Sequentiality of beetle communities in the longitudinal gradient of a lowland river in the context of the river continuum concept.

The main goal of the study was to recognize the mechanisms underlying assemblage structuring of aquatic beetle fauna inhabiting a medium-sized, lowland river exposed to anthropogenic pressures. An attempt was made to identify the impact of numerous abiotic factors on how beetle communities are formed, with particular emphasis on geomorphological and landscape-related factors, which tend to be omitted from many studies of aquatic organisms. Our intention was to refer the results of our study to the general assumptions of the River Continuum Concept. Field studies were conducted in 2010, at 13 sites located along the Krapiel River (north-western Poland). In total, 3,269 beetles were captured, representing 120 species and five ecological groups: crenophiles, rheophiles, rheobionts, stagnobionts a and stagnobionts b, which differ in environmental preferences. The core of the identified fauna was composed of stagnobionts, while rheophiles and rheobionts accounted for only 20% of the entire collected material. The formation of beetle assemblages was affected both by local factors, with an impact on aquatic environments, and by geomorphological factors, influencing a larger catchment. This was reflected in the high degree of conformity between dendrograms presenting similarities in the fauna at the studied sites, including the clustering of sites based on the abiotic factors that differentiated these sites. The presence of buffer zones, surfaces of patches denoted as "marshes" (marshland surface), "shrubs" (shrub surface), and "forests" (forest surface), and the distance to those patches seem to be the most important landscape factors affecting beetle communities. Of the factors influencing the aquatic environment, the following exerted the strongest effect: insolation, vegetation cover, presence of organic matter and BOD5, and anthropogenic pressure. The changes in assemblages of beetles determined in our study in the particular sections of the river course were a consequence of the effects of both internal factors and external ones, originating from the entire river's catchment, which is in accord with the basic assumptions of the RCC.

Anthropogenic transformations of river ecosystems are not always bad for the environment: Multi-taxa analyses of changes in aquatic and terrestrial environments after dredging of a small lowland river.

Rivers are one of the most commonly transformed aquatic ecosystems. Most papers present significantly negative effects of activities such as dredging or channel regulation on the ecological status of rivers. The purpose of this work was to compare the response of various groups of invertebrates (Mollusca, Hydrachnidia, Odonata, Heteroptera, Coleoptera and Trichoptera) to an intervention involving dredging in conjunction with the removal of riparian vegetation. Habitat diversity increased after the dredging, and more individuals and species were caught than before the dredging. The increase in habitat diversity after the dredging translated into an increase in the species diversity of most investigated groups. Individual groups of invertebrates showed varied responses to the dredging, depending on the role of the terrestrial phase in their life cycle: the greater the role of the terrestrial phase in the life cycle, the more the group was affected by changes in the terrestrial environment following the intervention. In consequence, the intervention had the greatest negative impact on insects, and among these, on adult Odonata. The following conclusions can be drawn: (1) Dredging can benefit a previously anthropogenically transformed river ecosystem by increasing habitat diversity; (2) Odonata are particularly useful for assessing the impact of this type of intervention on invertebrate communities. They can be considered good indicators of habitat disturbances in both aquatic and terrestrial ecosystems.

Freezing: how do water mites (Acari: Hydrachnidia) survive exposure to sub-zero temperatures?

Until now, very little is known about the ability of adult and deutonymph water mites (Acari, Hydrachnidia) to survive in sub-zero temperatures. Information concerns mainly water mites from vernal astatic waters, and the knowledge has never been experimentally verified. To determine the sensitivity of water mites to freezing, experiments were conducted on (1) the impact of acclimatization, (2) temperature, and (3) duration of freezing on survival, (4) the survival rate of water mites from various types of water bodies, and (5) the survival rate of water mites from different climatic zones. The experiments were carried out in a phytotron chamber, and water mites were placed in containers (10 × 10 × 5 cm) filled with 4/5 of water for 10 specimens each. Water mites were identified to the species level after finishing the experiments. The temperature was lowered 1 °C every hour until the target temperature was reached. After a certain period of freezing (depending on the treatment) the temperature was raised by 1 °C every hour until it reached 4 °C. The time of the experiment was measured from the moment the desired temperature was reached (below 0 °C) until the ice thawed and the temperature of 4 °C was reached again. The highest survival rates had Limnochares aquatica, Piona nodata, Sperchon clupeifer and Lebertia porosa, followed by L. insignis, Hygrobates longipalpis, H. setosus, Limnesia undulatoides, Piona pusilla, Arrenurus globator, Hydrodroma despiciens, Piona longipalpis, Sperchonopsis verrucosa, Unionicola crassipes and Mideopsis crassipes; no specimens of Torrenticola amplexa survived. The following conclusions were drawn: (1) water mites can survive freezing to -2 °C, lower temperatures are lethal for them; (2) they survived better the short period of freezing (24-48 h) than the long period (168 h); (3) resistance to freezing seems to be an evolutionary trait of individual species, only partly related to the living environment; and (4) freezing survival rates are linked to the region of Europe and are much lower in Southern than in Central Europe.

