Małgorzata Adamczuk

Crustacean communities as food resources for fish in shallow Polesie lakes with contrasting development of submerged macrophytes

The aim of the research was to evaluate crustacean forage resources for fish in five shallow lakes varied in respect to species richness and coverage of submerged macrophytes, and thus representing different alternative stable states. The results revealed that lakes with a high or moderate abundance of macrophytes and moderate visibility (macrophyte-dominated Lake Rotcze, phytoplankton-macrophyte dominated lakes Sumin and Głębokie) displayed reach crustacean forage base for fish. Poor feeding conditions were found in two extremely different lakes: turbid phytoplankton-dominated Lake Syczyńskie devoid of macrophytes, and heavily vegetated, clear-water macrophyte-dominated Lake Kleszczów. Possible reasons for these differences are discussed.

Different levels of precision in studies on the alimentary tract content of omnivorous fish affect predictions of their food niche and competitive interactions.

The food niche partitioning of omnivorous fish is commonly estimated on the basis of the alimentary tract content (ATC). However, since omnivorous fish utilise different ecological formations, data relating to ATC are very noisy, since an identified ATC comprises remains that can be determined according to the species level, determined only according to general food categories (i.e. higher taxonomic levels) as well as amounts of fragmented and digested remains that cannot be determined taxonomically. Thus, a variety of scales of precision can be applied during work on ATC. Up until now, there has been no evidence as to whether and how precision in ATC estimation can affect the results. This study aims at assessing how three different options of the same database influence the effectiveness and concurrency of indexes commonly used to describe the food niche of fish. The options include: (1) only general (higher than species level) food categories; (2) categories of different levels of generality; and (3) only detailed (species level) food categories. The study shows that the use of detailed (species level) food categories only, with the exclusion of general food categories, is the best method to recognise food niche partitioning and competitive interactions among fish. The food categories estimated in detail were cladocerans, and the possibility to use cladocerans as specific markers to find similarities in fish diets is discussed.

Ciliates as restoration indicators in peatbogs — 10 years of study

There is almost no information on how restoration of Sphagnum-dominated peatbogs, and in particular removal of reeds, affects the functioning of ciliate communities. Changes in vegetation patterns caused by restoration procedures may take years to be observed, while microbial processes already display effects after short-term exposure to changes in environmental conditions due to restoration. Based on the results of a long-term study, we assumed that mowing down of reeds causes changes in the physicochemical properties of peatbog water and sought to answer the question of how ciliate communities react to these changes and whether these microorganisms can play a significant role as bioindicators in evaluating the restoration process. Removal of reeds clearly modified the taxonomic composition and abundance of ciliates. This was reflected in an increase in the abundance and diversity of these protozoa and in a significant increase in the proportion of sphagnophilous species. Our results suggest an indicator species approach based on functional groups may be appropriate for biomonitoring peatbog restoration. A better understanding of what regulates microbial populations and activity in peatbogs and unravelling of these fundamental mechanisms are particularly critical in order to more accurately predict how peatbogs will respond to anthropogenic disturbances.

Ecology of ciliates in microbial mats in meltwater streams, King George Island, maritime Antarctica

Microbial communities living in microbial mats are known to constitute early indicators of ecosystem disturbance, but little is known about their response to environmental factors in the Antarctic. This paper presents the first major study on ciliates from microbial mats in streams on King George Island (Antarctica). The objective of the study is to investigate the structure and spatial distribution of ciliate communities and to identify the environmental factors determining the structure of the assemblages. Additionally, we compared ciliate communities inhabiting streams on King George Island with other isolated islands of the maritime Antarctic. Samples of microbial mats for ciliate analysis were collected from three streams fed by Ecology Glacier. Sampling was carried out three times from 17 January to 24 February 2012. The total numbers of ciliates were dominated by small taxa recognized as cosmopolitan, also recorded on other islands of the maritime Antarctic. The species richness, abundance, and biomass of ciliates differed significantly between the stations studied, with the lowest numbers in the middle course of the stream and the highest numbers in the microhabitats closest to the glacier and at the site where the stream empties into the pond. Variables that significantly explained the variance in ciliate communities in the transects investigated were total organic carbon, total nitrogen, temperature, dissolved oxygen, and conductivity. Further research is required to explain the impact of biotic factors on the presence of ciliates, including the abundance of bacteria, microalgae, and small metazoa.

Effects of experimental addition of nitrogen and phosphorus on microbial and metazoan communities in a peatbog

Interactions between microbial communities and the classical grazing food chain are essential for understanding the functioning of peatbog ecosystems. However, little is known of how short-term intensification of eutrophication processes may influence microbial and metazoan communities in transitional peatbog. We addressed the hypothesis that an increase in the concentration of nutrients will affect the species richness and abundance of microorganisms and small metazoans and cause changes in the food web structure in a peatbog. The experiments were performed in a transitional peatbog. Four experimental variants were conducted (control and nutrient-enriched: +P, +N and P+N). Increased habitat fertility was found to modify the taxonomic composition and functioning of microbial communities. We observed a strong reduction in the species richness of testate amoebae-top predators, and a substantial increase in the abundance of bacteria, flagellates and ciliates. A better understanding of which parameters regulate microbial populations in peatbogs is critical for more accurate prediction of how peatbogs will respond to global climate change or anthropogenic disturbances.

Ecology of testate amoebae (Protists) in a Sphagnum-dominated peat bog and the relationship between species assemblages and environmental parameters

Abstract Despite its ecological importance, little information is available regarding spatial and seasonal changes in the testate amoebae community in peat bogs. The objectives of this study were to examine the structure of communities and horizontal distribution of testate amoebae fauna, to improve the understanding of factors affecting the distribution of moss testate amoebae communities and to analyze the seasonal changes in testate amoebae communities in a Sphagnum-dominated peat bog (eastern Poland). A total of 45 testate amoebae species were identified in the samples. The highest species richness occurred in hollows dominated by Sphagnum angustifollum, much lower numbers of taxa were observed in hummocks dominated by Sphagnum magellanicum and Polytrichum. The Monte Carlo permutation test showed the significance of Ntot, temperature, pH, and the depth to the water table for the variability of testate amoebae in all microhabitats. Species found in spring samples were associated with the increased Ntot content. Species occurring in summer samples were associated with the increasing pH gradient and species developing in late spring and autumn preferred a greater depth to the water table.

Ecology of Ciliates in Microbial Mats in Small Ponds: Relationship to Environmental Parameters (King George Island, Maritime Antarctica)

The objective of the study was to investigate the taxonomic structure and spatial distribution of ciliate communities, and to identify the environmental factors determining the taxonomic structure of the assemblages. Additionally, we compared ciliate communities inhabiting ponds on King George Island (Antarctica) with those on other islands of the maritime Antarctic. The taxonomic richness, abundance and biomass of ciliates in microbial mats varied among ponds increasing with their eutrophication level. As the level of eutrophication increased, there was a decrease in the abundance of predatory and omnivorous ciliates and a decrease in that of algivorous taxa. The canonical correspondence analyses of the spatial distribution of ciliates showed that all environmental variables together explained 76% of the total variance. The Monte Carlo permutation test showed that dissolved orthophosphates, nitrate and total organic carbon had the most significant effect on the distribution of ciliates. The proportions of individual functional groups of ciliates varied among ponds. The proportion of heterotrophic taxa increased with the trophic state of the ponds, while the proportion of mixotrophic taxa decreased.