Species composition and seasonal succession of phytoplankton were analyzed in a lowland river located in South Banat (Ponjavica, Serbia). As a result of human activity, a network of irrigation channels was built on the Ponjavica River's upper and lower courses. These channels reduce the water level in the river and help to create favorable conditions for accelerated eutrophication processes. Eight phytoplankton divisions with 444 taxa were present. Physical and chemical testing of water, phytoplankton abundance and biomass, as well as chlorophyll a concentration showed a high level of eutrophication. Cyanobacterial biomass developed in 2002 with dominance of Microcystis aeruginosa and Aphanizomenon flos-aquae.Changes in phytoplankton composition were observed during 2008, characterized by the appearance and dominance of Cylindrospermopsis raciborskii when this species accounted for more than 85% of the total phytoplankton biovolume. The change in dominant phytoplankton functional groups was observed: codons H 1 and M characterizing summer in 2002 were replaced by codons S N and S 1 in 2008. This study compares the presence of C. raciborskii with other phytoplankton species in relation to water quality parameters. High abundance of this species correlated positively with biochemical oxygen demand and turbidity, and negatively with NO 3 -N concentrations during the study period.
Substrate specificity of the periphyton community is usually underestimated in both periphyton ecology and biomonitoring studies, thus different kinds of both natural and artificial substrates (of organic and inorganic origin) are employed. Periphyton colonization and successional trajectories are particularly debatable processes when different kinds of substrates are considered. In our field experiment, we deployed four kinds of artificial substrates (two inorganic ones – glass and ceramic, and two organic ones – willow and yew wooden tiles) for the development of periphyton in an urban reservoir referred to as Lake Savsko (Belgrade, Serbia). We comparatively investigated the structure, colonization process, diversity and successional trajectories of periphyton. We also assessed the relationship between the dynamics of algae growth forms (ecological groups) on different substrates and selected abiotic limnological factors. Our objective was to determine whether the type of substrate affects periphyton characteristics at various levels and whether an artificial substrate potentially affects the bioindication capacity of ecological groups. We concluded that all substrates behave similarly at the level of structure and colonization phases, but when considering diversity and successional trajectories, the substrate specificity was demonstrated. Our results suggest that communities developed on inert substrates (glass and ceramic) could provide more realistic insight into complex environmental changes.
The summer phytoplankton community was studied across both vertical and temporal scales in relation to environmental factors in the shallow recreational Sava Lake. The sampling was conducted weekly at four depths from mid-July until mid-September 2014, in order to detect short-term changes within the assemblages. Besides physical and chemical parameters, meteorological data was also included in the investigation, as that year was characterized with extreme rainfall, which caused serious flooding in the region. The community succession was characterized by a reverse in the cyanobacteria (Codon M) and chlorococcal green algae (Coda F and J). Statistical analyses (RDA) indicated that changes in the community composition and successional pattern could have been due to the mixing regime variations in the reservoir, most likely induced by weather disturbances, especially high precipitation and wind events. These events did not permit massive cyanobacterial development, although they most likely caused resuspension of dissolved phosphorus from the sediment. When observing functional groups, three groups could be distinguished by their response to the above-mentioned parameters: the first prefers high temperature and insolation (Lm, Y, Lo, Xph, W2 and M), the second is correlated with precipitation and wind (Td, C, K, MP and X2), while the third group tolerates cloudiness (H1, F, N, X1, D, J and P).
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