The importance of environmental differences in the structuring of rotifer functional diversity

A dynamic change in environmental conditions among floodplain habitats with different geomorphology might be a significant trigger in determining rotifer functional diversity. The aim of the study was to test the importance of environmental differences between several waterbody types, their positions within the floodplain and supporting microcrustacean communities in the structuring of rotifer functional feeding guilds. The study was conducted in Kopački rit floodplain during 2008 at five sites (two lakes, two channels and the main river). ANOSIM showed a significant difference in spatial distribution among rotifer feeding guilds. Redundancy analyses indicated biotic variables to significantly influence rotifer functional diversity in lake systems while in channel environments and the main riverbed guild representation was mainly influenced by limnological variables. Individual guild abundance changed relative to the site position within the floodplain as well, where the increased distance from the main riverbed resulted in increased rotifer numbers, and a different proportion of microfilter-feeders and macrofilter-feeders was recorded. The multiple linear regression showed a significant relation of macrofilter-feeder rotifers with microcrustaceans pointing to notable exploitative competition among these groups. The results highlight the ecological importance of all types of natural floodplain habitats necessary for preserving and maintaining the rotifer diversity.

Zooplankton in Ancient and Oligotrophic Lake Ohrid (Europe) in Association with Environmental Variables

Zooplankton is studied in the ancient, tectonic, oligomictic and oligotrophic Lake Ohrid (Macedonia, South Eastern Europe). The main aim of this study was to assess the seasonal and spatial patterns of the zooplankton functional feeding guilds in relation to the environmental conditions. Metalimnion of the lake was detected as the most productive environment, where biomass of the phytoplankton and abundance of the zooplankton reached their maxima. Pelagial zooplankton of low abundance (25 ± 22 ind. L−1) consisted of 16 species including two endemic copepods, Arctodiaptomus steindachneri (Richard, 1897) and Cyclops ochridanus (Kiefer, 1932). Copepods obtained remarkable share (60%) in the zooplankton assemblage. Microphagous zooplankton was mainly comprised of the most abundant rotifer Kellicottia longispina (Kellicott, 1879) in summer, and copepod nauplii during the spring Eudiaptomus gracilis (Sars, 1862) and C.ochridanus, and autumn C.ochridanus. Due to their requirements for the bacterio-detritus suspension, this microphagous zooplankton occupied aphotic hypolimnion during the entire study period. Raptorials were typically represented by copepodites and adult copepods in the metalimnion, and were significantly and positively affected by temperature (r = 0.417, p = 0.001), dissolved oxygen (r = 0.463, p = 0.0001) and, particularly, phytoplankton biomass (r = 0.708, p < 0.00001). This is the first study in which the link between the lower and higher trophic levels is investigated in Lake Ohrid.

Evaluation of Macroinvertebrate Data Based on Autoecological Information

Various data (biological, chemical, hydrological and morphological) have been gathered within the frame of the monitoring of the Water Framework Directive from 2007 in Hungary. This data only used a status assessment of certain water bodies in Hungary. The macroinvertebrates indicate many environmental factors well; therefore, they are very useful in detecting changes in the status of an environment. The main aim in this research was to investigate changes in environmental variables and decide how these variables cause big changes in the macroinvertebrate fauna. The macroinvertebrate data was processed using the ASTERICS 4.0.4 program. The program calculated some important metrics (i.e., microhabitat distributions, longitudinal zonation, functional feeding guilds, etc.). These metrics were compared with the chemical and hydrological data. The main conclusion is that if we have enough of a frequency and quality of macroinvertebrate data, we can understand changes in the environment of an ecosystem.

Fatty acids in profundal benthic invertebrates and their major food resources in Lake Erken, Sweden: seasonal variation and trophic indications

Fatty acid (FA) concentrations and their seasonal variations were quantified for profundal benthic invertebrates, surficial sediment, and sedimenting matter from Lake Erken, Sweden. Food quality for profundal zoobenthos, as indicated by the concentrations of long-chain polyunsaturated FA, ω3 FA, or eicosapentaenoic acid (EPA) in sediment and sedimenting matter, was highest in spring and autumn and markedly lower in summer. Surficial sediment was consistently lower in all FA than was sedimenting matter. Palmitoleic acid (16:1ω7) was the dominating FA in both sedimenting matter and sediment. In fauna samples, EPA, palmitic acid (16:0), palmitoleic acid, and vaccenic acid (18:1ω7) were among the dominant FA. Docosahexaenoic acid was found only in the predators Chaoborus and Procladius. Differences between functional feeding guilds were found for the diatom-indicating FA palmitoleic acid and the bacteria-specific FA isoseptadecanoic acid (17:0iso). Furthermore, principal components analysis showed marked differences in FA composition among taxa. These differences reflect the relative contribution of food from autotrophic (phytoplankton production) and heterotrophic sources (detrital food web) in profundal invertebrate taxa.