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Production and food web interactions of Arctic freshwater plankton and responses to increased DOC
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Limnologi. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
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2004 (English)In: Archiv für Hydrobiologie, ISSN 0003-9136, Vol. 159, no 3, 289-307 p.Article in journal (Refereed) Published
Abstract [en]

A gradient of dissolved organic carbon (DOC) was added to enclosures in a high Arctic lake (Svalbard, 79 N). The aim was to simulate the effect of increased concentrations of DOC that will be a predicted effect of increased temperature and precipitation. The study aimed to provide information on the overall effects of such increased levels of DOC on the pelagic food-web, as well as the increased attenuation of UV-radiation (UV-R) caused by increased DOC. The biomass development of phytoplankton, heterotrophic bacteria and ciliates from 15. July (shortly after ice-off) to 8. August revealed a consistent pattern across all enclosures. Initial phytoplankton biomass decreased from maxima around 600g Cl-1 towards 50g Cl-1 by the end of July. Similarly, ciliate biomass decreased from ~100 to 5g Cl-1, while heterotrophic bacteria decreased from initially 280 g Cl-1 to biomasses near 100 g Cl-1. Over the same period, zooplankton biomass (almost a monoculture of Daphnia tenebrosa) increased from <40 to some 170g Cl-1. These patterns were reflected also in decreasing absolute production of bacteria and phytoplankton, while production:biomass ratio remained fairly constant. In general, the study demonstrated a very dynamic system over the brief ice-free season, where Daphnia grazing had a strong impact on the unicellular biota. Additions of DOC initially stimulated planktonic production, yet this effect was soon overruled by Daphnia grazing. This stimulating effect could be a result both of increased UV-R attenuation and some growth stimulating effect. Since no corresponding stimulating effect was observed in the bag shielded with Mylar filter to screen off UV-B, the latter cause seems most likely.

Place, publisher, year, edition, pages
2004. Vol. 159, no 3, 289-307 p.
Keyword [en]
Arctic, dissolved carbon, UV-radiation, plankton, Daphnia, trophic interactions
National Category
URN: urn:nbn:se:uu:diva-72419DOI: 10.1127/0003-9136/2004/0159-0289OAI: oai:DiVA.org:uu-72419DiVA: diva2:100330
Available from: 2008-04-14 Created: 2008-04-14 Last updated: 2011-12-12Bibliographically approved

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