First detailed records of water mite larvae (Hydrachnidia: Hydrovolzidae, Hydryphantidae) parasitizing empidid flies (Diptera: Empididae: Clinocerinae).

Five species of the subfamily Clinocerinae from the Tatra Mountains (S Poland) were observed to be parasitized by larval water mites. Two of them: Kowarzia plectrum Mik, 1880 and Clinocera storchi Mik, 1880 are recorded from this massif for the first time. In addition, C. storchi, is new for Polish fauna. The most infected species was Clinocera appendiculata Zetterstedt, 1838, following by Wiedemannia mikiana (Bezzi, 1899), Clinocera storchi Mik, 1880, Kowarzia plectrum Mik, 1880 and Wiedemannia jazdzewski Niesiolowski, 1987. The highest number of hosts occurred in the case of Panisopsis curvifrons (Walter, 1907) with five host species, following by both Hydrovolzia placophora (Monti, 1905) and Protzia eximia (Protz, 1896) with one species each. In the case of Clinocera appendiculata more parasites were recorded on males than on females and in C. storchi more parasites were recorded on females. The abdomen of the hosts was the most often chosen by water mites larvae.

Peroxidation and unsaturation coefficients as biomarkers of environmental micro-exposure to molluscicides in Helix pomatia L.

This study was a follow-up of a previous study that investigated a set of selected fatty acids (FAs; 12 of 56 pools) in Helix pomatia L. as biomarkers of chemical stress induced by applying micro-doses of molluscicides. Here, the potential of rarely used peroxidation (PI) and unsaturation (UI) coefficients were tested as biomarkers. These indices were calculated based on the FA profiles of foot and hepatopancreas tissues of H. pomatia L. Snails were treated with three molluscicides: metaldehyde, methiocarb, and potassium chloride, in three doses each (5, 10, or 15 µl, 0.01% w/v concentration), for 12 weeks, under laboratory conditions. Correlations were evaluated between frequently used oxidation status indicators (catalase, glutathione peroxidase, selenium-dependent peroxidase, superoxide dismutase, glutathione transferase, glutathione reductase, glutathione, carbonyl protein, and thiobarbituric acid reactive substances, in the form of MDA) and UI and PI ratios. These results confirmed that fatty acids could be directly used as biomarkers of exposure and oxidative physiological status in snails. Moreover, the UI and PI, calculated based on FAs, clearly reflected the current oxidation status in snails. These indices changed with the application of micro-doses of molluscicides. In conclusion, these indices could serve as sensitive biomarkers of chemical stress in snails.

Water mites (Acari, Hydrachnidia) of riparian springs in a small lowland river valley: what are the key factors for species distribution?

This paper examines the impact of disturbance factors-flooding and intermittency-on the distribution of water mites in the riparian springs situated in the valley of a small lowland river, the Krapiel. The landscape factors and physicochemical parameters of the water were analysed in order to gain an understanding of the pattern of water mite assemblages in the riparian springs. Three limnological types of springs were examined (helocrenes, limnocrenes and rheocrenes) along the whole course of the river and a total of 35 water mite species were found. Our study shows that flooding influences spring assemblages, causing a decrease in crenobiontic water mites in flooded springs. The impact of intermittency resulted in a high percentage of species typical of temporary water bodies. Surprisingly, the study revealed the positive impact of the anthropogenic transformation of the river valley: preventing the riparian springs from flooding enhances the diversity of crenobiontic species in non-flooded springs. In the conclusion, our study revealed that further conservation strategies for the protection of the riparian springs along large rivers would take into account ongoing climatic changes and possible the positive impact of the anthropogenic transformation of river valleys.