UV-B effects on microplankton communities in Kongsfjord, Svalbard - A mesocosm experiment |
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Authors: | Sten-Åke Wängberg Kristin IM Andreasson Thomas Reinthaler |
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Institution: | a Department of Plant- and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE-40530 Göteborg, Sweden b DHI Water and Environment, Agern Allé 5, DK-2970 Hørsholm, Denmark c Royal Netherlands Institute for Sea Research (NIOZ), Department of Biological Oceanography, PO Box 59, 1790 AB, Den Burg, The Netherlands d NERI, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark |
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Abstract: | The effect of ambient ultraviolet radiation on microplankton communities in an Arctic fjord was measured in mesocosms incubated for 9 days at 2 or 5 meters depth. The mesocosms were either shielded from UV-B radiation by Mylar foil or received full radiation. The parameters measured were: microscopic counts of phytoplankton and micro-zooplankton, photosynthetic capacity, the wavelength-dependent inhibition of photosynthesis, and bacterial biomass and production. The results showed that UV-B radiation increased the photosynthetic capacity of the community but that the overall biomass of the plankton community was reduced. This indicates that UV-B exposure results in a net impairment of the plankton community in that it reduces the potential to allocate the photosynthetic product into new biomass or that the grazing pressure is higher in the UV-B exposed mesocosms. There were no differences in the wavelength dependence between communities exposed to UV-B versus not, but we observed a significantly lower dependence in communities from 2 m depth compared to those from 5 m, indicating that an acclimation of the photosynthetic apparatus to high radiation also reduces the wavelength dependence. A general effect was an increase in nanoflagellate and choanoflagellate biomass and a decreased in the biomass of ciliates and bacteria. The increase nanoflagellates was significantly larger in mesocosms shielded from UV-B, while choanoflagellates increased more in UV-B exposed mesocosms. |
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Keywords: | Arctic Flagellates Phytoplankton Primary production Ultraviolet |
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