Origin of phytoplankton and the environmental factors governing the structure of microalgal communities in lowland streams |
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Authors: | Kai Piirsoo Sirje Vilbaste Jaak Truu Peeter Pall Tiiu Trei Arvo Tuvikene Malle Viik |
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Institution: | (1) Centre for Limnology, Institute of Agricultural and Environmental Sciences, University of Life Sciences, Riia 181, Tartu, 51014, Estonia;(2) Faculty of Biology and Geography, University of Tartu, Riia 23, Tartu, 51010, Estonia |
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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. |
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Keywords: | Canonical correspondence analysis Epilithon Epiphyton Estonian rivers Phytoplankton Redundancy analysis |
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