Janusz Żbikowski

Factors influencing taxonomic composition and abundance of macrozoobenthos in extralittoral zone of shallow eutrophic lakes

Zoobenthos is an essential part of shallow lake ecosystems, exerting a considerable impact upon their functioning. We studied 13 eutrophic, shallow, polymictic lakes from Northern Poland to find out which environmental factors influence taxonomic composition, abundance and biodiversity of their zoobenthos. The Canonical Correspondence Analysis allowed to distinguish three lake types: (1) macrophyte-dominated lakes, with high plant cover and well illuminated bottom, inhabited by abundant, diverse benthic taxa; (2) deeper phytoplankton-dominated lakes, with shaded bottom, high sediment oxygen demand (SOD) and rather sparse zobenthos community, dominated by Chironomus and Chaoborus larvae; (3) shallower phytoplankton-dominated lakes, with intermediate amount of light at the bottom and lower SOD values and comparatively diverse zoobenthos, but with lower number of taxa than in the first group. Apart from plant presence, distinguishing between macrophyte-dominated lakes and the other types, the most important variable in the CCA was amount of light reaching the bottom. Probably the impact of light on the bottom fauna was indirect: light stimulated development of macrophytes or phytobenthos (depending on its intensity) and thus improved food and oxygen conditions. Zoobenthos was also affected by oxygen conditions (mainly SOD), presumably by short-time oxygen depletions occurring in the deep phytoplankton-dominated lakes and preventing survival of some benthic taxa.

Is Nuphar lutea (L.) Sm. a structuring factor for macrozoobenthos and selected abiotic parameters of water and bottom sediments throughout the year

Studies on the role of nymphaeids in water bodies are uncommon, despite the fact that they often dominate in eutrophic lakes. Therefore, we decided to evaluate the effect of a nymphaeid Nuphar lutea on its environment. We hypothesised that its presence can increase the diversity and abundance of zoobenthos, as well as modify selected abiotic parameters, both during the growing season (in the presence of leaves) and outside it (with underground structures only). Three pairs of stations (within and outside Nuphar stands) were established in two shallow, eutrophic lakes and sampled monthly during an entire year. Zoobenthos taxon richness, biodiversity and total density were higher among nymphaeids throughout the year. On the other hand, total zoobenthos biomass was not affected by the presence of plants. Most macroinvertebrates reached higher densities within Nuphar stands, the most abundant being Polypedilum nubeculosum, Potamothrix bavaricus, Ephemeroptera and Ceratopogonidae. In turn, Potamothrix hammoniensis, Chaoborus sp. and Tanypus sp. were more abundant outside the stands. Other taxa, including the dominants (Chironomus sp., Procladius spp., Einfeldiadissidens, Valvatapiscinalis), were not affected by the presence of Nuphar. Nuphar did not influence water temperature, oxygen concentration, and conductivity, though sediments within the stands exhibited lower water content and higher proportion of large organic particles. Thus, Nuphar effect on macroinvertebrates was probably direct, through increased habitat heterogeneity, physical stability of substratum and food availability. Our study has shown that nymphaeids, despite their structural distinctness, can affect positively bottom fauna similarly to other morphological groups of plants.

Digenean larvae—the cause and beneficiaries of the changes in host snails’ thermal behavior

Parasite-induced changes in host’s thermal preferences not only can be interpreted as a physiological defense response of the host but also can represent a pathological manifestation of the parasite. Both may become established in host-parasite relationships if they are beneficial for at least one of the counterparts. This study investigates parasite-induced changes in the thermoregulatory behavior of first intermediate hosts of Digenea (i.e. Lymnaea stagnalis and Planorbarius corneus), infected with Notocotylidae or Echinostomatidae larvae. The investigated parasite species developed different transmission strategies outside the body of a snail, which may imply a different effect on the behavior of their hosts. Notocotylus attenuatus in L. stagnalis and Notocotylus ephemera in P. corneus produce symptoms of anapyrexia, prolonging the lifespan of their hosts. By contrast, Echinoparyphium aconiatum in L. stagnalis and Echinostoma spiniferum in P. corneus interfere with defensive thermoregulatory behavior of host snails, causing their accelerated death. The results of laboratory research indicate that thermal preferences of the snails infected with all investigated trematodes facilitate the transmission of the parasites in environment.

