Seasonal dynamics of epilithic diatom community from the Vrla River (Southeastern Serbia)

Seasonal analysis of epilithic diatom community from the Vrla River was performed in four seasons a year (six times) at six sampling sites. Between the second (VR2) and the third sampling site (VR3) was located a trout fish farm. The highest number of diatom taxa was recorded in spring (149) and the lowest in autumn (93). The number of taxa that were found to be dominant during all four seasons was twenty-four. The relationship between 45 the best-fitted diatom taxa, which showed conspicuous seasonal dynamics, and seasons in which these taxa were recorded was illustrated using canonical correspondence analysis (CCA). The large number of taxa was identified in all four seasons or in winter period only. Few taxa were present only in spring and summer.

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

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.

Epilithic Diatom Abundance Study in the Batang Kuranji River in Padang City, West Sumatra

A study about abundant of epilithic diatom was conducted on 2017 in Kuranji River. The objective of this study was to clarify species and abundant of epilithic diatom in Batang Kuranji River. Samples were collected in 3 stations by purposive sampling and brushing method. The results showed that totally 82 species in 22 genera had been found. The total abundant of epilithic diatom was 15139,26 individual/cm2. The highest abundance of epilithic diatom was found in station I (Batu Busuak) and the lowest in station III (Sawah Liek). Synedra sp and Fragillaria sp were dominant group of diatoms which are found in almost all sites. Some physical and chemical water quality parameters were showed that Batang Kuranji River were polluted slightly by organic and inorganic materials.

The Effect of Monsoon Rainfall Patterns on Epilithic Diatom Communities in the Hantangang River, Korea

Most of Korea’s rivers and lakes are subject to physico-chemical disturbances, such as increased water quantity and flow rates, and influx of nitrogen and phosphorus, due to intense rainfall concentrated in the Asian monsoon season. To examine the influence of rainfall on epilithic diatom communities, we measured the diatom distribution and river water quality at 29 sites along the main-stream and tributaries of the Hantangang River, Korea, in the period of 2012–2015. Water quality parameters in the polluted sites had improved following rainfall, but the response of dominant species varied with water quality; the dominant species Nitzschia fonticola decreased in abundance regardless of sampling sites, and the abundance of Achnanthidium minutissimum in the clean sites and Nitzschia palea in the polluted sites increased after rainfall, respectively. The community dynamic index (CDI) showed that the most obvious shift of epilithic diatom community occurred in the mid-polluted sites in 2013 with the highest rainfall. This suggest that the effect of rainfalls on the epilithic diatom community is dependent on various parameters, such as the magnitude of rainfall, water quality and its biotic compositions of diatom communities, but it also indicates that improving the water quality of rivers is important to promote the resilience of diatom communities to extremes of precipitation. Further investigation is needed to generalize the effects of monsoon rainfall on the epilithic diatom communities, considering rivers with different environmental characteristics.

Diatom Biodiversity in Karst Springs of Mediterranean Geographic Areas with Contrasting Characteristics: Islands vs Mainland

Karst ecosystems are considered as priority environments for the protection of biodiversity on a global scale. This study provides a first comparative analysis of epilithic diatom flora from karst springs in two Mediterranean geographic areas (Spain and Italy) with contrasting characteristics (islands vs mainland). We investigated twenty-three springs with different anthropogenic impact levels once in the winter season between 2007 and 2017 (N = 23). A total of 176 diatom taxa (56 genera) were found of which 101 (44 genera) were observed in single sites. A general good biotic integrity was revealed by structural indices (species richness, diversity and evenness). However, crenophilous species were generally present and abundant in less impacted springs. Comparing islands and mainland, significant differences were found in species composition and diversity (H’) based on multivariate analyses (global R = 0.610; p = 0.001) and t-test (t = 2.304; p = 0.031). Discharge and Cl− were the most significant variables in determining diatom assemblages. Our results confirm the role of springs as multiple ecotones and refuges for rare species and suggest that the geographic insularity may be an important factor in maintaining diatom biodiversity.