Origin of phytoplankton and the environmental factors governing the structure of microalgal communities in lowland streams

Abstract

Information on the structure of microalgal assemblages in the epiphyton and epilithon is necessary to understand the origin of phytoplankton in lowland rivers. To this end, we carried out concurrent investigations on phytoplankton, epiphyton and epilithon in 18 reaches of three Estonian rivers during the midsummers of 2002 and 2003. A total of 251 taxa was recorded, of which 192 were epiphyton species, 158 were epilithon species and 150 were phytoplankton species. Canonical correspondence analysis (CCA), based on the 31 most abundant taxa, indicated differences in the structure of the algal assemblages between the different biotopes (phytoplankton, epiphyton and epilithon) as well as between the studied rivers. The composition of the phytoplankton clearly differed from that of the other biotopes, with prevailing small flagellates, a chrysophyte (Synura uvella) and cryptophytes (Rhodomonas lacustris and Cryptomonas erosa). The epiphyton was characterized by a large number of diatoms, while the epilithic community contained filamentous cyanobacteria (Phormidium tergestinum and Planktolyngya sp.) and a green alga (Stigeoclonium tenue) in addition to diatoms. Based on redundancy analysis (RDA), phosphorous was the most relevant parameter determining the distribution of species in the phytoplankton assemblages. Shading by trees on the river bank, dissolved oxygen concentration and water temperature as well as river width determined the distribution of species in the epiphyton. The data set on the epilithon did not reveal any significant relationships between species distribution and the measured environmental parameters.

Epiphyton in Agricultural Streams: Structural Control and Comparison to Epilithon

“…Diatoms and green algae were the main algae communities in epiphyton, which is consistent with previous studies [22,60], and the presence of cyanobacteria was negligible. In contrast, cyanobacteria were more abundant than green algae in epilithon, particularly during summer months in Aarhus, where discharge and DIN concentrations were low.…”

Assessment of water quality in a large lowland river (Narva, Estonia/Russia) using a new Hungarian potamoplanktic method

“…In running waters algal communities are influenced by the size of the catchment area (Billen et al, 1994), water residence time (Reynolds et al, 1991), and nutrient concentration (Van Nieuwenhuyse & Jones, 1996;Basu & Pick, 1997;Koch et al, 2004;Piirsoo et al, 2007). For streams and small rivers, benthic diatoms are good indicators (Ács et al, 2003, 2004, 2006Szabó et al, 2004;Hering et al, 2006;Hlúbiková et al, 2007;Kelly et al, 2009).…”

“…Earlier diatom indices were found to correlate with nutrient concentration in Estonian streams (Vilbaste, 2004;Vilbaste et al, 2007). The phytoplankton community is influenced by phosphorus concentration (Piirsoo et al, 2007). This means that both phytoplankton and benthic diatom metrics are sensitive to water quality.…”