Ketoprofen-induced inhibition of symptoms of behavioural fever observed in wintering Planorbarius corneus (L.) (Gastropoda: Planorbidae)

Research on behavioural fever in Planorbarius corneus was undertaken using a longitudinal thermal gradient. Before the experiment, snails were acclimated at 19 °C. Following injections of lipopolysaccharide (LPS, a pyrogenic agent), ketoprofen (an antipyretic) or saline solution (control), thermal behaviour of the animals was automatically recorded for 48 h. The results demonstrated that LPS-induced symptoms of behavioural fever were inhibited by ketoprofen. Additionally, it was observed that snails which, before the injection of LPS, were preinjected with ketoprofen showed symptoms of behavioural fever with a 20-h delay. This result shows the inhibitory effect of ketoprofen on the occurrence of behavioural fever symptoms in P. corneus. It may suggest some similarity in mechanism of enhanced thermal preference in snails to vertebrate fever— both effectively inhibited by aspirin-like anti-inflammatory compounds.

Reproduction of Potamothrix hammoniensis (Oligochaeta) in shallow eutrophic lakes

Abstract The aim of the study was to indicate the abiotic parameters of water and bottom sediments, which significantly affect the reproduction of Potamothrix hammoniensis in 9 shallow eutrophic lakes, of which 5 were dominated by macrophytes and 4 – by phytoplankton. Samples were collected once a month from January to December 2012. The percentage of Potamothrix hammoniensis individuals with a developed reproductive system varied in individual lakes and ranged from 14 to 72%. There was no correlation between the distinguished lake types and the proportion of sexually mature individuals. The reproductive activity was not observed in summer and early autumn. Among the measured parameters, the highest values of the Pearson correlation coefficient were found between the percentage of individuals with a developed reproductive system and the conductivity (r = 0.69; p < 0.001), pH (r = 0.51; p = 0.002) and the organic matter content in the sediments (r = −0.42; p = 0.012). It is worth noting that there was no correlation between the percentage of sexually mature specimens and the water temperature (r = −0.22, p = 0.204) and the oxygen concentration (r = −0.08; p = 0.648).

The muddy bottom sediments of the old river beds of the lower Vistula

Abstract The main objective of this study was to characterize the muddy bottom sediments of three hydrologically different old river beds of the lower Vistula, located in the vicinity of Toruń: Port Drzewny, Martwa Wisła and Przybysz. Samples were taken at monthly intervals from April to November 2015 from two (Martwa Wisła and Przybysz) or three sampling sites (Port Drzewny) located in the central parts of the reservoirs. The bottom sediments of these water bodies were characterized by a low water content and organic matter content expressed as a percentage of dry weight, high organic matter content expressed in units of weight, as well as a high sediment oxygen demand. The most distinct reservoir was Martwa Wisła, most likely due to the lack of a connection with the River Vistula.

Peculiarities of macrozoobenthos in the offshore zone of a small artificial post-gravel pit reservoir

Peculiarities of macrozoobenthos in the offshore zone of a small artificial post-gravel pit reservoir The offshore macrozoobenthos and selected environmental parameters were studied in a small artificial reservoir, created through sand and gravel extraction. The results are rather surprising. Despite the shallow depth and good wind exposure of the reservoir, a thermal and oxygen stratification developed in the summer, causing hypoxic conditions near the bottom, even though the organic matter content in the sediments was <5%. Furthermore, despite the high fish abundance, chaoborids prevailed in zoobenthos, while Tanytarsus sp. and Chironomus sp. co-dominated among chironomids. This study attempts to explain the observed phenomena, though the presented hypotheses still need further confirmation.