ABSTRACT

Abstract:There are hardly any data concerning the vertical micro−distribution of protozoa in water column in cryoconite holes on the glacier surface. Such comparisons can provide in− sights into the ecology of protozoa. The present research was made on Ecology Glacier (South Shetland Islands, Antarctic); vertical microzonation of ciliates in relation to physical and chemical parameters in cryoconite holes was studied. The density and biomass of protozoans significantly differed between the studied stations (cryoconite holes), with the lowest num− bers in the surface water and the highest in the bottom water. The surface waters were domi− nated by mixotrophic and omnivorous taxa, whereas the deepest sampling level has shown the increase of the proportion of bacterivore species. Ordination analysis indicated that TN and P−PO 4 can strongly regulate the abundance and species composition of protozoa. The redun− dancy analyses (RDA) showed that the ciliate communities can be separated into two groups. The first group included species associated with surface water: Halteria grandinella and Codonella sp. The second group included species that are associated with bottom water: Prorodon sp., Holosticha pullaster, Stylonychia mytilus−complex and small scuticociliates.

Complex interactions between bacteria and protists are essential to the ecosystem ecology of peatbogs. However, little is known about how short-term changes in environmental conditions may influence microbial and metazoan communities. Microbial processes and parameters may be used as sensitive indicators of eutrophication. We address the hypothesis that an increase in the concentration of nutrients (in an experiment simulating eutrophication) will affect species richness and abundance of microorganisms and small metazoans and will cause changes in food web structure in different types of peatbogs. The experiments were performed in a Sphagnum peatland and a carbonate fen. Four experimental treatments were established (control and fertilised: +P, +N, P+N). An increase in habitat fertility was found to modify the taxonomic composition and functioning of microbial communities. This was reflected in a decrease in the species richness of testate amoebae and a substantial increase in the abundance of bacteria, flagellates and ciliates in both types of peatbogs. A better understanding of which parameters regulate microbial populations in peatbogs is critical for more accurate prediction of how peatbogs will respond to global change or anthropogenic disturbances.

Bosmina longirostris is a small-bodied, filter-feeding cladoceran. The species is widely distributed throughout the world in temperate and tropical climates, where it persists in all kinds of freshwater bodies regardless of their trophy, acidification, or salinity. Its wide distribution causes B. longirostris to be one of the most taxonomically recognizable Cladocera species all over the world, despite the fact that the species is a well-known example of a taxon with confused taxonomy. Although B. longirostris often displays high abundances in the world's freshwaters and sporadic studies on its feeding suggest that the species can have an important role in energy transfer throughout the food web, B. longirostris is still perceived by scientists as having a minor role in the classical food web structure. This perception of B. longirostris as a food web component could be altered in the near future due to global climatic changes, including increases in temperature which may cause cyanobacterial blooms that may be more harmful to Daphnia than B. longirostris. The response of B. longirostris to environmental, competitive, and predatory conditions has been repeatedly studied to search for application of that species as indicator in ecological, neolimnological, and paleolimnological research. Regardless of its common use as test species in ecological and limnological studies, B. longirostris still lacks appropriate study by researchers because of its problematic systematics. Research directed at this species seems to be hampered by the absence of an accurate taxonomical revision of B. longirostris or group of cryptic species called B. longirostris.

Microbial communities living in mosses are known to constitute early indicators of ecosystem disturbances, but little is known about their response to envi-