Halophilic diatom taxa are sensitive indicators of even short term changes in lowland lotic systems

Abstract

-The occurrence and spread of halophilic diatom taxa in freshwater lotic ecosystems are infl uenced both by natural processes and anthropogenic pollution. Diatom assemblages were regularly monitored in lowland lotic systems in Hungary (Central Europe) during the unusually dry year of 2012. Highly pronounced changes in diatom composition were observed from spring to autumn. Halophilic taxa (especially Nitzschia sensu lato species) appeared in the dry autumn. In addition, the total relative abundances of halophilic species also increased up to autumn. Abundance of Nitzschia cf. lorenziana and Nitzschia tryblionella showed a positive correlation with chloride and phosphate concentration, while that of other taxa like Tryblionella apiculata or Tryblionella calida showed a positive correlation with the concentration of nitrate. Our fi ndings clearly demonstrated that these halophilic and mesohalophilic diatom taxa were sensitive indicators of even short-term changes in lowland lotic ecosystems, such as the increasing salt concentration from spring to autumn caused by the lack of rainfall and/or environmental loads.

Autumn drought drives functional diversity of benthic diatom assemblages of continental intermittent streams

“…The motile taxa have an advantage in resource acquisition under increased nutrient levels (Berthon et al, 2011;B-Béres et al, 2014B-Béres et al, ,2017Passy and Larson 2011). We also observed that halophilic taxa were more abundant in perennial rivers, likely due to increasing resource availability, as observed in the River Wipper (Ziemann et al, 2001) and in lowland small streams (Kókai et al, 2015). Finally, the presence of planktic taxa was another characteristic of diatom assemblages in our perennial streams, which may indicate a water velocity reduction (B-Béres et al, 2017;Rimet and Bouchez, 2012).…”

Colonisation processes in benthic algal communities are well reflected by functional groups

“…2, 3). Former research showed significant correlation between the medium sized group and the stream drying (Kókai et al, 2015). Thus, the strong positive correlation of S3SMCMa group to time, i.e.…”

“…Recent studies demonstrated that both single traits and functional groups of benthic diatoms or other benthic algal assemblages may be useful indicators of environmental changes in watercourses (Berthon et al, 2011;Stenger-Kovács et al, 2013;Kókai et al, 2015;B-Béres et al, 2014B-Béres et al, , 2016B-Béres et al, , 2017Lange et al, 2016;Marcel et al, 2017). Single traits or functional groups alone could indicate some physical and chemical changes in water courses (Kókai et al, 2015;Lengyel et al, 2015).…”

“…In contrast, small size enables the spread of the cells due to their slower settling. Furthermore, small sized taxa are able to live under highly disturbed circumstances (Stenger-Kovács et al, 2013;B-Béres et al, 2014B-Béres et al, , 2016Kókai et al, 2015). Thus, increase in the proportion of small sized groups was hypothesised with the increasing environmental disturbances.…”

“…Nowadays, the most often used cell size classification system was proposed by Berthon et al (2011), that contains five cell size classes (Table 1). The use of these classes in the assessment of the ecological status of watercourses either alone or together with other traits was validated by former researches (Berthon et al, 2011;Kókai et al, 2015;B-Béres et al, 2016B-Béres et al, , 2017.…”