilities and locate the population reproductive periods. Our results signal a possible scenario of microevolution with consequences on the production of the clams’ mucilaginous drogue line. Although some authors advocate a link between mucous threads formation and reproduction events, such a relationship was not observed in this study. By contributing to the understanding of a physiological trait of the Asian clam that is important for dispersal, this study may be of practical relevance for pest monitoring and control.

This paper reports data on a community of Trachelomonas species (Euglenophyta) occurring during Planktothrix agardhii bloom formation in a shallow, highly eutrophic dam reservoir. The results come from a long-term study of Siemianówka Dam Reservoir, located on the upper Narew River (NE Poland). From April to October 2007, 132 alga taxa were identified, including 32 Trachelomonas taxa, 23 of which are new for the reservoir; of those, three are first records for Poland: T. armata (Ehrenberg) Stein var. heterospina Swirenko, T. atomaria Skvortzov var. minor Hortobagi and T. minima Dreżepolski. One variety, T. curta var. pappilata Wołowski, is described as new for science. The ultrastructural details of Trachelomonas species are illustrated. The highest number of Trachelomonas taxa was recorded in August in the shore zone of the reservoir. At the end of summer 2007, the conspicuous development of P. agardhii (Gomont) Anagnostidis et Komarek, caused a rapid decrease of Trachelomonas biomass due to lower water transparency and the oxygen concentration. In addition, a decline in the Trachelomonas taxa and biomass was associated with a decrease of water temperature. The negative impact of extracellular microcystin on the Trachelomonas development requires further study.

We investigated the chemical characteristics of the astatic soda pans in the Carpathian Basin based on comprehensive new and archive data. Analysed parameters were salinity and ionic composition. The most frequent type of soda waters was the basic alkaline type (Na-HCO3) that represented more than half of the natural soda pans. Besides 11 subtypes occurred. The second and third most frequent types were the chloride (13%) and sulphate subtypes (11%), with the secondary dominance of these anions. The other subtypes meant <4% of the pans. Magnesium sometimes occurred as a secondary dominant cation beside sodium. Until now, this subtype of soda waters has not been published in any part of the world, because of the general rule of soda lake formation (depending on low levels of magnesium and calcium). We found a regionally constant correction factor [Salinity (mg.L−1)=0.8×El.Cond. (μS.cm−1)] for confidentially estimating salinity from electrical conductivity in these habitats. Salinity varied between sub- (0.5–3 g.L−1) and hypersaline (>50 g.L−1) ranges, with its mean value (∼4 g.L−1) in the hyposaline range (3–20 g.L−1). The basic alkaline type had random geographical distribution, while the other subtypes were restricted to certain regions of the Basin. The high number of subtypes reflects the high chemical diversity of alkaline soda pans in the relatively small territory of the Carpathian Basin.

The impact of fish and cyclopoid copepod predation on zooplankton communities was evaluated using large-volume mesocosms (depth 9.5 m; volume 13 m3) in the Římov reservoir (Czech Republic). Two yearling roach and perch individuals introduced into mesocosms represented the fish treatment, which was compared to cyclopoid copepods (initial abundance of 2 ind.L−1) and a control with no initial addition of predators. Our results clearly support the hypothesis that planktivorous fish feeding leads to the suppression of large-bodied cladocerans. In the presence of fish, the cladoceran community changed from a dominance of large-bodied Daphnia spp. at the beginning to dominance by the smaller Bosmina longirostris at the end of the experiment. Chlorophyll-a concentration and rotifer abundances increased in the absence of daphnids. In the absence of fish, the presence of large-bodied cladocerans resulted in decreasing chlorophyll-a concentration. Although no significant differences were observed between cyclopoid abundances in treatments stocked with cyclopoids and the control, the proportion of large cladocerans clearly showed the effect of the manipulation. The similar trends in both of these treatments did not confirm the importance of cyclopoid predation in our experiment. The overall strong effect of fish over cyclopoid predation suggests the main role of fish predation in the forming of zooplankton communities and in turn impacting phytoplankton biomass in mesocosms.

The new genus Metapelopia is established for species of Pentaneurini from the southeast Brazil. Generic diagnoses for larva, pupa and adult male are provided together with descriptions of all life stages of the new species Metapelopia corbii. The pupa and larva of an additional species in Metapelopia is described, but not formally named. In addition, keys to the males, pupae and larvae of genera in the Thienemannimyia group are provided.