title: Solar PAR and UVR modify the community composition and photosynthetic activity of sea ice algae.
abstract: The effects of increased photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic activity were studied in fast ice algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free ice covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic activity was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea ice, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic activity and community composition.
authors: Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, FI-10900 Hanko, Finland Department of Environmental Sciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland sara.enberg@helsinki.fi.
authors: Sara
authors: S
authors: Enberg
authors: Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, FI-10900 Hanko, Finland Finnish Environment Institute, Marine Research Centre, PO Box 140, FI-00251 Helsinki, Finland.
authors: Jonna
authors: J
authors: Piiparinen
authors: Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, FI-10900 Hanko, Finland Department of Environmental Sciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland.
authors: Markus
authors: M
authors: Majaneva
authors: Department of Biological and Environmental Science, PO Box 35, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
authors: Anssi V
authors: AV
authors: Vähätalo
authors: Finnish Environment Institute, Marine Research Centre, PO Box 140, FI-00251 Helsinki, Finland.
authors: Riitta
authors: R
authors: Autio
authors: Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, FI-10900 Hanko, Finland Department of Environmental Sciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland.
authors: Janne-Markus
authors: JM
authors: Rintala
mesh_terms: D056893:Alveolata; D001454:Baltic States; D018533:Biomass; D000460:Chlorophyta / Q000254:growth & development / Q000528:radiation effects*; D017377:Diatoms / Q000254:growth & development / Q000528:radiation effects*; D004141:Dinoflagellida / Q000254:growth & development / Q000528:radiation effects*; D046448:Ice Cover; D010788:Photosynthesis / Q000528:radiation effects*; D012914:Snow; D012993:Solar Energy; D014466:Ultraviolet Rays
keywords: Baltic Sea; UVR; algae; photosynthetic activity; sea ice