Epilithic Diatom Community Shows a Higher Vulnerability of the River Sava to Pollution during the Winter

Abstract

The aim of the research was to investigate the influence of environmental factors on the structure of epilithic diatom communities in the Sava River from the source to the state border 220 km downstream. The river had numerous human influences along its course, such as municipal and industrial wastewater, agriculture, hydroelectric power plants, etc. The main objective of the research was to find out the influence of human pressure on the structure of the epilithic diatom community under winter and summer conditions. Winter and summer samples were taken at nine sites. At each sampling site, a set of abiotic factors was measured and another set of environmental parameters was evaluated. The analyses showed that nitrogen and phosphorus concentrations increased downstream. We identified 118 different species of diatoms. The most common taxa were Achnanthidium minutissimum and A. pyrenaicum. Planktonic species Cyclotella meneghiniana was only found in the samples of the lower part of the Sava, which is unusual for the epilithic community. The composition of the epilithic diatom community was significantly influenced by conductivity and water temperature, pH and distance from the source. The similarity between diatom communities closer to the source of the river was higher than between communities from the lower part of the Sava River. The values of the trophic and saprobic indices increased downstream and showed that the pollution of the river with nutrients and organic matter increases with the distance from the source. Both indices were significantly higher in winter and showed a more impaired river ecosystem during the winter.

Epiphyton in Agricultural Streams: Structural Control and Comparison to Epilithon

“…Furthermore, the dominant epiphyton diatom species found was Cocconeis placentula var. euglypta whereas Achnanthidium minutissimum dominated in epilithon diatom community, which follows the findings in [23,55,56].…”

“…A higher biomass per substrate area for epilithon, compared with epiphyton have previously been found in river ecosystem [53] and lakes [54]. They emphasize that a higher epilithon biomass is most likely due higher stability [55,56] and the durability of gravel and stone substrates, whereas plant-decaying process and macrophyte allelopathic substances may lead to less biomass accrual on epiphyton [54]. Both biofilm communities showed a dominant heterotrophy similar to previous studies, e.g., [57,58].…”

Differences in Phytobenthic Diatom Community between Natural and Channelized River Sections

“…Factors that significantly influence the diatom community in both cases (taxa and ecological types) are temperature and average depth of the water. Temperature has been most frequently cited as a significant factor in shaping diatom community composition (e.g., Zelnik and Sušin [44], Toman et al [45], Izagirre and Elosegi [25], and Soininen [46]). In the case of ecological types, the total abundance of the other algae is also a significant factor opposing the proportion of the LP taxa (Figure 4), which cannot compete for nutrients and light with more prominent green algae or cyanobacteria.…”

Epilithic Diatoms Diversity in The Reservoir of Universitas Diponegoro, Semarang

“…The rock substrate is moist and can be passed by environmental stressors, therefore epilithic diatoms are used as bioindicators that are sensitive to environmental conditions (Gowan, 2018). Epilithic diatom communities are considered more stable than epiphytic and epipelic communities, because of the stability of their substrates (Zelnik, 2020 (Soeprobowati, 2001;Soeprobowati, 2010).…”